Original URL: http://www.theregister.co.uk/2012/12/24/elastic_wires/
Boffins build elastic wires with liquid metal
Headphone cable stretches, band keeps playing
Researchers at North Carolina State University have shown “conductive wires that can be stretched up to eight times their original length while still functioning.”
The wires have been tested, and demonstrated in the video below, to work perfectly well as headphone wires. Sound continues to reach the headphones even as the wires are stretched.
The wires themselves don’t stretch, but instead use a liquid alloy of gallium and indium housed in a very plastic polymer the researchers say, in the paper Ultrastretchable Fibers with Metallic Conductivity Using a Liquid Metal Alloy Core , is hollow fibre “composed of a triblock copolymer, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) resin.”
The paper says the fibres’ mechanical properties remain unchanged even when stretched and but that resistance increases when it is stretched. Nonetheless, even when the housing stretches, sufficient liquid metal remains to enable conductivity.
The paper also says production methods for this kind of fibre are well-known, which would make it easy to mass-produce except for the fact a broken wire will leak. That’s not good news on the durability front. It’s also unwelcome from a therapeutic point of view: you don’t want to eat Indium, while Gallium can stain the skin and may also be toxic.
Watch Video 
The researchers have tested the stretching wires in headphones and a battery charger. Conductive clothing is also on their minds.
Reg readers, one imagines, might like the idea of network cables with just an inch or three of extra potential to save the hassle that arises when a cable is just that much short of a port. ®