Dec. 18, 2012 at 2:29 PM ET
For those times when you need extra length in your headphones or phone charger, there’re now super-stretchable wires. In the not-too distant future, they could be woven into fabrics – think gym clothes with an embedded heart rate monitor to help you burn off the holiday fat.
The wire “has perfect electrical properties without compromising the mechanical properties at all,” Michael Dickey, an assistant professor of chemical and biomolecular engineering at North Carolina State University, told NBC News.
The wire evolved from earlier research on stretchable antennas that could be stretched about one a half times their original length. The wire is made of an elastic polymer and filled with a liquid metal alloy of gallium and indium. It can be stretched eight times its original length.
While stretchable wires have been made before, they usually involve a tradeoff electrical properties and mechanical properties. To make a stretchable material electrically conductive, for example, researchers might add metal particles. But that makes it less stretchy or less flexible.
The liquid-metal wires are “an order of magnitude more stretchable than the most conductive fiber and an order of magnitude more conductive than the most stretchable fiber,” Dickey said. “In other words, they kind of have the best of both worlds.”
Manufacturing the wires is simple, he noted. The only major concern is potential leakage of the metal if, for example, a curious child chews a set of headphones made with the wire.
The metal oxidizes quickly, meaning it forms a “solid skin that will prevent the metal from flowing out of the fiber,” Dickey said. But if a child were to intentionally make it come out, it might. And “it is yet to be determined what would happen if somebody swallowed some of the metal.”
Findings were reported Dec. 13 in the journal Advanced Functional Materials.