A Labriform-Inspired Multi-Stable Soft Robotic Swimmer

Pectoral-fin-based (labriform) swimming combines high-speed propulsion with agile maneuverability through rigid-flexible fin partitioning. Inspired by this principle, we present a multi-stable soft robotic swimmer composed of two wedge-shaped bistable actuators integrated with fin-like rigid-flexible morphologies. The bistable actuators generate large, rapid deformations for thrust production, while the compliant fin membranes enable drag-reducing feathering during recovery. An analytical model is developed to predict the shape of bistable actuators and is validated experimentally with a minimum prediction accuracy of 97.74%. Computational fluid dynamics (CFD) analysis reveals that bistable switching induces vortex dipole ejection, contributing to thrust generation. The proposed robot attains a maximum speed of 17.53$\text{cm.s}^{-1}$(1.10$\text{BL.s}^{-1}$), a turning radius of 0.58 per body length, and a turning speed of 31.51$^\circ$/s, highlighting our design in shaping both swimming speed and maneuverability. By integrating bistable actuation with bio-inspired fin morphologies, this work offers a principled design strategy for achieving fast and maneuverable swimming in robotic systems.