Bioinspired, Stimuli‐Responsive, Multifunctional Superhydrophobic Surface with Directional Wetting, Adhesion, and Transport of Water

Abstract

5047wileyonlinelibrary.com in order to facilitate the unique function of the "lotus effect" on various substrates. [ 2 ] Moreover, upon mimicking the micro-to nanoscale structural roughness of the natural plants and insects, engineered superhydrophobic surfaces with tunable contact angle (CA) and hysteresis have also been fabricated by carbon nanotubes, polymers, and metal oxides, using the techniques such as chemical deposition, sol-gel, etching, or nanoprinting. [ 3 ] Directional surfaces with controllable liquid transportation properties, i.e., water condensation and collection, are also achieved on the poly(methyl methacrylate)-nylon fi bers, patterned poly(acrylic acid)/ poly(allylamine hydrochloride)/SiO 2 /semifl uorosilane superhydrophobic surface and conical copper wire by mimicking the special hydrophilic/hydrophobic region distribution of spider silk, Namib beetle's back, and cactus spines, respectively. [ 4 ] Furthermore, antiicing, dry adhesion, and drag reduction superhydrophobic surfaces are obtained by mimicking the Nepenthes pitcher plants, gecko appendage, and water strider legs. [ 5 ] The antifouling effect of the superhydrophobic turkey egg surface has also been discovered recently, which can serve as a cost-effective model for the development of artifi cial antibacteria surfaces. [ 6 ] Compared to the natural biological surfaces, the functions of the artifi cial superhydrophobic surfaces are generally determined by their intrinsic compositions and structures, which make them relatively stationary to the external stimuli. However, natural surface and interface are generally stimuli-responsive. The examples include the self-healing of the living organism tissue surface and the snapping motion of the Venus fl ytrap originated from the elastic instability at the air-solid interface, or the switchable adhesion force of gecko toe pad and butterfl y wings. The stimuli-responsive features of the natural surfaces make them extremely adaptable and durable to the surrounding environment, so that the overall bioecology performance can be promoted to the optimal level. [ 7 ] With emerging demands of functionality and adaptability, it is obvious that the structural design of static superhydrophobic surface (SHS) cannot provide a reasonable solution to overcome the functional and performance challenges. Bioinspired, Bioinspired, Stimuli-Responsive, Multifunctional Superhydrophobic Surface with Directional Wetting, Adhesion, and Transport of Water Yang Liu , Xiaowen Wang , Bin Fei , Huawen Hu , Chuilin Lai , and John H. Xin * A novel smart stimuli responsive surface can be fabricated by the subsequent self-assembly of the graphene monolayer and the TiO 2 nanofi lm on various substrates, that is, fabrics, Si wafers, and polymer thin fi lms. Multiscale application property can be achieved from the interfacial interaction between the hierarchical graphene/TiO 2 surface structure and the underlying substrate. The smart surface possesses superhydrophobic property as a result of its hierarchical micro-to n...

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