The search for efficient power sources for wearables and Internet of Things (IoT) devices takes many directions. In the past, we’ve written about technology that harvests energy from knee movement, sunlight, nanotube yarn, and more. Scientists at the Electronics and Telecommunications Research Institute (ETRI) in South Korea designed a thermoelectric module that generates minute amounts of energy from human body heat.

Engineers at Purdue University’s Birck Nanotechnology Center developed a flexible thermoelectric fabric that solves a challenge common to many researchers working on body heat energy harvesting. According to the Purdue team, body heat energy solutions generally need to be as much as an inch thick to harvest sufficient power for sensors. An inch-thick layer or coating is a non-starter for many applications, and especially smart garments. Unless you’re an astronaut, a diver, or an Alpine sports enthusiasts, extra-thick clothing or patches present comfort and usability challenges.

The Purdue technology uses various thermoelectric yarns woven into polymer film or fabric sheets. By printing different yarns in a pattern, the material is able to draw energy from curved surfaces, such as parts of an arm, leg, abdomen, or shoulder. Electrically insulated thread passes through the 3D fabric to connect the hot and cold sides, similar to conventional thermoelectric power generators.

“There are several potential areas of application for this technology for both humans and animals,” said Birck research associate professor Kazuaki Yazawa. “It can be used for biomonitoring humans or animals, along with applications for industrial machining where the unreachable curved surface can be used for sensing and machine health monitoring.”

The rapid growth of IoT applications and biometric sensing devices fuel development in energy-harvesting technologies that hold the potential to eliminate recharging and replacing batteries.