The millimeter-scale RoboBee can fly, dive into water, swim around, and then take off into the air again. At just 175 milligrams, it's 1,000 times lighter than any other aerial-to-aquatic robot. Designed at Harvard's microrobotics laboratory, the RoboBee is outfitted with four tiny "floaties" and a chamber that converts water into oxyhydrogen, fuel that combusts to propel the robot out of the water.
"The RoboBee represents a platform where forces are different than what we – at human scale – are used to experiencing," says researcher Robert Wood. "While flying the robot feels as if it is treading water; while swimming it feels like it is surrounded by molasses. The force from surface tension feels like an impenetrable wall. These small robots give us the opportunity to explore these non-intuitive phenomena in a very rich way."
The gas increases the robot's buoyancy, pushing the wings out of the water and the floaties stabilize the RoboBee on the water's surface. From there, a tiny, novel sparker inside the chamber ignites the gas, propelling the RoboBee out of the water. The robot is designed to passively stabilize in air, so that it always lands on its feet.
"By modifying the vehicle design, we are now able to lift more than three times the payload of the previous RoboBee," said (researcher Yufeng) Chen. "This additional payload capacity allowed us to carry the additional devices including the gas chamber, the electrolytic plates, sparker, and buoyant outriggers, bringing the total weight of the hybrid robot to 175 miligrams, about 90mg heavier than previous designs. We hope that our work investigating tradeoffs like weight and surface tension can inspire future multi-functional microrobots – ones that can move on complex terrains and perform a variety of tasks."
"A biologically inspired, flapping-wing, hybrid aerial-aquatic microrobot" (ScienceRobotics)