Integrated soft robot capable of surviving extreme underwater shock loads
Xiaobo Liu, A-Man Zhang, Tuck-Whye Wong, Zhihan Zhang, Hongjia Zhang, Chao Zhang, Jie-Wei Wong, Xiangping Chen, Jia-Tee Low, Ke Bai, Wenbin Wu, Shimin Li, Tiefeng Li, Yihui Zhang, Guorui LiAbstract
Soft robots have been developed for underwater tasks owing to their compliant, damage-tolerant bodies, which foster an expectation that soft bodies are inherently robust in aquatic environments. However, most reported systems operate under moderate or quasi-static conditions, and overlook a critical vulnerability—when cavity-rich soft structures are subjected to underwater shocks, the embedded cavities collapse violently, triggering a phenomenon we term ‘soft-matter implosion’. This process generates internal pressures several times higher than the incident pressure and can severely damage onboard electronics. Using a simplified cavity-containing structure, we combine underwater impact experiments and finite element simulations to reveal the mechanism of soft-matter implosion and quantify the peak pressure under different parameters. These results inform a function-structure co-design framework that suppresses implosion while preserving overall flexibility. Guided by this framework, we built a rigid-casing-free, fully integrated manta‑ray‑inspired soft robot that survives single impacts up to 49.8 MPa and sequential impacts at 31.5 MPa, and resumes flapping locomotion after impact. This work establishes an impact‑resistant soft robot platform and provides a generalizable design strategy for durable, flexible machines operating in challenging underwater environments.