DECEMBER 2021 IEEE Spectrum

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Citation preview

Facebook’s Real Plan for Cryptocurrency Financial services is just a start P.10

Inside A DIY Rocket Program

Hacking Ham Radio for Phone-Free Texts It’s all in the Arduino P.14

The End of Diabetes? A smart artificial pancreas adjusts insulin on the fly P.38

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VOLUME 58 / ISSUE 12

DECEMBER 2021

The First Crowdfunded Astronaut

22

A DIY rocket is under con­ struction in a Copenhagen warehouse. By Mads Stenfatt

Creating the Artificial Pancreas

38

It dispenses just the right amount of insulin at just the right time. By Boris Kovatchev & Anna Kovatcheva

Ohm’s Law + Kirchhoff ’s Current Law = Better AI

44

Doing AI using analog circuits saves power. By Geoffrey W. Burr, Abu Sebastian, Takashi Ando & Wilfried Haensch NEWS 6 6G Power Struggles (p.6) Jupiter’s Electric Blanket (p.8) Facebook Cryptocurrency (p.10) HANDS ON 14 A self-contained messenger for ham radio. CROSSTALK Numbers Don’t Lie (p.18) Gizmo (p.20) Macro & Micro (p.21)

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PAST FORWARD Bright Lights of Christmas

76

FAR RIGHT: EVERETT COLLECTION HISTORICAL/ALAMY

THE INSTITUTE

AC Grid History

30

62

The first three‑phase AC electrical plant.

The Smartly Dressed Spacecraft

Electronic fabrics sensitive to vibration and charge could revolutionize space structures. By Juliana Cherston & Joseph A. Paradiso

Photo by Bob O’Connor

ON THE COVER: Photo by Mads Stenfatt

DECEMBER 2021  SPECTRUM.IEEE.ORG  1

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2  SPECTRUM.IEEE.ORG  DECEMBER 2021

BACK STORY

A Skydiver Who Sews

M

ads Stenfatt first contacted Copenhagen Suborbitals with some constructive criticism. In 2011, while looking at photos of the DIY rocketeers’ latest rocket launch, he had noticed a camera mounted close to the parachute apparatus. Stenfatt sent an email detailing his concern—namely, that a parachute’s lines could easily get tangled around the camera. “The answer I got was essentially, ‘If you can do better, come join us and do it yourself,’ ” he remembers. That’s how he became a volunteer with the world’s only crowdfunded crewed spaceflight program. As an amateur skydiver, Stenfatt [above] knew the basic mechanics of parachute packing and deployment. He started helping Copenhagen ­Suborbitals design and pack parachutes, and a few years later he took over the job of sewing the chutes. He had never used a sewing machine before, but he learned quickly over nights and weekends at his dining room table. One of his favorite projects was the design of a high-altitude parachute for the Nexø II rocket, launched in 2018. While puzzling over the design of a prototype’s air intakes, he found himself on a Danish sewing website looking at brassiere components. He decided to use bra underwires to stiffen the air intakes and keep them open, which worked quite well. Though he eventually went in a different design direction, the episode is a classic example of the Copenhagen Suborbitals ethos: Gather inspiration and resources from wherever you find them to get the job done. Today, Stenfatt serves as the team’s lead parachute designer, frequent spokesperson, and astronaut candidate, as he writes about in this issue on p. 22. He also continues to skydive in his spare time, with hundreds of jumps to his name. Having ample experience zooming down through the sky, he’s intently curious about what it would feel like to go the other direction. ■

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CONTRIBUTORS

 JULIANA CHERSTON ​​Cherston is a Ph.D. candidate in the Responsive Environments Group at the MIT Media Lab. In this issue, she and the group’s director, Joseph A. Paradiso, explain how they aim to transform the outer surfaces of spacecraft, space habitats, and spacesuits into sophisticated data-gathering instruments [p. 30]. “I serve as a bridge between other technologists and scientists on our team, which requires playing some of each role myself,” Cherston says.

 ALLISON MARSH Each month, Marsh, an associate professor of history at the University of South Carolina, features a different object in Past Forward that helps shed light on our shared past. This issue’s object [p. 76] is literally illuminating: a 1925 Christmas bulb shaped like a doll’s head. Marsh chose it to explore the history of Christmas lights “because it’s so creepy,” she says.

EDITOR-IN-CHIEF Susan Hassler, [email protected] EDITORIAL DIRECTORS Harry Goldstein (Digital), [email protected] Glenn Zorpette (Development), [email protected] FEATURES EDITOR Jean Kumagai, [email protected] MANAGING EDITOR Elizabeth A. Bretz, [email protected] SENIOR ART DIRECTOR Mark Montgomery, [email protected] PRODUCT MANAGER, DIGITAL Erico Guizzo, [email protected] SENIOR EDITORS Evan Ackerman (Digital), [email protected] Stephen Cass (Special Projects), [email protected] Samuel K. Moore, [email protected] Tekla S. Perry, [email protected] Philip E. Ross, [email protected] David Schneider, [email protected] Eliza Strickland, [email protected] NEWS MANAGER Mark Anderson, [email protected] ASSOCIATE EDITORS Willie D. Jones (Digital), [email protected] Michael Koziol, [email protected] THE INSTITUTE EDITOR-IN-CHIEF Kathy Pretz, [email protected] ASSISTANT EDITOR Joanna Goodrich, [email protected] SENIOR COPY EDITOR Joseph N. Levine, [email protected] COPY EDITOR Michele Kogon, [email protected] EDITORIAL RESEARCHER Alan Gardner, [email protected] CONTRIBUTING EDITORS Robert N. Charette, S ­ teven ­Cherry, Charles Q. Choi, Peter Fairley, Maria Gallucci, W. Wayt Gibbs, Mark Harris, Jeremy Hsu, Allison Marsh, Prachi Patel, Megan Scudellari, Lawrence Ulrich, Emily Waltz ADMINISTRATIVE ASSISTANT Ramona L. Foster, [email protected]

 BORIS KOVATCHEV Inspired by his father’s lifelong struggle with diabetes, Kovatchev, director of the University of Virginia’s Center for Diabetes Technology, used his skills as a mathematician to model how the body governs the concentration of glucose in the bloodstream. That work led to the advent of a functioning artificial pancreas, now used by millions and described by Kovatchev and his daughter Anna on page 38.

 GEOFFREY W. BURR Burr is an IEEE Fellow and a distinguished research staff member at IBM Research, in Almaden, Calif. Together with fellow IBM researchers Abu Sebastian in Zurich and Takashi Ando and IEEE Fellow Wilfried Haensch in Yorktown Heights, N.Y., Burr works on using analog circuits to improve AI, as they explain on page 44. The technology was originally aimed at brain-inspired neural networks, says Burr. But the algorithms involved were unproven. He steered the research toward more conventional AIs, so “we could quickly start to improve things instead of trying to guess what went wrong,” he says.

4  SPECTRUM.IEEE.ORG  DECEMBER 2021

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IEEE SPECTRUM (ISSN 0018-9235) is published monthly by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved. © 2021 by The Institute of Electrical and Electronics Engineers, Inc., 3 Park Avenue, New York, NY 10016-5997, U.S.A. Volume No. 58, Issue No. 12. The editorial content of IEEE Spectrum magazine does not represent official positions of the IEEE or its organizational units. Canadian Post International Publications Mail (Canadian Distribution) Sales Agreement No. 40013087. Return undeliverable Canadian addresses to: Circulation Department, IEEE Spectrum, Box 1051, Fort Erie, ON L2A 6C7. Cable address: ITRIPLEE. Fax: +1 212 419 7570. INTERNET: [email protected]. ANNUAL SUBSCRIPTIONS: IEEE Members: $21.40 included in dues. Libraries/institutions: $399. POSTMASTER: Please send address changes to IEEE Spectrum, c/o Coding Department, IEEE Service Center, 445 Hoes Lane, Box 1331, Piscataway, NJ 08855. Periodicals postage paid at New York, NY, and additional mailing offices. Canadian GST #125634188. Printed at 120 Donnelley Dr., Glasgow, KY 42141-1060, U.S.A. IEEE Spectrum circulation is audited by BPA Worldwide. IEEE Spectrum is a member of the Association of Business Information & Media Companies, the Association of Magazine Media, and Association Media & Publishing. IEEE prohibits discrimination, harassment, and bullying. For more information, visit https://www.ieee.org/web/aboutus/whatis/policies/p9-26.html.

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TELECOMMUNICATIONS

Geopolitics Is Already Shaping 6G Power struggles and clashing infrastructure priorities will forge next-gen networks BY MICHAEL KOZIOL

6  SPECTRUM.IEEE.ORG  DECEMBER 2021

hen wireless researchers or telecom companies talk about future sixth-generation (6G) networks, they’re talking mostly about their best guesses and wish lists. There are as yet no widely agreed upon technical standards outlining 6G’s frequencies, signal modulations, and waveforms. And yet the economic and political forces that will define 6G are already in play. And here’s the biggest wrinkle: Because there are no major U.S. manufacturers of cellular infrastructure equipment, the United States may not have the superpowers it thinks it does in shaping the future course of wireless communications. While many U.S. tech giants will surely be involved in 6G standards development, none of those companies make the equipment that will comprise the network. Companies like Ericsson (Sweden), Nokia (Finland), Samsung (South Korea), and Huawei (China) build the radio units, baseband units, and other hardware and software that go into cell towers and the wired networks that connect them. As one example, equipment manufacturers (such as China’s Huawei and ZTE) will probably push for standards that prioritize the distance a signal can travel, while minimizing the interference it experiences along the way. Meanwhile, device makers (like U.S. heavyweights Apple and Alphabet) will have more stake in standardizing signal modulations that drain their gadgets’ batteries the least. How such squabbles might be resolved, of course, is still an open question. But now is arguably the best time to begin asking it. 6G is—and isn’t yet—around the corner. When the Global Communications Conference (Globecom) begins in Madrid this December, attending researchers and telecom executives will find it features no fewer than five workshops devoted to 6G development. Compare that to the 2020 iteration of the IEEE Communication Society’s annual conference, which—pandemic not ­withstanding—

Photo-illustration by Edmon de Haro

DECEMBER 2021

included nothing 6G related beyond a 4-hour summit on the topic. And if you step back one year further to Globecom 2019, you’ll find that 6G was limited to a single technical talk. Cellular standards are developed and overseen by a global cellular industry consortium, the 3rd Generation Partnership Project (3GPP). Past wireless generations coalesced around universally agreed-upon standards relatively smoothly. But early research into 6G is emerging in a more tense geopolitical environment, and the quibbles that arose during 5G’s standardization could blossom into more serious disagreements this time around. At the moment, says Mehdi Bennis, a professor of wireless communications at the University of Oulu, in Finland, home of the 6G Flagship research initiative, the next generation of wireless standards is quite open ended. “Nobody has a clear idea. We maybe have some pointers.” To date, 6G has been discussed in terms of applications (including autonomous vehicles and holographic displays) and research interests—such as terahertz waves and spectrum sharing. So for the next few years, whenever a so-called “6G satellite” is launched, for example, take it with a grain of salt: It just means someone is testing technologies that may make their way into the 6G standards down the line. But such tests, although easily over­ hyped and used to set precedents and score points, are still important. The reason each generation of wireless—2G, 3G, 4G, and now 5G—has been so successful is because each has been defined by standards that have been universally implemented. In other words, a network operator in the United States like AT&T can buy equipment from Swedish manufacturer Ericsson to build its cellular network, and everything will function with phones made in China because they’re drawing on the same set of agreed-upon standards. (Unfortunately however, you’ll still run into problems if you try to mix and match infrastructure equipment from different manufacturers.)

5G and its predecessors have been successful because they’ve been universally implemented. 6G still has time to congeal—or not. In 2016, as the standards were being sorted out for 5G, a clash emerged in trying to decide what error-correcting technique would be used for wireless signals. Qualcomm, based in San Diego, and other companies pushed for low-density parity checks (LDPC), which had been first described decades earlier but had yet to materialize commercially. Huawei, backed by other Chinese companies, pushed for a new technique in which it had invested a significant amount of time and energy called polar codes. A deadlock at the 3GPP meeting that November resulted in a split standard: LDPC would be used for radio channels that send user data, while polar codes would be used for channels that coordinated those userdata channels. That Huawei managed to take polar codes from a relatively unknown mathematical theory and almost single-handedly develop it into a key component of 5G led to some proclamations that the company (and by extension, China) was winning the battle for 5G development. The implicit losers were Europe and the United States. The incident made at least one thing abundantly clear: There is a lot of money, prestige, and influence in the offing for a company that gets the tech it’s been championing into the standards. In May 2019, the U.S. Bureau of Industry and Security added Huawei to its Entity List—which places require-

ments on, or prohibits, importing and exporting items. Sources that IEEE Spectrum spoke to noted how the move increased tensions in the wireless industry, echoing concerns from 2019. “We are already seeing the balkanization of technology in many domains. If this trend continues, companies will have to create different products for different markets, leading to even further divergence,” Zvika Krieger, the head of technology policy at the World Economic Forum told MIT Technology Review at the time of the ban. The move curtailed the success Huawei originally saw from its 5G standards wins, with the rotating chairman, Eric Xu, recently saying that the company’s cellphone revenue will drop by US $30 billion to $40 billion this year from a reported $136.7 billion in 2020. As fundamental research continues into what technologies and techniques will be implemented in 6G, it’s too early to say what the next generation’s version of polar codes will be, if any. But already, different priorities are emerging in the values that companies and governments in different parts of the world want to see enshrined in any standards to come. “There are some unique, or at least stronger, views on things like personal liberty, data security, and privacy in Europe, and if we wish our new technologies to support those views, it needs to be baked into the technology,” said Colin Willcock, the chairman of the board for the Europe-based 6G Smart Networks and Services Industry Association, speaking at the Brooklyn 6G Summit in October. Bennis agrees: “In Europe, we’re very keen on privacy, that’s a big, big, I mean, big requirement.” Bennis notes that privacy is being built into 5G “a posteriori” as researchers tack it onto the established standards. The European Union has previously passed laws protecting personal data and privacy such as the General Data Protection Regulation (GDPR). So how will concepts like privacy, security, or sustainability be embedded

DECEMBER 2021  SPECTRUM.IEEE.ORG  7

NEWS

8  SPECTRUM.IEEE.ORG  DECEMBER 2021

SPACE

Jupiter’s Electric Blanket Auroras explain why the gas giant is so hot BY NED POTTER

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or all its other problems, Earth is lucky. Warmed mostly by the sun, 150 million kilometers away, shielded by a magnetosphere and a thin but protective atmosphere, Earth has a surface temperature that averages 14 °C—a good number to support liquid oceans and a riot of carbon-based life. Jupiter is a different story. Its upper atmosphere (Jupiter has no solid surface) has a temperature closer to what you’d find on Venus than on some of Jupiter’s own moons. Jupiter is 778 million km from the sun, where sunlight is less than 4 percent as intense as it is on Earth. By all rights, the plan-

et’s upper atmosphere should be about -70 °C. Instead, it exceeds 400 °C in places. Scientists have sometimes spoken of Jupiter as having an “energy crisis.” Now, an international team led by James O’Donoghue of JAXA, the Japanese space agency, says they’ve found an answer. Jupiter’s polar auroras are the largest and most powerful known in the solar system—and O’Donoghue says the energy in them, caused as Jupiter’s atmosphere is buffeted by solar wind, is strong enough to heat the outer atmosphere of the entire planet. “The auroral power...is actually 100 terawatts per hemisphere, and

J. NICHOLS/UNIVERSITY OF LEICESTER/ESA/NASA

in 6G—if at all? For instance, one future version of 6G could include differential privacy, in which data-set patterns are shared without sharing individual data points. Or it could include federated learning, a machine learning technique that instead of being trained on a centralized data set uses one scattered across multiple locations—thereby effectively anonymizing information that malicious actors in a network might otherwise put to nefarious purposes. These techniques are already being implemented in 5G networks by researchers, but integrating them into 6G standards would give them more weight. The Washington, D.C.–based Alliance for Telecommunications Industry Solutions launched the Next G Alliance in October 2020 to strengthen U.S. technological leadership in 6G over the course of the next decade. Mike Nawrocki, the alliance’s managing director, says the alliance is taking a “holistic” approach to 6G’s development. “We’re really trying to look at it from the perspective of what are some of the big societal drivers that we would envision for the end of the decade,” Nawrocki says, citing as one example the need to connect industries previously unconcerned with the wireless industry such as health care and agriculture. If different regions—the United States, Europe, China, Japan, South Korea, and so on—find themselves at loggerheads about how to define certain standards or support incompatible policies about the implementations or applications of 6G networks, global standards could ultimately, in a worst-case scenario, disintegrate. Different countries could decide it’s easier to go it alone and develop their own 6G technologies without global cooperation. This would result in balkanized wireless technologies around the world. Smartphone users in China might find their phones unable to connect with any other wireless network outside their country’s borders. Or, for instance, AT&T might, in such a scenario, no longer buy equipment from Nokia because it’s incompatible with AT&T ’s network operations. Although that’s a dire outcome, the industry consensus is that it’s not likely yet—but certainly more plausible than for any other wireless generation. n

TOP: J. O’DONOGHUE/JAXA; BOTTOM: J. O’DONOGHUE/JAXA (HEAT MAP); STSCI/NASA (PLANET)

I always like that fact,” says O’Donoghue. “I think that’s something like 100,000 power stations.” The auroras had been suspected as Jupiter’s secret heat source since the 1970s. But until now, scientists thought Jupiter’s giant, swirling east-west cloud bands might shear the heat away before it could spread very far from the poles. Winds in the cloud bands reach 500 kilometers per hour. To try to solve the mystery, the research team set out to create an infrared heat map of Jupiter’s atmosphere, something that had never been done in detail. They used the 10-meter Keck II telescope atop Mauna Kea in Hawaii, one of the five largest in the world, and took spectrographic readings on two nights: 14 April 2016 and 25 January 2017. Their heat map from the first night of observing showed that indeed the regions around the polar auroras were hottest, and the heat did spread from there—though the effect tailed off toward Jupiter’s equator. The heat was strong enough to propagate despite those powerful winds. But the auroras the team observed nine months later were about 100 °C hotter than on the first night, and so were temperatures at every point from there to the equator. It turned out, in fact, that on that night in 2017, Jupiter had been hit by a surge in solar wind—ionized particles that would compress Jupiter’s magnetic field and make the aurora more powerful. It was sheer luck, a “happy accident,” says O’Donoghue, that the surge of particles happened on the second night. Other researchers had already tried to explain Jupiter’s warmth by other means—perhaps some sort of acoustic-wave heating or convection from the planet’s core, for instance—but they couldn’t create convincing models that worked as well as the auroras. O’Donoghue and his colleagues say they went through more than a dozen drafts before their paper was accepted for publication in the journal Nature earlier this year. “We once thought that it could happen, that the aurora could be the source,” O’Donoghue says, “but we showed that it does happen.” n An expanded version of this article appears online as “Revealed: Jupiter’s Secret Power Source.”

