Imagine this scenario: A terror suspect is holding hostages in a public space. A police-operated drone with a camera swoops in to assess the situation and determines he is armed and dangerous.
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.