The stretchy device, which can be worn like a ring, contains a series of thin thermoelectric chips that are connected using liquid metal wires. (Image Credit: CU Boulder)

 

CU Boulder researchers have created an inexpensive wearable device that turns the human body into a battery. The device’s stretchability allows it to be worn like a ring, bracelet, or an accessory that comes in contact with the skin. It works by using thermoelectric generators to convert body heat into electricity. These devices are capable of generating 1V for every cm2 of skin space, which could provide power to watches or fitness trackers.

 

“In the future, we want to be able to power your wearable electronics without having to include a battery,” said Jianliang Xiao, senior author of the new paper and an associate professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder. Previously, scientists conducted experiments with other thermoelectric wearable devices, but this one is different. That’s because it heals itself when it becomes damaged and can be recycled, a cleaner alternative to conventional electronics.

 

“Whenever you use a battery, you’re depleting that battery and will, eventually, need to replace it,” Xiao said. “The nice thing about our thermoelectric device is that you can wear it, and it provides you with constant power.”

 

The device’s polyimine base has a series of thin thermoelectric chips integrated inside it, which are connected using liquid metal wires. The team’s final concept looks like a cross between a  plastic bracelet and a mini-computer motherboard.  “Our design makes the whole system stretchable without introducing much strain to the thermoelectric material, which can be really brittle,” Xiao said. A human generates heat while exercising. That heat is then dissipated to the cool air. Instead of wasting that flow of energy, the new device captures it. 

 

“The thermoelectric generators are in close contact with the human body, and they can use the heat that would normally be dissipated into the environment,” he said. The device’s power can also be upgraded by installing more generators.

 

“What I can do is combine these smaller units to get a bigger unit,” he said. “It’s like putting together a bunch of small Lego pieces to make a large structure. It gives you a lot of options for customization.” According to the team’s calculations, a device the size of a sports wristband could generate 5 volts for someone taking a walk.

 

These devices can be easily repaired if it gets damaged. All a wearer needs to do is pinch the damaged ends together, which seals back up after a few minutes. It can also be submerged into a special solution to separate the electronic components and liquefy the polyimine base. These can then be used again.

 

“We’re trying to make our devices as cheap and reliable as possible, while also having as close to zero impact on the environment as possible,” Xiao said.  Even though there are still some issues to solve in the design, the team thinks it could hit the market in 5 to 10 years.

 

 

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