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DECEMBER 2021  SPECTRUM.IEEE.ORG  9

SOCIAL MEDIA

Facebook Tiptoes Toward Cryptocurrency Rollout of the new Novi wallet hints at big ambitions BY EDD GENT

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acebook has finally made its long-awaited foray into cryptocurrencies, but the project is a shadow of its ambitious initial plans. The company has launched its Novi digital wallet, but without the Diem cryptocurrency, which was supposed to be the cornerstone of the enterprise. The limited pilot will be restricted to 200,000 users in the United States and Guatemala. And with the launch

10  SPECTRUM.IEEE.ORG  DECEMBER 2021

of Facebook-backed Diem still held up by regulatory concerns in the United States, Novi will instead allow users to exchange the USDP stablecoin from Paxos Trust Co., whose value is pegged to the U.S. dollar. Promotional material and comments from the head of Facebook Financial (F2) David Marcus suggest the pilot is focused on muscling into the lucrative remittance market. Remittances are pay-

ments made by foreign workers to their families back home, and experts say it is one of the most compelling use cases for blockchain-based payments. But the pilot represents a significant reduction in scope since Facebook first unveiled its plans for the Libra cryptocurrency (Diem’s precursor) back in 2019. “We started with Libra, which was intended as this all-conquering cryptocurrency that can be used for anything,” says Nick Maynard, head of research at Juniper Research. “What we’ve seen is a repeated scaling back of what they are trying to achieve.” That’s likely a reflection of the significant scrutiny the project has received, says Maynard. Although the pilot will lack the Diem cryptocurrency, the an­ nouncement was met by swift condemnation from U.S. lawmakers, who called for the company to immediately abandon the project in a letter to Facebook CEO Mark Zuckerberg. The company says it still plans to transition to Diem once it receives regulatory approval. But given the considerable heat Facebook has come under, Grace Broadbent, an analyst at Insider Intelligence, says starting small is a smart approach. And remittances are an obvious starting point, she adds. Sending money internationally traditionally relies on a complicated network of arrangements between individual banks. That means transactions pass through many intermediaries all keen to take a cut, which both slows things down and increases costs. A crypto­ currency running on a blockchain would allow these transactions to happen on the same shared ledger, which in theory should reduce the number of intermediaries involved. “We found that blockchain-based remittances is one of the most mature use cases [for the technology],” she says. “A lot of remittances’ pain points—like complexity, processing costs, [and] speed—really play to blockchain technology’s strengths.” It also represents a massive market, says Broadbent: Insider Intelligence forecasts worldwide remittances will be worth US $661 billion this year. But Novi seems unlikely to be able to capitalize on that value, as it has committed to charging zero fees for international transfers. F2’s Marcus has said the company

JAKUB PORZYCKI/NUR PHOTO/GETTY IMAGES

NEWS

“Being the first mover is more important than revenue itself because it’s a matter of becoming the infrastructure, the rails on which data and money flows.” — LUDOVICO RELLA, DURHAM UNIVERSITY

plans instead to use free person-to-person transfers to build up its user base, before branching out to become a more general payment provider and making money on merchant fees. The company’s ultimate goal is probably to create a super app in the mold of China’s WeChat, says Maynard, which has managed to combine both social and payment features in one place. And while marrying this with a homegrown cryptocurrency might reduce its processing costs, the real ambition is to become the main payments intermediary for its enormous global user base. “You don’t need the cryptocurrency to do that. Having the wallet will do all of that for you,” says Maynard. That might be easier said than done though. Getting merchants to accept new payment methods is notoriously challenging, says Maynard, as you not only need to demonstrate that large numbers of people want to use them, but also that you can provide the same kind of fraud-prevention and dispute-resolution services they’re used to from traditional players. Even with Facebook’s massive user base, that will take a long time, says Maynard. And it’s far from clear that people drawn in by cheap remittances will also use the app for everyday payments, particularly when they have to be made in cryptocurrency rather than local currency. Running a free global remittance service for potentially millions of users is also an expensive way to build up your user base, says Maynard. He suspects the company may take a similar approach to other cross-border payments services that offer free transfers, but then make money on less-than-favorable exchange rates. “Does Facebook have deep enough pockets to do this as a pure loss leader?

Yeah, of course they do,” says Maynard. “But fundamentally I don’t think they could create it on a massive scale outside of a pilot without having some kind of monetization.” Novi’s targeting of remittances could also hint at a deeper goal, says Ludovico Rella, a research associate at Durham University, in England. In certain corners of the tech industry there is an attitude that the Global South represents an empty space where first movers can easily install themselves as the predominant intermediary for everything from

payments to Internet connectivity. “Being the first mover is more important than revenue itself because it’s a matter of becoming the infrastructure, the rails on which data and money flows,” says Rella. Facebook was accused of doing exactly this when it tried to set up a free but restricted Internet service in India called Free Basics. If Novi can collect comprehensive data on the financial behavior of its users, it could allow the company to provide other financial services such as credit and insurance, says Rella. And while the company has committed not to share individual’s financial information with Facebook’s advertising business or third parties, Rella says it could still use analysis of aggregate data from many users to fine-tune its highly lucrative targeted advertising business. “It will be interesting to see how the promises and the public statements of Facebook will square with the business model they decide to adopt,” says Rella. Facebook did not respond to an interview request. n

JOURNAL WATCH

Could Starlink Be a Backup GPS? If GPS systems went down or were hacked tomorrow, the disruption to so many critical operations across the globe would be catastrophic, costing some countries more than US $1 billion a day. “There is an urgent need to find an alternative robust and accurate navigation system to GPS,” says Zak Kassas, an associate professor of electrical engineering and computer science at the University of California, Irvine. Fortunately, Kassas and his UC Irvine colleagues have devised an approach that harnesses the more abundant and closer-to-home satellites in low Earth orbit, such as the Starlink fleet of Internet satellites operated by SpaceX. His team’s new approach uses a receiver on the ground that tracks the phase of the underlying carrier wave emitted by a low-orbiting satellite. They developed an algorithm that then calculates the ground receiver’s position, velocity, and time in relation to the LEO satellites above. “They are about 20 times closer to Earth than GPS satellites, which means we receive their signals at considerably higher power than that of GPS. This makes them more difficult to jam or spoof and makes them reliable in environments where GPS signals are not,” explains Kassas. In the spring of 2021, the researchers successfully used six Starlink satellites to track their position accurately within just 7.7 meters. The results are described in a study published recently in IEEE Transactions on Aerospace and Electronic Systems.  —Michelle Hampson THE NEWS SECTION CONTINUES ON PAGE 50

DECEMBER 2021  SPECTRUM.IEEE.ORG  11

THE BIG PICTURE

Transforming Power Research Delft University of Technology opened its new Electrical Sustainable Power Lab on 1 October 2021. The lab, which replaced an older lab dedicated to high-voltage transmission experiments, is intended to take a holistic approach to designing new, sustainable electrical power systems in light of climate change. “The keyword of the lab is ‘system integration,’ ” says Miro Zeman, a professor of photovoltaic materials and devices at TU Delft. Researchers at the lab are not only interested in developing individual electrical components that can work with solar and wind sources but in ensuring that those individual components work efficiently and sustainably when put together. This particular image shows the lab’s high-voltage research area—the blue pylons are transformers. At the bottom right is a black cable being used in experiments to find alternatives to sulfur hexafluoride, a potent greenhouse gas that is commonly used as an electrical insulator. Behind the transformers— and protected from them by a Faraday cage—are additional labs devoted to developing switches and other electrical components. PHOTOGRAPH BY LUCAS VAN DER WEE

12  SPECTRUM.IEEE.ORG  DECEMBER 2021

DECEMBER 2021  SPECTRUM.IEEE.ORG  13

TECH TO TINKER WITH

The HamMessenger [right] lets you send short texts via a VHF radio without any additional equipment.

Phone-Free Texting HamMessenger makes it easy to SMS over VHF BY DALE THOMAS

14  SPECTRUM.IEEE.ORG  DECEMBER 2021

M

y first exposure to radio communication happened when I was around 5 or 6 years old. My dad was working as an airport electrician. He would bring walkie-talkies home, and my brothers and I would play with them around the yard. That’s as far as my radio experience went, until a friend and I decided to get our amateur radio licenses together. This was only months before the COVID-19 lockdown, so it turned out to

Illustrations by James Provost

DECEMBER 2021

The HamMessenger is compatible with most handheld VHF radios [left] by using an adapter cable [top, middle] that connects to a printed circuit board with a display, GPS receiver, and Arduino Pro acting as a modem [top right]. The PCB plugs into an Arduino Mega [middle right], a GPS antenna [top left], a mini keyboard [bottom middle], and batteries [bottom right].

be the perfect time to learn to communicate using amateur radio! However, I found that just talking over ham radio was boring for me. I started thinking about an old police scanner my dad owned and how we would sometimes hear odd sounds that sort of sounded like a dial-up modem. And that is when the lightbulb for HamMessenger turned on. What if I could find an easy way to communicate digitally with my handheld radio? I started learning about the many different types of digital communication modes that people use with ham radio, and I came across APRS (Automatic Packet Reporting System). APRS is a store-and-forward radio network protocol developed over 25 years ago by U.S. Navy researcher Robert Bruninga and was originally designed to track tactical

information in real time. APRS operates on a frequency within the VHF 2-meter band and is popular for applications like location transponders or weather stations. You can view APRS activity in your area at www.aprs.fi right now. APRS supports sending text messages, and if you’re in range of an Internet-connected gateway node you can even exchange SMS texts with cellphones and send one-line emails. Sending texts traditionally meant using a PC hooked up to a so-called terminal node controller (TNC) packet radio modem, which is in turn connected to a radio (signals are transmitted as audio tones, just like old dial-up modems). More recently, TNC modems that interface with smartphones have been created. And these are awesome projects! But at its core, HamMessenger was created in

the shadow of my simple childhood experiences. I wanted a portable device I could connect to my handheld radio that was completely self-contained, with a keyboard, screen, and GPS receiver all built in. First, I would need to nail down the hardware and software I was going to use. I found MicroAPRS, which is an open-source and Arduino-compatible firmware package for DIY packet radio modems. With MicroAPRS you can quickly implement a full-featured APRS modem with the ability to automatically switch the radio between receiving and transmitting. This was perfect. I could now focus on the rest of the HamMessenger. I thought about building it around a Raspberry Pi. That would have been cool, but a Pi is overkill. It would need a lot of

DECEMBER 2021  SPECTRUM.IEEE.ORG  15

HANDS ON

Email gateway

SMS gateway

The Automatic Packet Reporting System relies on a network of digital repeaters, or digipeaters, that repeatedly retransmit messages sent by handheld and other radios. Other digipeaters that pick up the signal in turn will retransmit the message up to a specified number of hops. Some digipeaters are connected to the Internet, which allows the user to send messages to distant digipeaters or relay them as cellphone SMS messages or emails.

power, and there’s a risk of corrupting the filesystem if you don’t do a controlled shutdown, a problem if the battery dies. I decided on a dual Arduino approach. An Arduino Pro Mini (US $10) would act as the modem, running MicroAPRS and communicating with the rest of the system via a serial connection. An Arduino Mega 2560 ($40) would be the central controller, tying together the modem, keyboard, display, and GPS. Rechargeable batteries with a battery-management board would provide the power. The GPS provides the location data that is integrated into most APRS transmissions. I chose a $10 NEO 6M-based GPS receiver that is popular with hobby­ists for things such as DIY drones. Like my modem, the NEO has a serial interface. In my initial design, the human input setup was very simple, with just three buttons. One button let me step through displayed menus and modify parameters, one button selected a submenu or set a parameter, and the last button let me cancel a parameter entry or navigate to a previous menu.

16  SPECTRUM.IEEE.ORG  DECEMBER 2021

Ultimately, because of the difficulty of using the buttons to enter text messages, I replaced them with a mini CardKB QWERTY keyboard ($8.50). However, the limits of the three-button system forced me to simplify the HamMessenger’s user interface as much as possible, something I am very thankful for now, as it means the HamMessenger is easy to operate with just a basic knowledge of APRS. For the display, I chose an OLED screen for its power efficiency. The only drawback for hobbyist OLEDs is their small size. The 0.96-inch displays are the most common, but I was able to find a $9 1.3-inch display that communicates via an I2C serial bus. The final modular component I needed for the HamMessenger was some nonvolatile storage for received messages. I decided on a micro-SD card reader because they natively speak the SPI interface protocol. All of these feed into the Arduino Mega. The Mega was chosen for the central controller as it doesn’t need a lot of power, yet has enough resources to

handle all the different module connections—two serial, two SPI, and one I2C connection. (Then I added a third serial port so you can control the HamMessenger with a PC or other device using an ASCII-based API.) I designed a shield (a printed circuit board that accommodates the modules and some supporting circuitry that simply plugs into the top of the Mega) using Autodesk’s Eagle, and then used the shield design files to help create a 3D-printed enclosure in Fusion 360 (full details are available on the HamMessenger GitHub page). Currently, the HamMessenger is still in a prototype stage, but it works well. I have a HamMessenger installed in my truck that doubles as a location beacon. It will never replace a cellphone for most people, of course, but those in places without coverage might find it useful. Still, it was primarily created as a way to promote electronics and alternative uses of amateur radio, and if you want an easy way to learn and blend these hobbies, then I think the HamMessenger is a great way to do that. n

SHARING THE EXPERIENCES OF WORKING ENGINEERS

DECEMBER 2021

Tech Pay Rises (Almost) Everywhere      The “Great Resignation” is pushing salaries up BY TEKLA S. PERRY

Percentage increase/decrease U.S. average

-1.1 2.1

U.K. average

Remote average

4.6

Remote average

Global average

6.2

Global average

Dallas

-9.5

Dallas

Atlanta

-5.5

Atlanta

-1

San Fransisco Bay Area

152,000

U.S. average

U.K. average

New York

102,000 143,000 138,000 124,000 136,000 151,000

New York

-0.3

165,000

San Fransisco Bay Area

London

Los Angeles

2.3

Los Angeles

Washington, D.C.

3

Washington, D.C.

Chicago

3.5

Chicago

Seattle

4.6

Seattle

Austin

5

Austin

144,000

San Diego

9.1

San Diego

144,000

G

lobally, tech salaries climbed an average of 6.2 percent to US $138,000, with the San Diego area clocking the biggest jump, at 9.1 percent, to $144,000. That’s according to Hired’s 2021 State of Tech Salaries report. The San Fran-

135,000 95,000 147,000 102,000 149,000 136,000 133,000

0 40 ,0 00 60 ,0 00 80 ,0 00 10 0, 00 0 12 0, 00 0 14 0, 00 0 16 0, 00 0 18 0, 00 0

158,000

20 ,0 0

0

2.1

10

London

8

Boston

6

1

4

Boston

2

Toronto

0

1

-2

Toronto

-4

Denver

-6

1

-8

Denver

-1 0

SOURCE: HIRED 2021 STATE OF TECH SALARIES

Salaries, in US $

cisco Bay area registered a slight decline, though average salaries there still top the charts at $165,000. New York City tech salaries slipped slightly as well, but the biggest drops came in Dallas and Atlanta. The driver seems to be the “Great Resignation” currently under-

way as workers change jobs at an accelerated rate in the hunt for better salaries, benefits, or work-life balance. The consequent urgent need of companies to replace departed tech employees is pushing salaries up in most areas, with just a few regions recording declines. n

DECEMBER 2021  SPECTRUM.IEEE.ORG  17

OPINION, INSIGHT, AND ANALYSIS

The Hyperloop Is Hyper Old Elon Musk merely renamed a 200-year-old dream

“L

ord how this world improves as we grow older,” reads the caption for a panel in the “March of Intellect,” part of a series of colored etchings published between 1825 and 1829. The artist, William Heath (1794–1840), shows many futuristic contraptions, including a four-wheeled steam-powered horse called Velocity, a suspension bridge from Cape Town to Bengal, a gun-carrying platform lifted by four balloons, and a giant winged flying fish conveying convicts from England to New South Wales, in Australia. But the main object is a massive, seamless metallic tube taking travelers from

18  SPECTRUM.IEEE.ORG  DECEMBER 2021

East London’s Greenwich Hill to Bengal, courtesy of the Grand Vacuum Tube Company. Heath was no science-fiction pioneer. His fanciful etching was just a spoof of an engineering project proposed in 1825 and called the London and ­Edinburgh Vacuum Tunnel Company, which was to be established with the capital of 20 million pounds sterling. The concept was based on a 1799 proposal made by George Medhurst: A rectangular tunnel was to move goods in wagons, the vacuum was to be created by the condensation of steam, and the impetus was to be “the pressure of the atmosphere, which...is so astonishing as almost to exceed belief.” Yes, this is the first known attempt at what during the second decade of the 21st century became known as the hyperloop. That word, coined by Elon Musk, constitutes his most publicized contribution to the technology. By the time Heath was drawing his intercontinental conveyor, enough was known about vacuum to realize that it would be the best option for achieving unprecedented travel speeds. But no materials were available to build such a tube—above all, there

LEFT: UNIVERSAL IMAGES GROUP/GETTY IMAGES; RIGHT: ÉMILE BACHELET COLLECTION/ARCHIVES CENTER/NATIONAL MUSEUM OF AMERICAN HISTORY (2)

William Heath’s 1829 engraving [above] pokes fun at a vacuum tube that conveys travelers from London to Bengal. A 1910 photograph shows a working model [bottom right] of Émile Bachelet’s magnetically levitated railway, in Mount Vernon, N.Y.; a public demonstration [top right] of the railway takes place in London in 1914.

