Reviewed by Lexie CornerApr 22 2025
In a study published in Nature Electronics, researchers demonstrated how their sweat sensor uses electrodermal activity (EDA), a skin electrical property, to monitor hydration levels during physical exercise.
The multimodal sweat sensor, placed on the skin, features a microfluidic channel and breathable μ-lace electrodes. The device’s compact form factor and ability to conform closely to the skin enable comfortable and stable wear. Image Credit: Image courtesy of the researchers
Dehydration can sneak up on anyone. Whether jogging or sitting at a computer, it's easy to lose track of fluid intake. However, a new, small sweat sensor could soon help solve this problem. Designed by UC Berkeley researchers, this wearable device can detect changes in hydration levels and signal when it's time to take a break and drink some water.
Until now, electrodermal activity (EDA), or skin conductance, was primarily considered useful for evaluating mental stress. These findings could expand EDA's role in physiological monitoring and, eventually, provide a simple solution to help prevent dehydration.
This work opens the door to everyday, passive monitoring of hydration and stress using familiar wearable devices like smartwatches.
Ali Javey, Study Principal Investigator and Professor, Electrical Engineering and Computer Sciences and Materials Science and Engineering, University of California, Berkeley
According to Seung-Rok Kim, a postdoctoral researcher in the Department of Electrical Engineering and Computer Sciences and co-lead author of the study, the device's novel design is essential for its effectiveness and usability.
“Because our sensor is thin, breathable, and comfortable to wear, it can be seamlessly integrated into the back of a watch or fitness tracker to provide real-time feedback without bulky equipment or disposable components. This makes it easier for individuals to continuously track their physical exertion, hydration status, and emotional stress throughout the day,” stated Kim.
Co-lead author Yifei Zhan, a graduate researcher in the Department of Electrical Engineering and Computer Sciences, noted that athletes could use the device to prevent dehydration during training, while office workers or students could use it to monitor stress and improve focus and balance.
By making physiological sensing more accessible and personalized, this technology empowers people to make better decisions about exercise, rest, and mental well-being.
Yifei Zhan, Study Co-Lead Author and Graduate Researcher and, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley
The scientific community has long debated the usefulness of EDA for tracking physical activity, primarily because intense perspiration during exercise can saturate the skin and interfere with the signal, making it difficult for sensors to detect electrical changes. The researchers addressed this challenge by using breathable, water-permeable electrodes that prevent sweat from accumulating on the skin’s surface.
To resolve a significant limitation of traditional commercial electrodes, which are non-permeable and trap perspiration beneath the sensor, the researchers developed and tested three types of water-permeable electrodes: carbon fiber fabric electrodes, spiral metal wire electrodes, and micro-lace electrodes. They monitored EDA on various body areas while subjects engaged in physical and mental tasks, such as cycling and IQ tests.
“By comparing the EDA signals with localized sweat measurements and overall fluid loss from body weight, we evaluated how well each electrode tracked sweat production,” said Zhan. “This approach allowed us to identify effective sensor designs and body sites for using EDA to monitor hydration and to distinguish between signals caused by physical exertion and those driven by mental stress,” added Zhan.
The study’s results indicate that skin conductance can reliably reflect perspiration rate and hydration levels during various mental and physical activities. The researchers now plan to explore how environmental factors like temperature, humidity, and skin type affect the EDA signal.
“These efforts will help improve both the accuracy and personalization of next-generation wearable health monitors,” stated Kim.
In addition to Kim and Zhan, Noelle Davis, a graduate researcher in the Department of Electrical Engineering and Computer Sciences, co-authored the study. Kim, Davis, and Javey are also affiliated with the Materials Science Division of the Lawrence Berkeley National Laboratory.
Journal Reference:
Kim, S.-R., et al. (2025). Electrodermal activity as a proxy for sweat rate monitoring during physical and mental activities. Nature Electronics. doi.org/10.1038/s41928-025-01365-7