Researchers at North Carolina State University have developed a new design for gathering body heat and converting it into electricity for use in wearable electronics, according to a recent press release. The research was published in Applied Energy.
The lightweight, wearable prototypes conform to the shape of the body and can generate more electricity than previous heat-gathering technologies, the release noted. The design includes a layer of thermally conductive material that rests on the skin and spreads heat outwardly. That material is topped with a polymer layer that prevents heat from dissipating through to the outside air. According to the release, this forces body heat to pass through a centrally-located wearable thermoelectric generator (TEG). Heat that is not converted into electricity passes through the TEG into an outer layer of thermally-conductive material, which rapidly dissipates the heat. The entire system is 2 millimeters, the release noted.
“TEGs generate electricity by making use of the temperature differential between your body and the ambient air,” Daryoosh Vashaee, PhD, an associate professor of electrical and computer engineering at North Carolina State University, said in the release. “Previous approaches either made use of heat sinks — which are heavy, stiff and bulky — or were able to generate only one microwatt or less of power per centimeter squared (μW/cm2). Our technology generates up to 20 μW/cm2 and does not use a heat sink, making it lighter and much more comfortable.”
Researchers found that the upper arm was the optimal location for heat harvesting. They incorporated the TEG into T-shirts, which were still capable of generating 6 μW/cm2, or as much as 16 μW/cm2 if a patient was running.
“The goal of the [project, conducted through the university’s National Science Foundation’s Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) program], is to make wearable technologies that can be used for long-term health monitoring, such as devices that track heart health or monitor physical and environmental variables to predict and prevent asthma attacks,” Vashaee said. “To do that, we want to make devices that do not rely on batteries, and we think this design and prototype moves us much closer to making that a reality.”
Hyland M, et al. Appl Engery. 2016;10.1016/j.apenergy.2016.08.150.
Disclosure: The research was funded with support from a National Science Foundation Research Experiences for Undergraduates grant under EEC-1160483, ECCS-1351533 and CMMI-1363485. The research was also funded by the Air Force Office of Scientific Research under grant FA9550-12-1-0225.