A novel film designed for flexible electronics can stretch to twice to size without breaking. Created by Rahul Panat and Indranath Dutta of Washington State University, the indium-plastic film could significantly advance robotic
skins, bendable batteries, wearable monitoring devices and sensors, and connected fabrics.
The tiny metal connections that go into flexible electronics are challenging to manufacture robustly because they must be able to stretch and bend a lot, while conducting electricity. In the past, manufacturers used tiny metal springs but these take up space and make it difficult to design complicated, high-density circuitry. Electricity also has to travel farther in coiled springs, requiring more power and bigger batteries.
“The circuitry ends up requiring a ton of real estate and bulky batteries,” said Panat.
Researchers have also experimented with gold, which works better than other materials but is prohibitively expensive, and copper, which severely cracks when it is stretches more than 30 percent or so.
The WSU researchers found that when they made a metal film out of indium, a fairly inexpensive metal compared to gold, and periodically bonded it to a plastic layer commonly used in electronics, they were able to stretch the metal film to twice its original length. When the pieces broke, it was actually the plastic layer that failed, not the metal.
“This is a quantum improvement in stretchable electronics and wearable devices,” said Panat.
While Panat is excited about the work and hopes it will be commercialized, the researchers also want to better understand the metal’s behavior.
“A metal film doubling its size and not failing is very unusual,” he said. “We have proposed a model for the stretchy metal but much work is needed to validate it. It’s a good situation to be in.”
A paper describing the research was recently published in Applied Physical Letters.