Roboden is cable you can stretch

A Japanese company has developed an electrical cable that can be stretched. Asahi Kasei says the cable, called Roboden, will expand by up to 40 percent of its length before hitting its limit. It was originally developed for use in robotics, where cables sometimes need to snake around joints that pivot or extend. Typically, spare cable has to be built into the wiring to accommodate this movement, and that can get snagged. Roboden can closely follow the robot's body and stretch as needed.