超疏水涂膜的研究进展

从固体表面的润湿性理论出发介绍了三种不同的接触角模型和理论方程,阐明了实现超疏水性的两个必要条件:低表面能表面和特定的细微粗糙度。同时综述了国内外制备超疏水涂膜时常用的疏水材料和制备粗糙表面的方法、动态疏水性及其应用前景。     

Wetting behavior of polymer coated nanoporous anodic alumina films: transition from super-hydrophilicity to super-hydrophobicity

We show that nanoporous anodic alumina films, with pore diameters in the range 10-80 nm, can be transformed from being very hydrophilic (or super-hydrophilic) to very hydrophobic (or super-hydrophobic) by coating the surface with a thin (2-3 nm) layer of a hydrophobic polymer. This dramatic transformation happens as a result of the interplay between surface morphology and surface chemistry. The coated surfaces exhibit 'sticky' hydrophobicity as a result of ingress of water into the pores by capillary action. The wetting parameters (contact angle and contact angle hysteresis) exhibit qualitatively different dependences on pore diameters in coated and uncoated films, which are explained by invoking appropriate models for wetting.     

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg-Mn-Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m² and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m² by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I_corr) with R_ct increasing two orders of magnitude of 16,500 Ω·cm² compared to that obtained for blank of 485 Ω·cm².     

复合纳米涂层配方的研究

为了制备超疏水性纳米有机涂层,以机械共混的方法,将一种新型纳米SiO2颗粒加入到了一种溶剂型光油中。为了进一步提高涂层的疏水性以及解决纳米粒子带来的问题,在体系中加入了异丙醇、三乙酸甘油酯以及硅油。结果表明:通过调整各组分的比例,水滴在涂层表面的接触角能够达到160°,实现了超疏水。     

聚醚/二苯甲酮侧基聚硅氧烷的膜形貌及亲疏水行为

用原子力显微镜AFM等仪器研究了单晶硅表面聚醚(PE)/二苯甲酮衍生物(UV)侧基聚硅氧烷PE-PUVSi的膜形貌及亲、疏水特性,探讨了空气湿度对PE-PUVSi膜形貌及表面性能的影响。结果表明,在单晶硅表面PE-PUVSi形成的硅膜呈非均一、微观相分离结构,其中UV侧基以直立纤细尖峰态分布在聚硅氧烷膜表面,而亲水性PE侧基则卷曲堆积成峰包。将PE-PUVSi硅膜在相对湿度(RH)为97%的空气中放置2.5 h,PE-PUVSi膜表面因吸附水而亲水性增加,其原有的纤细尖峰消失,而且膜表面平均粗糙度降低。     

透明超疏水涂膜的研究进展

透明超疏水涂膜不但具有超疏水表面的独特性能,而且对可见光具有良好的透光性,在生产和生活中有着广泛的应用潜力,已逐步成为超疏水表面领域的一个研究热点。介绍了超疏水涂膜的透明性,并归纳了近年来透明超疏水涂膜制备方法取得的新进展。根据现有的理论和研究,提出利用氟硅烷类低表面能物质,与溶胶-凝胶法、相分离技术、等离子体刻蚀等能提供表面微观结构和粗糙度的技术有机结合,并控制好粗糙度与可见光透过率之间的关系,可制备出适用的透明超疏水涂膜。     

Mechanically durable superhydrophobic surfaces

Development of durable non-wetting surfaces is hindered by the fragility of the microscopic roughness features that are necessary for superhydrophobicity. Mechanical wear on superhydrophobic surfaces usually shows as increased sticking of water, leading to loss of non-wettability. Increased wear resistance has been demonstrated by exploiting hierarchical roughness where nanoscale roughness is protected to some degree by large scale features, and avoiding the use of hydrophilic bulk materials is shown to help prevent the formation of hydrophilic defects as a result of wear. Additionally, self-healing hydrophobic layers and roughness patterns have been suggested and demonstrated. Nevertheless, mechanical contact not only causes damage to roughness patterns but also surface contamination, which shortens the lifetime of superhydrophobic surfaces in spite of the self-cleaning effect. The use of photocatalytic effect and reduced electric resistance have been suggested to prevent the accumulation of surface contaminants. Resistance to organic contaminants is more challenging, however, oleophobic surface patterns which are non-wetting to organic liquids have been demonstrated. While the fragility of superhydrophobic surfaces currently limits their applicability, development of mechanically durable surfaces will enable a wide range of new applications in the future.     

