Thermo-Responsive Smart Gating Wood Membranes

Membranes serve as the barriers that selectively allow some matter to pass through, such as gas, liquids, molecules and small particles. While smart membranes refer to membranes that have properties that could be remarkably changed by external stimuli, such as temperature, light or pH. Moreover, gating membranes refer to the opening or closing of membranes. Therefore, smart gating membranes have gained increasing attention in wide fields because of their energy-efficiency, easy operation and requiring no accessories compared to conventional actuator systems. However, current smart gating membranes still suffer from low flux, poor responsiveness, or stable actuation, which severely impede their practical applications. Inspired by the controlled opening and closure of plant stomata, we have developed a smart gating wood membrane, which takes advantage of the wood scaffolds hierarchical porous structure carrying thermo-responsive hydrogel gates. The inherent wood fibers and vessels with well-aligned pores and superior mechanical strength was employed as the fixed boundary of smart gating membrane. By <i>in situ</i> polymerization, Poly(N-isopropylacrylamide) hydrogel was introduced as thermo-responsive gate. The wood based smart gating membranes exhibited reversible and stable pore opening/closing over time under heating/cooling stimuli. The achieved rapid response and feasibility of scale-up open the venues for various practical applications. In this work, we demonstrated their potential as water flow manipulator. The smart gating wood membranes revealed remarkable and stable On/Off response under thermal stimuli.