Researchers’ Sweat-Based Sensor May Help Improve Sleep Quality

University of Texas at Dallas researchers, in partnership with Texas-based biotech company EnLiSense, have demonstrated a pioneering wearable perspiration-based sensor that measures two key hormones that regulate the body's sleep-wake cycle.

The electrochemical sensor continuously monitors cortisol, which promotes wakefulness, and melatonin, which signals the body to sleep. The bioengineers published a proof-of-validation study in the October issue of Biosensors and Bioelectronics: X. Using EnLiSense's Corti wearable device platform, the study is the first to demonstrate circadian rhythmicity of cortisol and melatonin levels measured through sweat. EnLiSense is commercializing the CORTI sensor platform.

Researchers said the technology offers a new approach to measuring the hormones when consumer interest in wearables to monitor sleep quality is growing.

"Precise and continuous evaluation of cortisol and melatonin is essential for understanding and managing circadian health," said Annapoorna Ramasubramanya, a biomedical engineering doctoral student and first author of the study. "Current methods involving salivary samples, however, are inconvenient for continuous monitoring."

Saliva samples are the gold-standard source for evaluating cortisol and melatonin levels. In sleep studies, patients must be awakened periodically so technicians can collect samples. The new technology could simplify the process by making it possible to measure the hormones continuously through passive sweat, the sweat naturally produced by the body without external stimulation.

In September, Ramasubramanya received a New Investigator Award at the World Sleep Congress 2025 in Singapore. The event was organized by the World Sleep Society, a nonprofit for professionals in sleep medicine and research.

Ramasubramanya's contribution to the project was to translate the device data to establish thresholds for use in stress, wellness and circadian rhythm monitoring.

Dr. Shalini Prasad, professor and department head of bioengineering in the Erik Jonsson School of Engineering and Computer Science and corresponding author of the study, recruited Ramasubramanya to work in her Biomedical Devices and Nanotechnology Lab after Ramasubramanya impressed her in her Nanotechnology and Sensors class.

"What Annapoorna has done is take the data reported by the device and contextualize the chemistry so you can explain what the information means," said Prasad, a Cecil H. and Ida Green Professor in Systems Biology Science. "These are the kinds of questions we couldn't answer before, and she has been able to make that possible."

"What Annapoorna has done is take the data reported by the device and contextualize the chemistry so you can explain what the information means. These are the kinds of questions we couldn't answer before, and she has been able to make that possible."

Dr. Shalini Prasad, a Cecil H. and Ida Green Professor in Systems Biology Science

In the study, 43 participants wore the sweat-based sensor for 48 hours. Researchers collected saliva samples 12 times during the experiment to compare them with results from the sensor. The results from both methods were similar, demonstrating the accuracy of the sensor.

The Corti device, developed by EnLiSense, contributes to chronobiology, a branch of biology concerned with natural physiological rhythms and cycles, by providing objective data that people could use to improve the quality of their sleep, Prasad said. Existing commercially available wearable devices provide estimates of sleep duration and stages based on movement, heart rate and sometimes body temperature.

"In the world we live in today, electronics play such an important role in our sleep quality. Our sleep patterns are changing. We don't have to be shift workers or flying airplanes to throw off our circadian rhythms. Just the fact that we live with so much technology has changed the way and the amount of sleep we are getting," Prasad said. "Mental health issues are also related to sleep quality."

Ramasubramanya's interest in circadian data analysis comes from an unexpected source: playing the veena, an Indian stringed instrument similar to the sitar. Ramasubramanya, who is from Bengaluru, has played Carnatic music, a classical music tradition from south India, for 16 years. The relationships between melody and rhythm in Carnatic music are built on mathematical principles such as ratios, divisions and patterns. These same principles were applied in the study.

"That instigated my interest in applying the principles of math and physics to the circadian data analysis, because playing the veena has a lot to do with how you're going to pull the string and how it's going to vibrate and sustain the sound," said Ramasubramanya, who studied computer engineering as an undergraduate in India. "How fast I'm going to play notes and the frequency I'm going to play certain notes is the mathematical part of it."

Prasad said Ramasubramanya stands out for her openness to learning from her mistakes.

"She's very willing to take feedback," Prasad said. "That makes her a researcher who can go far."

Study co-authors include research scientist Dr. Preeti Singh, research associate Dr. Kai-Chun Lin and Dr. Sriram Muthukumar, co-founder of EnLiSense, an Allen, Texas, company that develops lifestyle-based sensors and devices. Prasad also is a co-founder of EnLiSense.

Media Contact: Kim Horner, UT Dallas, 972-883-4463, [email protected], or the Office of Media Relations, UT Dallas, (972) 883-2155, [email protected].