Self-charging battery stretches over skin to power wearables

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Because the wires connecting the tiles are actually longer than the space between them, the device can be stretched out of shape

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While we've seen promising prototypes of computers that conform to the contours of human wrists and forearms, the technology isn't quite ready for mainstream adoption yet. But this hasn't stopped one forward-thinking team of researchers from coming up with a new way to power these wearable electronics, developing a soft, millimeter-scale battery that can be stretched over the skin like a band-aid.

Sensors that are wearable and flexible promise a diverse range of applications including things like health monitoring, ticketing for sporting events and robots with human-like sense of touch. Some of these need to be hooked up to an external power source, while others have shown the ability to harvest mechanical energy from movement to power themselves.

Looking to offer a power solution that is lightweight and has mechanics suitable for such applications, an international team of researchers led by material scientist John Rogers from the University of Illinois has brought solar cells into the mix and built an entirely new kind of battery.

To address some of the problems in building flexible power supplies, the researchers chopped a regular lithium-ion battery up into tiny ultrathin tiles. These tiles were then connected with wires and the array was integrated into a soft, rubbery material before receiving a final coat of stiffer rubber. Tiny solar cells were then layered on top of the battery cells, along with biosensors and chips.

The resulting device is super thin, waterproof and because the wires connecting the tiles are actually longer than the space between them, able to be stretched out of shape. Testing also demonstrated that it can be stretched up to 30 percent while maintaining functionality.

The team says this proof-of-concept device could be applied to human skin like a band-aid to offer an endless flow of biosensor data. It could also potentially be built into powered clothes to provide new ways of storing energy.

The research was published in the Proceedings of the National Academy of Sciences.

Source: PNAS via TechXplore

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