SARAH LAWSON/VIRGIN HYPERLOOP

NUMBERS DON’T LIE BY VACLAV SMIL

was no way to produce affordable high-tensile steel—nor were there ready means to enclose people in vacuum-moving containers. Less than a century later, Émile Bachelet, a French electrician who emigrated to the United States, solved the propulsion part of the challenge with his 19 March 1912 patent of a “Levitation trans� mitting apparatus.” In 1914, he presented a smallscale working model of a magnetically levitated train with a tubular prow, powerful magnets at the track’s bottom, and tubular steel cars on an aluminum base. Japanese researchers have been experimenting with a modern version of Bachelet’s maglev concept since 1969, testing open-air train models at a track in Miyazaki. Short trials were done in Germany and the Soviet Union. In 2002, China got the only operating maglev line—built by Siemens—running from the Shanghai Pudong International Airport to Shanghai; now China claims to be preparing to test it at speeds up to 1,000 kilometers per hour. But outside East Asia, maglev remained nothing but a curiosity until 2012, when Elon Musk put his spin on it. People unaware of this long history greeted the

Virgin Hyperloop, which aims to commercialize the concept, has built a test track in Las Vegas [above]. The passenger pod [top right] is magnetically levitated; it can be introduced into the vacuum tube through an air lock [bottom right] at the end.

hyperloop as stunningly original and fabulously transformative. A decade later we have many route propos�als, and many companies engaged in testing and design, but not a single commercial application that can demonstrate that this is an affordable, profitable, reliable, and widely replicable travel option. Vacuum physicists and railway engineers, who best appreciate the challenges involved in such projects, have pointed out a long list of fundamental difficulties that must be overcome before public-carrying vacuum tubes could be as common as steel-wheel high-speed rail. Other, nontrivial, problems run from the common and intractable—obtaining rights-of-way for hundreds, even thousands, of kilometers of track elevated on pylons in NIMBY-prone societies—to the uncommon and unprecedented: maintaining the thousandfold pressure difference between the inside and outside steel walls of an evacuated tube along hundreds of kilometers of track while coping with the metal’s thermal expansion. Before rushing to buy shares in a hyperloop venture in 2022, remember the 1825 London and ­Edinburgh Vacuum Tunnel Company. n

DECEMBER 2021  SPECTRUM.IEEE.ORG  19

CROSSTALK GIZMO  BY MATTHEW S. SMITH

When the Chips Are Down Auto sales are suffering from the chip shortage, but most consumer electronics are pouring into stores

H

ot consumer tech is hard to snag this holiday season. Get used to it. New-car shoppers in the United States, China, and everywhere else face slim inventory and dealers unwilling to budge on price. It’s all because of the global chip shortage, which has prompted the Biden administration to support legislation that includes US $52 billion in subsidies for U.S. semiconductor manufacturing. But the problem extends far beyond new cars. A report by The Information found that 70 percent of wireless retail stores in the United States faced smartphone shortages. Graphics card pricing remains well above the manufacturer’s suggested retail level and shows no sign of retreat. Game con� soles are drawing hundreds-long lines a full year after launch. Televisions are both more expensive and more difficult to find than last year. You might think this is a temporary, COVID-­ related supply-chain shortfall, but no. The problem is not the number of PlayStation 5 consoles in stock. The problem is the people in line ahead of you. Sony’s PlayStation 5 sales data illustrates the nature of the challenge. Global sales of the ­PlayStation 5 outpace those of the PlayStation 4 at this point in the product’s life cycle: The PS5 has sold more quickly than any other console in Sony’s history. The same pattern holds for PCs, smart�phones, video games, and tablets, which all saw an uptick in year-over-year sales during the first quarter of 2021. That’s quite an achievement, given the unprecedented, lockdown-driven highs of 2020. The serious chip shortage really is hobbling the production of automobiles, the largest and most expensive of all our consumer gadgets. But it’s a mistake to assume that this shortage limits supplies of lesser gadgets, most of which are in fact pouring into stores and then flying off the shelves.

20  SPECTRUM.IEEE.ORG  DECEMBER 2021

The automotive industry’s problems really are the result of a serious chip shortage. But that’s the exception: Most consumer tech is pouring into stores, then flying off the shelves.

You should expect unrelenting prices and very long lead times that only lengthen. If you want in-demand gear to unwrap for the holidays, whether it’s a game console or the new iPad Mini, it may already be too late to get it (from a retailer, at least—there’s always eBay). And you should plan to plan ahead for the next year, as there’s no sign that supply will catch up in 2022. This may annoy shoppers, but the disruption among consumer tech companies is even more dire. Record demand is typically a good thing, but the sudden surge has forced a competition for chip production that only the largest companies can win. Rumors hint that Apple has locked in most, if not all, leading-edge chip production from Taiwan Semi� conductor Manufacturing Co., the world’s largest independent semiconductor foundry. Apple’s order is said to include up to 100 million chips for new iPhones, iPads, and MacBooks. Even large companies like Qualcomm are struggling to compete with Apple’s size and volume. Big moves from big companies have the ­trickle-down effect of delaying innovative ideas from smaller players: a crank-powered game console, a cus�tomizable LED face mask, and a tiny, 200-watt USB charger are just three out of many examples. The result could be a subtle, unfortunate squeeze on tiny tech startups that can spoil the most conservative production timeline. Backers are likely to face e­ ver-increasing waits. Some will give up and demand a refund. So, should you learn to live with stock notifications and long lines indefinitely? Maybe not. Investment in production might well catch up with demand by 2023. Industry analysts worry this could lead to a price crash if semiconductor manufacturers over� shoot. Perhaps the summer of 2023 will be the year you can once again buy the latest consumer tech not just minutes but hours after it’s released. Until then, well, you’ll just have to be patient. n

Illustration by Adam Howling

MACRO & MICRO  BY MARK PESCE

Surviving the Robocalypse Automation is striking at the heart of knowledge work

D

oes the value of a job lie in how long it resists automation? Over the course of the pandemic, I saw a growing wave of mealtime deliveries: riders whizzing by silently on electric bicycles, ferrying takeout meals to folks in my urban neighborhood who don’t want to venture out of their homes. Under constant pressure to pick up and deliver meals before they go cold, these delivery workers toil for some of the lowest wages on offer. In the past, delivery was an entry-level position, a way to get a foot in the door, like working in the mail room. Today, it’s a business all on its own, with gigantic public companies such as Uber and Deliveroo provid�ing delivery services for restaurant owners. With that outsourcing, delivery has become a dead-end job. Success means only that you get to work the day shift. Just a few years ago, we believed these jobs would soon be gone—wiped out by Level 4 and Level 5 autonomous driving systems. Yet, as engineers better understand the immense challenges of driv-

Illustration by Harry Campbell

While it’s unlikely that most programming or copywriting will be done by machines anytime soon, those professions now face real competition from automation.

ing on roads crowded with some very irrational human operators, a task that once seemed straightforward now looks nearly intractable. Other tasks long thought to be beyond automation have recently taken great leaps forward, though. In June, for example, GitHub previewed its AI pair programmer, Copilot: a set of virtual eyes that works with developers to keep their code clean and logically correct. Copilot wouldn’t come up with a sophisticated algorithm on its own, but it shows us how automation can make weak programmers stronger. It won’t be long before massive AI language models like Microsoft and Nvidia’s Megatron-Turing Natural Language Generation (MT-NLG) make short work of basic business copywriting. Other writing jobs—digesting materials to extract key details, expressing them in accessible language, then preparing them for publication—are also surren� dering to automation. The elements for this transformative leap are already falling into place. While it’s unlikely that most programming or copywriting will be done by machines anytime soon, an increasing portion will. Those professions now face real competition from automation. Paradoxically, bicycle-based delivery looks likely to need a human mind for at least the next several years. In a world where software eats everything in sight, those bits that can’t be digested continue to require human attention. That attention requires people’s time—for which they can earn a living. What we pay people for performing their jobs will increasingly be measured against the cost of using a machine to perform that task. Some white-collar workers will, no doubt, suffer from these new forms of competition from machines. A century ago, farm labor faced a similar devaluation, as agriculture became mechanized. And while countless manufacturing jobs have succumbed to factory automation over the decades, Tesla production hiccups reveal what happens when you try to push automation too far on the factory floor. As the history of the Luddites so aptly demon�strates, the tension between machines and human labor isn’t new—but it’s growing again now, this time striking at the heart of knowledge work. To stay one step ahead of the machines, we’ll need to find the hard bits and maintain the skills required to keep crunching on them. Creativity, insight, wisdom, and empathy—these aptitudes are wholly human and look to remain that way into the future. If we lean into these qualities, we can resist the competitive rise of the machines. n

DECEMBER 2021  SPECTRUM.IEEE.ORG  21

CAN A DIY ROCKET BLAST AN

Copenhagen Suborbitals volunteers use a tank of argon gas to fill a tube within which engine elements are joined together [top left], weld a component of the Nexø II rocket [top right], work on a fuel tank for the next-gen Spica rocket [bottom right], and examine fuel injector elements under a microscope [bottom left]. CLOCKWISE FROM BOTTOM RIGHT: CARSTEN OLSEN (3); SARUNAS KAZLAUSKAS

22  SPECTRUM.IEEE.ORG  DECEMBER 2021

BY MADS STENFATT

THE FIRST CROWDFUNDED ASTRONAUT

AMATEUR INTO SPACE?

DECEMBER 2021  SPECTRUM.IEEE.ORG  23

That successful mission in August 2018 was a huge step toward our goal of sending an amateur astronaut to the edge of space aboard one of our DIY rockets. We’re now building the Spica rocket to fulfill that mission, and we hope to launch a crewed rocket about 10 years from now. Copenhagen Suborbitals is the world’s only crowdsourced crewed spaceflight program, funded to the tune of almost US $100,000 per year by hundreds of generous donors around the world. Our project is staffed by a motley crew of volunteers who have a wide variety of day jobs. We have plenty of engineers, as well as people like me, a pricing manager with a skydiving hobby. I’m also one of three candidates for the astronaut position. We’re in a new era of spaceflight: The national space agencies are no longer the only game in town, and space is becoming more accessible. Rockets built by commercial players like Blue Origin are now bringing private citizens into orbit. That said, Blue Origin, SpaceX, and Virgin Galactic are all backed by billionaires with enormous resources, and they have all expressed intentions to sell flights for hundreds of thousands to millions of dollars. Copenhagen Suborbitals has a very different vision. We believe that spaceflight should be available to anyone who’s willing to put in the time and effort.

C

openhagen Suborbitals was founded in 2008 by a selftaught engineer and a space architect who had previously worked for NASA. From the beginning, the mission was clear: crewed spaceflight. Both founders left the organization in 2014, but by then the project had about 50 volunteers and plenty of momentum. (Five current volunteers are

24  SPECTRUM.IEEE.ORG  DECEMBER 2021

pictured on the cover of this magazine: from left, author Mads Stenfatt, Martin Hedegaard Petersen, Jørgen Skyt, Carsten Olsen, and Anna Olsen.) The group took as its founding principle that the challenges involved in building a crewed spacecraft on the cheap are all engineering problems that can be solved, one at a time, by a diligent team of smart and dedicated people. When people ask me why we’re doing this, I sometimes answer, “Because we can.” Our goal is to reach the Kármán line, which defines the boundary between Earth’s atmosphere and outer space, 100 kilometers above sea level. The astronaut who reaches that altitude will have several minutes of silence and weightlessness after the engines cut off and will enjoy a breathtaking view. But it won’t be an easy ride. During the descent, the capsule will experience external temperatures of 400 °C and g-forces of 3.5 as it hurtles through the air at speeds of up to 3,500 kilometers per hour. I joined the group in 2011, after the organization had already moved from a maker space inside a decommissioned ferry to a hangar near the Copenhagen waterfront. Earlier that year, I had watched Copenhagen Suborbital’s first launch, in which the HEAT-1X rocket took off from a mobile launch platform in the Baltic Sea—but unfortunately crash-landed in the ocean when most of its parachutes failed to deploy. I brought to the organization some basic knowledge of sports parachutes gained during my years of skydiving, which I hoped would translate into helpful skills. The team’s next milestone came in 2013, when we successfully launched the Sapphire rocket, our first rocket to include

FROM LEFT: ESKIL J. NIELSEN-FERREIRA; CARSTEN OLSEN; JEV OLSEN

IT WAS ONE OF THE PRETTIEST SIGHTS I HAVE EVER SEEN: our homemade rocket floating down from the sky, slowed by a white-and-orange parachute that I had worked on during many nights at the dining room table. The 6.7-meter-tall Nexø II rocket was powered by a bipropellant engine designed and constructed by the Copenhagen Suborbitals team. The engine mixed ethanol and liquid oxygen together to produce a thrust of 5 kilonewtons, and the rocket soared to a height of 6,500 meters. Even more important, it came back down in one piece.

In 2018, the Nexø II rocket launched successfully [left] and returned safely to the Baltic Sea [far left].Below: During a test-firing in 2014, a welding error in the HEAT-2X rocket’s engine caused a massive fireball that destroyed the rocket.

NexoII info info. 15–20 words Igenimos rehendi Abem et,equi con nosantius, ommo ri sia ima coTus, quet aute excreFicte omnis 15–20 words

guidance and navigation systems. Its navigation computer used a 3-axis accelerometer and a 3-axis gyroscope to keep track of its location, and its thrust-control system kept the rocket on the correct trajectory by moving four servo-mounted copper jet vanes that were inserted into the exhaust assembly. Both the HEAT-1X and the Sapphire rockets were fueled with a combination of solid polyurethane and liquid oxygen. We were keen to develop a bipropellant rocket engine that mixed liquid ethanol and liquid oxygen, because such ­liquid-propellant engines are both efficient and powerful. The HEAT-2X rocket, scheduled to launch in late 2014, was meant to demonstrate that technology. Unfortunately, its engine went up in flames in a static test-firing some weeks before the scheduled launch. That test was supposed to be a controlled 90-second burn; instead, because of a welding error, much of the ethanol gushed into the combustion chamber in just a few seconds, resulting in a massive conflagration. I was standing a few hundred meters away, and even from that distance I felt the heat on my face. The HEAT-2X rocket’s engine was rendered inoperable, and the mission was canceled. While it was a major disappointment, we learned some valuable lessons. Until then, we’d been basing our designs on our existing capabilities—the tools in our workshop and the people on the project. The failure forced us to take a step back and consider what new technologies and skills we would need to master to reach our end goal. That rethinking led us to design the relatively small Nexø I and Nexø II rockets to demonstrate key technologies such as the parachute system, the bipropellant engine, and the pressure regulation assembly for the tanks.

F

or the Nexø II launch in August 2018, our launch site was 30 km east of Bornholm, Denmark’s easternmost island, in a part of the Baltic Sea used by the Danish navy for military exercises. We left Bornholm’s Nexø harbor at 1 a.m. to reach the designated patch of ocean in time for a 9 a.m. launch, the time approved by Swedish air traffic control. (While our boats were in international waters, Sweden has oversight of the airspace above that part of the Baltic Sea.) Many of our crew members had spent the entire previous day testing the rocket’s various systems and got no sleep before the launch. We were running on coffee. When the Nexø II blasted off, separating neatly from the launch tower, we all cheered. The rocket continued on its trajectory, jettisoning its nose cone when it reached its apogee of

DECEMBER 2021  SPECTRUM.IEEE.ORG  25

Volunteer Jacob Larsen holds a brass fuel injector that performed well in a 2021 engine test.

6,500 meters, and sending telemetry data back to our mission control ship all the while. As it began to descend, it first deployed its ballute, a balloon-like parachute used to stabilize spacecraft at high altitudes, and then deployed its main parachute, which brought it gently down to the ocean waves. The launch brought us one step closer to mastering the logistics of launching and landing at sea. For this launch, we were also testing our ability to predict the rocket’s path. I created a model that estimated a splashdown 4.2 km east of the launch platform; it actually landed 4.0 km to the east. This controlled water landing—our first under a fully inflated ­parachute—was an important proof of concept, since a soft landing is an absolute imperative for any crewed mission. The Nexø II’s engine, which we called the BPM5, was one of the few components we hadn’t machined entirely in our workshop; a Danish company made the most complicated engine parts. But when those parts arrived in our workshop shortly before the launch date, we realized that the exhaust nozzle was a little bit misshapen. We didn’t have time to order a new part, so one of our volunteers, Jacob Larsen, used a sledgehammer to pound it into shape. The engine didn’t look pretty—we nicknamed it the Franken-Engine—but it worked. Since the Nexø II’s flight, we’ve test-fired that engine more than 30 times, sometimes pushing it beyond its design limits, but we haven’t killed it yet. That mission also demonstrated our new dynamic pressure regulation (DPR) system, which helped us control the flow of fuel into the combustion chamber. The Nexø I had used a simpler system called pressure blowdown, in which the fuel tanks were one-third filled with pressurized gas to drive the liquid

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fuel into the chamber. With DPR, the tanks are filled to capacity with fuel and linked by a set of control valves to a separate tank of helium gas under high pressure. That setup lets us regulate the amount of helium gas flowing into the tanks to push fuel into the combustion chamber, enabling us to program in different amounts of thrust at different points during the rocket’s flight. The 2018 Nexø II mission proved that our design and technology were fundamentally sound. It was time to start working on the human-rated Spica rocket.

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ith its crew capsule, the Spica rocket will measure 13 meters high and will have a gross liftoff weight of 4,000 kilograms, of which 2,600 kg will be fuel. It will be, by a significant margin, the largest rocket ever built by amateurs. Its engine, the 100-kN BPM100, uses technologies we mastered for the BPM5, with a few improvements. Like the prior design, it uses regenerative cooling in which some of the fuel passes through channels around the combustion chamber to limit the engine’s temperature. To push fuel into the chamber, it uses a combination of the simple pressure blowdown method in the first phase of flight and the DPR system, which gives us finer control over the rocket’s thrust. The engine parts will be stainless steel, and we hope to make most of them ourselves out of rolled sheet metal. The trickiest part, the double-curved “throat” section that connects the combustion chamber to the exhaust nozzle, requires computer-controlled machining equipment that we don’t have. Luckily, we have good industry contacts who can help out.

CLOCKWISE FROM BOTTOM RIGHT: CARSTEN OLSEN (3); CASPAR STANLEY; CARSTEN BRANDT

THE SPICA ASTRONAUT’S 15-MINUTE RIDE TO THE STARS WILL BE THE PRODUCT OF MORE THAN TWO DECADES OF WORK.

PHOTO CREDIT FIRST LASTNAME

Artist renderings show the Spica rocket [top] and the crew capsule [bottom] in which the astronaut will be seated.

A volunteer helps assemble the two fuel tanks for the Spica rocket [left]. Bianca Diana [right] works on a drone she’s using to test a new guidance system for the Spica rocket.

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Copenhagen Suborbitals designed the BPM100 engine [bottom] for use in the Spica rocket. This engine will replace an old showerhead-style fuel injector [top, right] with a coaxial-swirl injector [top, left], which will be easier to manufacture. For the parachute that will deploy from the Spica’s booster rocket, the team tested a small prototype of a ribbon parachute [right].

