A spontaneous and controllable removal of condensed microdroplets at high supersaturation via self-propelled jumping is achieved by introducing a designed micropore array on a nanostructured superhydrophobic surface. The fabricated surface was demonstrated to delay the ice formation for 1 hour at -15 °C with a supersaturation of 6.97.

etc. However, the inherent poor durability of the materials that are mostly developed using polymeric hydrogel, metal oxide coatings and electrostatic multilayers often challenges the application of these wettability properties in practical scenarios. Here, 'amine-reactive' polymeric multilayers of nano-complex were developed to fabricate 'internal' underwater superoleophobic/superoleophilic coatings with impeccable physical/chemical durability. This allows the super-wetting properties to exist beyond the surface of the material and remain intact even after severe physical damage including erosion of the material and continuous exposure to an artificial-marine environment for more than 80 days. Moreover, this current design allowed for independent revalidation of some key hypotheses with direct experimental demonstrations, and provided a basis to develop highly durable super-oil-wettability properties under water. It is believed that this contemporary study will make a worthwhile contribution on developing multifunctional materials for widespread practical applications by exploiting these super-oil-wetting properties.]]>

Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.

在Q235钢上热浸镀锌后,经磷酸盐-铈盐-硬脂酸复合处理制备了超疏水膜层。采用接触角仪测定试样的接触角(WCA)和滚动角(WSA),研究了其疏水性;采用场发射扫描电子显微镜(FE-SEM)、能谱分析仪(EDS)、傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)研究试样的表面形貌和成分结构;采用电化学阻抗谱(EIS)和塔菲尔极化曲线(Tafel)研究试样的耐腐蚀性。结果表明,超疏水膜层通过界面空气膜层的捕获可以有效减少基体腐蚀,当硝酸铈处理时间为300 s时性能最好,在表面形成一层多孔的磷酸锌/ 铈盐微纳米复合结构;硬脂酸疏水改性后接触角达到162°,电化学阻抗增加了2个数量级,显示出良好的耐腐蚀性。

Although realizing dewetting transitions of droplets spontaneously on solid textured surfaces is quite challenging, it has become a key research topic in many practical applications that require highly efficient removal of liquid. Despite intensive efforts over the past few decades, due to impalement of vapor pockets inducing strong pinning of the contact lines, how to realize the self-removal of small droplets trapped in the textures remains an urgent problem. We report an in situ spontaneous dewetting transition of condensed droplets occurring on pillared surfaces with two-tier roughness, from the valleys to the tops of the pillars, owing to the nanotexture-enhanced superhydrophobicity, as well as the topology of the micropillars. Three wetting transition modes are observed. It is found that a further decreased Laplace pressure on the top side of the individual droplets accounts for such a surprising transition and self-removal of condensed water. An explicit model is constructed, which quite effectively predicts the Laplace pressure of droplets trapped by the textures. Our model also reveals that the critical size of the droplet for transition scales as the spacing of the micropillars. These findings are expected to be crucial to a fundamental understanding, as well as a remarkable strategy to guide the fabrication, of optimum super-water-repellant surfaces.

In conventional dropwise condensation on a hydrophobic surface, the condensate drops must be removed by external forces for continuous operation. This Letter reports continuous dropwise condensation spontaneously occurring on a superhydrophobic surface without any external forces. The spontaneous drop removal results from the surface energy released upon drop coalescence, which leads to a surprising out-of-plane jumping motion of the coalesced drops at a speed as high as 1 m/s. The jumping follows an inertial-capillary scaling and gives rise to a micrometric average diameter at steady state.

It was recently discovered that condensation growing on a nanostructured superhydrophobic surface can spontaneously jump off the surface, triggered by naturally occurring coalescence events. Many reports have observed that droplets must grow to a size of order 10 μm before jumping is enabled upon coalescence; however, it remains unknown how the critical jumping size relates to the topography of the underlying nanostructure. Here, we characterize the dynamic behavior of condensation growing on six different superhydrophobic nanostructures, where the topography of the nanopillars was systematically varied. The critical jumping diameter was observed to be highly dependent upon the height, diameter, and pitch of the nanopillars: tall and slender nanopillars promoted 2 μm jumping droplets, whereas short and stout nanopillars increased the critical size to over 20 μm. The topology of each surface is successfully correlated to the critical jumping diameter by constructing an energetic model that predicts how large a nucleating embryo needs to grow before it can inflate into the air with an apparent contact angle large enough for jumping. By extending our model to consider any possible surface, it is revealed that properly designed nanostructures should enable nanometric jumping droplets, which would further enhance jumping-droplet condensers for heat transfer, antifogging, and antifrosting applications.

The coalesce-induced condensate drop motion on some superhydrophobic surfaces (SHSs) has attracted increasing attention because of its wide potential applications. However, microscopic mechanism of spontaneous motion has not been discussed thoroughly. In this study, we fabricated two types of superhydrophobic copper surfaces with sisal-like nanoribbon structures and defoliation-like nanosheet structures by different wet chemical oxidation process and followed by same fluorization treatment. With lotus leaf and butterfly wing as control samples, the spontaneous motion phenomenon of condensate drops on these four kinds of SHSs was investigated by using optical microscope under ambient conditions. The results showed that among all four types of SHSs, only superhydrophobic copper surfaces with sisal-like nanoribbon structures showed obvious spontaneous motion of condensate drops, especially when the relative humidity was higher. The microscopic mechanism of spontaneous motion was discussed in relation to the states of condensate drops on different nanostructures. It shows that the instantaneous Cassie state of condensed droplets prior to coalescence plays a key role in determining whether the coalesced drop departs, whereas only SHS possessing nanostructures with small enough Wenzel roughness parameter r (at least <2.1) and nanogaps forming high enough Laplace pressure favors the formation of the instantaneous Cassie state by completing the Wenzel-Cassie transition.

