Looking to the natural world for engineering inspiration is an idea at least as old as Leonardo da Vinci. Copying nature directly, though, has often proved hard. For example, birds flap their wings to achieve both lift and propulsion, but flying machines that imitate this action have tended not to do well. Human engineering has found it easier to create aircraft by giving them fixed, rigid wings and propelling them with motors. Now scientists have built a robotic stingray that imitates the motion of its biological counterpart. Moreover, the robotic stingrays don’t move with the electric circuits and servomotors of conventional robots. Their muscle cells are powered by light and engineered to mimic the elegant undulations of a living stingray.
