The roboits use tiny wings because they are too small to use propellers, but the electronics and batteries they need to power and control their wings are too heavy for these miniature robots to carry.
RoboFly is slightly heavier than a toothpick and is powered by a laser beam. It uses an onboard photocell to converts infrared laser energy into enough electricity to operate its wings.
"Before now, the concept of wireless insect-sized flying robots was science fiction. Would we ever be able to make them work without needing a wire?" said Sawyer Fuller, an assistant professor in the UW Department of Mechanical Engineering. "Our new wireless RoboFly shows they're much closer to real life."
The engineering challenge is the flapping. This is a power-hungry process, and both the power source and the controller that directs the wings are too big and bulky to ride aboard a tiny robot. So Fuller's previous robo-insect, the RoboBee, received power and control through wires from the ground. For the Robofly they used the photocell with the IR laser.