Biomimetic adhesive-free self-splicing enables scalable wood film for programmable hygromorphic soft actuators

Stimulus-responsive actuators play a crucial role in the next-generation intelligent systems. However, challenges such as complex fabrication processes, limited sustainability, and poor tolerance to complex deformations remain. This study introduces a sustainable “top-down” self-splicing strategy to fabricate spliced transparent wood film (TWF) for programmable hygromorphic soft actuators. Natural wood was subjected to delignification followed by TEMPO-mediated oxidation, yielding TWF with exceptional hygroscopicity. Two adhesive-free self-splicing methods: biomimetic “Mortise and Tenon” interlocking and self-adhesion using oxidized wood fibers enable arbitrary shaping and large-scale integration of spliced TWF. Since hydrogen bonding dominates interfacial bonding strength, the self-spliced TWF exhibits excellent tensile strength (up to 131.8 MPa), surpassing most plastic films and TWF joined with commercial adhesives. Interestingly, benefiting from the hygroscopicity and designability of self-splicing TWF, the resulting hygromorphic soft actuator achieves continuous rapid deformation and recovery, and programmable morphing into complex configurations ( e.g. , spirals, biomimetic mimosa and petals). This adhesive-free self-splicing approach enables the scalable production of TWF and yielding soft actuators with versatile morphing capabilities, low production cost, and sustainability, highlighting their potential in soft robotics and smart materials.