A Switchable Cross‐Species Liquid Repellent Surface

Magnetic actuation provides a remote, nondestructive, and real-time way for controllable liquid manipulation, which has promising technological applications for areas ranging from digital microfluidics, biochemical assays, and microreactors, to liquid collection. However, conventional magnetic liquid manipulation usually relies on incorporating magnetic particles into a liquid to empower its motion in response to an external magnetic field, resulting in considerable limitations of magnetic actuation in various applications. Recently, a range of magnetoresponsive surfaces (MRSs) with elaborately designed surface structures and/or compositions have enabled on-demand liquid manipulation using magnetic fields, even when the liquids do not contain any magnetic particles. Here, the state-of-the-art of MRSs capable of manipulation of nonmagnetic liquids is reviewed. Their preparation, different manipulation modes, including directed propulsion, spreading, and rebound, and the underlying working mechanisms are discussed. Based on the working principles, MRSs are classified into three categories, including surfaces with magnetic bendable microstructures, surfaces with switchable topographies, and surfaces infused with ferrofluids. Their applications in microfluidics, microreactors, liquid distributors and pumps, fog collection, and anti-icing are presented. Finally, key challenges and the future prospects of MRSs are provided.

Section: Mrs Designmentioning

confidence: 99%

Section: Surfaces With Magnetic Micropillarsmentioning

confidence: 99%

Section: Surfaces With Magnetic Conical Microstructuresmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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et al. 2017

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133

Smart surfaces with tunable wettability have aroused much attention in the past few years. However, to obtain a surface that can reversibly transit between the lotus-leaf-like superhydrophobic isotropic and rice-leaf-like superhydrophobic anisotropic wettings is still a challenge. This paper, by mimicking microstructures on both lotus and rice leaves, reports such a surface that is prepared by creating micro/nanostructured arrays on the shape memory polymer. On the surface, the microstructure shapes can be reversibly changed between the lotus-leaf-like random state and the rice-leaf-like 1D ordered state. Accordingly, repeated switch between the superhydrophobic isotropic and anisotropic wettings can be displayed. Research results indicate that the smart controllability is ascribed to the excellent shape memory effect of the polymer, which endows the surface with special ability in memorizing different microstructure shapes and wetting properties. Meanwhile, based on the smart wetting performances, the surface is further used as a rewritable functional platform, on which various droplet transportation programmes are designed and demonstrated. This work reports a superhydrophobic surface with switchable isotropic/anisotropic wettings, which not only provides a novel functional material but also opens a new avenue for application in controlled droplet transportation.

Stimuli‐Responsive Bioinspired Materials for Controllable Liquid Manipulation: Principles, Fabrication, and Applications

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Many emerging interfacial technologies, such as self-cleaning surfaces, oil/ water separation, water collection, and microfluidics, are essentially liquid manipulation processes. In this regard, micro-nanostructures of the living organisms are highly preferable, by virtue of the evolutionary pressure and the adaptation to the specific environments, to inspire the optimization of man-made interfaces. With the increasing demands of modern life, research, and industry, intelligent materials with stimuli-responsive liquid manipulation functions have gained substantial attention from interfacial scientists. This review introduces the recent progress in the development of stimuli-responsive liquid-manipulating materials with bioinspired structures and surface chemistry according to two classified manipulation modes: (i) smart manipulation of liquid wetting behaviors, including lyophobic/lyophilic and superlyophobic/superlyophilic, and (ii) smart manipulation of liquid motion behaviors, including coalescence, transportation, rolling/adhesion, and sliding/pinning.At the beginning of the presentation of each classification, the theoretical basis and the sources of inspiration are introduced comprehensively to ensure a better understanding. This review mainly focuses on the mechanisms, fabrication, and applications of the state-of-the-art works related to smart and biomimetic liquid-manipulating materials. Finally, conclusions and future prospects are provided, and the remaining problems and promising breakthroughs in fabricating large-scale, cost-effective, and efficient smart liquid-manipulating materials are outlined.