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potentially dangerous phenomenon. We have a good idea of the cause of these oscillations, and we’re confident that a few design tweaks can solve the problem. We’ll soon commence building a full-scale BPM100 engine, which will incorporate a new guidance system for the rocket. Our prior rockets, within their engines’ exhaust nozzles, had metal vanes that we would move to change the angle of thrust. But those vanes generated drag within the exhaust stream and reduced effective thrust by about 10 percent. The new design has gimbals that swivel the entire engine back and forth to control the thrust vector. As further support for our belief that tough engineering problems can be solved by smart and dedicated people, our gimbal system was designed and tested by a 21-year-old undergraduate student from the Netherlands named Jop Nijenhuis, who used the gimbal design as his thesis project (for which he got the highest possible grade). We’re using the same guidance, navigation, and control (GNC) computers that we used in the Nexø rockets. One new challenge is the crew capsule; once the capsule separates from the rocket, we’ll have to control each part on its own to bring them both back down to Earth in the desired orientation. When separation occurs, the GNC computers for the two components will need to understand that the parameters for optimal flight have changed. But from a software point of view, that’s a minor problem compared to those we’ve solved already. My specialty is parachute design. I’ve worked on the ballute, which will inflate at an altitude of 70 km to slow the crewed capsule during its high-speed initial descent, and the main parachutes, which will inflate when the capsule is 4 km above the ocean. We’ve tested both types by having skydivers jump out of planes with the parachutes, most recently in a 2019 test of the ballute. The pandemic forced us to pause our parachute testing, but we should resume soon. For the drogue parachute that will deploy from the booster rocket, my first prototype was based on a design called

FROM RIGHT: CARSTEN OLSEN; MADS STENFATT; THOMAS PEDERSEN (2)

One major change was the switch from the Nexø II’s s­ howerhead-style fuel injector to a coaxial-swirl fuel injector. The showerhead injector had about 200 very small fuel channels. It was tough to manufacture, because if something went wrong when we were making one of those channels—say, the drill got stuck—we had to throw the whole thing away. In a coaxial-swirl injector, the liquid fuels come into the chamber as two rotating liquid sheets, and as the sheets collide, they’re atomized to create a propellant that combusts. Our swirl injector uses about 150 swirler elements, which are assembled into one structure. This modular design should be easier to manufacture and test for quality assurance. In April of this year, we ran static tests of several types of injectors. We first did a trial with a well-understood showerhead injector to establish a baseline, then tested brass swirl injectors made by traditional machine milling as well as steel swirl injectors made by 3D printing. We were satisfied overall with the performance of both swirl injectors, and we’re still analyzing the data to determine which functioned better. However, we did see some combustion instability—namely, some oscillation in the flames between the injector and the engine’s throat, a

­ upersonic X, which is a parachute that looks somewhat like a S flying onion and is very easy to make. However, I reluctantly switched to ribbon parachutes, which have been more thoroughly tested in high-stress situations and found to be more stable and robust. I say “reluctantly” because I knew how much work it would be to assemble such a device. I first made a 1.24-meter-diameter parachute that had 27 ribbons going across 12 panels, each attached in three places. So on that small prototype, I had to sew 972 connections. A full-scale version will have 7,920 connection points. I’m trying to keep an open mind about this challenge, but I also wouldn’t object if further testing shows the Supersonic X design to be sufficient for our purposes.

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e’ve tested two crew capsules in past missions: the Tycho Brahe in 2011 and the Tycho Deep Space in 2012. The next-generation Spica crew capsule won’t be spacious, but it will be big enough to hold a single astronaut, who will remain seated for the 15 minutes of flight (and for two hours of preflight checks). The first spacecraft we’re building is a heavy steel “boilerplate” capsule, a basic prototype that we’re using to arrive at a practical layout and design. We’ll also use this model to test hatch design, overall resistance to pressure and vacuum, and the aerodynamics and hydro­ dynamics of the shape, as we want the capsule to splash down into the sea with minimal shock to the astronaut inside. Once we’re happy with the boilerplate design, we’ll make the lightweight flight version. Three members of the Copenhagen Suborbitals team are currently candidates to be the astronaut in our first crewed mission—me, Carsten Olsen, and his daughter, Anna Olsen. We all understand and accept the risks involved in flying into space on a homemade rocket. In our day-to-day operations, we astronaut candidates don’t receive any special treatment or training. Our one extra responsibility thus far has been sitting in the crew capsule’s seat to check its dimensions. Since

our first crewed flight is still a decade away, the candidate list may well change. As for me, I think there’s considerable glory in just being part of the mission and helping to build the rocket that will bring the first amateur astronaut into space. Whether or not I end up being that astronaut, I’ll forever be proud of our achievements. People may wonder how we get by on a shoestring budget of about $100,000 a year—particularly when they learn that half of our income goes to paying rent on our workshop. We keep costs down by buying standard off-the-shelf parts as much as possible, and when we need custom designs, we’re lucky to work with companies that give us generous discounts to support our project. We launch from international waters, so we don’t have to pay a launch facility. When we travel to Bornholm for our launches, each volunteer pays his or her own way, and we stay in a sports club, sleeping on mats on the floor and showering in the changing rooms. I sometimes joke that our budget is about one-tenth what NASA spends on coffee. Yet it may well be enough to do the job. We had intended to launch Spica for the first time in the summer of 2021, but our schedule was delayed by the COVID-19 pandemic, which closed our workshop for many months. Now we’re hoping for a test launch in the summer of 2022, when conditions on the Baltic Sea will be relatively tame. For this preliminary test of Spica, we’ll fill the fuel tanks partway and will aim to send the rocket to a height of around 30 to 50 km. If that flight is a success, in the next test, Spica will carry more fuel and soar higher. If the 2022 flight fails, we’ll figure out what went wrong, fix the problems, and try again. It’s remarkable to think that the Spica astronaut’s eventual 15-minute ride to the stars will be the product of more than two decades of work. But we know our supporters are counting down until the historic day when an amateur astronaut will climb aboard a homemade rocket and wave goodbye to Earth, ready to take a giant leap for DIY-kind. n

WE BELIEVE THAT SPACEFLIGHT SHOULD BE AVAILABLE TO ANYONE WHO’S WILLING TO PUT IN THE TIME AND EFFORT. Spica’s two fuel tanks were manufactured in the Copenhagen Suborbitals workshop using plate steel.

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T H E S M A RT LY D R E S S E D S PAC E C R A F T

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WR AP P ED I N S E NSOR-R ICH ELEC TRON IC T EXTI LES, SPACE STRUC TU RES COU LD D OU BLE AS SC I ENTI FIC I NSTRU M ENTS By Juliana Cherston & Joseph A. Paradiso Photography by Bob O’Connor

MIT’s Juliana Cherston holds a sensored Betacloth swatch like the one that will fly on board the International Space Station in 2022. The swatch [far left] has three black fiber sensors woven into the material.

craft will launch from NASA Wallops, in Virginia, on a routine resupply mission to the International Space Station. Amid the many tonnes of standard crew supplies, spacewalk equipment, computer hardware, and research experiments will be one unusual package: a pair of electronic textile swatches embedded with impact and vibration sensors. Soon after the spacecraft’s arrival at the ISS, a robotic arm will mount the samples onto the exterior of Alpha Space’s Materials ISS Experiment (MISSE) facility, and control-room operators back on Earth will feed power to the samples. For the next six months, our team will conduct the first operational test of sensor-laden electronic fabrics in space, collecting data in real time as the sensors endure the harsh weather of low Earth orbit. We also hope that microscopic dust or debris, traveling at least an order of magnitude faster than sound, will strike the fabric and trigger the sensors. Our eventual aim is to use such smart electronic textiles to study cosmic dust, some of which has interplanetary or even interstellar origins. Imagine if the protective fabric covering a spacecraft could double as an astrophysics experiment, but without adding excessive mass, volume, or power requirements. What if this smart skin could also measure the cumulative damage caused by orbital space debris and micrometeoroids too small to be tracked by radar? Could sensored textiles in pressured spacesuits give astronauts a sense of touch, as if the fabric were their own skin? In each case, electronic fabrics sensitive to vibrations and charge could serve as a foundational technology.

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Already, engineered fabrics serve crucial functions here on Earth. Geotextiles made of synthetic polymers are buried deep underground to strengthen land embankments. Surgical meshes reinforce tissue and bone during invasive medical procedures. In space, the outer walls of the ISS are wrapped in a protective engineered textile that gives the station its white color. Called Beta cloth, the woven fabric covers the station’s metal shell and shields the spacecraft from overheating and erosion. Beta cloth can also be found on the exterior of Apollo-era spacesuits and Bigelow Aerospace’s next-generation inflatable habitats. Until it is possible to substantially alter the human body itself, resilient textiles like this will continue to serve as a crucial boundary—a second skin—protecting human explorers and spacecraft from the extremes of space. Now it’s time to bring some smarts to this skin. the Responsive Environments Group at MIT, has been working for well over a decade on embedding distributed sensor networks into flexible substrates. In 2018, we were kneedeep in developing a far-out concept to grapple an asteroid with an electronic web, which would allow a network of hundreds or thousands of tiny robots to crawl across the surface as they characterized the asteroid’s materials. The technology was curious to contemplate but unlikely to be deployed anytime soon. During a visit to our lab, Hajime Yano, a planetary scientist at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science, suggested a nearer-term possibility: to turn the Beta cloth blanket used on long-duration spacecraft into a science experiment. Thus began a collaboration that has OUR LAB,

JAXA/SPACE BD (4)

T

HIS COMING FEBRUARY, the Cygnus NG-17 space-

In the Japanese space agency’s control room [far left], engineers conduct a video inspection of sensored fabrics that have been flying on the ISS since October 2020. The swatches are mounted on the space station’s Exposed Experiment Handrail Attachment Mechanism (ExHAM) facility [3 photos above]. The experiment is studying the resiliency of different types of fabric sensors when they’re exposed to the harsh environment of low Earth orbit. The samples will be returned to Earth early next year for more careful analysis.

so far resulted in multiple rounds of prototyping and ground testing and two experiments in space. One of the tests is the upcoming launch aboard the Cygnus NG-17, funded by the ISS National Laboratory. As the ISS orbits Earth, and the local space environment changes, we’ll be triggering our sensors with known excitations to measure how their sensitivity varies over time. Concurrently, we’ll take impedance measurements, which will let us peek into the internal electrical properties of the fibers. Any changes to the protective capabilities of the Beta fabric will be picked up using temperature sensors. If the system functions as designed, we may even detect up to 20 micrometeoroid impacts across the fabric’s 10-by-10-centimeter area. A triggering system will flag any interesting data to be streamed to Earth in real time. A second in-space experiment is already underway. For more than a year, a wider range of our smart-fabric swatches has been quietly tucked away on a different section of the ISS’s walls, on Space BD’s Exposed Experiment Handrail Attachment Mechanism (ExHAM) facility. In this experiment, funded by the MIT Media Lab Space Exploration Initiative, the samples aren’t being powered. Instead, we’re monitoring their exposure to the space environment, which can be tough on materials. They endure repeated cycles of extreme heat and cold, radiation, and material-eroding atomic oxygen. Through real-time videography sessions we’ve been conducting with the Japan Aerospace Exploration Agency (JAXA), we’ve already seen signs of some anticipated discoloration of our samples. Once the samples return to Earth in late January via the SpaceX CRS-24 rocket, we’ll conduct a more

thorough evaluation of the fabrics’ sensor performance. By demonstrating how to sleekly incorporate sensors into mission-critical subsystems, we hope to encourage the widespread adoption of electronic textiles as scientific instrumentation. ELECTRONIC TEXTILES got an early and auspicious start in space.

In the 1960s, the software for the Apollo guidance computer was stored in a woven substrate called core rope memory. Wires were fed through conductive loops to indicate 1s and around loops to indicate 0s, achieving a memory density of 72 kilo­bytes per cubic foot (or about 2,500 kilobytes per cubic meter). Around the same time, a company called Woven Electronics (now part of Collins Aerospace) began developing fabric circuit board prototypes that were considered well ahead of their time. For a fleeting moment in computing, woven fabric circuits and core rope memory were competitive with silicon semiconductor technology. Electronic fabrics then fell into a long hiatus, until interest in wearable technology in the 1990s revived the idea. The MIT Media Lab pioneered some early prototypes, working, for instance, with Levi’s in the late ’90s on a jean jacket with an embroidered MIDI keyboard. Since then, researchers and companies have created a plethora of sensing technologies in fabric, especially for health-related wearables, like flexible sensors worn on the skin that monitor your well-being through your sweat, heart rate, and body temperature. More recently, sophisticated fiber sensors have been pushing the performance and capabilities of electronic textiles even

DECEMBER 2021  SPECTRUM.IEEE.ORG  33

our group has tackled three areas: We’ve built fabric sensors, we’ve worked with specialized facilities to obtain a baseline of the materials’ sensitivity to impact, and we’ve designed instrumentation to test these fabrics in space. We started by upgrading Beta cloth, which is a Teflon­impregnated fabric made of flexible fiberglass filaments that are so densely woven that the material feels almost like a thick sheet of paper. To this protective layer, we wanted to add the ability to detect the tiny submillimeter or micrometer-scale impacts from cosmic dust. These microparticles move fast, at speeds of up to 50 kilometers per second, with an average speed TO JUMP-START THIS RESEARCH,

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of around 10 km/s. A 10-micrometer iron-dominant particle traveling at that speed contains about 75 microjoules of kinetic energy. It isn’t much energy, but it can still carry quite a punch when concentrated to a small impact area. Studying the kinematics and spatial distributions of such impacts can give scientists insight into the composition and origins of cosmic dust. What’s more, these impacts can cause significant damage to spacecraft, so we’d like to measure how frequent and energetic they are. What kind of fabric sensors would be sensitive enough to pick up the signals from these minuscule impacts? Early on, we settled on using piezoelectric fibers. Piezoelectric materials produce surface charge when subject to mechanical deformation. When a piezoelectric layer is sandwiched between two electrodes, it forms a sensor that can translate mechanical vibration into current. Piezoelectric impact sensors have been used on spacecraft before, but never as part of a fabric or as dispersed fibers. One of the chief requirements for piezoelectrics is that the electric dipoles inside the material must all be lined up in order for the charge to accumulate. To permanently align the dipoles—a process called poling—we have to apply a substantial electric field of about 100 kilovolts for every millimeter of thickness. Early on, we experimented with weaving bare polyvinylidene difluoride yarn into Beta cloth. This single-material yarn has the advantage of being as fine and flexible as the fibers in clothing and is also radiation- and abrasion-resistant. Plus, the fiber-drawing process creates a crystalline phase structure that encourages poling. Applying a hefty voltage to the fabric, though, caused any air trapped in the porous material to become electrically conductive, inducing miniature lightning bolts across the material and spoiling the poling process. We tried a slew of tricks to minimize the arcing, and we tested piezoelectric ink coatings applied to the fabric.

ALLISON GOODE/AEGIS AEROSPACE

further. Our collaborators in the Fibers@MIT group, for example, use a manufacturing technique called thermal drawing, in which a centimeter-thick sandwich of materials is heated and stretched to submillimeter thickness, like pulling a multicolored taffy. Incredibly, the internal structure of the resulting fiber remains highly precise, yielding functional devices such as sensors for vibration, light, and temperature that can be woven directly into fabrics. But this exciting progress hasn’t yet made its way to space textiles. Today’s spacesuits aren’t too different from the one that Alan Shepard wore inside Freedom 7 in 1961. Recent suit designs have instead focused on improving the astronaut’s mobility and temperature regulation. They might have touch-screen-compatible fingertips, but that’s about as sophisticated as the functionality gets. Meanwhile, Beta cloth has been used on space habitats in more or less its present form for more than a half century. A smattering of fabric antennas and fiber-optic strain sensors have been developed for rigid composites. But little has been done to add electronic sensory function to the textiles we use in space.

BOB O’CONNOR

Juliana Cherston prepares a smartfabric system in the clean room at Alpha Space in Houston [left]. Electronics in the silver flight hardware box [above] stream data to the computer in the blue box. The system, set for launch in February, will be mounted on the Materials ISS Experiment facility. At right, the green laser in the LaserInduced Particle Impact Test facility at MIT’s Institute for Soldier Nanotechnologies accelerates particles to supersonic speeds.

Ultimately, though, we determined that multimaterial fiber sensors were preferable to single-material yarns, because the dipole alignment needs to occur only across the very tiny and precise distances within each fiber sensor, rather than across a fabric’s thickness or across a fabric coating’s uneven surface. We chose two different fiber sensors. One of the fibers is a piezoceramic nanocomposite fiber designed by Fibers@MIT, and the other is a polymer we harvested from commercial piezoelectric cabling, then modified to be suitable for fabric integration. We coated these fiber sensors in an elastomeric conductive ink, as well as a white epoxy that keeps the fibers cool and resists oxidation.

To produce our fabric, we worked with space-textile manufacturer JPS Composite Materials, in Anderson, S.C. The company helped insert our two types of piezoelectric fibers at intervals across the fabric and ensured that our version of Beta cloth still adhered to NASA specifications. We have also worked with the Rhode Island School of Design on fabric manufacturing. To test the sensitivity of our fabric, we have been using the Laser-Induced Particle Impact Test (LIPIT) platform designed by Keith Nelson’s group at MIT’s Institute for Soldier Nanotechnologies. This benchtop apparatus is designed for investigating how materials respond to microparticle impacts, such as in needle-free drug delivery and cold-sprayed industrial

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ISS is an electrically conductive synthetic fur made of silvered Vectran fibers. More typically used to reinforce electrical cables, badminton string, and bicycle tires, Vectran is also a key component in inflatable spacecraft. In our case, we manufactured it like a carpet or a fur coat. We believe this design may be well suited to catching the plumes of charge ejected from impact, which could make for an even more sensitive detector. MEANWHILE, THERE’S GROWING INTEREST in porting sen-

sored textiles to spacesuits. A few members in our group have worked on a preliminary concept that uses fabrics containing

BOB O’CONNOR (5)

coatings. In our tests, we used the platform’s high-speed particles to simulate space dust. In a typical experiment, we spread steel particles ranging from a few micrometers to tens of micrometers onto gold film atop a glass substrate, which we call a launchpad. For each shot, a laser pulse vaporizes the gold film, exerting an impulsive force on the particles and accelerating them to speeds of many hundreds of meters per second. A high-speed camera captures the impact of the gold particles on our target fabric swatch every few nanoseconds, equivalent to hundreds of millions of frames per second. So far, we’ve been able to detect electrical signals not only when the particles struck a sensor’s surface but also when particles struck 1 or 2 cm away from the sensor. In some camera footage, it’s even possible to see the acoustic wave created by the indirect impact propagating along the fabric’s surface and eventually reaching the piezoelectric fiber. This promising data suggests that we can space out our sensors across the fabric and still be able to detect the impacts. Now we’re working to nail down just how sensitive the fabric is—that is, what ranges of particle mass and velocity it can register. We’re soon scheduled to test our fabric at a Van de Graaff accelerator, which can propel particles of a few micrometers in diameter to speeds of tens of kilometers per second, which is more in line with interstellar dust velocities. Beyond piezoelectrics, we’re also interested in detecting the plumes of electric charge that form when a particle strikes the fabric at high speed. Those plumes contain clues about the impactor’s constituent elements. One of our samples on the

To make a piezoelectric fiber sensor [2 photos, top left], researchers at the Fibers@MIT group sandwich materials together and then heat and stretch them like taffy. The faint copper wires are used to make electrical contact with the materials inside the fiber. The fibers can then be woven into Beta cloth. A replica [2 photos, top right] of the smart-textile payload that’s launching in February shows the electronics and internal layers. At bottom [left to right] Juliana Cherston and Joe Paradiso of MIT’s Responsive Environments Group and Wei Yan of the Fibers@MIT group are part of the team behind the smart-textile experiment.

