LED lights are far more efficient than incandescents, but enough light to drive photosynthesis will still require significant power, so one still might ask where the power is going to come from.
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.