A wearable device turns the touch of a finger into a source of power for small electronics and sensors. Engineers have developed a thin, flexible strip that can be worn on a fingertip and generate small amounts of electricity when a person’s finger sweats or presses on it.
The sweat-fueled device generates power even while the wearer is asleep or sitting still. This is potentially a big deal for the field of wearables because researchers have now figured out how to harness the energy that can be extracted from human sweat even when a person is not moving.
The device also generates extra power from light finger presses. It derives most of its power from sweat produced by the fingertips, which are 24-hour factories of perspiration. The fingertips are one of the sweatiest spots on the body; each one is packed with over a thousand sweat glands and can produce between 100 to 1000 times more sweat than most other areas on the body.
But not just any sweat-fueled device can work on the fingertip. Collecting sweat from such a small area and making it useful required some innovative materials engineering. The researchers had to build different parts of the device to be super absorbent and efficient at converting the chemicals in human sweat into electrical energy.
The device is a thin, flexible strip that can be wrapped around the fingertip like a Band-Aid. A padding of carbon foam electrodes absorbs sweat and converts it into electrical energy. The electrodes are equipped with enzymes that trigger chemical reactions between lactate and oxygen molecules in sweat to generate electricity. Underneath the electrodes is a chip made of a piezoelectric material, which generates additional electrical energy when pressed.
As the wearer sweats or presses on the strip, the electrical energy gets stored in a small capacitor and is discharged to other devices when needed.