Stretching Electronics’ Limits

“Stretchable” electronics have been around for a while, but now, Northwestern University researchers have designed electronics that can stretch to more than 200 percent of their original size. That is four times greater than any existing pliable electronic. To achieve such malleability, the inventors used a combination of porous polymer and liquid metal.

Sometimes called “elastronics,” applications for the technology include cyber skin for robotic devices, imparting a network of sensors on a fully comformable, stretchable cyber skin; in vivo implantable sponge-like electronics; and flesh-like devices with embedded electronic nervous systems.

A paper on the subject was published on June 26 in the journal Nature Communications. “Three-dimensional Nanonetworks for Giant Stretchability in Dielectrics and Conductors” was co-authored by ten researchers from the Evanston, Ill.-based university’s McCormick School of Engineering, Korea Advanced Institute of Science and Technology in South Korea, Dalian University of Technology in China, and the University of Illinois at Urbana-Champaign.

“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 and Environmental Engineering and Mechanical Engineering at Northwestern. “With that level of stretchability we could see medical devices integrated into the human body.”

One of the major obstacles to developing electronics that can stretch to such a high degree is that when solid, conductive metal is stretched beyond a certain point, conductivity drops significantly. The porous material used by this research team alleviates this problem. These highly stretchable electronics are made from highly porous three-dimensional structure using a polymer material, poly(dimethylsiloxane), that can stretch to three times its original size. Then they placed a liquid metal (EGaIn) inside the pores, allowing constant electric flow even when the material is excessively stretched.

“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.”