No More Propellers: With Two Wings, MIT's Robot Can Fly and Swim Underwater

Researchers at the Massachusetts Institute of Technology (MIT) have created an innovative robot capable of operating both in the air and underwater using only the same pair of wings. The project, described in the journal Science, is inspired by "puffins" and other seabirds that utilize their wings for both flying and swimming, despite the significant physical differences between air and water.

The goal of the group led by mechanical engineer Raphael Zufferey was to develop a platform that is as mechanically simple as possible, without additional components dedicated to transitioning between the two environments. The result is an amphibious robot weighing about 230 grams, with a wingspan of just under 90 centimeters, capable of transitioning from water to air in less than a second.

One of the most interesting aspects of the project is the design of the structure. Engineers decided to completely eliminate the legs, which are present in seabirds to facilitate takeoff from the water's surface. The absence of this element reduced construction complexity and allowed the robot to rely solely on wing propulsion to emerge from the water and gain altitude.

The configuration of the wings follows a different philosophy compared to natural designs. Many aquatic birds fold their wings during swimming, a solution that would require additional joints and motors. The MIT team opted for flexible wings made of translucent nylon fabric reinforced with carbon fiber rods, materials that allow the necessary compromise to operate in both environments without mechanical modifications.

During flight, the wings beat at a frequency between five and six oscillations per second. When the robot needs to leave the water, the frequency increases to about ten beats per second, a value sufficient to generate the thrust needed to break the surface and immediately start flying.

The robot's body also adopts an unconventional solution. The central structure remains open, and electronic components are individually protected from water, instead of enclosing the entire system in a watertight hull. Water can freely enter the frame without compromising the electronics' operation. This choice keeps the overall weight down and ensures neutral buoyancy, a characteristic that prevents the robot from spontaneously rising or sinking during underwater operations. Tests conducted in Lake Geneva have demonstrated the prototype's ability to quickly surface and begin flying almost seamlessly.

Current performance is already interesting from an operational standpoint. With a single charge, the MIT robot can travel nearly 6.5 kilometers in flight or over 1.6 kilometers underwater. Researchers believe that a platform of this kind could find use in environmental monitoring, for example, reaching remote coastal areas, landing on water, and collecting data related to algal blooms, marine life, or changes in coastlines.

The project took about two years to develop, and the research group is already working on new versions equipped with sensors for scientific data collection, as well as further refinements to flight and swimming dynamics. For the authors of the research, nature observation continues to serve as the primary reference for developing increasingly efficient and versatile robotic systems.