'Rubber-band' electronics could aid human health

Posted by Kate Taylor

Researchers say they've developed electronic devices that are as stretchable as a rubber band, making them potentially implantable into the human body for medical monitoring.

A team headed by Northwestern University's McCormick School of Engineering says its design allows electronics to bend and stretch to more than 200 percent their original size - four times greater than is possible with today’s technology.

"With current technology, electronics are able to stretch a small amount, but many potential applications require a device to stretch like a rubber band," says professor Yonggang Huang.

"With that level of stretchability we could see medical devices integrated into the human body."

The key is a combination of a porous polymer and liquid metal. Circuits made purely from solid metals that are on the market today can survive a small amount of stretch, but their electrical conductivity plummets by 100 times when stretched. "This conductivity loss really defeats the point of stretchable electronics," says Huang.

Huang’s team created a highly porous three-dimensional structure using a polymer material called poly(dimethylsiloxane) (PDMS),  that can stretch to three times its original size. Then they placed a liquid metal (EGaIn) inside the pores, allowing electricity to flow consistently even when the material is massively stretched.

The result is a material that is both extremely conductive and very, very stretchy.

"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."