A Northwestern professor has helped create the first stretchable lithium-ion battery, the University announced Wednesday.

The flexible device is cordless and can be recharged wirelessly. It continues to operate when twisted, stretched or folded, according to a University news release.

The battery was created by Yonggang Huang, a McCormick professor, and John Rogers, a science and engineering professor and a Swanlund Chair at the University of Illinois at Urbana-Champaign.

Huang and Rogers said the battery can work inside the human body and can measure brain waves or heart activity. The power and voltage are comparable to a rigid battery but the new discovery will be able to expand up to 300 percent of its original size.

The researchers have worked together to develop stretchable electronics for the last six years. They had previously developed stretchable electronic circuits but not batteries.

Huang created the key to developing the battery — a unique design that works as a “spring within a spring.” The metal wire that connects the different battery components is in the shape of an “S” and that “S” is made up of even smaller “S’s” that will expand once the large “S” has been stretched to capacity.

“We call this ordered unraveling,” Huang said in the release. “And this is how we can produce a battery that stretches up to 300 percent of its original size.”

The Initiative for Sustainability and Energy helped support the research, which was published on Feb. 26 in the online journal Nature Communications, according to the release.

In addition to Huang and Rogers, three other NU researchers worked on the paper, Yihui Zhang, Yewang Su and Huanyu Cheng.

— Ally Mutnick