vibration, pressure, proximity, and touch sensors to discriminate between a glove, metallic equipment, and rocky terrain— just the sorts of surfaces that astronauts wearing pressurized suits would encounter. This sensor data is then mapped to haptic actuators on the astronauts’ own skin, allowing wearers to vividly sense their surroundings right through their suits. How else might a sensored fabric enhance human engagement with the space environment? For long-duration missions, explorers residing for months inside a spacecraft or habitat will crave experiential variety. Fabric and thin-film sensors might detect the space weather just outside a spacecraft or habitat and then use that data to alter the lighting and temperature inside. A similar system might even mimic certain external conditions. Imagine feeling a Martian breeze within a habitat’s walls or the touch of a loved one conveyed through a spacesuit. And in the far future, such fabrics could help advance frontier science, allowing massively distributed scientific measurements across hundreds of spacecraft throughout the solar system. In particular, we’re fascinated by recent research indicating that dust from a near-Earth supernova explosion is still raining down on our planet. With a wide network of electronic fabrics that are sensitive enough, we could assess the kinematics of this interstellar dust. Because spacecraft

skins face all directions simultaneously, it might be possible to detect the faintest fluctuations in cosmic dust, which will allow scientists to hunt for objects like comet tails, explore the giant cloud of interstellar dust that our solar system is currently traversing—known as the Local Fluff—and maybe even detect microparticles ejected from this million-year-old supernova. To this end, it may be fruitful to deploy sensored fabrics outside the orbital plane of the solar system, where interstellar dust dominates. To engineer a fabric that can survive extreme conditions, we foresee experimenting with piezoelectric materials that have intrinsic thermal and radiation resilience, such as boron nitride nanotubes, as well as devices that have better intrinsic noise tolerance, including sensors based on glass fibers. We also envision building a system that can intelligently adapt to local conditions and mission priorities, by self-regulating its sampling rates, signal gains, and so on. Space-resilient electronic fabrics may still be nascent, but the work is deeply cross-cutting. Textile designers, materials scientists, astrophysicists, astronautical engineers, electrical engineers, artists, planetary scientists, and cosmologists will all have a role to play in reimagining the exterior skins of future spacecraft and spacesuits. This skin, the boundary of person and the demarcation of place, is real estate ripe for development. n

DECEMBER 2021  SPECTRUM.IEEE.ORG  37

Creating the Artificial Pancreas

The Tandem insulin pump, no bigger than a mobile phone, infuses insulin under the skin at the command of Control-IQ software, which has received blood-glucose data from a Dexcom G6 sensor. MATT HARBICHT/TANDEM DIABETES CARE/GETTY IMAGES

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This wearable device senses blood glucose and administers insulin accordingly By Boris Kovatchev & Anna Kovatcheva

DECEMBER 2021  SPECTRUM.IEEE.ORG  39

In some ways, this is a family story. Peter Kovatchev was a naval engineer who raised his son, Boris, as a problem solver, and who built model ships with his granddaughter, Anna. He also suffered from a form of diabetes in which the pancreas cannot make enough insulin. To control the concentration of glucose in his blood, he had to inject insulin several times a day, using a syringe that he kept in a small metal box in our family’s refrigerator. But although he tried to administer the right amount of insulin at the right times, his blood-glucose control was quite poor. He passed away from diabetes-related complications in 2002. one eye on their blood-glucose levels, which they measured many times a day by pricking their fingers for drops of blood. It was easily the most demanding therapy that patients have ever been required to administer to themselves. No longer: The artificial pancreas is finally at hand. This is a machine that senses any change in blood glucose and directs a pump to administer either more or less insulin, a task that may be compared to the way a thermostat coupled to an HVAC system controls the temperature of a house. All commercial artificial pancreas systems are still “hybrid,” meaning that users are required to estimate the carbohydrates in a meal they’re

about to consume and thus assist the system with glucose control. Nevertheless, the artificial pancreas is a triumph of biotechnology. It is a triumph of hope, as well. We well remember a morning in late December of 2005, when experts in diabetes technology and bioengineering gathered in the Lister Hill Auditorium at the National Institutes of Health in Bethesda, Md. By that point, existing technology enabled people with diabetes to track their blood-glucose levels and use those readings to estimate the amount of insulin they needed. The problem was how to remove human intervention from the equation. A distinguished scientist took the podium and explained that biology’s glucose-regulation mechanism was far too complex to be artificially replicated. We disagreed, and after 14 years of work we were able to prove the scientist wrong. It was yet another confirmation of Arthur Clarke’s First Law: “When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”

I The original artificial pancreas, called the Biostator, is shown here in hospital use in about 1977. It delivered insulin and glucose directly into the veins and could not be adapted to home use.

40  SPECTRUM.IEEE.ORG  DECEMBER 2021

n a healthy endocrine system, the fasting blood-glucose level is around 80 to 100 milligrams per deciliter of blood. The entire blood supply of a typical adult contains 4 or 5 grams of sugar— roughly as much as in the paper packet that restaurants offer with coffee. Consuming carbohydrates, either as pure sugar or as a starch such as bread, causes blood-glucose levels to rise. A normally functioning pancreas recognizes the incoming sugar rush and secretes insulin to allow the body’s cells to absorb it so

WILLIAM CLARKE/UNIVERSITY OF VIRGINIA

Boris now conducts research on bioengineered substitutes for the pancreas; Anna is a writer and a designer. A person who requires insulin must walk a tightrope. Blood-glucose concentration can swing dramatically, and it is particularly affected by meals and exercise. If it falls too low, the person may faint; if it rises too high and stays elevated for too long, the person may go into a coma. To avoid repeated episodes of low blood glucose, patients in the past would often run their blood glucose somewhat high, laying themselves open to long-term complications, such as nerve damage, blindness, and heart disease. And patients always had to keep

that it can be used as energy or stored for such use later on. This process brings the glucose level back to normal. However, in people with type 1 or insulin-requiring type 2 diabetes— of whom there are nearly 8.5 million in the United States alone—the pancreas produces either no insulin or too little, and the control process must be approximated by artificial means. In the early days, this approximation was very crude. In 1922, insulin was first isolated and administered to diabetic patients in Canada; for decades after, the syringe was the primary tool used to manage diabetes. Because patients in those days had no way to directly measure blood glucose, they had to test their urine, where traces of sugar proved only that blood-glucose levels had already risen to distressingly high levels. Only in 1970 did ambulatory blood-glucose testing become possible; in 1980 it became commercially available. Chemically treated strips reacted with glucose in a drop of blood, changing color in relation to the glucose concentration. Eventually meters equipped with photodiodes and optical sensors were devised to read the strips more precisely. The first improvement was in the measurement of blood glucose; the second was in the administration of insulin. The first insulin pump had to be worn like a backpack and was impractical for daily use, but it paved the way for all other intravenous blood-glucose control designs, which began to emerge in the 1970s. The first commercial “artificial pancreas” was a refrigerator-size machine called the Biostator, intended for use in hospitals. However, its bulk and its method of infusing insulin directly into a vein prevented it from advancing beyond hospital experiments. That decade also saw work on more advanced insulin-delivery tools: pumps that could continually infuse insulin through a needle placed under the skin. The first such commercial pump, Dean Kamen’s AutoSyringe, was introduced in the late 1970s, but the patient still had to program it based on periodic blood-­glucose measurements done by finger sticks. Through all this time, patients continued to depend on this method. Finally, in 1999, Medtronic introduced the first continuous glucose monitor portable enough for outpatient use. A thin electrode is inserted under the skin with a

Illustration by Chris Philpot

The artificial pancreas reproduces the healthy body’s glucose-control system, which begins when carbohydrates are digested into glucose and ferried by the blood to the pancreas. Sensing the increased glucose concentration, the pancreas secretes just enough insulin to enable the body’s cells to absorb the glucose.

FOOD

INSULIN

STOMACH

SENSOR

INFUSION SET

PANCREAS INTESTINE

INSULIN ENTERS THE BLOODSTREAM

DIGESTION BREAKS FOOD DOWN INTO GLUCOSE GLUCOSE ENTERS THE BLOODSTREAM

LOW BLOOD GLUCOSE

HIGH BLOOD GLUCOSE

PANCREAS

GLUCAGON IS RELEASED BY ALPHA CELLS OF THE PANCREAS

INSULIN IS RELEASED BY BETA CELLS OF THE PANCREAS

THE LIVER RELEASES GLUCOSE INTO THE BLOOD

FAT CELLS TAKE IN GLUCOSE FROM THE BLOOD

Two control systems based in the pancreas cooperate to keep blood-glucose concentrations within healthy bounds. One uses insulin to lower high levels of glucose, the other uses another hormone, called glucagon, to raise low levels. Today’s artificial pancreas relies on insulin alone, but two-hormone systems are being studied.

NORMAL BLOOD

DECEMBER 2021  SPECTRUM.IEEE.ORG  41

F

undamentally, blood-glucose management is a problem in optimization, one that is complicated by meals, exercise, illness, and other external factors that can affect metabolism. In 1979, the basis for solving this problem was introduced by the biomedical engineers Richard Bergman and Claudio Cobelli, who described the human metabolic system as a series of equations. In practice, however, finding a solution is hard for three main reasons: Insulin-action delay: In the body, insulin is secreted in the pancreas and shunted directly into the bloodstream. But when injected under the skin, even

the fastest insulins take from 40 minutes to an hour to reach the peak of their action. So the controller of the artificial pancreas must plan on lowering blood glucose an hour from now—it must predict the future. Inconsistency: Insulin action differs between people, and even within the same person at different times. Sensor inaccuracy: Even the best continuous glucose monitors make mistakes, sometimes drifting in a certain direction—showing glucose levels that are either too low or too high, a problem that can last for hours. What’s more, the system must take into account complex external influences so that it works just as well for a middle-aged man sitting at a desk all day as for a teenager on a snowboard, rocketing down a mountainside. To overcome these problems, researchers have proposed various solutions. The first attempt was a straightforward ­proportional-integral-derivative (PID) controller in which insulin is delivered proportionally to the increase of blood-­ glucose levels and their rate of change. This method is still used by one commercial system, from Medtronic, after many improvements of the algorithm that adjusts the reaction of the PID to the pace

The Control-IQ software predicts the rise in glucose concentration, to above 162 milligrams per decaliter of blood, by calculating extra doses of insulin, called correction boluses [below]. A correction can be administered every hour, as needed. This is in addition to the continuous infusion of insulin throughout the day, known as the basal rate, which is varied every 5 minutes, according to the person’s insulin needs.

The Minimed 770G artificial pancreas, a hybrid system [right], manages metabolic insulin dosages—it modulates the basal rate but does not administer correction boluses. It is descended from the first such system approved for general use.

42  SPECTRUM.IEEE.ORG  DECEMBER 2021

of subcutaneous insulin transport. A more sophisticated approach is the predictive control algorithm, which uses a model of the human metabolic system, such as the one proposed in 1979 by Bergman and Cobelli. The point is to predict future states and thereby partially compensate for the delayed diffusion of subcutaneous insulin into the bloodstream. Yet another experimental controller uses two hormones—insulin, to lower blood-glucose levels, and glucagon, to raise it. In each of these approaches, modeling work went far to create the conceptual background for building an artificial pancreas. The next step was to actually build it. To design a controller, you must have a way of testing it, for which biomedical engineering has typically relied on animal trials. But such testing is time consuming and costly. In 2007, our group at the University of Virginia proposed using computer-simulation experiments instead. Together with our colleagues at the University of Padua, in Italy, we created a computer model of glucose-insulin dynamics that operated on 300 virtual subjects with type 1 diabetes. Our model described the interaction over time of glucose and insulin by means of differential equations representing the best available estimates of human physiology. The parameters of the equation differed from subject to subject. The complete array of all physiologically feasible parameter sets described the simulated population. In January 2008, the U.S. Food and Drug Administration (FDA) made the unprecedented decision to accept our simulator as a substitute for animal trials in the preclinical testing of artificial pancreas controllers. The agency agreed that such in silico simulations were sufficient for regulatory approval of inpatient human trials. Suddenly, rapid and cost-effective algorithm development was a possibility. Only three months later, in April of 2008, we began using the controller we’d designed and tested in silico in real people with type 1 diabetes. The UVA/Padua simulator is now in use by engineers worldwide, and animal experiments for testing new artificial pancreas algorithms have been abandoned. Meanwhile, funding was expanding for research on other aspects of the arti-

LEFT: TANDEM DIABETES CARE; RIGHT: MEDTRONIC

needle and then connected to the monitor, which is worn against the body. Abbott and Dexcom soon followed with devices presenting glucose data in real time. The accuracy of such meters has consistently improved over the past 20 years, and it is thanks to those advances that an artificial pancreas has become possible. The ultimate goal is to replicate the entire job of the pancreatic control system, so that patients will no longer have to minister to themselves. But mimicking a healthy pancreas has proven exceptionally difficult.

Perhaps one day it will make sense to implant the artificial pancreas within the abdominal cavity, where the insulin can be fed directly into the bloodstream, for still faster action. ficial pancreas. In 2006 the JDRF (formerly the Juvenile Diabetes Research Foundation) started work on a device at several centers in the U.S. and across Europe; in 2008 the U.S. National Institutes of Health launched a research initiative; and from 2010 to 2014, the European Union–funded AP@Home consortium was active. The global frenzy of rapid prototyping and testing bore fruit: The first outpatient studies took place from September 2011 through January 2012 at camps for diabetic children in Israel, Germany, and Slovenia, where children with type 1 diabetes were monitored overnight using a laptop-based artificial pancreas system. Most of these early studies rated the artificial pancreas systems as better than manual insulin therapy in three ways. The patients spent more time within the target range for blood glucose, they had fewer instances of low blood glucose, and they had better control during sleep—a time when low blood-glucose levels can be hard to detect and to manage. But these early trials all relied on laptop computers to run the algorithms. The next challenge was to make the systems mobile and wireless, so that they could be put to the test under reallife conditions. Our team at UVA developed the first mobile system, the Diabetes Assistant, in 2011. It ran on an Android smartphone, had a graphical interface, and was capable of Web-based remote observation. First, we tested it on an outpatient basis in studies that lasted from a few days to 6 months. Next, we tried it on patients who were at high risk because they had suffered from frequent or severe bouts of low blood glucose. Finally we stresstested the system in children with type 1 diabetes who were learning to ski at a five-day camp. In 2016, a pivotal trial ended for the first commercial hybrid system—the MiniMed 670G—which automatically controlled the continuous rate of insulin throughout the day but not the addi-

tional doses of insulin that were administered before a meal. The system was cleared by the FDA for clinical use in 2017. Other groups around the world were also testing such systems, with overwhelmingly good results. One 2018 meta-analysis of 40 studies, totaling 1,027 participants, found that patients stayed within their blood-glucose target range (70–180 mg/dL) about 15 percent more of the time while asleep and nearly 10 percent more overall, as compared to patients receiving standard treatment. Our original machine’s third-­generation descendant—based on Control-IQ technology and made by Tandem Diabetes Care in San Diego—underwent a sixmonth randomized trial in teenagers and adults with type 1 diabetes, ages 14 and up. We published the results in the New England Journal of Medicine in October 2019. The system uses a Dexcom G6 continuous glucose monitor—one that no longer requires calibration by finger-stick samples—an insulin pump from Tandem, and the control algorithm originally developed at UVA. The algorithm is built right into the pump, which means the system does not require an external smartphone to handle the computing.

C

ontrol-IQ still requires some involvement from the user. Its hybrid control system asks the person to push a button saying “I am eating” and then enter the estimated amount of carbohydrates; the person can also push a button saying “I am exercising.” These interventions aren’t absolutely necessary, but they make the control better. Thus, we can say that today’s controllers can be used for full control, but they work better as hybrids. The system has a dedicated safety module that either stops or slowly attenuates the flow of insulin whenever the system predicts low blood glucose. Also, it gradually increases insulin dosing overnight, avoiding the tendency toward morning highs and aiming for normalized glucose levels by 7 a.m.

The six-month trial tested Control-IQ against the standard treatment, in which the patient does all the work, using information from a glucose monitor to operate an insulin pump. Participants using Control-IQ spent 11 percent more time in the target blood-glucose range and cut in half—from 2.7 percent to 1.4 percent— the time spent below the low-glucose redline, which is 70 mg/dL. In December 2019, the FDA authorized the clinical use of Control-IQ for patients 14 and up, and our system thus became the first “interoperable automated insulin-­ dosing controller,” one that can connect to various insulin pumps and continuous glucose monitors. Patients can now customize their artificial pancreases. The FDA approval came almost 14 years to the day after the expert in that Maryland conference room stated that the problem was unsolvable. A month after the approval, Control-IQ was released to users of Tandem’s insulin pump as an online software upgrade. And in June 2020, following another successful clinical trial in children with type 1 diabetes between 6 and 13 years old, the FDA approved Control-IQ for ages 6 and up. Children can benefit from this technology more than any other age group because they are the least able to manage their own insulin dosages. In April 2021, we published an analysis of 9,400 people using Control-IQ for one year, and this real-life data confirmed the results of the earlier trials. As of 1 September 2021, Control-IQ is used by over 270,000 people with diabetes in 21 countries. To date, these people have logged over 30 million days on this system. One parent wrote Tandem about how eight weeks on the Control-IQ had drastically reduced his son’s average blood-glucose concentration. “I have waited and toiled 10 years for this moment to arrive,” he wrote. “Thank you.” Progress toward better automatic control will be gradual; we anticipate a smooth transition from hybrid to full autonomy, when the patient never intervenes. Work is now underway on using faster-acting insulins that are in clinical trials. Perhaps one day it will make sense to implant the artificial pancreas within the abdominal cavity, where the insulin can be fed directly into the bloodstream, for still faster action. What comes next? Well, what else seems impossible today? n

DECEMBER 2021  SPECTRUM.IEEE.ORG  43

Ohm’s Law (V = IR)

Kirchhoff’s

Neural-network processing done in memory with analog circuits will save energy 44  SPECTRUM.IEEE.ORG  DECEMBER 2021

Current Law (∑ IIN = ∑ IOUT)

Better AI :)

BY GEOFFREY W. BURR, ABU SEBASTIAN, TAKASHI ANDO & WILFRIED HAENSCH DECEMBER 2021  SPECTRUM.IEEE.ORG  45

Machine learning and artificial intelligence (AI) have already penetrated so deeply into our life and work that you might have forgotten what interactions with machines used to be like. We used to ask only for precise quantitative answers to questions conveyed with numeric keypads, spreadsheets, or programming languages: “What is the square root of 10?” “At this rate of interest, what will be my gain over the next five years?” But in the past 10 years, we’ve become accustomed to machines that can answer the kind of qualitative, fuzzy questions we’d only ever asked of other people: “Will I like this movie?” “How does traffic look today?” “Was that transaction fraudulent?” Deep neural networks (DNNs), systems that learn how to respond to new queries when they’re trained with the right answers to very similar queries, have enabled these new capabilities. DNNs are the primary driver behind the rapidly growing global market for AI hardware, software, and services, valued at US $327.5 billion this year and expected to pass $500 billion in 2024, according to the International Data Corp.

