Inspired by Puffins: MIT and EPFL Jointly Develop Air-Water Amphibious Flapping-Wing Drone

Researchers have long sought to build robotic systems capable of both flying through the air and diving underwater — a challenge the Atlantic puffin handles with ease.

Taking a cue from nature, engineers at MIT and the École Polytechnique Fédérale de Lausanne (EPFL) have jointly developed a novel Flapping-wing Aerial-Aquatic Vehicle (FAAV). Weighing less than 300 grams, the robot features a central fuselage, two flexible wings, and a steerable tail.

During field tests on Lake Geneva, the vehicle successfully swam beneath the surface, then beat its wings to break through the water and climb into the air.

"Our dream vision is for oceanographers, marine biologists, and members of coastal communities to be able to launch this robot from a boat or from shore. It can fly close to a target area — say, an iceberg, a harbor installation, or above a pod of whales," said Raphael Zufferey, Assistant Professor of Mechanical Engineering at MIT.

"It can dive in to take measurements or collect samples, then fly back to relay data at a fraction of the cost. And then go out and dive again," Zufferey added.

How the FAAV Works

The engineering team initially assumed that a dual-medium robot would require complex, heavy morphing structural components — but nature proved otherwise.

Researchers reviewed biological data on kingfishers, petrels, and puffins, and found that smaller birds maintain the same physical locomotion mechanism in both media, simply adjusting their flapping rate. Puffins flap roughly 10 times per second in air and slow to about 4 times per second when diving underwater.

The team replicated this behavior with considerable precision. The FAAV is driven by a small waterproof electric motor and a mechanical crankshaft, flapping its flexible, nanoparticle-coated wings at a steady 5 Hz.

The key to the vehicle's success lies in wing flexibility: the wings must be soft enough to reduce stroke amplitude in water, yet stiff enough to generate lift in air.

The FAAV cruises at 1 m/s underwater and reaches 6 m/s in the air.

The Challenge of Water-to-Air Transition

Breaching the water surface proved to be the hardest obstacle, requiring enormous thrust during the transition.

To overcome surface tension, the engineers found the robot must approach the surface at a steep 70-degree pitch angle. Too shallow an angle traps the wingtips in the water; too steep, and the vehicle flips backward and crashes.

Notably, the robot accomplishes the water-to-air transition without any legs or feet.

Real puffins and ducks typically use webbed feet to paddle through the surface tension. Zufferey and his team discovered that the robot only needs the right combination of wing area, flapping frequency, and tail pitch angle to lift off successfully — demonstrating that, at least in robotics, leg-paddling is entirely unnecessary for takeoff.

Next Steps: Toward Ocean Science Applications

MIT's AURA Laboratory has already begun the next phase of development. Future iterations will feature advanced wings capable of twisting and changing direction, enabling the drone to cope with strong winds and rough coastal waves.

Currently, ocean data collection depends heavily on large research vessels that cannot safely navigate hazardous shallow reefs or broken ice fields. The FAAV could change that — deployable once per hour rather than once per week, autonomously traveling between a research base and fragile marine ecosystems.

The research was published in the peer-reviewed journal Science on July 9.

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