Preparation and response study of microcrystalline cellulose/fish bladder gelatin actuator

Humidity-driven smart materials have attracted increasing attention due to their capability of autonomous actuation without external energy input, offering significant potential in soft robotics and adaptive systems. However, natural polymer-based actuators often suffer from insufficient mechanical strength and limited structural stability, which restrict their practical applications. In this study, a novel biomimetic water-driven actuator was developed based on silane-modified microcrystalline cellulose (KMCC) and fish bladder gelatin (FG). A bilayer anisotropic structure inspired by natural hygroscopic systems was designed, and the effects of KMCC content and structural parameters on deformation behavior were systematically investigated through experimental characterization and finite element simulation. The results demonstrate that the incorporation of KMCC significantly enhances the mechanical and thermal properties of the composite hydrogel. The tensile strength increased from 0.258 MPa (pure FG) to 0.477 MPa at 10% KMCC, while the thermal decomposition temperature improved by approximately 11.81 °C. The actuator exhibited excellent reversible deformation behavior, with a maximum bending curvature of 0.083 at 10% KMCC content. Increasing KMCC content led to reduced deformation amplitude but improved structural stability. Furthermore, the actuator achieved controllable twisting deformation, with a maximum torsion angle of 2.04π and deflection of 66.93 mm at a 20° layer angle. Finite element simulation results were in good agreement with experimental data, confirming the reliability of the deformation mechanism. he deformation mechanism is governed by moisture diffusion and hydrogen bond reconstruction, which induce anisotropic volume changes and interfacial stress mismatch in the asymmetrical structure. This study provides a feasible strategy for enhancing the performance of water-driven actuators through material interface modification and structural design, offering new insights for the development of high-performance smart materials in soft robotics and adaptive systems.