Researchers have been hot on the trail of the perfect battery (or at least the functional one) that can be flexible and light without losing performance. A flexible battery is greatly needed as the research for flexible electronic devices advances. After all, what is a flexible gadget without a flexible power source to make it run?
The latest improvement comes from researchers from Northwestern University and University of Illinois, who have created a battery that can stretch three times its size while maintaining performance, and it can be charged wirelessly through inductive charging. This could potentially be the powersource for flexible electronics being devised for everything from pacemakers to bendy cell phones.
"Batteries are particularly challenging because, unlike electronics, it's difficult to scale down their dimensions without significantly reducing performance," John Rogers of the University of Illinois at Urbana-Champaign told BBC news. "We have explored various methods, ranging from radio frequency energy harvesting to solar power."
The team's new idea was to use "serpentine" connections - wires that loop back on themselves in a repeating S shape, with that string of loops itself looped into an S shape. Stretching out the polymer in which the tiny solar cells were embedded first stretches out the larger S; as it is stretched further, the smaller turns straighten - but do not become taut, even as the polymer was stretched to three times its normal size. The team says the stretchy battery can be charged "inductively" - that is, wirelessly over a short distance. Prof Rogers said that the uses for such batteries and the stretchy circuits they power were myriad.
“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,” Yonggang Huang, an engineer at Northwestern and one of the paper’s co-authors, said in a statement.
The experimental battery charges wirelessly and works for eight to nine hours on one charge. It can be recharged 20 times without losing any capacity, notes Popular Science.
The research was published yesterday in Nature Communications.