Researchers at the University of Washington have developed the first flexible wearable thermoelectric device that converts body heat into electricity.

Photo credit: Advanced Energy Materials

"If we capture the heat energy that we waste in the environment, it's a 100 percent gain," said Mohamed Marakudi, an assistant professor of mechanical industry at the University of Washington. But to use this energy for self-powered electronics, higher power densities are needed. Stretchable electronics made from 3D printing can be more efficient and seamlessly integrated into wearable devices."

The researchers have created a prototype device that remains fully functional even after more than 15,000 stretching cycles at 30 percent strain, ideal for wearable electronics and flexible robots. Compared with previous stretchable thermoelectric generators, the power density of the device is improved by 6.5 times.

To create the prototype device, the researchers 3D-printed composites with engineered functional and structural properties in each layer, filled with liquid metal alloys that provide high electrical and thermal conductivity. These alloys address the limitations of previous devices, including inability to stretch, inefficient heat transfer, and complex manufacturing processes. The team also embedded hollow microspheres to direct heat to semiconductors in the core layer and reduce the weight of the device.

The researchers say they can print the device on stretchy textile fabrics and curved surfaces, suggesting future applications for clothing and other objects. A unique aspect of the study is that it covers the entire spectrum, from material synthesis to device fabrication and characterization, giving researchers the freedom to design new materials and be creative.