An exciting field of research is emerging around wearable devices that can be powered by human sweat, pushed forward by advances made by a team of engineers at UC San Diego. In the past, they have produced a temporary tattoo that worked as a sweat-powered bio-battery, a similarly-powered wearable vitamin C sensor, and a smart shirt that generates electricity via sweat and movement. Their new development, however, can generate power even if the user is asleep or standing still, opening up new possibilities in the wearable space; removing restrictions on when and how wearables can act as power sources makes them more practical, convenient, and accessible.
This new type of wearable—a thin, Band-Aid-like strip—contains a mix of components that can both absorb sweat and convert it into energy. The device consists of carbon foam electrodes that absorb sweat and use embedded enzymes to trigger chemical reactions between lactate and oxygen molecules within it. The energy this generates is then stored in a small capacitor. Fitted to the fingertips, it can take advantage of the more than a thousand sweat glands found there; described by the author of the paper published in Joule as 24-hour factories of perspiration, the fingertips produce up to one thousand times as much sweat as most other areas of the body.
A subject who wore the device on one fingertip for ten hours of sleep generated almost 400 millijoules of energy—enough to power a watch for 24 hours. Compare this to a device that harvests just as you exercise, which generates millijoules for the hundreds of joules expended. The return on investment is very high. And while most of the energy is generated via sweat, a piezoelectric material under the device’s electrodes also generates electricity in response to pressure, so activities like texting provide an extra boost. A video overview of the research as well as their recently published paper was presenting the full study. Their ultimate goal is to make it a practical device, not just a cool proof of concept, and use it to power useful electronics in everyday life.
