New and Improved RoboBee Flies, Dives, Swims, Then Flies Again

A Harvard engineering lab has been building a robotic bee for more than 25 years, and it can now do things that even real bees can't manage.

For more than 25 years now, a quiet little design lab at Harvard has been working on a unique robotics project — perfecting the world's first and only RoboBee.

Research published Oct. 25 in the journal Science Robotics details the latest iteration of the little bot, which was first conceived by mechanical engineering student Robert Wood in 1991. Since then, the RoboBee project has been a perennial work-in-progress for scientists and students at the Harvard School of Engineering and Applied Sciences and the Wyss Institute for Biologically-Inspired Engineering.

Even in its most basic configuration, the RoboBee is a mechanical marvel. Its tiny polymer wings – designed to mimic real insect wings – are powered by small ceramic “muscles” that convert electrical pulses into kinetic energy, making the RoboBee the world's smallest flapping-wing aircraft.  

Every few years, designers officially publish new research on various RoboBee models under development. (One version of the bot can stick to walls, for instance.) This latest version of the RoboBee is the most ambitious yet, as it can fly, dive into water, swim around, and propel out of the water.

Those are tricky maneuvers for any robot, and it's taken years of development to get larger amphibious drones to manage the trick. But because the RoboBee weighs in at a featherweight 175 milligrams (0.006 of an once), the tiny machine must actually overcome forces of mass, volume, and surface tension that are completely different than what a bird-sized robot has to deal with. It also requires a multi-modal locomotive system that lets the bot both fly and swim.

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The RoboBee is 1,000 times lighter than any other aerial-aquatic robot, and this difference in scale is what's kept decades worth of Harvard engineering students busy with the design. In the official announcement of the new research, Wood — now a professor of engineering and applied sciences at Harvard — said that the robot's extremely tiny size makes it a unique engineering challenge.

“The RoboBee represents a platform where forces are different than what we — at human scale — are used to experiencing," he said.

The RoboBee engineering team, with support from the National Science Foundation, is working on the millimeter scale, confronting the problem of surface tension, which transforms the surface of any body of water into something akin to a brick wall. For the bot to dive, its impact must be forceful enough to break that surface tension. But surface tension works both ways. To get back out again, the RoboBee must generate enough force to pop through from below.

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Engineers outfitted the RoboBee with four bouyent outriggers — robotic floaties, essentially. To achieve liftoff from the surface into the air, the RoboBee uses a small electrolytic plate that converts water into oxyhydrogen, a combustible fuel. A tiny spark mechanism inside the bot ignites the gas, powering the RoboBee upward like a minuscule rocket ship. Once in the air, the bot stabilizes itself, and lands. In order for the bot to return to flight mode, it first has to dry off.

The RoboBee remains a kind of a perpetual research platform without any practical applications. But researchers might one day deploy aerial-aquatic robots to remote areas in order to gather biological samples on land, in the air, or under water. And, equipped with onboard sensors, the bots might map areas that larger devices or humans can't fit into — a task that could easily benefit search-and-rescue efforts.

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