To address the issues of poor operational flexibility and ecological disturbance risks in traditional underwater robots, as well as the low manufacturing accuracy and low functional integration of current photo-responsive soft systems, in this study, we developed a poly(N-isopropylacrylamide)/multiwalled carbon nanotube (MWCNT) photothermal composite hydrogel and a biomimetic modular soft robot inspired by the giant river shrimp. We systematically clarified the effects of material composition and structural thickness on the expansion, mechanical, and photoresponsive properties of the hydrogel to screen out the optimal formulation. The high-precision manufacturing of the hydrogel structure was achieved through a custom digital micromirror device based on an ultraviolet three-dimensional printing system, and a specialized predehydration impregnation cycle was combined to ensure the uniform dispersion of MWCNTs in the complex hydrogel structure. The structure of the robot was analyzed through transient fluid-solid coupling velocity simulation and finite element method analysis. Experimental results demonstrated that the robot exhibited rapid response and multidirectional flexible movement capabilities. This bionic soft robot possesses multimode controllable movement, underwater cargo transportation and targeted placement capabilities, and has good cyclic stability. Compared with the previously reported similar light-driven hydrogel robots, its speed fluctuation during eight consecutive cycles is relatively small, and the average error of 10 repeated targeted placements is approximately 2 mm, which can meet the basic requirements for precise underwater operations at the microscale. In this work, we establish a comprehensive theoretical and technical framework for the development of underwater soft robot technology for applications in unstructured aquatic environments.

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• Biomimetic & bio-inspired materials
• Functional materials
• Composite materials