Programmable Sponge for Hydro‐Active Morphing Module with Light Weight and High‐Volume Change

Abstract Sponge materials offer a unique combination of porosity, flexibility, compressibility, and responsiveness, yet their potential as primary elements in shape‐morphing systems remains underexplored. Here, a modular shape‐morphing platform constructed entirely from pre‐compressed cellulose sponges, referred to as “foambots” is presented. Each block is geometrically patterned to induce anisotropic swelling, enabling programmable volumetric morphing upon hydration without external power or electronics. By stacking and orienting foambots in designed configurations, complex 3D structures capable of untethered transformation in aquatic environments are created. The large volumetric expansion (≈1:10 before and after morphing) allows for a unique compact form for easy transport and deployment. How key design parameters (block length, hole position, and orientation) govern bending behavior are systematically investigated, and inverse design strategies to achieve target geometries are demonstrated. Using this approach, two functional applications are realized, leveraging foambots's programmable large volumetric expansion for deployable floating structures: a wearable flotation module that wraps around the user's limb, and a self‐propelling boat capable of expanding ≈463% of its original size when deployed, autonomous deploying, and traveling on water. These results establish cellulose sponge as a unique, sustainable material for morphing applications and introduce a scalable, low‐cost strategy for creating deployable and reconfigurable soft structures.