UC Irvine unveils battery-free sweat sensor

UC Irvine researchers said on May 13 that they had built a wireless, battery-free wearable sweat sensor that can track multiple biomarkers continuously without an onboard power source. The device, described in a paper published the same day in Nature Biomedical Engineering, is designed as a flexible skin patch that analyzes molecules in sweat. The researchers said the system can monitor cortisol, glucose, lactate and urea and transmit readings to an Android smartphone or a custom wristwatch-style reader. The work was led by Rahim Esfandyar-pour, an assistant professor of electrical engineering and computer science at the University of California, Irvine. ### How does the device work without a battery? Nature Biomedical Engineering said the sensor is wireless and battery-free, with the system using a passive design rather than a conventional onboard battery pack. UC Irvine said the patch combines sweat sensing with wireless data transmission and was built for use outside laboratory and clinical settings. Rahim Esfandyar-pour said the device’s distinguishing feature is that it can restore its own sensing surface after repeated measurements. (news.uci.edu) He said that regeneration addresses a common problem in wearable biosensing, where molecules remain bound to the sensing layer and reduce performance over time. ### Which biomarkers does it measure? (nature.com) UC Irvine said the patch simultaneously measures four sweat biomarkers: cortisol, glucose, lactate and urea. The university said those markers are associated with stress response, metabolic activity, physical exertion and kidney function. The Nature Biomedical Engineering summary said the system enabled real-time and long-term monitoring of those same four analytes in naturalistic settings. (news.uci.edu) The paper described the platform as a multimodal molecular sweat sensor rather than a single-purpose monitor. ### What makes this different from earlier sweat sensors? The paper said the device incorporates “in situ” regeneration, meaning the sensing components can be refreshed during use instead of being replaced manually after fouling. (news.uci.edu) UC Irvine said the system can also induce perspiration when needed, a feature aimed at improving use outside controlled lab conditions. The researchers said reliable operation was validated for up to 21 days in both ex situ and in situ conditions. (nature.com) That 21-day figure is one of the clearest technical markers in the study because long-term stability has been a recurring challenge for wearable sweat sensors. ### Was this tested on people or only in the lab? Nature Biomedical Engineering said the device showed stable performance in “real-world environments,” and the abstract described monitoring in naturalistic settings for up to 21 days. (nature.com) UC Irvine said the sensor was designed to be worn continuously outside laboratory or clinical settings. The public materials released on May 13 did not present the device as a cleared medical product or announce commercial availability. (preview-nature.com) The university and journal summary framed the work as a research study and a platform for long-term health monitoring. ### What did the researchers say it could be used for? (nature.com) UC Irvine said the platform could support future work in chronic disease management, stress and mental health monitoring, sports performance, preventive medicine, early disease detection research and remote community health monitoring. Those uses were presented by the researchers as potential applications, not as approved clinical indications. (news.uci.edu) Esfandyar-pour said chronic illnesses and stress-related conditions affect hundreds of millions of people worldwide and that consistent monitoring can help with earlier diagnosis and disease management. He said the IREM-W2MS3 system was built to provide stable, ongoing sweat monitoring over long periods. (news.uci.edu) ### What comes next for the project? The next public milestone is the May 13 publication of the full study in Nature Biomedical Engineering, where the device is identified as IREM-W2MS3 and Esfandyar-pour is listed as senior author. UC Irvine said the work was funded by the Samueli School of Engineering, and the university’s release points readers to the peer-reviewed paper for the technical details behind the 21-day monitoring results. (news.uci.edu)