A flexible, human sweat-powered fuel cell has been designed by researchers from the University of California San Diego The wearable biofuel cell powers a diode attached to the black armband on the forearm. Source: Xiaohong Chen/CNRS/Université Grenoble Alpesand Université Grenoble Alpes-CNRS, France.

Powered by sweat, the fuel cell is ideal for wearable electronics. Multi‐walled carbon nanotubes serve as the electrode material in the biofuel cells, which deliver an open circuit voltage of 0.74 V and a high‐power density of 520 µW/cm². Flexible connectors are screen-printed directly onto the material, which also embeds enzymes and cross-linked polymers.

The device conforms to the skin and supplies electric power by oxygen reduction and by oxidation of lactate in perspiration. Tests demonstrated sufficient power production to operate an LED when connected with a voltage booster, and to generate a maximum power of 450 µW when worn by a volunteer.

The next goal is to increase the fuel cell voltage to power large portable devices.