VIDEO: This Temporary Tattoo Will Soon Be Creating Power From Body Sweat To Charge Your Smartphone

A tattoo biosensor (enlarged above) detects lactate levels during exercise; a biobattery using the technology could power electronics. Image: Joseph Wang

Working up a sweat exercising may not only be good for you but it could also power your electronic devices.

Researchers announced they have designed a sensor in the form of a temporary tattoo which can both monitor a person’s progress during exercise and produce power from their perspiration.

The team described the approach in a presentation to the 248th National Meeting & Exposition of the American Chemical Society, the world’s largest scientific society, in San Francisco.

The device works by detecting and responding to lactate which is present in sweat.

The more intense the exercise, the more lactate the body produces.

During strenuous physical activity, the body needs to generate more energy, so it activates a process called glycolysis which produces energy and lactate, the latter of which scientists can detect in the blood.

Professional athletes monitor their lactate levels during performance testing as a way to evaluate their fitness and training program.

Dr Wenzhao Jia, a postdoctoral student in the lab of Dr Joseph Wang, at the University of California San Diego, and colleagues developed a faster, easier and more comfortable way to measure lactate during exercise.

They imprinted a flexible lactate sensor onto temporary tattoo paper.

The sensor has an enzyme which strips electrons from lactate, generating an electrical current.

The researchers applied the tattoo to the upper arms of 10 healthy volunteers.

Then the team measured the electrical current produced as the volunteers exercised at increasing resistance levels on a stationary bicycle for 30 minutes. In this way, they could continuously monitor sweat lactate levels over time and with changes in exercise intensity.

The team then made a sweat-powered biobattery. Batteries produce energy by passing current, in the form of electrons, from an anode to a cathode. In this case, the anode contained the enzyme which removes electrons from lactate, and the cathode contained a molecule that accepts the electrons.

People who were less fit (exercising fewer than once a week) produced more power than those who were moderately fit (exercising one to three times per week).

Enthusiasts who worked out more than three times per week produced the least amount of power.

The researchers say that this is probably because the less-fit became fatigued sooner, causing glycolysis to kick in earlier, forming more lactate. The maximum amount of energy produced by a person in the low-fitness group was 70 microWatts per square centimetre of skin.

“The current produced is not that high, but we are working on enhancing it so that eventually we could power some small electronic devices,” Jia says.

Watch the biobattery in action:

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