The Naval Research Laboratory (NRL) has developed an actively controlled curvature robotic fin based on the pectoral fin of a coral reef fish, the bird wrasse (Gomphosus varius). This fin, which generates 3D vectored thrust through actuation of fin and fin rib stroke angles, has been integrated onto a man-portable, unmanned underwater vehicle called WANDA – Wrasse-inspired Agile Near-shore Deformable-fin Automaton.

The technology consists of a base housing, multiple spanwise rotating ribs, and a skin-like membrane. The base and ribs are actuated by motors causing shape deformation of the membrane. By weighting and combining various fin gaits, WANDA performs controlled maneuvers including forward, reverse and vertical translation, and turn-in-place rotation. The controlled shape-changing fins provide more effective propulsion forces at slow speeds and in flow-changing or cluttered environments, and WANDA’s design provides a large platform body, allowing for payloads or sensor platforms.

Various enabling technologies are also being developed in conjunction with the WANDA Unmanned Underwater Vehicle (UUV) platform. These include artificial lateral line sensors for near-field object and flow detection, biochemical sensors for trace level detection of chemical signatures, and a hybrid flying swimmer platform (Flimmer) for fast, long range ingress of a UUV. The technology lends itself to a number of missions where screw propellers are not optimal, including stealth, and low-speed underwater monitoring and inspection. NRL is interested in an industry partner to collaborate on further testing and advancing beyond the prototype stage.


  • Flexible: Individual rotational actuation of each fin rib enables variable deflections between the ribs, allowing greater control over thrust, direction, and magnitude.
  • Durable: Resistance to fouling and prop tangling from near shore vegetation and debris
  • Quiet: Fins have a unique sound profile that is different from traditional propellers
  • Convenient: Compact and easy-to-assemble rib actuator housing

Available for License: US Patent No. 9,045,211

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