A new wearable device turns the touch of a finger into a source of power for small electronics and sensors – even when the wearer is sleeping, reports Tech Xplore. Engineers at the University of California San Diego 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 the strip. It generates power even while asleep or sitting still. This work is a step forward to making wearables more practical, convenient and accessible for the everyday person.” The new wearable energy harvester is described in a paper published July 13 in Joule. The device generates extra power from light finger presses – so activities such as typing, texting, playing the piano, or tapping in Morse code can become sources of energy. The device derives most of its power from sweat produced by the fingertips, which are 24-hour factories of perspiration. Fingertips are packed with more than 1,000 sweat glands and can produce 100 to 1,000 times more sweat than most other areas on the body. 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 to 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 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. The researchers had a subject wear the device on one fingertip while doing sedentary activities. From 10 hours of sleep, the device collected almost 400 millijoules of energy – enough to power an electronic wristwatch for 24 hours. From one hour of casual typing and clicking on a mouse, the device collected almost 30 millijoules.