Convolutional neural networks first fueled this revolution by providing superhuman image-recognition capabilities. In the last decade, new DNN models for natural-language processing, speech recognition, reinforcement learning, and recommendation systems have enabled many other commercial applications. But it’s not just the number of applications that’s growing. The size of the networks and the data they need are growing, too. DNNs are inherently scalable—they provide more reliable answers as they get bigger and as you train them with more data. But doing so comes at a cost. The number of computing operations needed to train the best DNN models grew 1 billionfold between 2010 and 2018, meaning a huge increase in energy consumption. And while each use of an already-trained DNN model on new data—termed inference— requires much less computing, and therefore less energy, than the training itself, the sheer volume of such inference calculations is enormous and increasing. If it’s to continue to change people’s lives, AI is going to have to get more efficient.

Artificial neurons (i) Activation function OUTPUT =

f(∑WijXi) Weights of connections ( j)

Multiply (Ohm’s Law)

Accumulate (Kirchhoff’s Current Law)

AI’s Fundamental Function The most basic computation in an artificial neural network is called multiply and accumulate. The output of artificial neurons [left, yellow] are multiplied by the weight values connecting them to the next neuron [center, light blue]. That neuron sums its inputs and applies an output function. In analog AI, the multiply function is performed by Ohm’s Law, where the neuron’s output voltage is multiplied by the conductance representing the weight value. The summation at the neuron is done by Kirchhoff’s Current Law, which simply adds all the currents entering a single node.

46  SPECTRUM.IEEE.ORG  DECEMBER 2021

PHASE-CHANGE MEMORY Chalcogenide

Insulator

Nonvolatile Memories for Analog AI

We think changing from digital to analog computation might be what’s needed. Using nonvolatile memory devices and two fundamental physical laws of electrical engineering, simple circuits can implement a version of deep learning’s most basic calculations that requires mere thousandths of a trillionth of a joule (a femtojoule). There’s a great deal of engineering to do before this tech can take on complex AIs, but we’ve already made great strides and mapped out a path forward. THE BIGGEST TIME and energy costs in most computers occur when lots of data has to move between external memory and computational resources such as CPUs and GPUs. This is the “von Neumann bottleneck,” named after the classic computer architecture that separates memory and logic. One way to greatly reduce the power needed for deep learning is to avoid moving the data—to do the computation out where the data is stored. DNNs are composed of layers of artificial neurons. Each layer of neurons drives the output of those in the next layer according to a pair of values—the neuron’s “activation” and the synaptic “weight” of the connection to the next neuron. Most DNN computation is made up of what are called vector-matrix-multiply (VMM) operations—in which a vector (a one-dimensional array of numbers) is multiplied by a two-dimensional array. At

RESISTIVE RAM

FLASH MEMORY

ELECTROCHEMICAL RAM Control gate Floating gate

Gate/reservoir Electrolyte

Vacancy

Insulator

Channel

Phase-change memory’s conductance is set by the transition between a crystalline and an amorphous state in a chalcogenide glass. In resistive RAM, conductance depends on the creation and destruction of conductive filaments in an insulator. Flash memory stores data as charge trapped in a “floating gate.” The presence or

the circuit level these are composed of many multiply-accumulate (MAC) operations. For each downstream neuron, all the upstream activations must be multiplied by the corresponding weights, and these contributions are then summed. Most useful neural networks are too large to be stored within a processor’s internal memory, so weights must be brought in from external memory as each layer of the network is computed, each time subjecting the calculations to the dreaded von Neumann bottleneck. This leads digital compute hardware to favor DNNs that move fewer weights in from memory and then aggressively reuse these weights. A RADICAL NEW APPROACH to energy­-efficient DNN hardware occurred to us at IBM Research back in 2014. Together with other investigators, we had been working on crossbar arrays of nonvolatile memory (NVM) devices. Crossbar arrays are constructs where devices, memory cells for example, are built in the vertical space between two perpendicular sets of horizontal conductors, the so-called bitlines and the wordlines. We realized that, with a few slight adaptations, our memory systems would be ideal for DNN computations, particularly those for which existing weight-reuse tricks work poorly. We refer to this opportunity as “analog AI,” although other researchers doing similar work also

absence of that charge modifies conductances across the device. Electrochemical RAM acts like a miniature battery. Pulses of voltage on a gate electrode modulate the conductance between the other two terminals by the exchange of ions through a solid electrolyte.

use terms like “processing-in-memory” or “compute-in-memory.” There are several varieties of NVM, and each stores data differently. But data is retrieved from all of them by measuring the device’s resistance (or, equivalently, its inverse—conductance). Magnetoresistive RAM (MRAM) uses electron spins, and flash memory uses trapped charge. Resistive RAM (RRAM) devices store data by creating and later disrupting conductive filamentary defects within a tiny metal-insulator­metal device. Phase-change memory (PCM) uses heat to induce rapid and reversible transitions between a high-conductivity crystalline phase and a low-conductivity amorphous phase. Flash, RRAM, and PCM offer the lowand high-resistance states needed for conventional digital data storage, plus the intermediate resistances needed for analog AI. But only RRAM and PCM can be readily placed in a crossbar array built in the wiring above silicon transistors in high-performance logic, to minimize the distance between memory and logic. We organize these NVM memory cells in a two-dimensional array, or “tile.” Included on the tile are transistors or other devices that control the reading and writing of the NVM devices. For memory applications, a read voltage addressed to one row (the wordline) creates currents proportional to the NVM’s conductance that can be detected on the

columns (the bitlines) at the edge of the array, retrieving the stored data. To make such a tile part of a DNN, each row is driven with a voltage for a duration that encodes the activation value of one upstream neuron. Each NVM device along the row encodes one synaptic weight with its conductance. The resulting read current is effectively performing, through Ohm’s Law (in this case expressed as “current equals voltage times conductance”), the multiplication of excitation and weight. The individual currents on each bitline then add together according to Kirchhoff’s Current Law. The charge generated by those currents is integrated over time on a capacitor, producing the result of the MAC operation. These same analog in-memory summation techniques can also be performed using flash and even SRAM cells, which can be made to store multiple bits but not analog conductances. But we can’t use Ohm’s Law for the multiplication step. Instead, we use a technique that can accommodate the one- or two-bit dynamic range of these memory devices. However, this technique is highly sensitive to noise, so we at IBM have stuck to analog AI based on PCM and RRAM. Unlike conductances, DNN weights and activations can be either positive or negative. To implement signed weights, we use a pair of current paths—one adding charge to the capacitor, the other subtracting. To implement signed exci-

DECEMBER 2021  SPECTRUM.IEEE.ORG  47

tations, we allow each row of devices to swap which of these paths it connects with, as needed. With each column performing one MAC operation, the tile does an entire vector-matrix multiplication in parallel. For a tile with 1,024 × 1,024 weights, this is 1 million MACs at once. In systems we’ve designed, we expect that all these calculations can take as little as 32 nanoseconds. Because each MAC performs a computation equivalent to that of two digital operations (one multiply followed by one add), performing these 1 million analog MACs every 32 nanoseconds represents 65 trillion operations per second. We’ve built tiles that manage this feat using just 36 femtojoules of energy per operation, the equivalent of 28 trillion operations per joule. Our latest tile designs reduce this figure to less than 10 fJ, making them 100 times as efficient as commercially available hardware and 10 times better than the system-level energy efficiency of the latest custom

y1

digital accelerators, even those that aggressively sacrifice precision for energy efficiency. It’s been important for us to make this per-tile energy efficiency high, because a full system consumes energy on other tasks as well, such as moving activation values and supporting digital circuitry. THERE ARE SIGNIFICANT challenges to overcome for this analog-AI approach to really take off. First, deep neural networks, by definition, have multiple layers. To cascade multiple layers, we must process the VMM tile’s output through an artificial neuron’s activation—a nonlinear function—and convey it to the next tile. The nonlinearity could potentially be performed with analog circuits and the results communicated in the duration form needed for the next layer, but most networks require other operations beyond a simple cascade of VMMs. That means we need efficient analog-to-digital conversion (ADC) and modest amounts of parallel digital compute between the

tiles. Novel, high-efficiency ADCs can help keep these circuits from affecting the overall efficiency too much. Recently, we unveiled a high-performance PCMbased tile using a new kind of ADC that helped the tile achieve better than 10 trillion operations per watt. A second challenge, which has to do with the behavior of NVM devices, is more troublesome. Digital DNNs have proven accurate even when their weights are described with fairly low-precision numbers. The 32-bit floating-point numbers that CPUs often calculate with are overkill for DNNs, which usually work just fine and with less energy when using 8-bit floating-point values or even 4-bit integers. This provides hope for analog computation, so long as we can maintain a similar precision. Given the importance of conductance precision, writing conductance values to NVM devices to represent weights in an analog neural network needs to be done slowly and carefully. Compared with traditional memories, such as SRAM and

X1

X1

X2

y2 X2

Xi Xi

y1

yj

Vector-Matrix Multiplication with Analog AI

y2

Vector-matrix multiplication (VMM) is the core of a neural network’s computing [left]; it is a collection of multiply-and-accumulate processes. Here the activations of artificial neurons [yellow] are multiplied by the weights of their connections [light blue] to the next layer of neurons [green]. For analog AI, VMM is performed on a crossbar array tile [center]. At each cross point, a nonvolatile memory cell

48  SPECTRUM.IEEE.ORG  DECEMBER 2021

yj

encodes the weight as conductance. The neurons’ activations are encoded as the duration of a voltage pulse. Ohm’s Law dictates that the current along each crossbar column is equal to this voltage times the conductance. Capacitors [not shown] at the bottom of the tile sum up these currents. A neural network’s multiple layers are represented by converting the output of one tile into the voltage duration pulses needed as the input to the next tile [right].

DRAM, PCM and RRAM are already slower to program and wear out after fewer programming cycles. Fortunately, for inference, weights don’t need to be frequently reprogrammed. So analog AI can use time-consuming ­write-­verification techniques to boost the precision of programming RRAM and PCM devices without any concern about wearing the devices out. That boost is much needed because nonvolatile memories have an inherent level of programming noise. RRAM’s conductivity depends on the movement of just a few atoms to form filaments. PCM’s conductivity depends on the random formation of grains in the polycrystalline material. In both, this randomness poses challenges for writing, verifying, and reading values. Further, in most NVMs, conductances change with temperature and with time, as the amorphous phase structure in a PCM device drifts, or the filament in an RRAM relaxes, or the trapped charge in a flash memory cell leaks away. There are some ways to finesse this problem. Significant improvements in weight programming can be obtained by using two conductance pairs. Here, one pair holds most of the signal, while the other pair is used to correct for programming errors on the main pair. Noise is reduced because it gets averaged out across more devices. We tested this approach recently in a multitile PCM-based chip, using both one and two conductance pairs per weight. With it, we demonstrated excellent accuracy on several DNNs, even on a recurrent neural network, a type that’s typically sensitive to weight programming errors. Different techniques can help ameliorate noise in reading and drift effects. But because drift is predictable, perhaps the simplest is to amplify the signal during a read with a time-dependent gain that can offset much of the error. Another approach is to use the same techniques that have been developed to train DNNs for low-precision digital inference. These adjust the neural-network model to match the noise limitations of the underlying hardware. As we mentioned, networks are becoming larger. In a digital system, if the network doesn’t fit on your accelerator, you bring in the weights for each layer of the DNN from external memory chips.

But NVM’s writing limitations make that a poor decision. Instead, multiple analog AI chips should be ganged together, with each passing the intermediate results of a partial network from one chip to the next. This scheme incurs some additional communication latency and energy, but it’s far less of a penalty than moving the weights themselves.

rithm we developed at IBM, called TikiTaka, uses such techniques to train DNNs successfully even with highly asymmetric RRAM devices. Finally, we are developing a device called electrochemical random-access memory (ECRAM) that can offer not just symmetric but highly linear and gradual conductance updates.

UNTIL NOW, we’ve only been talking about inference—where an alreadytrained neural network acts on novel data. But there are also opportunities for analog AI to help train DNNs. DNNs are trained using the back­ propagation algorithm. This combines the usual forward inference operation with two other important steps—error backpropagation and weight update. Error backpropagation is like running inference in reverse, moving from the last layer of the network back to the first layer; weight update then combines information from the original forward inference run with these backpropagated errors to adjust the network weights in a way that makes the model more accurate. The backpropagation step can be done in place on the tiles but in the opposite manner of inferencing—applying voltages to the columns and integrating current along rows. Weight update is then performed by driving the rows with the original activation data from the forward inference, while driving the columns with the error signals produced during backpropagation. Training involves numerous small weight increases and decreases that must cancel out properly. That’s difficult for two reasons. First, recall that NVM devices wear out with too much programming. Second, the same voltage pulse applied with opposite polarity to an NVM may not change the cell’s conductance by the same amount; its response is asymmetric. But symmetric behavior is critical for backpropagation to produce accurate networks. This is only made more challenging because the magnitude of the conductance changes needed for training approaches the level of inherent randomness of the materials in the NVMs. There are several approaches that can help here. For example, there are various ways to aggregate weight updates across multiple training examples, and then transfer these updates onto NVM devices periodically during training. A novel algo-

THE SUCCESS OF analog AI will depend on achieving high density, high throughput, low latency, and high energy efficiency—simultaneously. Density depends on how tightly the NVMs can be integrated into the wiring above a chip’s transistors. Energy efficiency at the level of the tiles will be limited by the circuitry used for analog-to-digital conversion. But even as these factors improve and as more and more tiles are linked together, Amdahl’s Law—an argument about the limits of parallel computing— will pose new challenges to optimizing system energy efficiency. Previously unimportant aspects such as data communication and the residual digital computing needed between tiles will incur more and more of the energy budget, leading to a gap between the peak energy efficiency of the tile itself and the sustained energy efficiency of the overall analog-AI system. Of course, that’s a problem that eventually arises for every AI accelerator, analog or digital. The path forward is necessarily different from digital AI accelerators. Digital approaches can bring precision down until accuracy falters. But analog AI must first increase the signal-to-noise ratio (SNR) of the internal analog modules until it is high enough to demonstrate accuracy equivalent to that of digital systems. Any subsequent SNR improvements can then be applied toward increasing density and energy efficiency. These are exciting problems to solve, and it will take the coordinated efforts of materials scientists, device experts, circuit designers, system architects, and DNN experts working together to solve them. There is a strong and continued need for more energy-efficient AI acceleration, and a shortage of other attractive alternatives for delivering on this need. Given the wide variety of potential memory devices and implementation paths, it is quite likely that some degree of analog computation will find its way into future AI accelerators. n

DECEMBER 2021  SPECTRUM.IEEE.ORG  49

NEWS CONTINUED FROM PAGE 11

either burning them using lots of energy or grinding them up and dissolving them in acids. Most large recycling companies, which have mainly been recycling consumer-electronics batteries, and upcoming battery-recycling startups use these methods to produce separate elements to sell to battery-material companies that will in turn make the high-grade materials for car and battery makers. But the real value of an EV battery is in the cathode, Wang points out. Cathode materials are proprietary combinations BY PRACHI PATEL of metals including nickel, manganese, and cobalt that are crafted into particles with specific sizes and structures. ithium-ion batteries, with The recycled material had a more Battery Resourcers’ recycling techtheir  use of riskily mined porous microscopic structure that is nology produces various ready-to-use metals, tarnish the green image better for lithium ions to slip in and out NMC cathode materials based on what of electric vehicles. Recycling to of. The result: batteries with an energy a car company wants. That means selling recover those valuable metals would density similar to those made with com- the recycled materials could turn a profit, minimize the social and environmental mercial cathodes, but that also lasted something recycling companies say can be impact of mining, keep millions of tons 53 percent longer. hard to do. “We are the only company that of batteries from landfills, and cut the While the recycled batteries weren’t gives an output that is a cathode material,” energy use and emissions created from tested in cars, they were tested at industri- he says. “Other companies [sell] elements, making batteries. so their value added is less.” But while the EV battery-recyIts technology involves cling industry is starting to take shredding batteries and removoff, getting carmakers to use recying the steel cases, aluminum cled materials remains a hard sell. and copper wires, plastics, and “In general, people’s impression pouch materials for recycling. is that recycled material is not as The remaining black mass is good as virgin material,” says Yan dissolved in solvents, and the Wang, a professor of mechanical graphite, carbon, and impuriengineering at Worcester Polyties are filtered out or chemically technic Institute, in Massachuseparated. Using a patented setts. “Battery companies still chemical technique, the nickel, hesitate to use recycled material manganese, and cobalt are then in their batteries.” mixed in desired ratios to make A new study by Wang and a cathode powders. team that includes researchers A few other researchers and from the U.S. Advanced Battery outfits such as the ReCell Center, Consortium (USABC), Chinese a battery-­recycling research A team from Worcester Polytechnic Institute and battery company A123 Systems, collaboration supported by the other institutions experimented with these and others shows that battery 1-ampere-hour and 10-Ah battery cells containing U.S. Department of Energy, are and car manufacturers needn’t recycled cathode materials. also developing direct recycling worry. The results, published technology. But they likely will in the journal Joule, show that batteries ally relevant scales. The researchers made not be producing high volumes of recywith recycled cathodes can be as good 11-ampere-hour industry-standard pouch cled cathode material any time soon. as, or even better than those using newly cells loaded with materials at the same Battery Resourcers, meanwhile, is unearthed materials. density as EV batteries. Engineers at A123 already selling its recycled materials to The team tested batteries with recy- Systems did most of the testing, Wang says, battery manufacturers on a small scale. cled NMC111 cathodes, the most common using a protocol devised by the USABC to The company plans to open its first comflavor of cathode, which contain a third meet commercial viability goals for plug-in mercial plant in the United States, which each of nickel, manganese, and cobalt. hybrid electric vehicles. He says the results will be able to process more than 9,000 The cathodes were made using a pat- prove that recycled cathode materials are tonnes of batteries, in 2022. In Septemented recycling technique that Battery a viable alternative to pristine materials. ber, it raised US $70 million, with which Resourcers, a Massachusetts startup EV batteries are complex beasts and it plans to launch two more facilities, in Wang cofounded, is now commercializing. recycling them isn’t easy. It involves Europe, by the end of 2022. n BATTERIES

Battery Recycling Really Works Repurposed cathodes can be even better than shiny new ones

50  SPECTRUM.IEEE.ORG  DECEMBER 2021

WORCESTER POLYTECHNIC INSTITUTE

L

CULTIVATING THE NEXT GENERATION OF AFRICAN TECHNOLOGY LEADERS Faculty Positions at CMU-Africa

Join Carnegie Mellon University in Africa to educate the extraordinary master students in our programs who are becoming the next generation of technology leaders on the continent.

We invite you to be part of a movement for change.

We are looking for top teaching and research faculty at all levels to be based at our beautiful campus in Kigali in the land of a thousand hills, Rwanda. Kigali in recent years has become an epicenter of tech innovation and provides the perfect setting for a world class institution to develop tech leaders that create innovative solutions for local and international challenges. Carnegie Mellon University Africa (CMU-Africa) invites applications for teaching track and research track faculty positions at all levels (i.e., Assistant, Associate and Full Professor) at its campus in Kigali, Rwanda. CMU-Africa offers three Master’s degree programs, Information Technology, Electrical and Computer Engineering and Engineering Artificial Intelligence, and has about 25 faculty members dedicated to teaching, research and entrepreneurship activities. CMUAfrica faculty are leading research projects of importance to Africa, e.g., forecasting the economic and mortality impacts of COVID-19 for Rwanda and beyond, enhancing cybersecurity capacity in Africa, and strengthening the teacher management system in Rwanda. For full Job description and Qualification criteria, Visit http://apply.interfolio.com/96623 CMU is an equal opportunity employer and is committed to increasing the diversity of its community.