溶液浓度和非溶剂比例对PVC膜形貌和疏水性能的影响

目的 研究溶液质量分数和非溶剂体积分数对PVC薄膜表面形貌和疏水性能的影响,以获得具有超疏水表面的PVC薄膜。方法 以四氢呋喃为良溶剂、乙醇为非溶剂,利用非溶剂诱导相分离的原理,采用旋涂法在玻璃基底上制备超疏水的聚氯乙烯（PVC）涂膜;通过对PVC样品的疏水性、表面形貌、结晶性能和热性能进行分析,探究溶液质量分数以及非溶剂的体积分数对PVC样品性能的影响。结果扫描电镜和接触角测试表明,添加一定体积分数的乙醇使得所制备的PVC样品形成了多孔膜层以及纳米级聚合物球粒,从而提高了PVC样品的疏水性。XRD测试结果表明,添加乙醇并不会改变PVC样品的无定形结构。结论 PVC溶液质量分数对所制备PVC样品的疏水性能和表面结构没有明显影响,乙醇体积分数为30%～40%时,可形成表面水接触角大于150°的超疏水表面。     

Bioinspired aquatic microrobot capable of walking on water surface like a water strider

Walking on the water surface is a dream of humans, but it is exactly the way of life for some aquatic insects. In this study, a bionic aquatic microrobot capable of walking on the water surface like a water strider was reported. The novel water strider-like robot consisted of ten superhydrophobic supporting legs, two miniature dc motors, and two actuating legs. The microrobot could not only stand effortlessly but also walk and turn freely on the water surface, exhibiting an interesting motion characteristic. A numerical model describing the interface between the partially submerged leg and the air-water surface was established to fully understand the mechanism for the large supporting force of the leg. It was revealed that the radius and water contact angle of the legs significantly affect the supporting force. Because of its high speed, agility, low cost, and easy fabrication, this microrobot might have a potential application in water quality surveillance, water pollution monitoring, and so on.     

Hydrophobic and hydrophilic surface nano-modification of PET fabric by plasma process

Polyethylene terephthalate (PET) fabrics were treated by radio frequency inductively coupled plasma (RF-ICP) to modify their hydrophobic and hydrophilic properties. Types of gases which were SF6, O2, N2 and Ar, treatment time, pressure and RF power were varied systematically. The water droplet contact angle measurements showed that, treating with SF6 plasma would result in the increase of hydrophobicity of PET samples while treating with O2, N2 and Ar plasmas would yield hydrophilic properties. In both hydrophobic and hydrophilic cases, the surface morphology of PET fibers was roughened after exposed to plasma. Hence, it is not obvious that these surface roughness induced by plasma is sufficient to yield the increase in hydrophobicity by the well known lotus effect.     

Universal, geometry-driven hydrophobic behaviour of bare metal nanowire clusters

A parallel array of isolated metal nanowires is expected to be hydrophilic. We show, however, that a clustering of such nanowires brought about by vacuum drying produces a 'dual-scale roughness' and confers a strongly hydrophobic property to the surface. The mean size of the nanowire clusters as well as the contact angle are both found to be related to the wire length, and the critical wire length above which the surface becomes hydrophobic is ≈10?μm. Surface roughness is generally known to enhance water-repellent properties, but this is the first report of roughness-induced hydrophobicity on a bare (uncoated) metallic surface.     

Subtractive Structural Modification of Morpho Butterfly Wings

Different from studies of butterfly wings through additive modification, this work for the first time studies the property change of butterfly wings through subtractive modification using oxygen plasma etching. The controlled modification of butterfly wings through such subtractive process results in gradual change of the optical properties, and helps the further understanding of structural optimization through natural evolution. The brilliant color of Morpho butterfly wings is originated from the hierarchical nanostructure on the wing scales. Such nanoarchitecture has attracted a lot of research effort, including the study of its optical properties, its potential use in sensing and infrared imaging, and also the use of such structure as template for the fabrication of high‐performance photocatalytic materials. The controlled subtractive processes provide a new path to modify such nanoarchitecture and its optical property. Distinct from previous studies on the optical property of the Morpho wing structure, this study provides additional experimental evidence for the origination of the optical property of the natural butterfly wing scales. The study also offers a facile approach to generate new 3D nanostructures using butterfly wings as the templates and may lead to simpler structure models for large‐scale man‐made structures than those offered by original butterfly wings.     

