Robot swims and flies like diving birds, could revolutionize ocean sampling

The robot represents a convergence of biomimetic engineering and practical ocean science. Engineers have long studied diving birds—about 100 species can both swim and fly—to understand how animals move through two physically distinct fluids. Air and water have vastly different densities and viscosity, so wings that work in one medium must be carefully adapted for the other. By testing combinations of wing size, flapping frequency, and tail angle in a water tank and Lake Geneva, the team discovered that an 80-centimeter wing with around 5 hertz flapping frequency and a 70-degree pitch angle allows smooth transitions from water to air.

A key insight emerged from comparing the robot's design to its biological inspirations. Most diving birds use their feet to paddle at the surface before taking flight; the EPFL–MIT team found that their wing-only design eliminates this requirement. This difference is significant for engineering because it simplifies the robot's mechanics and reduces moving parts, making it more durable and easier to control. The hydrophobic wing coating helps shed water, mimicking adaptations in real diving birds.

The practical motivation is clear: oceanographers and marine biologists struggle to sample hazardous aquatic environments—floating ice, whale pods, isolated facilities—without risking expensive research vessels. A small, autonomous, wing-flapping robot that can launch from a boat, fly to a target, dive for samples, and return could dramatically reduce cost and risk. The researchers are now refining the design to allow the wings to turn as well as flap, and to validate performance in realistic choppy waters and wind before deploying the robot for real ocean science missions.