Wearable biosensors like smartwatches have become increasingly popular in recent years thanks to their great potential for monitoring people’s health. However, finding a suitable power source for these devices has proven challenging. On one hand, conventional button batteries are too bulky, while on the other, thinner batteries pose power capacity problems.

But what if we could use our own sweat to power these devices? That’s the question that has driven a team of scientists in Japan to develop a prototype biofuel cell that generates electric power from lactate chemicals in the wearer’s sweat.

The novel technology resembles a bandage that one can wear on the arm, alongside the user’s wearable. It contains a water-repellent paper substrate that carries the sweat efficiently towards an array of tiny biofuel cells. Inside the biofuel cells, electrochemical reactions between lactate from sweat and a special enzyme take place, producing a current that’s then transferred to the device.

“We managed to drive a commercially available activity meter for 1.5 hours using one drop of artificial sweat and our biofuel cells,” explains study lead author Professor Isao Dr. Shitanda. “We expect they should be capable of powering all sorts of devices, such as smartwatches and other commonplace portable gadgets.”

According to the study authors, the novel sweat-based powering technology could soon find use in a variety of popular wearable devices, including Fitbit and Apple Watch, and help this growing industry overcome its battery-related problems.