The first healthcare device powered by body heat, made possible by the use of liquid-based metals

In an age of technology everywhere, we’re all too familiar with the inconvenience of a dead battery. But for those who rely on a wearable healthcare device to monitor glucose levels, reduce jitters, or even track heart activity, spending time charging it can be a big risk.

For the first time, researchers from Carnegie Mellon University’s Department of Mechanical Engineering have shown that a healthcare device can be powered solely by body heat. By combining a pulse oximetry sensor with a flexible, stretchable, wearable thermoelectric power generator made of liquid metal, semiconductors, and 3D-printed rubber, the team has introduced a promising way to solve battery life problems.

“This is the first step toward battery-free wearable electronics,” said Mason Zadan, a graduate student and first author of the study published in Advanced functional materials.

Designed to achieve high mechanical and thermoelectric performance through seamless materials integration, the system features advancements in soft materials, TEG die design, low-power PCB design and built-in power management.

“Compared to our previous studies, this design increases the power density by about 40 times or 4,000%. The liquid metal epoxy composite increases the thermal conductivity between the thermoelectric element and the device’s body-to-body interface,” explained Carmel Majidi, professor of mechanical engineering and director of the Soft Machines Laboratory.

To test the device’s output voltage, participants rested and moved while wearing chest and wrist monitors.

“We saw improved performance when the device was on the participant’s wrist and when they were moving,” Zadan said. “When the participant was moving, one side of the device was cooled by increased airflow, and the other side was heated by increased body temperature. Walking and running created the perfect temperature difference.”

Going forward, Dr. Dinesh K. Patel, a research scientist on the team, is eager to work on improving electrical efficiency and exploring how to additively manufacture the device. “We want to take it from proof of concept to a product that people can start using.”

The research was conducted in collaboration with Arieca Inc., the University of Washington and Seoul National University.