- If you are what you eat, does that mean that your watch could actually be… You?
Yesterday we covered the story of a guitarist turning his dead uncle’s remains into an instrument. We’re continuing in more or less the same vein today, but this time we’re exploiting a living human body.
Turning a person into a battery sounds like something out of The Matrix movies. If you haven’t seen them, in the films a malevolent race of machines farms human beings for producing bioelectricity.
But now scientists have indeed figured out how to use the human body to power electric devices. And don’t worry, the solution doesn’t require sealing anyone into a goo-filled canister.
In a new study, published in the journal Science Advances, researchers created a stretchy, flexible device. It can be worn like a ring or a bracelet, and it generates electricity from contact with human skin.
“In the future, we want to be able to power your wearable electronics without having to include a battery,” said the study’s senior author Jianliang Xiao from the Department of Mechanical Engineering at the University of Colorado Boulder.
It’s an ambitious goal, but a welcome one. Imagine never having to charge your smart watch because it powers itself from just cuddling with your wrist.
Actually, it sounds a bit creepy when we put it that way.
A Miracle Material
The new device differs from the human batteries in The Matrix films in power output as well. Xiao’s invention produces only one volt of energy for every square centimeter of skin it touches.
If that doesn’t sound like much, that’s because it isn’t. That’s actually less voltage per area than most modern lithium batteries produce.
Still, it’s enough to power the aforementioned smart watch or a fitness tracker.
“Whenever you use a battery, you’re depleting that battery and will, eventually, need to replace it. The nice thing about our thermoelectric device is that you can wear it, and it provides you with constant power,” Xiao said.
The stretchy-stretchy material the device is made from is called polyimine. To this base, the researchers added thermoelectric chips and connected them with liquid metal wires.
The use of liquid metal allows the device to stretch without damaging the electronics. Xiao describes the final product as a cross between a plastic bracelet and a computer motherboard.
“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 pull power from of your body heat. That means that when you get hot and sweaty while exercising, your fitness tracker will actually have more juice to run on.
“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,” explained Xiao.
If more power is needed, Xiao said that it’s easy to add more generator blocks to the device. He likened it to playing with Lego blocks.
“What I can do is combine these smaller units to get a bigger unit. 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,” said Xiao.
According to the researchers’ calculations, a person taking a brisk walk could generate five volts of electricity with a bracelet the size of a regular watch wristband. That’s more power than most watch batteries produce.
Good for the Planet
There are also other benefits that set Xiao’s human-powered battery apart from existing ones. First of all, it’s more environmentally friendly.
There’s no need to mess around with hazardous chemicals since the power comes from your own body. The device’s stretchy nature also means that one size fits everybody, so manufacturers won’t need to waste resources to make several different sizes.
Additionally, the device is fully recyclable. A used wristband can be placed into a solvent that separates the electronics from the polyimine, allowing all of them to be reused.
The device can even heal itself when it’s damaged. If it tears, you can just pinch the torn edges together — in a few minutes they’ll seal back up just like human skin.
“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.
Making a Mechanical Man
This isn’t the first time Xiao has tried melding electronics with the human body. He has previously worked on “electronic skin,” or wearable devices that also look and behave like human skin.
The electronic skin could help create more lightweight and environmental watches and other such devices.
“Smart watches are functionally nice, but they’re always a big chunk of metal on a band. If we want a truly wearable device, ideally it will be a thin film that can comfortably fit onto your body,” said Wei Zhang, who also works on the electronic skin.
There’s just been one problem – so far the android skin has needed an external power source. Now, Xiao’s new invention could change that.
Maybe we can all soon just look at our actual wrist to check the time. No watch needed.