Stretchy, recyclable wearable adheres to human skin

A wearable electronic device that can stretch and adhere to human skin has been developed by researchers at the University of Colorado Boulder.

 The device is able to heal itself, much like real skin, and can perform a range of sensory tasks, from measuring the body temperature of users to tracking their daily step counts.

The skin is also reconfigurable, meaning that it can be shaped to fit anywhere on a human body.

“If you want to wear this like a watch, you can put it around your wrist,” said research lead Jianliang Xiao. “If you want to wear this like a necklace, you can put it on your neck.”

The team believe their device could allow people to collect accurate data about their bodies, all while cutting down on the world’s surging quantities of electronic waste.

“Smart watches are functionally nice, but they’re always a big chunk of metal on a band,” said researcher Wei Zhang. “If we want a truly wearable device, ideally it will be a thin film that can comfortably fit onto your body.”

To manufacture the product, screen printing was used to create a network of liquid metal wires which are then sandwiched in between two thin films made out of a highly flexible and self-healing material called polyimine.

The resulting device is a little thicker than a plaster and can be applied to skin with heat. It can also stretch by 60 per cent in any direction without disrupting the electronics inside, the team reports

“It’s really stretchy, which enables a lot of possibilities that weren’t an option before,” Xiao said.

It can already carry out many functions that popular wearable fitness devices like Fitbits do, such as reliably measuring body temporary, heart rate, movement patterns and more.

If the electronic skin is sliced, the wearer can pinch the broken areas together and the bonds which hold together the polyimine material will begin to reform. Within 13 minutes, the damage will be almost entirely undetectable.

“Those bonds help to form a network across the cut. They then begin to grow together,” Zhang said. “It’s similar to skin healing, but we’re talking about covalent chemical bonds here.”

The project could also represent a new approach to manufacturing electronics that could be more environmentally friendly. By 2021, estimates suggest that humans will have produced over 55 million tons of discarded smart phones, laptops and other electronics.

Materials from the stretchy device can be easily reacquired by dunking it into a recycling solution that will depolymerize the polyimine and or separate it into its component molecules, while the electronic components sink to the bottom. Both the electronics and the stretchy material can then be reused.

“Our solution to electronic waste is to start with how we make the device, not from the end point, or when it’s already been thrown away,” Xiao said. “We want a device that is easy to recycle.”