A thermoelectric wearable device worn as a ring. (Credit: Xiao Lab)
Researchers at 抖阴旅行射听Boulder have developed a new, low-cost wearable device that transforms the human body into a biological battery.听
The device, , is stretchy enough that you can wear it like a ring, a bracelet or any other accessory that touches your skin. It also taps into a person鈥檚 natural heat鈥攅mploying thermoelectric generators to convert the body鈥檚 internal temperature into electricity.听
鈥淚n the future, we want to be able to power your wearable electronics without having to include a battery,鈥� said Jianliang Xiao, senior author of the new paper and an associate professor in the Paul M. Rady Department of Mechanical Engineering at 抖阴旅行射 Boulder.
The concept may sound like something out of The Matrix film series, in which a race of robots have enslaved humans to harvest their precious organic energy. Xiao and his colleagues aren鈥檛 that ambitious: Their devices can generate about 1 volt of energy for every square centimeter of skin space鈥攍ess voltage per area than what most existing batteries provide but still enough to power electronics like watches or fitness trackers.听
Scientists have previously experimented with similar thermoelectric wearable devices, but Xiao鈥檚 is stretchy, can heal itself when damaged and is fully recyclable鈥攎aking it a cleaner alternative to traditional electronics.听
鈥淲henever you use a battery, you鈥檙e depleting that battery and will, eventually, need to replace it,鈥� Xiao said. 鈥淭he nice thing about our thermoelectric device is that you can wear it, and it provides you with constant power.鈥�
High-tech bling
The project isn鈥檛 Xiao鈥檚 first attempt to meld human with robot. He and his colleagues previously experimented with designing 鈥渆lectronic skin,鈥� wearable devices that look, and behave, much like real human skin. That android epidermis, however, has to be connected to an external power source to work. 听
Until now. The group鈥檚 latest innovation begins with a base made out of a stretchy material called polyimine. The scientists then stick a series of thin thermoelectric chips into that base, connecting them all with liquid metal wires. The final product looks like a cross between a plastic bracelet and a miniature computer motherboard or maybe a techy diamond ring. 听
鈥淥ur design makes the whole system stretchable without introducing much strain to the thermoelectric material, which can be really brittle,鈥� Xiao said.
Just pretend that you鈥檙e out for a jog. As you exercise, your body heats up, and that heat will radiate out to the cool air around you. Xiao鈥檚 device captures that flow of energy rather than letting it go to waste.
鈥淭he thermoelectric generators are in close contact with the human body, and they can use the heat that would normally be dissipated into the environment,鈥� he said.
Lego blocks
He added that you can easily boost that power by adding in more blocks of generators. In that sense, he compares his design to a popular children鈥檚 toy.听
鈥淲hat I can do is combine these smaller units to get a bigger unit,鈥� he said. 鈥淚t鈥檚 like putting together a bunch of small Lego pieces to make a large structure. It gives you a lot of options for customization.鈥�
Xiao and his colleagues calculated, for example, that a person taking a brisk walk could use a device the size of a typical sports wristband to generate about 5 volts of electricity鈥攚hich is more than what many watch batteries can muster.
Like Xiao鈥檚 electronic skin, the new devices are as resilient as biological tissue. If your device tears, for example, you can pinch together the broken ends, and they鈥檒l seal back up in just a few minutes. And when you鈥檙e done with the device, you can dunk it into a special solution that will separate out the electronic components and dissolve the polyimine base鈥攅ach and every one of those ingredients can then be reused.
鈥淲e鈥檙e trying to make our devices as cheap and reliable as possible, while also having as close to zero impact on the environment as possible,鈥� Xiao said.
While there are still kinks to work out in the design, he thinks that his group鈥檚 devices could appear on the market in five to 10 years. Just don鈥檛 tell the robots. We don鈥檛 want them getting any ideas.听
Coauthors on the new paper include researchers from China鈥檚 Harbin Institute of Technology, Southeast University, Zhejiang University, Tongji University and Huazhong University of Science and Technology.
