Super stretchy wearable converts body heat to electricity

Described in Advanced Materials, the prototype device consists of rigid thermoelectric semiconductors connected with printed liquid metal traces. Liquid metal droplets are embedded in the outer layers to improve heat transfer to the semiconductors and maintain flexibility. The semiconductors are surrounded by 3D-printed composites with low thermal conductivity, enhancing energy conversion and reducing weight.

To demonstrate the device in action, senior author Mohammad Malakooti, UW assistant professor of mechanical engineering, attached the prototype to his arm where it powered a small LED light.

"I had this vision a long time ago," said, Malakooti. "When you put this device on your skin, it uses your body heat to directly power an LED. As soon as you put the device on, the LED lights up. This wasn't possible before."

According to the researchers, the prototype was built form scratch, starting with simulations to determine the best combination of materials. All components, apart from the semiconductors, were then created in the lab. Due to the thermoelectric profile of the device, Malakooti said it could also be used to harvest waste heat in data centres.  

"You can imagine sticking these onto warm electronics and using that excess heat to power small sensors," he said.

"This could be especially helpful in data centres, where servers and computing equipment consume substantial electricity and generate heat, requiring even more electricity to keep them cool. Our devices can capture that heat and repurpose it to power temperature and humidity sensors. This approach is more sustainable because it creates a standalone system that monitors conditions while reducing overall energy consumption. Plus, there’s no need to worry about maintenance, changing batteries or adding new wiring."

Additional co-authors are Youngshang Han, a UW doctoral student in mechanical engineering, and Halil Tetik, who completed this research as a UW postdoctoral scholar in mechanical engineering and is now an assistant professor at Izmir Institute of Technology. Malakooti and Han are both members of the UW Institute for Nano-Engineered Systems. This research was funded by the National Science Foundation, Meta and The Boeing Company.