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Flexible Battery Can Be Stretched to 300 Percent Normal Size

By Wesley Fenlon

An array of batteries embedded in a flexible polymer may be another step down the road of stretchable, wearable electronics.

Flexible displays are incredibly exciting technology, but they're only part of a solution. If your end goal is to, say, roll up a TV, slap a rubber band around it, and carry it with you anywhere you go, all of the other TV components have to be just as flexible as the screen itself. You can put a slightly curved display on a phone or watch, and that's cool, but not as cool as a wholly flexible device. Researchers from the University of Illinois, Northwestern may have solved another piece of the puzzle with a flexible battery. The material can be stretched to 300 percent of its original size without breaking or tearing.

Smithsonian Mag details the stretchable battery's debut in the journal Nature Communications. The journal abstract sums up the project well: "Here we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual ‘self-similar’ interconnect structures between them. The result enables reversible levels of stretchability up to 300%...Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact."

Essentially, many small lithium ion batteries are embedded in a stretchy polymer and connected with S-Shaped wires that can handle being stretched out and pulled taut. A statement released before the journal article adds more detail:

"The unique mechanism is a 'spring within a spring': The line connecting the components is a large 'S' shape and within that 'S' are many smaller 'S's.' When the battery is stretched, the large 'S' first stretches out and disappears, leaving a line of small squiggles. The stretching continues, with the small squiggles disappearing as the interconnect between electrodes becomes taut."

The battery can be recharged wirelessly, and its creators propose it could even be used alongside monitoring devices inside the human body, where rigid batteries are impractical. Flexible, wearable electronics will likely be easier to work with. There's a catch, of course: the prototype battery array can power a single LED light for about 8-9 hours on a charge, which is great, but nothing compared to what it would take to power a smartphone or similar device all day.

Since the S-shaped wires connecting the batteries are the breakthrough technology here, perhaps the li-ion batteries themselves could quickly and easily be improved in future iterations. By the time we've figured out how to make bendable CPUs and other chips, we might have the battery capacity to power them.