Study of the surface structure of butterfly wings using the scanning electron microscopic moiré method

Scanning electron microscopic (SEM) moiré method was used to study the surface structure of three kinds of butterfly wings: Papilio maackii Menetries, Euploea midamus (Linnaeus), and Stichophthalma howqua (Westwood). Gratings composed of curves with different orientations were found on scales. The planar characteristics of gratings and some other planar features of the surface structure of these wings were revealed, respectively, in terms of virtual strain. Experimental results demonstrate that SEM moiré method is a simple, nonlocal, economical, effective technique for determining which grating exists on one whole scale, measuring the dimension and the whole planar structural character of the grating on each scale, as well as characterizing the relationship between gratings on different scales of each butterfly wing. Thus, the SEM moiré method is a useful tool to assist with characterizing the structure of butterfly wings and explaining their excellent properties.     

Fabrication of super-hydrophobic film with dual-size roughness by silica sphere assembly

Two simple approaches were developed for the fabrication of super-hydrophobic film with dual-size roughness by taking advantage of assembling silica micro- and nanospheres. Electrostatic adsorbing technique and template-directed self-assembly were used here. The dual-size surface, which mimics the surface topology of lotus leaves, comprises both the micro-scale and nano-scale roughness. After the roughened surface was chemically modified with a layer of fluoroalkylsilane, super-hydrophobicity with a water contact angle higher than 160° and sliding angle as low as 0.5° can be achieved. The simplicity and cheapness of this procedure may make widespread applications of this super-hydrophobic film possible.     

Patterned hydrophobic-hydrophilic templates made from microwave-plasma enhanced chemical vapor deposited thin films

In the present research, nano-structured materials exhibiting super-hydrophobic behavior obtained by microwave-plasma enhanced chemical vapor deposition (MPECVD) had their surface chemical status altered through vacuum ultraviolet (VUV) light irradiation. Falling water droplets rolled and bounced without wetting or spreading over the initially super-hydrophobic surfaces. We demonstrate a surface preparation technique to create a patterned super-hydrophobic/super-hydrophilic substrate in which micropatterns with super-hydrophobic and super-hydrophilic regions were prepared through irradiation with VUV light. To confirm the method, growth of water droplets is observed in situ on such super-hydrophobic/super-hydrophilic micropatterns. We discuss the applicability of the super-hydrophobic/super-hydrophilic pattern to the bottom-up assembling of materials, like site-selective electroless Cu plating on patterned substrates made of paper and selective cell culture experiments.     

Self-assembly of one-side-functionalized graphene nanosheets in bilayered superstructures for drug delivery

In this article, we describe the one-side functionalization of graphene nanosheets with hydrophilic catechol-bearing pyrrolidine rings. For this purpose, we used, for the first time, a solvothermal alternative of 1,3 dipolar cycloaddition of azomethine ylide. To achieve asymmetrical reaction, graphene nanosheets were initially and during reaction deposited on glass substrate. The result of one-side functionalization of graphene was the formation of amphiphilic few-layered graphene nanosheets. The modified side becomes hydrophilic due to the attachment of catechols, while the nonmodified side remains hydrophobic. In the literature, there are limited examples of functionalized graphene with different sides, the so-called Janus-type graphenes. These amphiphilic graphene nanosheets dispersed in water were self-organized in bilayer superstructures, with hydrophilic outer surface and hydrophobic internal space. The later can host hydrophobic molecules such as anticancer drugs and could be used in drug delivery systems. As an example, camptothecin, a drug practically insoluble in water, was used here to show that it can be transferred to water phase using graphene as transporter.     

