A novel leaf inspired hydrogel film based on fiber reinforcement as rapid steam sensor

Abstract

Intelligent hydrogel films with bilayer structures are promising materials as smart devices. Although the design of bilayer hydrogels with excellent mechanical properties, tough interfacial adhesion and rapid shape deformation is important, their construction in simple route is still challenging. In this work, inspired by leaf structure, an extremely simple casting strategy is established for preparing bilayer intelligent hydrogel films with bacterial cellulose (BC) for reinforcement. Driven by active diffusion of aqueous NIPAM/clay pre-gel solution into BC network, a tough fiber reinforced Gel@BC bilayer hydrogel with double network interface could be directly fabricated. The as-prepared Gel@BC bilayer hydrogel possessed exceptional mechanical properties since BC acted as the continuous reinforcement phase like vein of the leaves. The interfacial toughness reached ~102 J/m2 because the PNIPAM/clay nanocomposite hydrogel was filled into BC network to form the double network structure at the interface. Due to the anisotropic swelling induced by bilayer structure, the Gel@BC bilayer hydrogel provided remarkable rapid temperature-induced tunable shape transformation and exhibited a reversible bending behavior. In particular, the non-swelling characteristic of BC is beneficial for the mechanical stable and shape deformation of Gel@BC even in hot environment. This simple continuous fiber reinforcement strategy provides significant guidance for fabricating biomimetic actuators with applications in soft robotics such as bionic stomata for environment regulation and circuit switch as steam detectors.