This Skin Patch Reads Your Sweat And Knows If You’re Dehydrated

Tough workout? Your future exercise tracker will give you more data

Credit: J. Rogers, Northwestern University
Nov 23, 2016 at 2:00 PM ET

Your Fitbit can tell you how many miles you biked and what your heart rate was, but your body is pouring out so much data that these devices can’t measure — and it’s in your sweat. With a new skin patch, future wearable devices might give a read out of your sweat that gives better feedback on your workout.

Researchers from University of Illinois at Urbana-Champaign have created a wireless stick-on patch that measures sweat to monitor data like hydration level, according to a study published Wednesday in Science Translational Medicine.

A person’s sweat contains molecules that indicate their overall health. For example, electrolytes, such as sodium and chloride, are lost during exercise and can indicate how well an athlete will recover after a workout And lactate levels, produced when the body is working hard, can reflect if an athlete will soon hit an exhaustion wall. Though there aren’t yet any wearables on the market to detect sweat, scientists have also used sweat analysis for decades, often to diagnose diseases such as cystic fibrosis (the disease causes people with CF to have more salt in their sweat).

This patch, made of a flexible, transparent silicone, contains five fluid-detection systems, each a different color for different elements of sweat (orange is lactate content, red is pH, blue is chloride, yellow is glucose; the blue serpentine channel in the device is overall sweat level) that change color as the device fills. To read the patch, the researchers used a smartphone to take a picture of the device; software analysis after the fact indicates the levels of the compounds it detected.

In lab-based tests, the device yielded just as reliable and specific as traditional sweat analysis. The researchers also tested their patch on 12 individuals who wore the patch on their forearm or lower back during a long-distance bike race in Tucson, Arizona, showing that it could be worn comfortably for several hours on end.

Other researchers are also working on sweat-based wearable sensors for similar purposes. But the results of this study indicate that this may be the most accurate and user-friendly one to date.

The researchers hope to further develop their device to do readouts in real-time for athletes. They also hope to make their device useful in a medical capacity, to help diagnose diseases where biomarkers can be found in sweat, or for other bodily fluids such as tears and saliva.