Exceptionally strong and weldable MXene-xanthan gum films for smart humidity-driven and photothermal marangoni actuators

The rapid advancement of smart actuators has highlighted the challenge of preparing mechanically robust, large-scale films for their fabrication. In this study, xanthan gum, renowned for its excellent water absorption properties, was combined with MXene to create a nacre-inspired composite film reinforced by abundant hydrogen bonds. This unique structure significantly enhances the film's mechanical properties, improving tensile strength and toughness, enabling it to withstand crumpling and folding without damage. MXG exhibited excellent weldability, facilitating the production of large-scale films. The incorporation of micro-wrinkles endows the film with anisotropic mechanical behavior, while its strong water absorption capacity enables programmable humidity-driven actuation under a gradient. The actuator demonstrates rapid response speeds, substantial bending curvatures, and excellent cyclic stability. Furthermore, leveraging the photothermal properties of MXene, the film generates a photothermal Marangoni effect under light irradiation, enabling programmable and directional movement on water surfaces. With superior mechanical performance, weldability, and photothermal responsiveness, this composite film shows great potential for manufacturing large-scale actuators with applications in cargo transportation, intelligent robotics, and soft devices.