A new device could turn your sweat into electricity

Researchers from UC San Diego Jacobs School of Engineering have developed an extremely thin and flexible wearable strip that can stick to your fingertip and generate small amounts of electricity. It can then be used as a source of power for small electronics.

The electricity is generated when your finger sweats and can be worn even when sleeping. The device can also generate extra power when you press on it. So you can continue typing on your computer, texting, or even play the piano.

“Unlike other sweat-powered wearables, this one requires no exercise, no physical input from the wearer in order to be useful. This work is a step forward to making wearables more practical, convenient and accessible for the everyday person,” explained co-first author Lu Yin, a nanoengineering PhD student in a release. The findings were published on July 13 in the journal Joule.

Explaining why the fingertip was chosen, Yin explained: “The reason we feel sweatier on other parts of the body is because those spots are not well ventilated. By contrast, the fingertips are always exposed to air, so the sweat evaporates as it comes out. So rather than letting it evaporate, we use our device to collect this sweat, and it can generate a significant amount of energy.”

“We envision that this can be used in any daily activity involving touch, things that a person would normally do anyway while at work, at home, while watching TV or eating,” said Joseph Wang, a professor of nanoengineering and the study’s senior author in the release. “The goal is that this wearable will naturally work for you and you don’t even have to think about it.”

Decoding the device

You can wrap the device around your fingertip like a Band-Aid and electrodes in it absorb the sweat and convert it to electrical energy. There is also a chip underneath these electrodes that helps to generate additional electrical energy when tapped or pressed on.

The team found that when worn for 10 hours of sleep, the device was able to collect 400 millijoules of energy, and during one hour of casual typing on the computer keyboard and clicking a mouse, it collected 30 millijoules. And this is just from one fingertip. Strapping devices on the rest of the fingertips would generate 10 times more energy, the researchers said.

“Free energy” from sleep?
Wearable bioenergy harvesters that used to require quite a workout to generate a small power are no more!
Check out our recent paper on @Joule_CP on wearable biofuel cell harvesting energy from a touch of your fingertip!https://t.co/2zK038cAlt

— Lu Yin (@YinLu_CLT) July 13, 2021

“Compare this to a device that harvests energy as you exercise,” explained Yin. “When you are running, you are investing hundreds of joules of energy only for the device to generate millijoules of energy. In that case, your energy return on investment is very low. But with this device, your return is very high. When you are sleeping, you are putting in no work. Even with a single finger press, you are only investing about half a millijoule.”

The team has planned more studies to combine the device with other energy harvesters and create new self-powered wearable systems.