Human Body Becomes Battery With Wearable Device

A newly developed wearable device allows the human body to act as a battery by utilizing energy from body heat. The low-cost, stretchy device developed by researchers at the University of Colorado Boulder can be worn like a ring or bracelet. By using thermoelectric generators, the body’s internal temperature is converted into electricity.

The research was published in Science Advances. 

Jianliang Xiao is senior author of the research paper and an associate professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder. 

“In the future, we want to be able to power your wearable electronics without having to include a battery,” said Xiao.

Co-authors of the paper included various researchers from China’s Harbin Institute of Technology, Southeast University, Zhejiang University, Tongji University, and Huazhong University of Science and Technology. 

The wearable devices generate around 1 volt of energy per square centimeter of skin space, which is less voltage per area than most existing batteries. And despite this, they generate enough power for electronic devices such as watches. Since the fully recyclable device is stretchy, it can heal itself when damaged. 

“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

The wearable device’s base is made out of polyimine, which is responsible for its stretchiness. A series of thin thermoelectric chips are inserted into the base, all connected with liquid metal wires.

“Our design makes the whole system stretchable without introducing much strain to the thermoelectric material, which can be really brittle,” Xiao said.

“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 continued.

By adding on more blocks of generators, the power can be increased.

“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 brisk walk while wearing a sports wristband-type device could generate around 5 volts of electricity. The team’s device is also extremely resilient, with two broken ends able to be pinched together to seal back up within minutes. After the device is used, it can be placed in a special solution that separates the electronic components while dissolving the polyimine base, which makes all of it reusable.

“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.

Xiao believes the device could hit the market in five to ten years.