The desperate effort this week to find two hikers who disappeared at the bottom of the Grand Canyon represented the National Park Service’s most extensive use yet of drones in a search-and-rescue mission.
Robots clean rivers and sort waste, monitor ecosystems, and inspect renewable-energy infrastructure. But even the greenest robot has an environmental footprint.
EPFL engineers have designed acoustic cavities that convert sound waves into thrust, propelling small robots and ultralight aerial vehicles without on-board actuators or electronics.