Bio-Inspired Robot Swims & Flies, Revolutionizing Ocean Exploration

Engineers at MIT and EPFL designed a bio-inspired flapping-wing aerial-aquatic vehicle capable of swimming underwater and breaching the surface to fly through the air.

Published in the journal Science, the study introduced a vehicle weighing under 300 grams designed to help researchers analyze the flight mechanics of diving birds like puffins, petrels, and gulls. The flapping-wing aerial-aquatic vehicle features a central fuselage, a steerable motorized tail, and two flexible flapping wings driven by a waterproof electric motor, battery, and crankshaft system. To aid in shedding water, the thin membrane wings are coated with hydrophobic nanoparticles.

Operating across both mediums requires navigating fluid dynamics where water is 1,000 times denser than air.

“You have to do some adaptation to make that transition work. But there’s a solution that exists in nature,” says Raphael Zufferey, assistant professor of mechanical engineering at MIT and lead author of the study. “Birds like puffins can fly very fast through the air, and can dive and swim through water at speeds of 3 meters per second. They’re able to do pretty amazing things. So we knew is was possible. Just no one had tried this in a mobile robotic system.”

During experiments in a water tank and at Lake Geneva, the research team evaluated three wing spans measuring 60, 80, and 100 centimeters. The medium-sized wings provided the necessary flexibility to minimize flapping amplitude underwater while retaining sufficient rigidity to generate aerial lift. To launch successfully from the water into the air, the robot required a steep pitch angle of 70 degrees, preventing its wingtips from touching the surface during flapping.

The system achieved underwater swimming speeds near 1 meter per second at a flapping frequency of 5 hertz, alongside aerial flight speeds of approximately 6 meters per second at a similar frequency. Surprisingly, the vehicle completed these transitions without needing to paddle feet across the water’s surface.

“If you look at birds, most birds need to paddle at the surface to take off. And the question was, do we need the same for robots? And it turns out we don’t,” Zufferey says.

Zufferey heads the AURA Lab at MIT, where researchers build small-scale aerial and aquatic vehicles designed to unobtrusively monitor marine ecosystems. The vehicle offers a practical alternative for environmental sampling in challenging locations such as icebergs, ports, or near marine life.

“Our dream vision is for oceanographers, marine biologists, and members of coastal communities to launch this robot from a boat, or from shore, and it would fly close to the area of interest, such as an iceberg or a port facility, or over a pod of whales,” Zufferey says. “It would dive into the water to take a measurement or collect a sample, and fly back to deliver the data at a fraction of the cost of traditional methods. Then it could go back out to dive for more.”

Future developments will focus on enabling the wings to turn and testing performance under turbulent wind and wave conditions.

“One of the major challenges in ocean science is collecting data both frequently and across many locations, which is something this robot could do in the future,” Zufferey says. “You could send this out not just every week, but every hour. It could fly out at high speeds, dive in fly back, deliver its data, and go back out, multiple times.”

The research team included co-authors from EPFL and Northwest Indian College, with support provided in part by a Marie Skłodowska-Curie Actions fellowship grant.