Chinese Academy of Sciences Engineers Fast, 3D-Maneuverable Soft Robotic Fish

Researchers at the Shenyang Institute of Automation, part of the Chinese Academy of Sciences, have developed an electrohydraulically actuated soft robotic fish that pairs high-speed swimming with three-dimensional maneuvering, as reported by TechXplore (https://techxplore.com/news/2026-10-soft-robotic-fish-combines-high.html). The development targets a core challenge in bioinspired soft robotics, where structural compliance has frequently limited swimming velocity and spatial control.

The study, led by Yiwei Zhang and published October 5 in IEEE/ASME Transactions on Mechatronics, couples a rigid-flexible electrohydraulic propulsion system with dynamic buoyancy regulation. To achieve rapid movement, the team built an actuator with two degrees of freedom, integrating localized rigid constraints to reduce structural deformation. Dual driving units execute alternating movements that mimic antagonistic biological muscle contractions, producing high-frequency tail oscillations.

In experimental testing, the robotic fish achieved a top swimming speed of 2.13 body lengths per second, or approximately 26 centimeters (10 inches) per second, with a minimum cost of transport of 9.4 J/(kg·m). According to the researchers, this establishes a new speed record for soft robotic fish employing body-caudal-fin propulsion.

For multi-axis control, the platform incorporates an artificial swim bladder that operates via a liquid-to-gas phase transition. By shifting local buoyancy, the mechanism generates a pitching moment that adjusts posture between −20 degrees and 58 degrees. Coordinated actuation allows the unit to perform horizontal cruising, turning, S-shaped paths, ascending, diving, and spiral ascents, presenting a viable architecture for underwater environmental monitoring and resource exploration.