Wrinkled smart surfaces: Enhanced switchable wettability and directional liquid transportation

Abstract

Smart surfaces that can convert external stimuli to changes of surface properties are playing a significant role in both fundamental research and practical applications. However, it is still a challenge to create smart surfaces with good switchability in a facile and controllable way. Herein, a wrinkled smart surface is prepared by a strategy which combines stimuli-responsive polymers and surface wrinkles, where polymers provide surface responsiveness and wrinkles result in enhancement and a regulation effect. A model system composed of the pH-responsive polymer PDEAEMA grafted on the surface of a wrinkled Au/PS bilayer via Au-SH bonding is presented. The contact angle (CA) difference between acidic/basic droplets is found to be much larger for wrinkled surfaces (~117°) than that of flat surfaces (~30°), suggesting that wrinkles can significantly reinforce the switchability of wetting. Moreover, by taking advantage of wrinkles in sample processing and high controllability, we further optimize the wrinkle structure and incorporate asymmetric patterns into the wrinkled smart surface, thereby achieving directional manipulation of acidic and basic droplets/liquids. Due to the excellent capability found in this study, wrinkled smart surfaces may find potential applications in sensors, microfluidics, separation, and smart interfacial design.