As electronics increasingly fuse with the human body, stretchability is likely to be a key asset both for the electronics, and their batteries. Nobody wants to carry around a Duracell value-pack on their arm.
Researchers have come up with a stretchable battery that can be "folded, twisted, and mounted on a human elbow." It works for 8 or 9 hours before needing to be recharged--wirelessly.
The battery is capable of powering a small LED (see the video above). Yonggang Huang, of Northwestern, and the University of Illinois’ John Rogers, recently wrote up the work in the journal Nature Communications.
"We start with a lot of battery components side by side in a very small space, and we connect them with tightly packed, long wavy lines," Huang, told Phys.org. "These wires provide the flexibility. When we stretch the battery, the wavy interconnecting lines unfurl, much like yarn unspooling. And we can stretch the device a great deal and still have a working battery."
The battery stretches up to 300% its starting size, and was charged 20 times in the test without losing capacity. We await the first application (hopefully it will be more useful than a watch).