We may be wearing fitness trackers powered by our own body heat in the not too distant future.
A team of researchers from North Carolina State University have developed a new lightweight, patch that produces electricity from body heat to power wearable devices. The prototype is much more efficient than existing Thermoelectric Generators (TEGs).
“TEGs generate electricity by making use of the temperature differential between your body and the ambient air,” says Daryoosh Vashaee, an associate professor of electrical and computer engineering at NCSU.
“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 doesn’t use a heat sink, making it lighter and much more comfortable.”
The design begins with a layer of thermally conductive material, which is then topped with a polymer layer that prevents the heat from dissipating to the outside air. This forces the body heat to pass through a centrally-located TEG. The entire system is extremely thin and flexible.
The NCSU team embedded its new design into t-shirts and armbands, discovering the prime location for body heat harvesting in the process. They found that the upper arm was the best location. While the skin temperature is higher around the wrist, the irregular contour limited the surface area of contact. Meanwhile, a chest band didn’t allow enough air to flow, as it would normally be covered by clothing.
“T-shirt TEGs are certainly viable for powering wearable technologies, but they’re just not as efficient as the upper arm bands,” Vashaee says.
The ultimate goal of the team is to make wearable technology that doesn’t rely on batteries and can be used for long-term health monitoring. Researchers believe the new design and prototypes have moved them a step closer to making this a reality. Lets hope they are right!
The findings are published in the journal Applied Energy, in a paper titled “Wearable thermoelectric generators for human body heat harvesting.”
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