Stretchable Batteries Are Here, Now What?

The mighty wheel of technological progress has taken another significant spin Tuesday after scientists announced the arrival of stretchable batteries.

Yeah. You heard it right: flexible, stretchable lithium-ion battery – which means stretchable electronics are around the corner. Think of a rubber, bouncy smarthphone or heart monitors threaded into cardiac tissue.

The invention – credited to Yonggang Huang, an engineer at Northwestern University, and the materials wizard John Rogers at the University of Illinois – was published today in the journal Nature Communications.

“We can stretch the device a great deal — up to about 300 percent — and still have a working battery,” Huang noted.

“Such stretchable batteries enable true integration with stretchable electronics in a small package,” he continued.

The background of the research team means that medical applications will be primarily targeted, but there are other applications for bendy batteries such as wearable solar cells and electric-eye cameras that make studio-quality photographs.

To make the battery, the researchers start with tiny, individual, rigid battery storage components arranged next to each other. The bendy and stretchy characteristics stem from tightly packed, wavy wires that connect these components.

“When we stretch the battery, the wavy interconnects unravels, much like yarn unspooling, while the storage components almost keep undeformed, because of their much larger rigidity than the interconnects” Huang explained.

Huang and Rogers have demonstrated a battery that continues to work -- powering a commercial light-emitting diode (LED) -- even when stretched, folded, twisted and mounted on a human elbow. The battery can work for eight to nine hours before it needs recharging, which can be done wirelessly.

"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," said Huang. "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."

Rogers is also known for winning the prestigious $500,000 Lemelson-MIT Prize in 2011 for his work on flexible electronics designed for integration with the human body.