A wearable sensor developed by Stanford researchers can diagnose diseases by measuring molecular constituents of sweat, such as chloride ions and glucose.
A wristband–type wearable sweat sensor could transform diagnostics and drug evaluation for cystic fibrosis, diabetes and other diseases.

The sensor collects sweat, measures its molecular constituents and then electronically transmits the results for analysis and diagnostics, according to a study led by researchers at the Stanford University School of Medicine, in collaboration with the University of California–Berkeley. Unlike old–fashioned sweat collectors, the new device does not require patients to sit still for a long time while sweat accumulates in the collectors.

“This is a huge step forward,” said Carlos Milla, MD, associate professor of pediatrics at Stanford.

The study was published online April 17 in the Proceedings of the National Academy of Sciences journal. Milla shares senior authorship with Ronald Davis, PhD, professor of biochemistry and of genetics at Stanford. Former Stanford postdoctoral scholar Sam Emaminejad, PhD, and UC–Berkeley postdoctoral scholar Wei Gao are co–lead authors.

The two–part system of flexible sensors and microprocessors sticks to the skin, stimulates the sweat glands and then detects the presence of different molecules and ions based on their electrical signals. The more chloride in the sweat, for example, the more electrical voltage is generated at the sensor’s surface. The team used the wearable sweat sensor in separate studies to detect chloride ion levels – high levels are an indicator of cystic fibrosis – and to compare levels of glucose in sweat to that in blood. High blood glucose levels can indicate diabetes.

Conventional methods for diagnosing cystic fibrosis – a genetic disease that causes mucus to build up in the lungs, pancreas and other organs – require that patients visit a specialized center and sit still while electrodes stimulate sweat glands in their skin to provide sweat for the test. The electrodes can be annoying, especially for kids, in whom CF is most often diagnosed, Milla said. Then, children have to sit still for 30 minutes while an instrument attached to their skin collects sweat. Even then, the test isn’t over, he said. Families wait while a lab measures the chloride ions in the sweat to determine if the child has cystic fibrosis.

Milla said this cumbersome method hasn’t changed in 70 years. By comparison, the wearable sweat sensor stimulates the skin to produce minute amounts of sweat, quickly evaluates the contents and beams the data by way of a cellphone to a server that can analyze the results. The test happens all at once and in real time, Milla said, making it much easier for families to have kids evaluated.