Future health monitors and other wearable devices could be powered by an innovative strip that generates electricity from the sweat on your fingertips and simple taps and presses.
The flexible 1cm squared device consists of a thin piece of foam connected to a circuit with electrodes and generates small amounts of current from a person’s sweat or when pressed.
Attaching the devices to a person’s fingertips allows them to produce electricity while typing, texting, playing the piano or even sleeping, researchers from the University of California found.
The team observed how a device worn on a single fingertip collected close to 4,000 millijoules of energy – enough to power an electronic wristwatch for 24 hours – during 10 hours of sleep, and almost 30 millijoules from an hour of typing and clicking on a computer mouse.
They used the collected energy to run a sensor and a connected display, and two other sensors designed to detect vitamin C and sodium respectively – demonstrating how the tech could power future health-monitoring wearables.
The fingertips are among the sweatiest spots on the human body, with each tip containing more than 1,000 sweat glands, according to the report, published in journal Joule.
As fingertip sweat usually evaporates on contact with air, the device’s carbon foam electrodes absorb it and use enzymes to trigger chemical reactions between lactate and oxygen molecules to produce electricity.
Physical taps and presses are converted into current thanks to a layer of piezoelectric material underneath the electrodes. The energy is then stored in a small capacitor and discharged to other devices.
“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 the study’s senior author Joseph Wang, a professor of nanoengineering at UC San Diego Jacobs School of Engineering.
“The goal is that this wearable will naturally work for you and you don’t even have to think about it.”