Assistant Professor in Artificial Intelligence Electrical and Computer Engineering Herbert Wertheim College of Engineering University of Florida

Associate/Assistant Professor in Intelligent Transportation (Ref. No.: IOTSC/AAP/IT/10/2021)

The University of Macau (UM) is the only public comprehensive university in the Macao Special Administrative Region (MSAR) located at the west bank of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). The GBA is rapidly developing into one of the leading technology and innovation hubs of the world. With a scenic campus of approximately 1 km2 on Hengqin island, UM has achieved significant progress in the past decade as evidenced by its rising international repute, state-of-the-art teaching and research facilities, and the establishment of three State Key Laboratories in microelectronics, Chinese medical sciences, and internet of things for smart city. To support economic diversification of MSAR and deepen collaboration between MSAR and Guangdong Province in Hengqin island, UM will continue to invest in cutting-edge research and develop interdisciplinary programmes in key strategic areas including precision oncology, advanced materials, regional oceanography, artificial intelligence and robotics, data science, cognitive and brain science and economics and finance. Leveraging its ‘4-in-1’ model of education and the largest residential college system in Asia, UM provides all-round undergraduate education, nurturing talent to support social and economic development in MSAR and the GBA as a whole. With unprecedented growth and opportunities for development, UM offers promising career prospects to academics at all levels. It may be noted that English is the working language and the primary medium of instruction at UM. The State Key Laboratory of Internet of Things for Smart City (University of Macau) invites applications for the position of Associate/Assistant Professor, who will also be a joint faculty member in the Faculty of Science and Technology, in the following disciplines: • Intelligent Transportation • Big Data Analysis in Urban Transportation • Autonomous Driving • Vehicle to Everything Technology and Applications State Key Laboratory of Internet of Things for Smart City (University of Macau) - SKL-IOTSC The State Key Laboratory of Internet of Things for Smart City (University of Macau) is expected to promote smart city development in prospective of IoT, Big Data Technology and Engineering in Macao and inject a fresh impetus to the development of the Greater Bay Area by enhancing research and training in the field and providing technical support plans for improving economic performance, people’s quality of life, and social management. More details about the State Key Laboratory are available from https://skliotsc.um.edu.mo/. Faculty of Science and Technology - FST Faculty of Science and Technology aims to provide programmes for undergraduate and graduate education with quality reaching international standard. It strives to become a research active unit advancing the knowledge of engineering and science, and serves the community and industry as an agent of technological innovation and educational advancement. Currently, about 90 faculty members from diverse international backgrounds serve in this faculty. More details about the Faculty of Science and Technology are available from http://www.fst.um.edu.mo/. Qualifications 1. A PhD degree in Computer Science, Traffic Engineering or related disciplines; 2. A distinguished record of internationally-recognized research and scholarship; 3. Demonstrable competence in communication; and 4. English is the working language, while knowledge in Chinese/Portuguese will be an advantage. The selected candidate is expected to assume duty in the 1st quarter of 2022. Remuneration A taxable annual remuneration starting from MOP828,100 (approximately USD102,230) will be commensurate with the successful applicants’ academic qualification and relevant professional experience. The current local maximum income tax rate is 12% but is effectively around 5% - 7% after various discretionary exemptions. Apart from competitive remuneration, UM offers a wide range of benefits, such as medical insurance, provident fund, on-campus accommodation/housing allowance and other subsidies. Further details on our package are available at: https://career.admo.um.edu.mo/learn-more/. Application Procedure Applicants should visit https://career.admo.um.edu.mo/ for more details, and apply ONLINE. Review of applications will commence upon receiving applications and continue until the position is filled. Applicants may consider their applications not successful if they are not invited for an interview within 3 months of application. Human Resources Section, Office of Administration University of Macau, Av. da Universidade, Taipa, Macau, China Website: https://career.admo.um.edu.mo/; Email: [email protected] Tel: +853 8822 8577; Fax: +853 8822 2412 The effective position and salary index are subject to the Personnel Statute of the University of Macau in force. The University of Macau reserves the right not to appoint a candidate. Applicants with less qualification and experience can be offered lower positions under special circumstances. ***Personal data provided by applicants will be kept confidential and used for recruitment purpose only*** ** Under the equal condition of qualifications and experience, priority will be given to Macao permanent residents**

The Department of Electrical and Computer Engineering (ECE) in the Herbert Wertheim College of Engineering (HWCOE) at the University of Florida (UF) invites applications for four full-time, ninemonth tenure-track faculty positions at the rank of Assistant Professor. The open positions are for candidates working in one or more of the following areas related to Artificial Intelligence (AI): Machine Learning and Climate, Self-Aware AI Computing Systems, AI of Things, and Cognitive Architectures. The successful candidates are expected to have a doctoral degree in a relevant engineering field at the time of hire. The anticipated start date for the position is Fall 2022 with some flexibility for a later start based on individual needs. The University of Florida is an equal opportunity institution. Additional information about the position, department, and application package is available at https://facultyjobs.hr.ufl.edu/posting/96173 https://facultyjobs.hr.ufl.edu/posting/96127 https://facultyjobs.hr.ufl.edu/posting/96148 https://facultyjobs.hr.ufl.edu/posting/96168 Please email any questions to [email protected]

ELECTRICAL AND COMPUTER ENGINEERING COLORADO STATE UNIVERSITY The Department of Electrical and Computer Engineering (ECE) within Walter Scott, Jr. College of Engineering at Colorado State University (CSU) is searching for an ECE Department Head to provide leadership for the 26 tenured, tenure-track, and instructional faculty, including 3 University Distinguished Professors and a University Distinguished Teaching Scholar, 25 administrative and research staff, 408 undergraduates and 159 graduate students. This is a full-time, 12-month appointment, 5-year term, tenured full-professor faculty position, reporting directly to the Dean of the Walter Scott, Jr. College of Engineering. Applications and nominations will be considered until the position is filled; however, applications should be received by full consideration date to ensure full consideration. Full consideration date: 1/31/2022. The desired start date for this position is July 1, 2022. To view full posting and apply, visit: https://jobs.colostate.edu/postings/94402

http://www.um.edu.mo

68  SPECTRUM.IEEE.ORG  DECEMBER 2021

CSU is an EO/EA/AA employer and conducts

Faculty Position in Electrical Engineering Department of Electrical, Computer, and Systems Engineering Case Western Reserve University, Cleveland, Ohio The Department of Electrical, Computer, and Systems Engineering at Case Western Reserve University (CWRU) invites applications for a tenure-track faculty position in Electrical Engineering at the Assistant Professor level. Appointments will be considered for starting dates as early as July 1, 2022. Candidates must have a Ph.D. degree in Electrical Engineering or a related field. The search is focused in the areas of micro/nanosystems and integrated circuits, with a strong emphasis in applications related to human health and symbiotic integration of humans with machines in wearable and implantable fashion. In micro/nanosystems, the department is looking for candidates with expertise in novel devices, heterogeneous integration, flexible/ wearable systems and advanced packaging. In circuits and instrumentation, the department is particularly interested in candidates with expertise in analog/mixedsignal integrated circuits for sensor interfacing. The department is particularly interested in candidates with experience in both focus areas. Additional information about the position, department, and application package is available at https://engineering.case.edu/ecse/employment. CWRU provides reasonable accommodations to applicants with disabilities. Applicants requiring a reasonable accommodation for any part of the application and hiring process should call 216-368-3066.

Associate/Assistant Professor in Intelligent Sensing and Network Communication (Ref. No.: IOTSC/AAP/ISNC/06/2021) The University of Macau (UM) is the only public comprehensive university in the Macao Special Administrative Region (MSAR) located at the west bank of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). The GBA is rapidly developing into one of the leading technology and innovation hubs of the world. With a scenic campus of approximately 1 km2 on Hengqin island, UM has achieved significant progress in the past decade as evidenced by its rising international repute, state-of-the-art teaching and research facilities, and the establishment of three State Key Laboratories in microelectronics, Chinese medical sciences, and internet of things for smart city. To support economic diversification of MSAR and deepen collaboration between MSAR and Guangdong Province in Hengqin island, UM will continue to invest in cutting-edge research and develop interdisciplinary programmes in key strategic areas including precision oncology, advanced materials, regional oceanography, artificial intelligence and robotics, data science, cognitive and brain science and economics and finance. Leveraging its ‘4-in-1’ model of education and the largest residential college system in Asia, UM provides all-round undergraduate education, nurturing talent to support social and economic development in MSAR and the GBA as a whole. With unprecedented growth and opportunities for development, UM offers promising career prospects to academics at all levels. It may be noted that English is the working language and the primary medium of instruction at UM. The State Key Laboratory of Internet of Things for Smart City (University of Macau) invites applications for the position of Associate/Assistant Professor in the following disciplines: • Internet of things • Intelligent sensing • Communications and networking State Key Laboratory of Internet of Things for Smart City (University of Macau) - SKL-IOTSC The State Key Laboratory of Internet of Things for Smart City (University of Macau) is expected to promote smart city development in prospective of IoT, Big Data Technology and Engineering in Macao and inject a fresh impetus to the development of the Greater Bay Area by enhancing research and training in the field and providing technical support plans for improving economic performance, people’s quality of life, and social management. More details about the State Key Laboratory are available from https://skliotsc.um.edu.mo/. Faculty of Science and Technology - FST Faculty of Science and Technology aims to provide programmes for undergraduate and graduate education with quality reaching international standard. It strives to become a research active unit advancing the knowledge of engineering and science, and serves the community and industry as an agent of technological innovation and educational advancement. Currently, about 90 faculty members from diverse international backgrounds serve in this faculty. More details about the Faculty of Science and Technology are available from http://www.fst.um.edu.mo/.

The department of Electrical and Computer Engineering (EECE) at Marquette University seeks candidates for a tenure-track faculty position in Computer Engineering starting in August 2022. Appointment will be at the assistant-professor level. Faculty duties include teaching at the undergraduate and graduate levels, research, and supervision of graduate students. Candidates with expertise in computer vision are especially encouraged to apply. The EECE Department has 15 faculty, including 3 IEEE Fellows and one IEEE Technical Field Award recipient, one full-time adjunct, several part-time adjuncts, and nearly 180 undergraduate and 70 graduate students. EECE offers ABET-accredited B.S. degrees in Electrical Engineering and Computer Engineering. Graduate degrees include five-year B.S./M.S., two certificates, M.S., and Ph.D. EECE research is on a steep upward trajectory, both in terms of funding and graduate enrollment, with many ongoing internal and external collaborations, including the industry. Please submit a complete application by January 15, 2022. Review of applications will continue until the position is filled. Please include a letter of intent, curriculum vitae, teaching philosophy, research statement, and a list of three references. For further information and application go to: https:// employment.marquette.edu/postings/15534. Marquette University is an Equal Opportunity Employer; those from underrepresented groups are encouraged to apply.

Qualifications 1. A PhD degree in Computer Science, Electrical and Electronic Engineering or related disciplines; 2. A distinguished record of internationally-recognized research and scholarship; 3. Demonstrable competence in communication; and 4. English is the working language, while knowledge in Chinese/Portuguese will be an advantage. The selected candidate is expected to assume duty in the 1st quarter of 2022. Remuneration A taxable annual remuneration starting from MOP828,100 (approximately USD102,230) will be commensurate with the successful applicants’ academic qualification and relevant professional experience. The current local maximum income tax rate is 12% but is effectively around 5% - 7% after various discretionary exemptions. Apart from competitive remuneration, UM offers a wide range of benefits, such as medical insurance, provident fund, on campus accommodation/housing allowance and other subsidies. Further details on our package are available at: https://career.admo.um.edu.mo/learn-more/. Application Procedure Applicants should visit https://career.admo.um.edu.mo/ for more details, and apply ONLINE. Review of applications will commence upon receiving applications and continue until the position is filled. Applicants may consider their applications not successful if they are not invited for an interview within 3 months of application. Human Resources Section, Office of Administration University of Macau, Av. da Universidade, Taipa, Macau, China Website: https://career.admo.um.edu.mo/; Email: [email protected] Tel: +853 8822 8577; Fax: +853 8822 2412 The effective position and salary index are subject to the Personnel Statute of the University of Macau in force. The University of Macau reserves the right not to appoint a candidate. Applicants with less qualification and experience can be offered lower positions under special circumstances. ***Personal data provided by applicants will be kept confidential and used for recruitment purpose only*** ** Under the equal condition of qualifications and experience, priority will be given to Macao permanent residents**

http://www.um.edu.mo http://www.um.edu.mo

DECEMBER 2021  SPECTRUM.IEEE.ORG  69

Ming Hsieh Department of Electrical and Computer Engineering University of Southern California Faculty Positions Ming Hsieh Department of Electrical and Computer Engineering The University of Southern California, one of the nation’s top research universities, invites applications for tenured and tenure-track positions in the Ming Hsieh Department of Electrical and Computer Engineering (https://minghsiehece.usc.edu/) in the USC Viterbi School of Engineering. We are looking for outstanding faculty candidates in all areas of Electrical and Computer Engineering at all ranks. The USC Viterbi School of Engineering is committed to increasing the diversity of our faculty and welcome applications from women, those of African, Hispanic and Native American descent, veterans, and individuals with disabilities. While outstanding candidates from all areas of electrical and computer engineering will be considered, candidates with research interests in the following areas are especially encouraged to apply: trust/privacy/ security, experimental quantum engineering, circuits and systems for AI at the edge, computing for ML and AI at scale, energy-efficient sensing and computing, bio-sensors and bio-interface circuits and systems, computational imaging systems, and human-centered machine intelligence.

Open Faculty Positions in ESE Multiple Faculty Positions The School of Engineering and Applied Science at the University of Pennsylvania is growing its faculty by 33% over a five-year period. As part of this initiative, the Department of Electrical and Systems Engineering is engaged in an aggressive, multi-year hiring effort for multiple tenure-track positions at all levels. Candidates must hold a Ph.D. in Electrical Engineering, Computer Engineering, Systems Engineering, or related area. The department seeks individuals with exceptional promise for, or proven record of, research achievement, who will take a position of international leadership in defining their field of study and who will excel in undergraduate and graduate education. Leadership in cross-disciplinary and multi-disciplinary collaborations is of particular interest. We are interested in candidates in all areas that enhance our research strengths in: 1. Nanodevices and nanosystems (nanoelectronics, MEMS/NEMS, power electronics, nanophotonics, nanomagnetics, quantum devices, integrated devices and systems at nanoscale); 2. Circuits and computer engineering (analog, RF, mm-wave, digital circuits, emerging circuit design, computer engineering, IoT, beyond 5G, and cyberphysical systems); 3. Information and decision systems (control, optimization, robotics, data science, machine learning, communications, networking, information theory, signal processing). Diversity candidates are strongly encouraged to apply. Interested persons should submit an online application by following the links above and include curriculum vitae, research, teaching, and diversity statements, and at least three references. Review of applications will begin on January 4, 2022. https://apptrkr.com/2522480

Faculty members are expected to teach undergraduate and graduate Department of Electrical and courses, mentor undergraduate, graduate, and post-doctoral researchers, Computer Engineering and develop a strong funded research program. Interdisciplinary and Graduate School of Engineering and Management collaborative research is strongly encouraged. Applicants must have a Air Force Institute of Technology (AFIT) Ph.D. degree, or the equivalent, in electrical and computer engineering or Dayton, Ohio Faculty Position a related field and a strong research and publication record. Applications must include a letter clearly indicating area(s) Department of specialization, a of Electrical The Department Electrical and Computer Engineering at the Air Force and ofComputer Engineering Institute of Technology is seeking applications for a tenured or tenure-track detailed curriculum vitae, a concise statement of current and future position. All academic will be considered. Applicants must Graduate Engineering andranks Management research directions, and contact information for at least four professionalSchool offaculty have an earned doctorate in Electrical Engineering or a closely affiliated references. Applicants are encouraged to include a succinct statement on disciplineof by the time of their appointment (anticipated 1 September 2022). Air Force Institute Technology (AFIT) fostering an environment of diversity and inclusion. This material should We are particularly interested in applicants specializing in one or more Dayton, Ohio be submitted electronically at https://facultypositions.usc.edu/FAS/ of the following areas: radar cross section analysis, low observables, electromagnetic scattering analysis, computational electromagnetics, application/position?postingId=REQ20108603. Review of applications Faculty Position antennas and propagation, or microwave theory and measurements. will begin immediately. Applications submitted after January 15th, 2022, Applicants having experience in the electromagnetic survivability may not be considered. are highly desired. This atposition The Department of Electricalcommunity and Computer Engineering the Airrequires Forceteaching at the graduate level as wellfor as aestablishing sustaining a strong Institute of Technology is seeking applications tenured and or tenureThe USC Viterbi School of Engineering is among the top tier of Department of Defense relevant externally funded research program with track faculty position. All academic ranks be considered. Applicants a sustainable recordwill of related peer-reviewed publications. engineering schools in the world. It counts 189 full-time, tenure-track

must have an earned doctorate in Electrical Engineering, Computer

The Air Force Institute of Technology (AFIT) is the premier Department faculty members, and is home to the Information Sciences Institute. Engineering, Computer Science, or ainstitution closelyforaffiliated discipline by thetechnology, of Defense graduate education in science, The School is affiliated with the Alfred E. Mann Institute fortheir Biomedical time of appointment (anticipated September 2020). engineering, 1and management, and has a Carnegie Classification Engineering, the Institute for Creative Technologies, and the USC as a High Research Activity Doctoral University. The Department of We are particularly in applicants specializing oneaccredited or moreM.S. of and Ph.D. Electrical and Computer Engineeringinoffers Stevens Center for Innovation. Research expenditures typically exceed interested the following areas: autonomy, artificial intelligence / machine learning, degree programs in Electrical Engineering, Computer Engineering, and $210 million annually. Computer Science as well asand an MS degreeCandidates program in Cyber navigation with or without GPS, cyber security, VLSI. inOperations. USC is an equal opportunity, affirmative action employer. All qualified applicants other areas of will specializationFor aremore alsoinformation encouraged apply. on the to position andThis how position to apply, please visit https://www.afit.edu/ENG/page.cfm?page=1232 receive consideration for employment without regard to requires race, color, religion, sex, at the graduate teaching level as well as establishing and

a strong DoD relevant externally funded research program sexual orientation, gender identity, national origin, protectedsustaining veteran status, disability, Applicants must be U.S. citizens and currently hold or be able with to obtain a security clearance. More information on AFIT and the Department of Electrical and a sustainable of related peer-reviewed publications. or any other characteristic protected by law or USC policy. USC will considerrecord for Computer Engineering can be found at http://www.afit.edu/ENG/. Review of employment all qualified applicants with criminal histories in a Air manner consistent applications will begin onisJanuary 3, 2022. TheDepartment United States Air Force The Force Institute of Technology (AFIT) the premier of is an equal with the requirements of the Los Angeles Fair Chance Initiative for Hiring(DoD) ordinance. affirmative action employer. Defense institution foropportunity, graduate education in science, technology,

70  SPECTRUM.IEEE.ORG  DECEMBER

engineering, and management, and has a Carnegie Classification as a High Research Activity Doctoral University. The Department of Electrical and Computer Engineering offers accredited M.S. and Ph.D. degree 2021programs in Electrical Engineering, Computer Engineering, and Computer Science as well as an MS degree program in Cyber Operations.

