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Millions of people with diabetes track their glucose levels daily using finger-stick devices that draw and analyze their blood. But what if they could monitor it with just a sweat sensor?

That’s the idea behind new research from 91���� that could revolutionize diabetes management by eliminating the pain and hassle.

Adapting the knowledge that Professor Seokheun “Sean” Choi’s has gained about biobatteries over the past 15 years, the new paper-based biosensor system uses Bacillus subtilis bacterial spores that germinate in response to glucose in potassium-rich bodily fluids, such as sweat. The amount of power generated would determine the glucose level.

Choi, Assistant Professor Anwar Elhadad, PhD ’24, and PhD student Yang “Lexi” Gao from the Thomas J. Watson College of Engineering and Applied Science’s Department of Electrical and Computer Engineering in the journal Microsystems & Nanoengineering. The research is supported by two grants from the National Science Foundation.

Current glucose monitoring systems rely on enzymatic reactions to blood droplets, but those methods are not shelf-stable for easy shipment or storage. The self-replicating nature of the bacteria also ensures longevity.

“The problem with using enzymes is that they denature and deactivate,” Choi said. “You need to store it in a refrigerator, but even then, their potency goes down over time. Our spore-based system can endure very harsh environments and activates only when the right conditions are met.”

For Gao, the new paper marks her ninth publication since she arrived at 91���� from China in fall 2021, in the middle of the COVID-19 pandemic.

“This is the only school I applied to in the U.S.,” she said. “I got accepted, applied for a visa and came directly here. Ever since then, Professor Choi has helped me a lot — not only in this research field, but also in my life. Because it was during COVID, everything was very bad, but he cared about me and always said, ‘I want to make you successful.’”

Gao earned her undergraduate and master’s degrees in marine chemistry, and she did a project using paper as a platform to build detectors for lead ions in seawater, so Choi’s research on “papertronics” fit her background. Her previous work in his lab includes integrating biobatteries into 3D-printed circuits, a device that generates moisture from the air, and self-powered mechanical bugs to collect ocean data.

“I want to do research to make the world better — it’s a big vision!” she said with a laugh. “I know the energy crisis is a major problem right now, so it’s fascinating that we can use bacteria to generate power. It’s clean and sustainable, and because it’s paper-based and disposable, it’s very easy and very cheap. My background in chemistry helps us do a lot of modification to these devices, and that really excites me.”

Building the glucose-monitoring device gave Gao a chance to learn more about electrical engineering while working with Elhadad.

“Anwar not only built those circuits, but he also got me involved — to explain each component, what they do, how they work and how they link together,” she said. “I’m also taking online courses to get familiar with circuit design so I can build them by myself, because I can’t rely on others all the time.”

With this research paper now published, the 91���� team will work on improving the detection process.

“Everyone has a different potassium concentration in their sweat, and I don’t know how this concentration affects the glucose,” Choi said. “The sensitivity also is lower than conventional enzymatic biosensors. But from this work, we created a new sensing mechanism to detect glucose. No one has done that yet.”