Prototype robot swims, dives and flies out of the water

Gulls and puffins plunge into the sea, swim, then burst back into the air. A robot built by engineers at MIT and at the École polytechnique fédérale de Lausanne (EPFL) now does the same in tests, in a water tank and on Lake Geneva. The team is led by Raphael Zufferey, an assistant professor of mechanical engineering at MIT. The machine is a prototype, and it weighs less than 300 grams, about half a pound.

Inside the central fuselage sit a battery and a waterproof electric motor. The motor drives a crankshaft, a rotating arm that turns spinning motion into up-and-down motion, and that crankshaft pumps two flexible wings at preset frequencies. The wings are thin membranes coated with hydrophobic nanoparticles, which repel water and help wick it away. A motorized tail changes its angle so the robot can climb or dive.

The researchers tested combinations of wing size, flapping frequency and tail angle until the robot could move smoothly from swimming to flying. The best results came from medium-size wings, flexible enough to limit how far they beat in water and firm enough to keep the robot aloft in air. Speeds and flapping frequencies were close to those of real birds, and a 70-degree pitch, a relatively steep angle, allowed the leap from water into air. Many diving birds paddle their feet to take off from the surface, but the robot needed no feet at all.

For oceanographers, marine biologists and coastal communities, the appeal is reach. Zufferey imagines launching the vehicle from a boat or from shore, flying it close to an iceberg, a port facility or a pod of whales, then diving for a measurement or a sample and flying back to deliver the data, at what he describes as a fraction of the cost of traditional methods. The team has announced no date and no partner for such missions. Its next steps are wings that can turn as well as flap, and tests in choppy water and in wind.

Zufferey points to frequency as much as to reach: « You could send this out not just every week, but every hour. » That is a vision for a machine still at prototype stage, and the robot has not yet been tested under turbulent conditions. The researchers hope to deploy it to help answer questions in ocean science, and they give no timeline for doing so.