Faculty Position in Electrical Engineering Department of Electrical, Computer, and Systems Engineering Case Western Reserve University, Cleveland, Ohio The Department of Electrical, Computer, and Systems Engineering at Case Western Reserve University (CWRU) invites applications for a tenure-track faculty position in Electrical Engineering at the Assistant Professor level. Appointments will be considered for starting dates as early as January 1, 2022. Candidates must have a Ph.D. degree in Electrical Engineering or a related field. The search is focused on the broader area of robotics. The department is particularly interested in candidates with expertise in human-in-theloop and human-collaborative robotic systems. Candidates specializing in machine learning as applied to robotic and other embodied artificially intelligent systems, and/or modeling of human behavior in human-robot systems will be of particular interest. Additional information about the position, department, and application package is available at https://engineering.case.edu/ecse/employment. CWRU provides reasonable accommodations to applicants with disabilities. Applicants requiring a reasonable accommodation for any part of the application and hiring process should call 216-368-3066.

Chair/Distinguished/Full Professor in Urban Big Data and Intelligent Technology (Ref. No.: IOTSC/CDF/BD/09/2021) The University of Macau (UM) is the only public comprehensive university in the Macao Special Administrative Region (MSAR) located at the west bank of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). The GBA is rapidly developing into one of the leading technology and innovation hubs of the world. With a scenic campus of approximately 1 km2 on Hengqin island, UM has achieved significant progress in the past decade as evidenced by its rising international repute, state-of-the-art teaching and research facilities, and the establishment of three State Key Laboratories in microelectronics, Chinese medical sciences, and internet of things for smart city. To support economic diversification of MSAR and deepen collaboration between MSAR and Guangdong Province in Hengqin island, UM will continue to invest in cutting-edge research and develop interdisciplinary programmes in key strategic areas including precision oncology, advanced materials, regional oceanography, artificial intelligence and robotics, data science, cognitive and brain science and economics and finance. Leveraging its ‘4-in-1’ model of education and the largest residential college system in Asia, UM provides all-round undergraduate education, nurturing talent to support social and economic development in MSAR and the GBA as a whole. With unprecedented growth and opportunities for development, UM offers promising career prospects to academics at all levels. It may be noted that English is the working language and the primary medium of instruction at UM. The State Key Laboratory of Internet of Things for Smart City (University of Macau) invites applications for the position of Chair/Distinguished/Full Professor, who will also be a joint faculty member in the Faculty of Science and Technology, in the following disciplines: • Big Data Analysis Technologies • Artificial Intelligence (AI) (e.g. Machine Learning (ML), Intelligent Information Processing) State Key Laboratory of Internet of Things for Smart City (University of Macau) - SKL-IOTSC The State Key Laboratory of Internet of Things for Smart City (University of Macau) is expected to promote smart city development in prospective of IoT, Big Data Technology and Engineering in Macao and inject a fresh impetus to the development of the Greater Bay Area by enhancing research and training in the field and providing technical support plans for improving economic performance, people’s quality of life, and social management. More details about the State Key Laboratory are available from https://skliotsc.um.edu.mo/. Faculty of Science and Technology - FST Faculty of Science and Technology aims to provide programmes for undergraduate and graduate education with quality reaching international standard. It strives to become a research active unit advancing the knowledge of engineering and science, and serves the community and industry as an agent of technological innovation and educational advancement. Currently, about 90 faculty members from diverse international backgrounds serve in this faculty. More details about the Faculty of Science and Technology are available from http://www.fst.um.edu.mo/.

What + If = IEEE

Qualifications 1. A PhD degree in Science, Engineering or related disciplines; 2. Candidates should have considerable experience in academic development planning, curriculum design and research development, and strive to pursue excellence in teaching, research and service with outstanding academic leadership skills for research and development; 3. A distinguished record of internationally-recognized research and scholarship; 4. Demonstrable competence in communication; and 5. English is the working language, while knowledge in Chinese/Portuguese will be an advantage. The selected candidate is expected to assume duty in the 1st quarter of 2022.

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Remuneration A taxable annual remuneration starting from MOP1,210,300 (approximately USD149,420) will be commensurate with the successful applicants’ academic qualification and relevant professional experience. The current local maximum income tax rate is 12% but is effectively around 5% - 7% after various discretionary exemptions. Apart from competitive remuneration, UM offers a wide range of benefits, such as medical insurance, provident fund, on campus accommodation/housing allowance and other subsidies. Further details on our package are available at: https://career.admo.um.edu.mo/learn-more/. Application Procedure Applicants should visit https://career.admo.um.edu.mo/ for more details, and apply ONLINE. Review of applications will commence upon receiving applications and continue until the position is filled. Applicants may consider their applications not successful if they are not invited for an interview within 3 months of application. Office of the Vice Rector (Academic Affairs) University of Macau, Av. da Universidade, Taipa, Macau, China Website: https://career.admo.um.edu.mo/; Email: [email protected] Tel: +853 8822 8061; Fax: +853 8822 2452 The effective position and salary index are subject to the Personnel Statute of the University of Macau in force. The University of Macau reserves the right not to appoint a candidate. Applicants with less qualification and experience can be offered lower positions under special circumstances. ***Personal data provided by applicants will be kept confidential and used for recruitment purpose only*** ** Under the equal condition of qualifications and experience, priority will be given to Macao permanent residents**

http://www.um.edu.mo

DECEMBER 2021  SPECTRUM.IEEE.ORG  71

Electrical Engineering Tenure-Track Faculty Position in Power Electronics The Department of Electrical Engineering (EE) in the School of Electrical Engineering and Computer Science (EECS) at the Pennsylvania State University invites applications for a tenure-track or tenured faculty position. We seek exceptional candidates interested in establishing and sustaining outstanding research programs in modeling simulation and design of power electronics hardware and wide-bandgap devices in power converters for applications including smart grid, electric vehicles, robotics, and data centers. The EE department has a variety of related research activities and state-of-the-art power system facilities including a Real Time Digital Simulator and a Regenerative Grid Simulator. These research activities are connected to university-level research institutes, such as the Institutes of Energy and the Environment (iee.psu.edu) and the Materials Research Institute (mri.psu.edu). Successful candidates will be expected to propose an exciting research plan and to be inspiring teachers at both the undergraduate and graduate levels. Candidates must have a doctorate in electrical engineering, or a related discipline completed before the position's start date. Successful candidates for Assistant Professor will demonstrate a strong research potential and commitment to graduate and undergraduate education. Candidates for Associate Professor will have a strong track record of research, publications, and funding. Candidates for Full Professor will have a track record of research, publications, and funding that distinguishes them nationally and internationally. The EE Department has 40 tenured/tenure-track faculty members, with annual research expenditures of over $18 million. The undergraduate (juniors and seniors) and graduate programs enroll over 450 and 240 students, respectively. The Department is committed to advancing diversity, equity, and inclusion in all of its forms. We embrace individual uniqueness, foster a culture of inclusion that supports both broad and specific diversity initiatives, and leverage the educational and institutional benefits of diversity. We value inclusion as a core strength and an essential element of our public service mission. In welcoming every candidate, we strive to meet the needs of professional families by actively assisting with partner-placement needs. Additional information about the Department can be found at www.eecs.psu.edu. Applications will be considered until the positions are filled. Applicants should submit the following: cover letter, curriculum vita, statement of research, statement of teaching, statement of commitment to fostering diversity and inclusion, and the names and addresses of four references. Please address all inquiries and nominations to Prof. Daniel Lopez ([email protected]), Chair of the Search Committee, or Ms. Taylor Doksa ([email protected]). Application reviews will begin on December 1, 2021, and will continue until the positions are filled. To Apply, visit: https://apptrkr.com/2600150 CAMPUS SECURITY CRIME STATISTICS: For more about safety at Penn State, and to review the Annual Security Report which contains information about crime statistics and other safety and security matters, please go to http://www.police.psu.edu/clery/, which will also provide you with detail on how to request a hard copy of the Annual Security Report. Penn State is an equal opportunity, affirmative action employer, and is committed to providing employment opportunities to all qualified applicants without regard to race, color, religion, age, sex, sexual orientation, gender identity, national origin, disability or protected veteran status.

72  SPECTRUM.IEEE.ORG  DECEMBER 2021

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THE UNT G. BRINT RYAN COLLEGE OF BUSINESS IS NOW SEEKING:

PROFESSOR & G. BRINT RYAN ENDOWED CHAIR OF ARTIFICIAL INTELLIGENCE AND/OR CYBERSECURITY APPLY TODAY:

Chair/Distinguished/Full Professor in Intelligent Sensing and Network Communication (Ref. No.: IOTSC/CDF/ISNC/06/2021) The University of Macau (UM) is the only public comprehensive university in the Macao Special Administrative Region (MSAR) located at the west bank of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). The GBA is rapidly developing into one of the leading technology and innovation hubs of the world. With a scenic campus of approximately 1 km2 on Hengqin island, UM has achieved significant progress in the past decade as evidenced by its rising international repute, state-of-the-art teaching and research facilities, and the establishment of three State Key Laboratories in microelectronics, Chinese medical sciences, and internet of things for smart city. To support economic diversification of MSAR and deepen collaboration between MSAR and Guangdong Province in Hengqin island, UM will continue to invest in cutting-edge research and develop interdisciplinary programmes in key strategic areas including precision oncology, advanced materials, regional oceanography, artificial intelligence and robotics, data science, cognitive and brain science and economics and finance. Leveraging its ‘4-in-1’ model of education and the largest residential college system in Asia, UM provides all-round undergraduate education, nurturing talent to support social and economic development in MSAR and the GBA as a whole. With unprecedented growth and opportunities for development, UM offers promising career prospects to academics at all levels. It may be noted that English is the working language and the primary medium of instruction at UM. The State Key Laboratory of Internet of Things for Smart City (University of Macau) invites applications for the position of Chair/Distinguished/Full Professor, who will also be a joint faculty member in the Faculty of Science and Technology, in the following disciplines: • Internet of things • Intelligent sensing • Communications and networking State Key Laboratory of Internet of Things for Smart City (University of Macau) - SKL-IOTSC The State Key Laboratory of Internet of Things for Smart City (University of Macau) is expected to promote smart city development in prospective of IoT, Big Data Technology and Engineering in Macao and inject a fresh impetus to the development of the Greater Bay Area by enhancing research and training in the field and providing technical support plans for improving economic performance, people’s quality of life, and social management. More details about the State Key Laboratory are available from https://skliotsc.um.edu.mo/. Faculty of Science and Technology - FST Faculty of Science and Technology aims to provide programmes for undergraduate and graduate education with quality reaching international standard. It strives to become a research active unit advancing the knowledge of engineering and science, and serves the community and industry as an agent of technological innovation and educational advancement. Currently, about 90 faculty members from diverse international backgrounds serve in this faculty. More details about the Faculty of Science and Technology are available from http://www.fst.um.edu.mo/. Qualifications 1. A PhD degree in Computer Science, Electrical and Electronic Engineering or related disciplines; 2. Candidates should have considerable experience in academic development planning, curriculum design and research development, and strive to pursue excellence in teaching, research and service with outstanding academic leadership skills for research and development; 3. A distinguished record of internationally-recognized research and scholarship; 4. Demonstrable competence in communication; and 5. English is the working language, while knowledge in Chinese/Portuguese will be an advantage. The selected candidate is expected to assume duty in the 1st quarter of 2022. Remuneration A taxable annual remuneration starting from MOP1,210,300 (approximately USD149,420) will be commensurate with the successful applicants’ academic qualification and relevant professional experience. The current local maximum income tax rate is 12% but is effectively around 5% - 7% after various discretionary exemptions. Apart from competitive remuneration, UM offers a wide range of benefits, such as medical insurance, provident fund, on campus accommodation/housing allowance and other subsidies. Further details on our package are available at: https://career.admo.um.edu.mo/learn-more/. Application Procedure Applicants should visit https://career.admo.um.edu.mo/ for more details, and apply ONLINE. Review of applications will commence in August 2021 and continue until the position is filled. Applicants may consider their applications not successful if they are not invited for an interview within 3 months of application. Office of the Vice Rector (Academic Affairs) University of Macau, Av. da Universidade, Taipa, Macau, China Website: https://career.admo.um.edu.mo/; Email: [email protected] Tel: +853 8822 8061; Fax: +853 8822 2452 The effective position and salary index are subject to the Personnel Statute of the University of Macau in force. The University of Macau reserves the right not to appoint a candidate. Applicants with less qualification and experience can be offered lower positions under special circumstances. ***Personal data provided by applicants will be kept confidential and used for recruitment purpose only*** ** Under the equal condition of qualifications and experience, priority will be given to Macao permanent residents**

http://www.um.edu.mo DECEMBER 2021  SPECTRUM.IEEE.ORG  73

Faculty Position Professor (Tenured) and Center Director Winston Chung Global Energy Center (WCGEC) University of California, Riverside The University of California, Riverside’s (UCR) Marlan and Rosemary Bourns College of Engineering (BCOE) invites applications for a Professor with Tenure position, who will serve as the Director of the BCOE Winston Chung Global Energy Center (WCGEC). The successful candidate will be responsible for managing and leading the Center, in addition to regular faculty duties that involve research and teaching. Successful candidates should have a proven and active record of vibrant leadership experience and externally funded research. While all qualified candidates will be considered, distinguished scientists in academia, senior industry leaders, and senior lead scientists in government research laboratories are particularly encouraged to apply. Apply at https://aprecruit.ucr.edu/JPF01467. Details and application materials can be found at http://www.engr.ucr.edu/about/employment.html. Review of applications will begin December 14, 2021; the position is open until filled. The successful candidate is expected to begin July 1, 2022. Salary is commensurate with experience. Advancement through the faculty ranks at the UC is through a series of structured, merit-based evaluations, occurring every 2-3 years, each of which includes substantial peer input. UCR is a world-class research university with an exceptionally diverse undergraduate student body. Its mission is explicitly linked to providing routes to educational success for underrepresented and firstgeneration college students. A commitment to this mission is a preferred qualification. EEO/AA/ADA/Vets Employer or any other characteristic protected by law.

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University of California COVID-19 Vaccination Program Policy. As a condition of employment, you will be required to comply with the University of California SARS-CoV-2 (COVID-19) Vaccination Program Policy. All covered individuals under the policy must provide proof of full vaccination or, if applicable, submit a request for exception (based on medical exemption, disability, and/or religious objection) or deferral (based on pregnancy) no later than the applicable deadline. For new University of California employees, the applicable deadline is eight weeks after their first date of employment.

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Endowed Professor Position in Electrical and Computer Engineering The Department of Electrical and Computer Engineering at San Diego State University has recently received a $3.5M gift from Eric and Peggy Johnson to establish The fred harris Endowed Chair in Digital Signal Processing. This endowment is to honor emeritus professor fred harris and his legacy of excellence and teaching in digital signal processing. Applications are invited for a tenured, endowed full professor position in the broad area of digital signal processing, with an anticipated start date of August 2022. The areas of interest include, but are not limited to, audio, image, and video processing, signal processing over networks, signal processing in communication systems, biomedical signal processing, and signal processing in cyber-physical systems. The applicants must hold a tenured associate or full professor appointment with a Ph.D. in Electrical Engineering, Computer Engineering, or closely related discipline, with an outstanding track record of scholarship and externally funded research. Additional information and application procedure are available at http://apply.interfolio.com/98514. Inquiries can be sent to Professor Sunil Kumar, Search Committee Chair, at [email protected]. The Department of Electrical and Computer Engineering at San Diego State University also invites applications for a full-time tenure-track faculty position in Renewable Energy at the rank of Assistant Professor, with an anticipated start date of August 2022. Applicants must hold a Ph.D. in Electrical Engineering or a closely related discipline. Qualified applicants must have expertise in renewable energy systems that may include one or more of the following areas: renewable energy systems grid integration and its scientific foundations; advanced power electronics for grid applications and transportation electrification; big data analytics, forecasting, and artificial intelligence for renewable energy applications; and cybersecurity for the electric grid with the high-penetration level of renewable energy resources. Additional information and application procedures are available at https://apply.interfolio.com/98712. Requests for additional information should be directed to Professor Satish Sharma, Search Committee Chair, via email [email protected]. The successful candidate will be expected to establish and maintain a strong externally funded research program, achieve excellence in teaching at the undergraduate and graduate levels, advise students, and participate in departmental governance. The Department of Electrical and Computer Engineering is strongly committed to excellence in both research and teaching at the graduate and undergraduate levels. The department offers an ABETaccredited B.S. degree program in Electrical Engineering and Computer Engineering, M.S. program in Electrical Engineering and Computer Engineering, and a joint Ph.D. program in Electrical Engineering. The ECE Department has over 30 full-time and part-time faculty members, including 3 IEEE Fellows. Research areas in the department includeanalog and digital integrated circuits, computer networks, embedded systems, signal processing and communication systems, antennas, RF and electromagnetic compatibility, machine learning and artificial intelligence, power electronics and smart grid. Additional information about the department and university can be found at http://electrical.sdsu.edu/ and http://www.sdsu.edu. We encourage candidates to send applications as soon as possible. Application review will start from January 15, 2022, and will continue until the position is filled. Candidates should submit a cover letter, curriculum vitae, and teaching and research statements, diversity statement, and names and contact information of three (3) references. SDSU is a Title IX and equal opportunity employer.

DECEMBER 2021  SPECTRUM.IEEE.ORG  75

It’s a Wonderful Light Whether for religious or secular celebrations, twinkling lights mark many of December’s festivities. In recent years, the variety and functionality of electric lights have exploded, abetted by

76  SPECTRUM.IEEE.ORG  DECEMBER 2021

BY ALLISON MARSH

cheap and colorful LEDs and compact electronics. Homeowners can illuminate the eaves with iridescent icicles, shroud their shrubs with twinkling mesh nets, or mount massive menorahs on their minivans. But decorative lights aren’t new. Edward Johnson, vice president of the Edison Electric Light Co., is credited with introducing the first electric Christmas lights on 22 December

1882. At the time, few households had electricity, and so holiday lights remained the playthings of the wealthy elite until electrification and more affordable fixtures (like this creepy 1925 doll’s head bulb) spread to the masses. n FOR MORE ON THE HISTORY OF DECORATIVE LIGHTING, SEE spectrum.ieee.org/ pastforward-dec2021

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