A group of scientists have revealed the RoboBee – an aerial-to-aquatic robot that can fly, dive into water, swim, propel itself back out of water, and land safely.
The team of scientists from Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically-Inspired Engineering at Harvard have said the air-to-water microrobot could be used for search and rescue missions, research studies or environmental monitoring.
“This is the first microrobot capable of repeatedly moving in and through complex environments,” said Yufeng Chen, who was a graduate student in the Harvard Microrobotics Lab and is first author of the paper, published in Science Robotics.
“We designed new mechanisms that allow the vehicle to directly transition from water to air, something that is beyond what nature can achieve in the insect world.”
Because water is 1,000 times denser than air, the RoboBee’s wing flapping speed must vary widely between its two environments.
So that the RoboBee can operate repeatedly in both air and water, the scientists employed a “Goldilocks combination” of wing size and flapping rate, which sees the robot flaps its wings at 220 to 300 hertz in air and nine to 13 hertz in water.
Another major challenge the team had to address was the fact that water’s surface tension is more than 10 times the weight of the RoboBee and three times its maximum lift, so it is akin to flying into a brick wall.
To solve that problem, the researchers retrofitted the RoboBee with four buoyant outriggers — essentially robotic floats — and a central gas collection chamber. Once the RoboBee swims to the surface, an electrolytic plate in the chamber converts water into oxyhydrogen, a combustible gas fuel.
“Because the RoboBee has a limited payload capacity, it cannot carry its own fuel, so we had to come up with a creative solution to exploit resources from the environment,” said Elizabeth Farrell Helbling, graduate student in the Hravard Microrobotics Lab.
“Surface tension is something that we have to overcome to get out of the water, but is also a tool that we can utilize during the gas collection process.”
The Harvard Office of Technology Development has filed a patent application for the RoboBee, and the team are now exploring commercialisation opportunities.
However, currently, because of the lack of onboard sensors and limitations in the current motion-tracking system, the RoboBee cannot fly immediately after propelling itslef out of water, but the team hopes to address that with future research.
“The RoboBee represents a platform where forces are different than what we – at human scale – are used to experiencing,” said Robert Wood, Charles River Professor of Engineering and Applied Sciences at Harvard and Core Faculty Member of the Wyss Institute.
“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.”