Body Heat Converted Into Electricity Powers Health Sensors

There has been an increasing number of wearable technologies that have health sensors as medical tools to track a person’s well-being. Many of these devices need to be charged or are battery-powered. 

A handful of researchers want to take batteries out of the equation and instead, use waste body heat and convert that into useful electricity to power sensors. 

“The average person is something like an 80-watt light bulb,” said Jamie Grunlan, Texas A&M University’s Linda & Ralph Schmidt ’68 Professor in Mechanical Engineering.

Grunlan and his team of researchers are working on using the waste heat the body gives off and converting that into useful electricity. The idea is to create printable, paintable thermoelectric technology that looks like ink and can coat a wearable fabric, similar to dyeing colors onto cloth. Once a person wears the fabric, devices such as health sensors can be powered.

“Our coating coats every fiber within that textile, and so what’s drawing it is simply that textile needs to just be touching the heat source or be close enough to the heat source to be feeling the heat source,” Grunlan said. 

Military and sporting goods companies have applications for this type of technology because there is not a large battery pack worn on the body that could be a cause of injury if the person would fall.

“They would love to power health sensors off of body heat and then wirelessly transmit that data to wherever,” Grunlan explained. “You’d like to know if somebody had a concussion or was dehydrated or something like that while it’s happening in real time.”

As a person generates heat, the temperature outside is colder than what’s against the body. The temperature differential generates a voltage. 

The goal is to design technology that can get one volt or up to 10 percent efficiency and beyond. So, for example, a researcher would try to get eight watts from a person who is generating 80 watts.

The ingredients in this thermoelectric recipe include carbon nanotubes, polymers and a carbon material called graphene, which is a nanoparticle. 

Researchers are trying to perfect the recipe of this ink-like material. 

“The one voltage is realistic, but how much material do we need to get that one voltage because we need as little as possible?” said Carolyn Long, a Ph.D. graduate student at Texas A&M. 

“So, different polymers, different amounts of the multi-walled or double-walled nanotubes, adding the graphene, which order it needs to go in exactly to create the best pathway for the electrons for the thermoelectric material,” said Long of the various experiments she and her lab mates have conducted.

The aim is to create a product that can be mass produced. 

“It will happen. It’s not will it happen. It’s when. Is it a year, or is it five years?” Grunlan said.

That will depend on how much funding and manpower is available to make this technology a reality.

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