Plasma and thermoforming treatments to tune the bio-inspired wettability of polystyrene

This paper shows the effects on wettability of plasma and thermoforming treatments on 14 different polystyrene (PS) surfaces, with a comparison with a lotus leaf. Quantitative roughness analyses of PS surfaces and lotus leaf, by three-dimensional optical profilometer and scanning electron microscope, have been carried out. We characterized the water drop sliding by measuring the contact angle, sliding angle, sliding volume and sliding speed. A relevant correlation between technological treatment, surface roughness parameters and wetting measurements clearly emerges, suggesting the plasma/thermoforming treatment as a process for enhancing the hydrophilic/hydrophobic behavior of PS surfaces. Determination of the static and resistant forces of the drop sliding on the surfaces concludes the paper.     

燃烧合成疏水BN粉体和超疏水涂层的制备及其性能表征

具有分级结构的BN纳米薄膜展现出优异的超疏水性, 但由于该薄膜的制备过程复杂、成本昂贵, 不适宜大规模的生产和应用。与之相比, 基于疏水BN粉体的超疏水涂层的应用会更为便捷。本研究采用镁热还原氮化燃烧合成法结合酸洗工艺制备了疏水的单相BN粉体, 水接触角为(144.6±2.4)°, 疏水性可以归因于BN粉体颗粒具有的微纳分级结构。在此基础上, 以这种燃烧合成的疏水BN粉体为填料制备的BN/氟硅树脂复合涂层进一步表现出超疏水性, 其中质量分数30% BN/FSi树脂涂层的水接触角为(151.2±0.7)°, 滚动角约为8°。该涂层与文献报道的通过CVD方法制备的BN纳米薄膜的性能相当, 但工艺更加简单。这是一种利用陶瓷粉体的疏水性来制备超疏水有机无机复合涂层的简便易行的新方法, 有望获得广泛的工程应用。     

Hydrophobic–hydrophilic dichotomy of the butterfly proboscis

Mouthparts of fluid-feeding insects have unique material properties with no human-engineered analogue: the feeding devices acquire sticky and viscous liquids while remaining clean. We discovered that the external surface of the butterfly proboscis has a sharp boundary separating a hydrophilic drinking region and a hydrophobic non-drinking region. The structural arrangement of the proboscis provides the basis for the wetting dichotomy. Theoretical and experimental analyses show that fluid uptake is associated with enlargement of hydrophilic cuticular structures, the legulae, which link the two halves of the proboscis together. We also show that an elliptical proboscis produces a higher external meniscus than does a cylindrical proboscis of the same circumference. Fluid uptake is additionally facilitated in sap-feeding butterflies that have a proboscis with enlarged chemosensory structures forming a brush near the tip. This structural modification of the proboscis enables sap feeders to exploit films of liquid more efficiently. Structural changes along the proboscis, including increased legular width and presence of a brush-like tip, occur in a wide range of species, suggesting that a wetting dichotomy is widespread in the Lepidoptera.     

Temperature-responsive chromatographic separation of amino acid phenylthiohydantions using aqueous media as the mobile phase

Recently, green chemistry has become one of the most important subjects of science for environmental pollution prevention. Here, we report development of a novel chromatographic technology for phenylthiohydantoin (PTH)-amino acid analyses in which only aqueous solution is used as the mobile phase. We have devised HPLC adsorbents (stationary phase) by modifying the surfaces of microparticulate silica gel using functional polymers. The thermoresponsive copolymer, poly(N-isopropylacrylamide-co-n-butyl methacrylate) (IBc) was used to modify the silica stationary phase surfaces. This polymer-grafted surface exhibits temperature-regulated hydrophilic/hydrophobic property changes in water. PTH-amino acid interactions with this surface are readily modulated by changing the column temperature using an isocratic aqueous mobile phase. Increasing hydrophobic interactions between more hydrophobic PTH-amino acids with hydrophobized polymer-grafted surfaces at elevated mobile phase temperatures is used for the effective separation of PTH-amino acids in aqueous solution. This study is aimed at the development of novel separation processes, which are also environmentally benign, for use with biochemical substances in order to meet the growing needs of the life sciences and biotechnology. The method is useful for various separations in life science so that proteins can maintain their biological activity and enzymes, their enzymatic activity.