Flexible wearable device harvests thermal energy

The team, from University of Washington, published its research in Advanced Energy Materials. The device is described as soft and stretchable, yet sturdy and efficient.

“It’s a 100 per cent gain if we harvest thermal energy that would otherwise be wasted to the surroundings,” said Mohammad Malakooti, a UW assistant professor of mechanical engineering. “Because we want to use that energy for self-powered electronics, a higher power density is needed.

“We leverage additive manufacturing to fabricate stretchable electronics, increase their efficiency and enable their seamless integration into wearables while answering fundamental research questions.”

According to the team, the device remains fully functional after more than 15,000 stretching cycles at 30 per cent strain — a highly desirable feature for wearable electronics and soft robotics. Researchers also found that it showed a 6.5 times increase in power density compared to previous stretchable thermoelectric generators.

To create the flexible devices, the researchers 3D printed composites with engineered functional and structural properties at each layer. The filler material contained liquid metal alloys, which provide high electrical and thermal conductivity. The team said that the alloys address limitations in previous devices, including an inability to stretch, inefficient heat transfer and a complex fabrication process.