A bioinspired mechano-catalytic hydrogel leaf for self-adaptive water purification

Stimulus-responsive hydrogels have emerged as versatile platforms for soft robotics and environmental remediation, yet most systems remain limited to either mechanical actuation or catalytic function, with few achieving synergistic coupling where motion actively optimizes chemical performance. Moreover, existing platforms often require elaborate fabrication and cannot autonomously adapt their catalytic interface to dynamic environmental conditions. Inspired by the nastic movement of Mimosa - where environmental triggers induce rapid mechanical response to optimize function - this study reports a bioinspired bilayer hydrogel leaf that couples autonomous actuation with on-demand photocatalysis. The reactive PAM-FeCu layer, embedded with Fe₃O₄/CuS heterojunctions, enables photothermal conversion and synergistic ROS-mediated purification/antibacterial effects, while the PNIPAM layer drives thermo-responsive bending under near-infrared irradiation. The leaf undergoes rapid thermally induced opening (0°-360° bending within 22 s), which exposes the catalytic layer to maximize light harvesting and interfacial mass transfer. This mechano-catalytic coupling achieves a ∼2.6-fold enhancement in methylene blue degradation compared to static counterparts, along with limited Fe/Cu ion leaching, and >90% bactericidal efficiency against S. aureus and E. coli. The bilayer architecture also enables multidirectional locomotion (bending, grasping, and floating-mediated transfer) in aqueous media, allowing autonomous navigation and localized purification in complex flow environments. Additionally, the system retains catalytic activity in real river and lake water, while maintaining structural integrity. Overall, this mechano-catalytic feedback strategy shifts photocatalyst design from a static optimization paradigm to self-regulating systems that integrate environmental stimulus-responsive actuation with catalysis, offering a paradigm for next-generation adaptive purification platforms.