Wearable thermoelectric generators move closer to reality

October 11, 2017 // By Nick Flaherty
Researchers at the Georgia Institute of Technology backed by beverage company PepsiCo have demonstrated paper-based wearable thermoelectric generators that harvest energy from body heat to power simple biosensors.

The researchers used conducting polymers in symmetrical fractal wiring patterns to cut the size of the generators needed to provide the voltage and power requirements for specific applications. The modular generators could be inkjet printed on flexible substrates, including fabric, and manufactured using inexpensive roll-to-roll techniques.

"The attraction of thermoelectric generators is that there is heat all around us," said Akanksha Menon, a researcher in the Woodruff School of Mechanical Engineering at the Georgia Tech (above). "If we can harness a little bit of that heat and turn it into electricity inexpensively, there is great value. We are working on how to produce electricity with heat from the body."

The team in the laboratory of Assistant Professor Shannon Yee designed a device with thousands of dots composed of alternating p-type and n-type polymers in a closely-packed layout. Their pattern converts more heat per unit area due to large packing densities enabled by inkjet printers. By placing the polymer dots closer together, the interconnect length decreases, which in turn lowers the total resistance and results in a higher power output from the device.

"Instead of connecting the polymer dots with a traditional serpentine wiring pattern, we are using wiring patterns based on space filling curves, such as the Hilbert pattern - a continuous space-filling curve," said Kiarash Gordiz, a fellow researcher. 

The researchers use commercially-available p-type materials, and are working with chemists at Georgia Tech to develop better n-type polymers for future generations of devices that can operate with small temperature differentials at room temperatures. 

"One future benefit of this class of polymer material is the potential for a low-cost and abundant thermoelectric material that would have an inherently low thermal conductivity," said Yee, who directs the lab. "The organic electronics community has made tremendous advances in understanding electronic and optical properties of polymer-based materials. We are building upon that knowledge to understand thermal and thermoelectric transport in these polymers to enable new device