A prototype wearable can continuously monitor several health stats — glucose, alcohol, and lactate levels — simultaneously in real time. The device is about the size of a stack of six quarters. It is applied to the skin through a Velcro-like patch of microscopic needles, or microneedles, that are each about one-fifth the width of a human hair.
Wearing the device is not painful — the microneedles barely penetrate the surface of the skin to sense biomolecules in interstitial fluid, which is the fluid surrounding the cells beneath the skin. The device can be worn on the upper arm and sends data wirelessly to a custom smartphone app.
The wearable consists of a microneedle patch connected to a case of electronics. Different enzymes on the tips of the microneedles react with glucose, alcohol, and lactate in interstitial fluid. These reactions generate small electric currents, which are analyzed by electronic sensors and communicated wirelessly to an app that the researchers developed. The results are displayed in real time on a smartphone.