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Flexible Batteries Will Bring Digital Clothing Sooner Than Later

Wearable tech is hard because bodies are soft. So here’s a wearable battery that flexes the way people do.

Flexible Batteries Will Bring Digital Clothing Sooner Than Later
[Image: Flickr user Martin Abegglen]

You, my dear human, are essentially a bag of water held up against gravity by various wonders of physics, chemistry, and biology. Computers, on the other hand, tend to be square slab-like things with awkward angles and uncompromisingly hard corners. Making computers conform to human bodies–one important aspect of wearable technology–is tricky because most of the components in a computer really don’t like to bend in quite the same way as do, say, your clothes. Enter a wholly new type of rechargeable battery from scientists at the Advanced Institute of Science and Technology (KAIST) in South Korea. It’s not just bendy…it’s actually ultra-flexible.

Battery chemistry actually often relies on fairly squishy materials–something you’ll know if an AA cell has ever leaked on you or you’ve prodded a lithium cell inside a laptop. Yet key parts of traditional batteries just aren’t flexible, typically including things like the electrodes. Innovations have been made in creating slightly flexible battery tech that’s an evolution of existing designs, with LG’s clever system in the news recently.

But the Korean team didn’t take this approach and instead thought sideways about what material you could make a lithium battery out of. Amazingly they settled on, actually, material–technically polyester yarn, the kind of stuff you’d probably find in a good portion of your clothing.

To turn polyester into a system capable of enabling current flow inside a lithium-ion cell, the team coated the yarn’s fibers with nickel to create the current collector and then with polyurethane to create electrodes. The material is capable of being laid down in wide but shallow layers, including separators to keep the electrical parts from short-circuiting. Sealing the layers together like this and including conductive thread to give the current some wires to flow in leads to a very flexible battery that’s actually based on textiles–meaning it could be sewn into clothing in the same way you’d apply a leather patch.

And lest you think this tech just couldn’t work, the team’s battery survived a torture-folding test of over 5,500 deep fold-unfold cycles and still retained nearly 92% of its charge-holding capacity. Even more interesting is the fact that the experimental battery they made had a capacity of just 13 mAh (the iPhone 5S for comparison has a 1560 mAh unit). But because the structure of the battery is–unlike most cells–very adjustable in the manufacturing process by simply weaving it differently, it’s easy to bump up the capacity.

As a final show-off the KAIST team also demonstrated that the cell was compatible with a flexible solar cell, so theoretically it could be easy to make a wearable digital computer that had a fully flexible battery powered by an external solar cell.

That wearable jacket computer you’ve been fantasizing about just got a lot more plausible.

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