“Rubber-band” electronics design stretches 200 percent

Researchers at the McCormick School of Engineering at Northwestern University recently developed electronics that bend and stretch to more than 200 percent their original size using a combination of a porous polymer and liquid metal.

“With current technology, electronics are able to stretch a small amount, but many potential applications require a device to stretch like a rubber band,” said Yonggang Huang, Joseph Cummings Professor of Civil, Environmental and Mechanical Engineering, who conducted the research with partners at the Korea Advanced Institute of Science and Technology (South Korea), Dalian University of Technology (China), and the University of Illinois at Urbana-Champaign. “With that level of stretchability we could see medical devices integrated into the human body.”

One challenge has been overcoming a loss of conductivity in stretchable electronics. Circuits made from solid metals, for example, can survive a small amount of stretch, but electrical conductivity declines by 100 times when stretched.

Huang’s team solved the problem by created a porous three-dimensional structure using a polymer material — poly(dimethylsiloxane) (PDMS) – infused with liquid metal (EGaIn), allowing electricity to flow consistently even when the material is excessively stretched.

The result is a material that is both highly stretchable and extremely conductive.
“By combining a liquid metal in a porous polymer, we achieved 200 percent stretchability in a material that does not suffer from stretch,” Huang said. “Once you achieve that technology, any electronic can behave like a rubber band.”

A paper about the findings, “Three-dimensional Nanonetworks for Giant Stretchability in Dielectrics and Conductors,” was published June 26 in the journal Nature Communications. Graduate student Shuodao Wang at Northwestern University is a co-author of the paper.