Earlier this year, we wrote about a breakthrough study from the University of Tokyo, where scientists invented a sustainable smart-watch battery that uses nothing but the wearer’s sweat to generate electricity.

Following in the footsteps of that innovation, engineers at the University of California, San Diego have developed a device that harvests sweat from the tip of your fingers, with incredible performance efficiency. The novel technology could potentially help power a number of small wearable electronics. The device is a biofuel cell that is powered by lactate, a compound found in sweat. The electrodes in the device use enzymes that trigger chemical reactions between lactate and oxygen to generate electricity. 

Typically, human-powered wearables require a great deal of exercise to fully work. This novel invention, however, can just produce energy during the night, when you’re asleep. The device involves a series of one-centimeter-squared finger pads made of flexible foam that contains a hydrogel. The hydrogel enables the technology to absorb as much sweat as possible.

According to Euronews, the device can operate without any physical activity and is even able to successfully produce 300 millijoules (mj) of power per square centimeter of skin during a 10-hour sleep. The process essentially requires nothing else but access to the sweat glands at the end of our fingertips.

Now you might be wondering why the researchers would choose our fingers to source the sweat instead of, let’s say, our armpits. Well, the choice is quite well reasoned — our fingertips have the highest concentration of sweat glands anywhere on the human body, including under the arms, or on our backs.

The team now plans to integrate the new technology into actual wearables, starting with a pair of smart gloves. Eventually, the researchers plan to use the technology to power devices in a wireless capacity by using its sensory capabilities to connect to our smartphones.

“There’s a lot of exciting potential,” says senior author Joseph Wang. “We have ten fingers to play with.”