Well, this could be useful: Researchers at the University of California San Diego announced this week that they’ve designed a sort of temporary tattoo that produces power from perspiration — enough to potentially run your smartphone or MP3 player during a workout.

Presenting in San Francisco at the 248th National Meeting & Exposition of the American Chemical Society (ACS), the research team said the device also works as a sensor for monitoring your progress during exercise. The sensor monitors lactate levels, naturally present in perspiration, which can indicate the efficacy of a particular workout routine.

Electronic Telekinesis From Temporary Tattoo

It works like this: A flexible lactate sensor is embedded into the temporary tattoo paper, which is about the size of a large postage stamp. The sensor contains an enzyme that pulls electrons from the lactate, generating a small electrical current. That current then powers a tiny battery. For those doing the math at home, the maximum output delivered in testing was 70 microwatts per square centimeter of skin.

That’s enough to power a digital watch, using the current device, but researchers hope to bump those numbers up by way of more efficient electronics, or possibly just bigger tattoos.

“The current produced is not that high, but we are working on enhancing it so that eventually we could power some small electronic devices,” said researcher Wenzhao Jia in a statement accompanying the release of the research.

Adhesive Tattoo Unlocks Your Phone

The lactate sensor also has potential health benefits. During strenuous exercise, the body activates a process called glycolysis, which produces both energy and lactate. Abnormally high levels of lactate can be an early indicator of heart or lung disease.

The research team tested the device by applying the temporary tattoo to the upper arms of volunteers, who then exercised on a stationary bike for 30 minutes. Interestingly, the volunteers who were less fit — exercising fewer than once a week — actually generated more electrical current than those that worked out more regularly. The researchers said this is likely because less-fit people get fatigued earlier, jump-starting the glycolysis process.

Via EurekAlert

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