Robust and Versatile Moisture-responsive Actuators Based on Polydopamine-Modified Bacterial Cellulose Nanofibers

The rapid development of moisture-responsive actuators has attracted considerable research attention in fields such as flexible electronics and soft robotics. However, the fabrication of robust cellulose-based actuators with superior mechanical strength and excellent moisture responsiveness remains a significant challenge. Herein, inspired by the adhesive properties of mussels, we developed a homogeneous moisture-responsive actuator (BCNF/PDA) by integrating bacterial cellulose nanofibers (BCNF) with polydopamine (PDA). The catechol and amino groups in PDA form strong interactions with BCNF through multiple covalent and noncovalent bonds, endowing the resulting actuator with high tensile strength (336 MPa), a high Young’s modulus (7.12 GPa), excellent toughness (12.4 MJ m–3), and rapid hygroscopic actuation performance. Owing to the fast moisture adsorption/desorption capabilities of BCNF and PDA, an effective moisture gradient is established within the actuator, enabling stable and rapid hygroscopic deformation. Consequently, the actuator exhibits a fast response, large deformation (133°), and high actuation force output (9.3 N m–2). Furthermore, its feasibility as a mechanical arm, smart switch and smart curtain for moisture control was demonstrated in a prototype device, highlighting the great potential of this type of actuator for practical applications.