Just as a community microgrid combines different power sources with energy storage, a wearable microgrid developed at the University of California San Diego integrates different energy harvesting technologies to power small electronics. The wearable e-textile microgrid system is composed of sweat-powered biofuel cells, motion-powered triboelectric generators and energy-storing supercapacitors.
Each flexible component is screen printed onto a shirt and embedded in a way that optimizes the amount of energy collected. The biofuel cells that harvest energy from sweat and deliver continuous low voltage power are located inside the shirt at the chest as the motion-activated triboelectric generators, which provide high voltage pulses, are positioned outside the shirt on the forearms and sides of the torso near the waist. These devices harness energy from the swinging movement of the arms against the torso while walking or running. Supercapacitors outside the shirt on the chest temporarily store energy from both devices for discharge to power small electronics. Flexible silver interconnections are also printed on the shirt and insulated by waterproof coating.
When tested on a subject during 30-minute sessions that consisted of 10 minutes of exercise followed by 20 minutes of resting, the wearable system was demonstrated to power either an LCD wristwatch or a small electrochromic display.
Future iterations of the wearable microgrid described in Nature Communications might include a system that harvests energy from passive activities, such as sitting at a desk.