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 Fibres 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 — via redwolf.newsvine.com