Work

Knifefish-inspired robotic fish enhances locomotion performance by undulatory anal fin propulsion and flexible body

Year: 2026

Type: article

Abstract: Complex underwater terrains require robots that can maneuver efficiently through confined, vegetation-rich spaces while minimizing hydrodynamic disturbance. Inspired by the black ghost knifefish, we developed Naiad, a bio-inspired robotic fish that combines a flexible body with a servo-actuated anal fin. Coordinated body deformation and undulatory ribbon-fin propulsion enabled forward and reverse swimming, turning, and vertical maneuvering. In experiments, Naiad reached 0.20 body lengths per second (BL/s) and a minimum cost of transport (COT) of 3.42. It also achieved a maximum turning rate of 23.67°/s (0.41 rad/s) and a minimum turning radius of 0.31 body lengths (BL). Demonstrations in a confined obstacle-rich channel and an outdoor lake further showed multi-gait maneuverability under aquatic conditions. These results demonstrate that integrating body flexibility with undulatory fin propulsion enhances locomotor versatility. This approach provides a design strategy for agile underwater robots in confined environments and supports applications in exploration and environmental monitoring.

Source: iScience

DOI: 10.1016/j.isci.2026.117819