Watch a cyborg stingray made of rat heart cells swim using light

Or at least a coin-sized cyborg stingray made from rat heart cells that can be controlled underwater using light. Designed by Kevin Kit Parker from Harvard University's Wyss Institute and his team, the 16-millimetre-long soft robot has a gold skeleton overlaid with a flexible polymer. Its muscles are made up of about 200,000 rat heart cells laid down in layers. "My building material is alive," says Parker. To get the tiny robot to move, the team tweaked the rat-cell genes to make them light-sensitive.