The coalescence-induced condensate drop motion on some superhydrophobic surfaces (SHSs) has attracted increasing attention because of its potential applications in sustained dropwise condensation, water collection, anti-icing, and anticorrosion. However, an investigation of the mechanism of such self-propelled motion including the factors for designing such SHSs is still limited. In this article, we fabricated a series of superhydrophobic copper surfaces with nanoribbon structures using wet chemical oxidation followed by fluorization treatment. We then systematically studied the influence of surface roughness and the chemical properties of as-prepared surfaces on the spontaneous motion of condensate drops. We quantified the "frequency" of the condensate drop motion based on microscopic sequential images and showed that the trend of this frequency varied with the nanoribbon structure and extent of fluorination. More obvious spontaneous condensate drop motion was observed on surfaces with a higher extent of fluorization and nanostructures possessing sufficiently narrow spacing and higher perpendicularity. We attribute this enhanced drop mobility to the stable Cassie state of condensate drops in the dynamic dropwise condensation process that is determined by the nanoscale morphology and local surface energy.

Despite the recent demands of bioinspired superhydrophobic surfaces with self-cleaning properties in various industrial applications, a low-cost fabrication method for superhydrophobic films with excellent stability has rarely been studied. Herein, we report a robust superhydrophobic organic- inorganic hybrid composites film produced via a facile one-step solution-process. As coating materials for the facile one-step fabrication of the robust superhydrophobic films, we included Al₂O₃ nanoparticles for micro/nano hierarchical dual-scale structures, alkylsilane for low surface energy, and organic cross-linkers for increasing the stability of the hybrid composite films. Based on the hydrophobicity and stability tests of the hybrid composite films, the optimized composition of the robust superhydrophobic hybrid composite films showed high water contact angles (>150°) and low sliding angles (<5°) as well as excellent mechanical and thermal stability (up to 350 °C).

Current treatments for traumatic oral mucosal wounds include the gold standard of autologous tissue and alternative tissue-engineered grafts. While use of autografts has disadvantages of minimal availability of oral keratinized tissue, second surgery, and donor site discomfort, tissue-engineered grafts are limited by their unavailability as off-the-shelf products owing to their fabrication time of 4-8 weeks. Hence, the current work aimed to develop a potentially cost-effective, readily available device capable of enhancing native mucosal regeneration. Considering the key role of epidermal growth factor (EGF) in promoting mucosal wound regeneration and the advantages of mucoadhesive delivery systems, mucoadhesive films composed of polyvinylpyrrolidone and carboxymethylcellulose were developed to provide sustained release of EGF for a minimum of 6 h. Bioactivity of released EGF supernatants was then confirmed by its ability to promote proliferation of BALB/3T3 fibroblasts. Efficacy of the developed system was then investigated in vitro using buccal tissues (ORL 300-FT) as a potential replacement for small animal studies. Although the mucoadhesive films achieved their desired role of delivering bioactive EGF in a sustained manner, treatment with EGF, irrespective of its release from the films or solubilized in medium, caused a hyperparakeratotic response from in vitro tissues with distinguishable histological features including thickening of the spinous layer, intra- and intercellular edema, and pyknotic nuclei. These significant morphological changes were associated with no improvements in wound closure. These observations raise questions about the potential of using in vitro tissues as a wound healing model and substitute for small animal studies. The mucoadhesive delivery system developed, however, with its potential for sustained release of bioactive growth factors and small molecules, may be loaded with other desired compounds, with or without EGF, to accelerate the process of wound healing.

Dropwise condensation is a phenomenon of common occurrence in everyday life, the understanding and controlling of which is of great interest to applications ranging from technology to nature. Scalable superhydrophobic textures on metals are of direct relevance in improving phase change heat transport in realistic industrial applications. Here we reveal important facets of individual droplet growth rate and droplet departure during dropwise condensation on randomly structured hierarchical superhydrophobic aluminum textures, that is, surfaces with a microstructure consisting of irregular re-entrant microcavities and an overlaying nanostructure. We demonstrate that precoalescence droplet growth on such a surface can span a broad range of rates even when the condensation conditions are held constant. The fastest growth rates are observed to be more than 4 times faster as compared to the slowest growing droplets. We show that this variation in droplet growth on the hierarchical texture is primarily controlled by droplet growth dynamics on the nanostructure overlaying the microstructure and is caused by condensation-induced localized wetting nonuniformity on the nanostructure. We also show that the droplets nucleating and growing within the microcavities are able to spontaneously navigate the irregular microcavity geometry, climb the microtexture, and finally depart from the surface by coalescence-induced jumping. This self-navigation is realized by a synergistic combination of self-orienting Laplace pressure gradients induced within the droplet as it dislodges itself and moves through the texture, as well as multidroplet coalescence.