Design and analysis of water-powered soft robotic arms: effects of chamber geometry on flexibility and load capacity

Abstract With the increasing demand for ocean resource exploitation, deep-sea exploration, and environmental protection, the importance of underwater operation technologies has become more prominent. Traditional rigid robotic arms lack flexibility in complex underwater environments, limiting their effectiveness in diverse tasks. Flexible robotic arms, with their pliable structures, offer superior adaptability. However, the influence of geometric design on the performance of water-driven actuators remains unclear, hindering their optimization. This study systematically investigates a three-degree-of-freedom water-powered soft actuator, analyzing how chamber geometry affects its bending performance and load capacity. Through static analysis, finite element simulations, and experimental validation, the effects of chamber shapes (sector, semicircular, and circular), lengths, and cross-sectional areas on actuator performance are evaluated. Results indicate that sector chambers provide optimal bending and load capacity, while semicircular and circular chambers offer comparable precision and adaptability. Optimizing chamber length and cross-sectional area is critical for enhancing performance in complex environments. Furthermore, the inclusion of a stretch limiting layer and the design of water supply channels passing through the actuator significantly improve stability and load-bearing capacity. This study provides theoretical guidance for designing underwater soft actuators, supporting applications such as shipwreck salvage, artifact retrieval, and biological sample collection.