Versatile fabric makes and stores its own energy

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The researchers had to learn to use a loom to weave their power-storing fabric(Credit: UCF)

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With the rise of mobile technologies comes a need for mobile power sources, and it's hard to think of a more discreet way to do this than weaving them right into our clothes. Such a task requires new advances in flexible electronics that can both harvest and store energy, and scientists are now claiming another step forward towards this goal in the form of solar-power producing filaments that could one day lace everything from the sweater of the heavy smartphone user to power-generating outerwear for soldiers in the field.

Medical sensing and clothes that track fitness metrics are just a couple of areas where flexible electronics could be a real boon, and already some great strides are being made towards this reality. We have seen experimental power-generating fabrics that draw energy from sunlight and mechanical movement, along with flexible and self-healing batteries that can store said energy without breaking apart. Brands like Tommy Hilfiger have even tried to bring more rudimentary forms of this tech to consumers with solar power jackets that stow energy in battery packs in the pockets.

But more sophisticated solutions may be on the way, like that developed by scientists at the University of Central Florida. The device is a little similar the Band-Aid-like self-charging battery that we looked at in May, in that it powers itself with energy from the sun. But while those scientists solved the problem by chopping a conventional lithium-ion battery into a bendable array of ultrathin tiles, the Florida team is shooting for something more inconspicuous. It instead employs tiny ribbons that can be threaded neatly through clothes, an approach it says was inspired by Marty McFly's self-lacing sneakers in Back to the Future II.

"The idea came to me: We make energy-storage devices and we make solar cells in the labs, why not combine these two devices together?" said Associate Professor Jayan Thomas, a nanotechnology scientist at the University of Central Florida's NanoScience Technology Center.

The filaments are crafted from copper and are thin, flexible and lightweight. On one side is a solar cell and on the other is a supercapacitor. As the cell is exposed to sunlight, the electrons are passed directly to its reverse side and held in its energy-storing layers. When lighting up the ribbons with simulated solar light, the team found that the supercapacitor offered an energy density of 1.15 mWh cm³, and a power density of 243 mW cm³. The team also demonstrated its readiness for the world by weaving the ribbons successfully into a square of yarn.

With the ability to harvest and store energy without needing to shuttle it off to a battery for safekeeping, these ribbons could one day be fed into jackets and sweaters to keep phones, mobile devices and things like fitness trackers topped up. The team says powering electric cars is even a possibility, but it is the military where it sees real potential.

"A major application could be with our military," says Thomas. "When you think about our soldiers in Iraq or Afghanistan, they're walking in the sun. Some of them are carrying more than 30 lb (13.6 kg) of batteries on their bodies. It is hard for the military to deliver batteries to these soldiers in this hostile environment. A garment like this can harvest and store energy at the same time if sunlight is available."

The research was published in the journal Nature Communications.

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