SoftRafts: floating and adaptive soft modular robots

Abstract Modular robots offer adaptability and reconfigurability, yet their application in aquatic environments and dynamic multi-tasking—particularly for manipulation—remains underexplored. We hypothesize that incorporating soft-bending capabilities into modular designs can significantly enhance versatility in such settings. In this work, we introduce a variable-stiffness soft modular robot that integrates rigid 3D-printed components, soft foam, a cable-driven actuation mechanism, and a propeller for aquatic propulsion. Permanent magnets enable fast, passive inter-module connections. This robot can bend, steer, and connect with others, supporting a variety of functions. It acts as a gripper to retrieve debris from water surfaces, assembles into a floating raft for drone landings, and forms a snake-like chain that transitions seamlessly between land and water. Additionally, multiple robots can collaborate in swarm-like behaviors to transport payloads. Our findings demonstrate that combining soft deformation with modularity enables a multifunctional robotic platform capable of navigating and interacting in complex, aquatic environments.