Dielectric Elastomer-Based Biomimetic Twin-Tailed Robotic Fish with Fast and Flexible Swimming

Soft underwater robots, due to their flexible materials, low driving noise, and outstanding human-machine interaction capabilities, have enormous potential applications in underwater rescue, underwater sample collection, marine resource exploration, and other fields, arousing widespread research interest. However, current soft underwater robots based on smart materials have several shortcomings, such as slow swimming speeds, poor flexibility, weak driving force, and poor load capacity, making them difficult to apply in real task environments. Here, we designed a soft twin-tailed robotic fish driven by cylindrical dielectric elastomer actuators that can achieve fast and flexible swimming and efficient transportation. The designed dielectric elastomer actuators can realize large bending angles (84°) and high output force (53 mN), enabling the soft robot to swim quickly. The twin-tailed robotic fish is driven by two-degree-of-freedom actuators, realizing an average swimming speed of 0.35 BL/s and a maximum instantaneous swimming speed of 14.5 cm/s (0.85 BL/s). Furthermore, to demonstrate its application potential, robotic fish can transport goods to the desired location through two modes of movement (straight line movement and turning). This work not only lays the foundation for the development and application of soft swimming robots but also provides a reference for research on high-performance soft actuators applied to underwater robots.