Stretchable fuel cell is powered by sweat

A new flexible fuel cell stretches with movement and is powered by human sweat.

With the advent of wearable technology comes the need for novel ways to efficiently power the increasing number of devices that are becoming available. Some recent developments have included a micro-battery powered by saliva and a device that can generate energy from movement. However, one limiting factor has been the flexibility of the energy source. Now, a team of engineers at the University of California at San Diego have developed stretchable fuel cells that extract energy from sweat.

The engineers at the university’s Center for Wearable Sensors used lithography techniques to print 3D cathode and anode rays as rows of dots – half of the dots make up the anode and half the cathode. These are connected by spring-like structures, allowing flexibility without deforming the anode and cathode. Researchers then screen printed layers of an enzyme that oxidises the lactic acid in sweat, to generate a current, on top of the anode and cathode dots. As the user sweats, the cell generates a current that can then be used to power small devices such as LEDs and Bluetooth. To increase power density, a 3D carbon nanotube structure was also screen printed on top of the anodes and cathodes. This allows more of the enzyme to be placed on each dot.

While the flexible biofuel cell has successfully been used to light up LEDs in the lab, researchers report that the cell only works for a short time, as the lactic acid in sweat becomes diluted during exercise. Researchers are now working on a way to store the energy generated while the lactic acid concentration is high, and then release it gradually. What uses might there be for a fuel cell that can generate energy from sweat?