This Temporary Tattoo Is Actually a Battery That's Powered By Your Sweat

What if the sweat produced by your body could power your gadgets? And what if the connection between the two could be made by a temporary tattoo, the more you sweat, the more power the tattoo generates? That's exactly what researchers at UC San Diego have developed—and one day, it could power your wearables.

Interestingly, the prototype presented at the national meeting of the American Chemical Society yesterday didn't start out as a biobattery. No, rather, the team of engineers from UC San Diego actually went looking for a better way to measure lactate—the stuff your body makes when you're working out hard, and a marker of fitness, among other things.

According to PhysOrg, right now gauging lactate levels requires a blood test. The UC San Diego team went looking for a way to measure it: Sweat. So they did what any tween would do. They tried out a temporary tattoo. By embedding a lactate sensor in the patch, they were able to monitor how much lactate each wearer was generating at any given moment—without any blood tests whatsoever.

So here's the really neat part: The process of measuring lactate involves "removing electrons" from it—which made the research team realize that they had created one half of a battery cell. "We came up with this idea of harvesting energy from the body in a non-invasive manner," says UC nanoengineering professor Dr. Joseph Wang in a new video about the research. All they needed to do was add a cathode. "In this case, the anode contained the enzyme that removes electrons from lactate, and the cathode contained a molecule that accepts the electrons," explains PhysOrg.

The resulting ultra-stripped-down device is what Wang calls "the first example of a biofuel cell that harvests energy from body fluid." The research was published last year, but a brand-new video of the prototype was released to illustrate Wang's presentation of the device to the American Chemical Society this week, showing the process of applying the tattoo and working out with it.

What's so interesting about their prototype is that it's not just a battery—it's a sensor for a specific kind of health measurement that also happens to take advantage of the vast wealth of energy produced by the body. It's a completely symmetrical solution to a tracking gadget: The metric it tracks is the metric that powers it. [YouTube; PhysOrg]