Tracking health is no sweat with new device

Wearable electronic analyzes chemicals in perspiration

health tracker

TECH MERGER  A new health tracker can analyze chemicals in sweat by combining flexible sensors with a traditional electronic circuit board.

W. Gao et al/ Nature 2016

Fitness trackers just got an upgrade.

A new electronic health-monitoring device can sense a person’s temperature, analyze chemicals in a drop of sweat, and send the data wirelessly to a smartphone app — all in a package about the size of a few postage stamps.

The gadget could help athletes instantly gauge their hydration level, or give scientists an easy and noninvasive way to collect data for medical studies.

Researchers have built sweat sensors before, but the new device “just represents a whole nother level of sophistication,” says materials scientist John Rogers of the University of Illinois at Urbana-Champaign.

Previous sensors have detected only a single chemical. The new sensor can measure four chemicals — glucose, lactate, sodium and potassium — simultaneously ­and in real time, Ali Javey and colleagues report January 27 in Nature.

Traditional electronics rely on “brains” made of tiny circuits laid out on silicon chips. “But the problem with silicon chips is that they’re way too small and rigid,” says Javey, an electrical engineer at University of California, Berkeley.They’re great for data processing — not for making sensors that hug the skin. For that, rubbery electronics that can twist and flex are ideal (SN: 11/17/12, p. 18). But they don’t have the processing power of silicon-based versions.

So scientists typically use flexible electronics for sensing and let traditional electronics do the “thinking,” and connect the two via long wires, says Dae-Hyeong Kim, a bioengineer at Seoul National University in South Korea. Javey’s team merged the two technologies together into a single, wireless device. “This level of integration is amazing,” Kim says.

The researchers tested their sweat-sensing device on volunteers in and out of the lab. In one test, 12 volunteers wore the device tucked into a headband while running outdoors. Six runners drank water every five minutes; the other six didn’t drink at all. After about an hour and a half, the sweat sensor picked up a sign of dehydration in the nondrinkers: an uptick in sodium levels.

Javey says tweaking the device could make it useful beyond athletics: Researchers could one day use it to diagnose lead poisoning in children without drawing blood, or perhaps even to detect molecules in sweat that are linked to depression. 

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