Manta Ray-Inspired Soft Swimmers Actuated by Bistable Actuators.

Manta rays exhibit highly agile and complex swimming patterns through undulatory pectoral fin flapping, inspiring the development of efficient and controllable swimming robots. However, integrating high propulsion efficiency,maneuverability, and untethered operation into a single robotic platform remains a grand challenge. Here, we propose a bioinspired bistable flapping soft swimming robot that mimics manta ray motion to address this issue. The flapping wings employ pre- stretched elastomeric matrix composites (EMC) to achieve bistable shapes, enabling reconfigurable mono/bistable transitions and multimodal swimming behaviors through simple frequency modulation of fluidic actuation. An analytical model is employed to conduct a sensitivity analysis, identifying key parameters that influence the bistability and shapes of the actuators. Computational Fluid Dynamics (CFD) simulations show a peak instantaneous thrust of up to 17.2 N. Experimental parametric studies are performed with dynamic tests to assess the impact of critical parameters on swimmer performance and to optimize the robot's design. An untethered swimming robot is integrated with a microfluidic pressure modulation control system for remote operation and multi-modal manoeuvrability. By allowing real-time modulation of swimming modes, the robot demonstrates the ability to navigate complex trajectories and avoid obstacles in unstructured aquatic environments.