Photo: John Rogers/Northwestern University. A soft, skin‐mounted microfluidic device for capture, collection and analysis of sweat. Sweat could be the next thing wearable devices sense to track your health, researchers say. A new microfluidic skin patch capable of collecting and analyzing sweat has survived tests that included a grueling 104-kilometer bike race.
And the next-generation wearable device has attracted the attention of companies such as cosmetics giant L’Oreal and a major sports beverage maker—not to mention the U.S. military. It could even pave the way for a painfree, bloodless method of prescreening people for diabetes in the future, according to its inventors. 
The flexible sweat sensor collects sweat in a tiny tubing system as it’s worn against the skin. Different sections of the sensor slowly change color as they react to different levels of certain chemicals found within sweat. Any smartphone with the right app can take a picture of the sweat sensor to automatically interpret the color changes and biochemistry of the sweat as certain health signs. To tests the device’s ruggedness, volunteers even wore the sweat sensor during a long-distance, outdoor bicycling race. 
“This is radically different from current-generation wearable devices that are a block of electronics strapped to the body,” says John Rogers, a physical chemist and materials scientist at the University of Illinois at Urbana-Champaign. “This allows a clinical-like precision measurement of health markers that physicians know how to interpret.”
By: spectrum.ieee.org
