Cool new printable thermoelectric generators transform body heat into electricity. Printed on paper or cloth, these generators can power wearable devices such as sensors. Thermoelectric generators are nothing new. Until now, though, they were made of inflexible inorganic materials too toxic for use in wearables. Beyond that were the challenges of generating sufficient power from small skin contact areas and minimizing power-sucking internal resistance.

Researchers at the Georgia Institute of Technology designed a device with thousands of tightly packed dots made up of alternating p-type and n-type polymers. Inkjet printers enable the dots to be packed closer together, in turn allowing the conversion of more heat to power per unit. The devices’ symmetrical fractal wiring patterns make it possible to cut them to size to provide specific power needs and manufacture inexpensively. The researchers are exploring printing the circuits on fabric that could be easily integrated into clothing. “We want to integrate our device into the commercial textiles that people wear every day,” said Akanksha Menon, a Ph.D. student in the Woodruff School of Mechanical Engineering at Georgia Tech. “People would feel comfortable wearing these fabrics, but they would be able to power something with just the heat from their bodies.”

The electricity generated by body heat would be in the range of microwatts to milliwatts, enough to power simple heart rate sensors or possibly supplement batteries in more complex devices. And who wouldn’t want a personal air conditioner? By transferring thermal energy from one side of the device to the other in some parts of the body, wearers would have the perception of comfort.  Now researchers are tackling problems such as keeping the generators dry and making them comfortable for wearers. The research, supported by PepsiCo, Inc. and the Air Force Office of Scientific Research, was reported Sept. 28 online in the Journal of Applied Physics.