Purdue researcher develops technology powered by body heat

Kazuaki Yazawa, a research associate professor at Purdue University, Indiana, has developed technology that can be woven into a specially designed fabric, harnessing human body heat to power IoT devices.

The question of how to power the burgeoning IoT is one that many companies have attempted to answer. Radio waves, Wi-Fi backscatter, Low Power Wide Area Networks, light, graphene – all have been put forward as potential ways to keep IoT devices ticking over. This week, a new possibility has emerged from the Birck Nanotechnology Center at Purdue University, Indiana: body heat.

The concept of powering an IoT device through nothing more than body heat will be of particular interest to developers working in wearables. Connected medical devices, such as respiration and heart-rate monitors are an obvious application.

Research associate professor Kazuaki Yazawa has labelled his creation ‘flexible thermoelectric generator technology’. It uses semiconductor strings woven into a fabric, takes heat from any type of surface it meets and converts it into a small amount of electricity.

Conventional thermoelectric generators require elements to be at least one-inch thick in order to generate a decent power output – hardly suitable for a wearable device of any sort.

Yazawa believes that his solution, which uses woven semiconductor strings to replace traditional thermoelectric generators, will be more flexible and easier to manage. “The only way to reduce the thickness of the module is by designing the thermoelectric generator using a weaving technique. This allows the technology to be very flexible and dense,” he said.

Body heat could replace batteries

The key to any wearable hoping to harvest power from body heat will be flexibility. If something is to be built into clothing or fabric, it needs to be manageable. “Lengthening the threads and using a unique combination of insulation makes the generator more flat and manageable,” said Yazawa. “This makes it ideal for use in clothing or any shape that can be wrapped in a flexible fabric that has waste heat, such as a chimney or coffee cup.”

“These semiconductor strings are able to harness the maximum amount of heat from the body or other ambient heat sources, providing reliable power for IoT devices and eliminating the need for batteries.”

It’s clear to see how this technology could be applied in the world of healthcare, where the use of IoT devices is predicted to empower both patients and professionals. “Heart monitors, respiration and perspiration monitors are very useful for the elderly or those recovering from a trauma. There also is a huge market for wearables in sports to optimize human performance,” he said.

“If you have a patient or an athlete who is overheating, real-time information of their vitals could be used by coaches and medical professionals to better monitor and treat their players or patients. These types of devices need energy to be actively charged so they can be used continually.”

Possibility for automated cooling?

Theoretically, anything that takes heat out of a system is going to provide some kind of cooling effect. Yazawa has suggested that his technology could be used for some kind of cooling wearable, although the potential applications for that are still unclear.

“Anything that takes heat and converts it to another form of energy is also providing a cooling effect,” he said. “Therefore, this technology also could provide a continuous cooling treatment. This could be especially beneficial from a sports or military perspective. The flexible substrate could be applied to undergarments and when athletes are running the technology could help give that little bit of charge.”

Developers will not have to wait long to work on potential body-heat powered IoT devices. The Purdue Research Foundation’s Office of Technology Commercialization has patented the technology and it is already available for license.

“We have analyzed and modeled the technology. It has been validated in the lab,” Yazawa said, and “is ready for further testing and development.”