Manta Ray Underwater Robot

Conventional autonomous underwater vehicles rely on spinning propellers to generate thrust — a mechanism borrowed from surface shipping that was never optimised for quiet, slow-speed manoeuvrability in confined or sensitive environments. Propeller noise disrupts cetacean communication, and cavitation bubbles erode hardware at depth. The rotating shaft also represents a single mechanical point of failure in environments where recovery is difficult or impossible.

Manta rays solved underwater propulsion differently. Their enormous, flexible pectoral fins undulate in smooth travelling waves, generating lift-based thrust through a mechanism called batoid locomotion. Crucially, manta rays can modulate frequency, amplitude, and phase of fin oscillation independently on each side, allowing three-dimensional vectored thrust with no moving parts other than the fins themselves. The result is near-silent, highly efficient cruising and exceptional low-speed agility.

Researchers at Festo and Virginia Tech developed autonomous underwater vehicles whose silicone-over-carbon-fibre pectoral fins replicate manta locomotion. Servo-driven ribs bend the fin in coordinated waves; by adjusting the phase difference between port and starboard fins, the vehicle turns, pitches, or hovers without any rudder or thruster assembly. Festo's BionicManta demonstrated stable operation in open water, while Virginia Tech's version targeted reef survey applications where propeller noise and turbulence would disturb wildlife.

The broader implication extends beyond marine robotics. Oscillating-fin propulsion is scalable from millimetre-scale surgical microrobots to large underwater gliders. The same principle — distributed, phase-controlled flexible surface deformation — offers a blueprint for any situation where quiet, efficient, low-turbulence locomotion matters more than maximum speed.