Silver and copper might help your clothes monitor you

Researchers at Duke University used silver-coated copper nanowires and silicon rubber to create a new conductive “felt” that can be easily patterned onto fabrics to create flexible wires.

The felt carries electricity even when bent, stretched and twisted over and over again. This means that it could be used to embed electronics such as fitness trackers and health monitors into shirts, hats, and shoes.

In a university press release, the scientists explain that to produce a flexible wire, they first suck a solution of copper nanowires and water through a stencil, creating a stack of interwoven nanowires in the desired shape. Then, the interwoven nanowires are heated to 300 F to melt the contacts together, and finally, silicone rubber is added to fill in the gaps between the wires.

The material maintains its conductivity when twisted and stretched. Photo by Matthew Catenacci, Duke University.

"The material is similar to the interwoven fibers that comprise fabric felt, but on a much smaller scale," said Benjamin Wiley, an associate professor of chemistry at Duke whose lab spearheaded the study.

To show the pliability of their new material, the scientists molded the nanowire felt into a variety of squiggly, snaking patterns. Stretching and twisting the wires up to 300 times did not degrade the conductivity. This is the most innovative quality of their invention, as other wires made of silver are also flexible but they stop working properly after a short period of time and are more expensive to produce.

“This material retains its conductivity after stretching better than any other material with this high of an initial conductivity. That is what separates it,” Wiley said.