Researchers at the University of Colorado Boulder have developed a new low-cost wearable device that turns the human body into a biological battery.
The device, described today in the journal Science Advances, it is stretchy enough that you can wear it as a ring or bracelet. It taps into a person's natural heat, using a tiny thermoelectric generator to convert the body's core temperature into electricity.
"In the future, we want to be able to power wearable electronics without including a battery," he says Jianliang Xiao, senior research author and associate professor in the Paul M. Rady Department of Mechanical Engineering at the University of Colorado Boulder.
The concept of wearable thermoelectric
It looks like it came out of The Matrix movie series, where a race of robots enslave humans to harvest their precious organic energy. Xiao and her colleagues aren't that ambitious (and thank goodness): their devices can generate approx 1 volt of energy for every square inch of space on the skin, less voltage per area than that provided by most existing batteries, but still sufficient to power electronic devices such as watches or fitness trackers.
Scientists have already experimented with devices wearable similar thermoelectrics, but Xiao's is elastic, can be cured if damaged and is completely recyclable. This makes it a cleaner alternative to traditional electronics.
Every time you use a battery, you are draining it and will eventually need to be replaced. The great thing about our thermoelectric device is that you can wear it and it provides you with constant power
Jianliang Xiao
Skin technology
The project is not Xiao's first attempt to fuse the human with the robot. He and his colleagues have already pioneered the design of "electronic skin," wearable devices that look and behave very much like real human skin. But even that "android skin" had to be connected to an external power source to function.
And now? The latest innovation of the team from a base made with an elastic material called polyamine. The scientists then insert a thin thermoelectric chip next to each other. A network of chips all connected with liquid metal wires. The final product looks like a cross between a plastic bracelet and a miniature computer motherboard, or perhaps a hi-tech diamond ring.
"Our design makes the whole system stretchable without introducing too much tension on the thermoelectric material, which can be really brittle," Xiao said.
Imagine you are out for a jog. As you exercise, your body warms up and radiates heat. Xiao's device captures that flow of energy. A mini thermoelectric generator in close contact with the human body can use this heat which would normally be dissipated into the environment.
A thermoelectric brick
The modularity of this thermoelectric system can vary by adding or removing more generator blocks. "What we can do is combine these smaller units to make a larger unit," says Xiao. "It's like putting a bunch of little Lego pieces together to make a big structure. It gives you a lot of options for customization."
Xiao and his colleagues calculated, for example, that a brisk walking person could use a device the size of a typical sports bracelet. to generate about 5 volts of electricity, which is more than many watch batteries can collect.
The new devices are as strong as biological tissues. If a wearable thermoelectric device tears, for example, you can pinch the broken ends together and they'll seal again in minutes. And at the end of the cycle the device can be immersed in a special solution that will separate the electronic components and dissolve the polyamine base: each of these ingredients can be reused.
