Yei Hwan Jung and Juhwan Lee/UW
The circuits, designed in a serpentine shape, interact wirelessly with other devices and can be worn like temporary tattoos.
A team of UW scientists has made a breakthrough creating stretchable integrated circuits that can be worn, paving the way for a number of futuristic devices, perhaps one day even an “Iron Man” suit.
The engineers published their findings in the journal Advanced Functional Materials in May. According to Zhenqiang “Jack” Ma, the Vilas Distinguished Achievement Professor in electrical and computer engineering who led the project, it marks the beginning of a new phase where technology is finally realizing the prospect that “everything will be interconnected.”
Describing the high-frequency, wearable integrated circuits as a “platform” for future advancement in a myriad of industries, Ma says the device affixes to the skin like a bandage or a temporary tattoo and acts as a transmission line with high-speed 5G network capabilities. It can then “be reshaped or redesigned” to wirelessly connect other devices performing a specific function — for example, eliminating the need for hospital patients to be physically wired to multiple devices to read their vital signs.
While Ma says “quite a few people” have already released variations of wearable integrated circuits, they’ve largely been low-speed, low-frequency models. Ma was convinced he and his team could solve the missing link and introduce a much faster version into the market.
After experimenting with about 200 different designs over more than two years, computer and electrical engineering doctorate students Yei Hwan Jung and Juhwan Lee, alongside other team members, tested and developed a double-wired transmission line design in a twisted, serpentine shape, an approach much more “unusual” than the typical single-wire or parallel-wire style, Lee says. Electromagnetic waves transmitted through the line are coupled together, minimizing interference and frequency loss even when the device is bent, folded and stretched.
The result is a device composed of tiny layers of silicone polymers and criss-crossing, interlocking metal blocks so thin — about 0.02 millimeters thick, or a “fraction of the thickness of your hair,” Jung says — it could also be implanted non-invasively in the body.
Venturing into uncharted territory presented many challenges, especially with “no resources to look at.” Once the design was finalized, the team had to figure out how to stretch the device and measure it simultaneously, Lee said.
“Even the measuring tools are not designed for such unconventional devices,” Jung adds. “For this one, you have to test whether it’s performable when it’s stretched, and find out when it fails. That took a lot of time.”
Ma says his team spent hundreds of “very costly” hours in the lab at the Wisconsin Energy Institute — an expense alleviated by a Presidential Early Career Award for Scientists and Engineers grant Ma received in 2008 from the Department of Defense. He’s since used more than $1 million in funding toward numerous “high-impact” projects, including the world’s fastest flexible transistor and a biodegradable, wood-based computer chip created in collaboration with the U.S. Department of Agriculture
Ma filed a patent for the stretchable integrated circuits through the Wisconsin Alumni Research Foundation earlier this year — he has about 30 patents through WARF, more than any other individual or department, and expects to have 40 by early next year. Since filing the patent, Ma and his team have been in touch with both Mayo Clinic and the Department of Defense, on potential applications for the device. One “vision” of Ma’s is to attach it to soldiers’ uniforms in order to power “sophisticated wireless communication much better than a phone” over long distances — or, in Lee’s words, aim even higher and make “an Iron Man suit.”
But those visions are hardly limiting on the device’s potential in other sectors, especially considering the relatively cheap cost of materials needed to produce it.
“The defense application here can be easily moved to civilian and commercial sectors, because the performance is so much better,” Ma explains. “You save power, you get more functionalities, and everything becomes wireless.”
Ma and his team are developing other projects, including researching ways vision-impaired people can potentially regain their sight by regrowing photoreceptor cells; they are also looking into how people could control their artificial limbs through the triggering of electrodes in the brain.
And while they’re versed in every minute detail of the discoveries they share with the world, Ma says how those devices are ultimately used is “beyond [their] imagination.”
“Our goal is to develop the platform technology, and then enable everything that people want to do in the future,” he adds. “We feel like through our work, we really created a new window of exploration where we can go forward.”
