Researchers at MIT and EPFL have developed FAAV, a lightweight robot inspired by diving birds that can move through both air and water. Weighing just 250 grams, the flapping-wing machine uses a carbon-fiber frame, a small tail, and flexible membrane wings to travel across two very different environments.
In tests, FAAV reached about 6.3 meters per second in the air and nearly 1 meter per second underwater. Its most notable feature is the ability to rise from the water and return to flight without propellers, wing folding, or paddling feet. The system was designed to show how a single wing mechanism can adapt to the resistance of both air and water.
Flexible wings, efficient motion
The key to the robot's performance is wing flexibility. Underwater, the wings bend dramatically, reducing drag and easing the load on the motor. In the air, they stiffen enough to create lift. A single electric motor powers the full motion cycle, while silicone coating keeps the robot waterproof without adding much weight.
The engineers also found that the robot naturally settles into an efficient flapping rhythm shared by many flying and swimming animals. That result offers fresh insight into how birds and other species balance speed, control, and energy use when moving between dense and light fluids.
Although FAAV is not yet fully autonomous, the team sees strong potential for future field use. A robot like this could one day help oceanographers, marine biologists, and coastal teams gather data near reefs, ice edges, or marine habitats, then return to deliver it quickly. The project was published in Science.
As this kind of bio-inspired engineering advances, it could open a new era of compact explorers that move seamlessly between environments and expand the reach of scientific observation.