Effect of deposition parameters on the wettability and microstructure of superhydrophobic films with hierarchical micro-nano structures

Superhydrophobic films with hierarchical micro-nano structures were deposited on glass substrates by solution immersion method from a solution containing cobalt chloride, urea and cetyl trimethyl ammonium bromide (CTAB). Subsequently the films were hydrophobized with a low surface energy material like octadecanoic acid under ambient conditions resulting in superhydrophobic surfaces with water contact angle (WCA) of about 168° and contact angle hysteresis of 1°. The effect of deposition parameters such as solution composition, temperature, deposition time and alkanoic acid treatment on surface morphology and wettability of the films was studied. Mechanism of formation of cobalt chloride carbonate hydroxide film is discussed. Addition of CTAB to the solution resulted in a change in the surface morphology of the deposited films with flower-like structures. The wettability of films obtained under different process conditions was correlated to surface roughness using Wenzel and Cassie models.     

Self-assembly of amino-functionalized monolayers on silicon surfaces and preparation of superhydrophobic surfaces based on alkanoic acid dual layers and surface roughening

Reproducibly smooth amino-functionalized surfaces were obtained by deposition of aminopropyltrimethoxysilane (APTMS) at the vapor/solid interface. Characteristics of these amino-functionalized surfaces were evaluated based on atomic force microscopy, water contact angle measurement and X-ray photoelectron spectroscopy. The results showed that APTMS modified surfaces are very homogeneous and the chemical reactivity of modified surfaces can be ensured with high free amino content. Furthermore, for the purpose of tailoring the wettability of silicon surface, dual self-assembled films were achieved by performing reaction between amino-functionalized surface and n-alkanoic acids with different chain length. The wettability of the self-assembled films can be adjusted with altering the hydrocarbon chain length of alkanoic acids. Moreover, cooperation of dual self-assembled films with surface roughening, superhydrophobic surfaces with CA larger than 153 degrees were obtained. Thus, the wettability of modified surfaces can be altered greatly with changing hydrocarbon chain length of self-assembled films.     

Protein immobilization on epoxy-activated thin polymer films: effect of surface wettability and enzyme loading

A series of epoxy-activated polymer films composed of poly(glycidyl methacrylate/butyl methacrylate/hydroxyethyl methacrylate) were prepared. Variation in comonomer composition allowed exploration of relationships between surface wettability and Candida antartica lipase B (CALB) binding to surfaces. By changing solvents and polymer concentrations, suitable conditions were developed for preparation by spin-coating of uniform thin films. Film roughness determined by AFM after incubation in PBS buffer for 2 days was less than 1 nm. The occurrence of single CALB molecules and CALB aggregates at surfaces was determined by AFM imaging and measurements of volume. Absolute numbers of protein monomers and multimers at surfaces were used to determine values of CALB specific activity. Increased film wettability, as the water contact angle of films increased from 420 to 550, resulted in a decreased total number of immobilized CALB molecules. With further increases in the water contact angle of films from 55 degrees to 63 degrees, there was an increased tendency of CALB molecules to form aggregates on surfaces. On all flat surfaces, two height populations, differing by more than 30%, were observed from height distribution curves. They are attributed to changes in protein conformation and/or orientation caused by protein-surface and protein-protein interactions. The fraction of molecules in these populations changed as a function of film water contact angle. The enzyme activity of immobilized films was determined by measuring CALB-catalyzed hydrolysis of p-nitrophenyl butyrate. Total enzyme specific activity decreased by decreasing film hydrophobicity.     

水溶性聚合物和两亲聚合物——10.两亲聚合物PAMC_(16)S的自组装有序膜

用自组装技术在金(纯金和经阳极氧化的金)表面上获得了新型两亲聚合物PAMC_(16)S的有序膜。用接触角测试,XPS谱和电化学分析等方法对自组装膜进行了表征。根据膜表面的润湿性,金表面的自组装膜是疏水的,亲水的磺酸基团连于金表面,而疏水的碳氢链从表面伸展出。XPS实验结果支持金表面上单层膜的疏水结构。聚合物单层膜复盖的金电极起到含有针孔缺陷的阻膈型电极的作用。单层膜在法拉第反应中显示很强的吸附稳定性,说明聚合物LB膜在潜在应用中有其特有的特点。     

Biomimetic Fabrication of Polymer Film with High Adhesive Superhydrophobicity by Duplicating Locust Wing Surface

Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the natural and artificial locust wing surfaces were investigated by means of a scanning electron microscope(SEM) and a video-based contact angle meter. The natural locust wing surface exhibits complicated hierarchical structures and high adhesive superhydrophobicity(contact angle 152°). The prepared polymer film faithfully reproduces the surface microstructures of the bio-template, and displays a good hydrophobicity and high adhesion(contact angle 144°). The complex wettability of the natural and artificial locust wing surfaces ascribes to the cooperative effect of hydrophobic composition and multi-dimensional rough microstructures. This work not only promotes our understanding of the wetting mechanism on bio-surfaces, but offers an inexpensive and effective approach for biomimetic fabrication of multi-functional interfacial materials.     

Particle zips: vertical emulsion films with particle monolayers at their surfaces

Vertical emulsion films with particle monolayers at their surfaces have been studied by direct microscope observations. The effects of particle wettability and surface coverage on the structure and stability of water films in octane and octane films in water have been investigated. Monodisperse silica particles (3 microm in diameter) hydrophobized to different extents have been used. It is found that the structure and stability of emulsion films strongly depend on the film type (water-in-oil or oil-in-water), the particle contact angle, the interactions between particles from the same and the opposite monolayer, and the monolayer density. Stable films are observed only when the particle wettability fulfills the condition for stable particle bridges--in agreement with the concept that hydrophilic particles can give stable oil-in-water emulsions, whereas hydrophobic ones give water-in-oil emulsions. In the case of water films with dilute disordered monolayers at their surfaces, the hydrophilic particles are expelled from the film center toward its periphery, giving a dimple surrounded by a ring of particles bridging the film surfaces. In contrast, the thinning of octane films with dilute ordered monolayers at their surfaces finally leads to the spontaneous formation of a dense crystalline monolayer of hydrophobic particles bridging both surfaces at the center of the film. The behaviors of water and octane films with dense close-packed particle monolayers at their surfaces are very similar. In both cases, a transition from bilayer to bridging monolayer is observed at rather low capillary pressures. The implications of the above finding for particle stabilized emulsions are discussed.     

含二氮杂萘酮结构聚醚砜酮膜的微波等离子体处理研究

含二氮杂萘酮结构型聚醚砜酮(ＰＰＥＳＫ)是近年来本研究组开发成功的新型耐高温聚合物[1].该聚合物具有优异的力学性能和突出的耐热性,玻璃化转变温度(Ｔｇ)为265～305℃(随砜酮比不同而变化),其结构式如下:ＯＮＮＯＳＯＯＯＮＮＯＣＯ　　研究表明,用ＰＰＥＳＫ制成的气体分离膜对Ｏ2/Ｎ2、ＣＯ2/Ｎ2有良好的气体渗透性和透过选择性[2,3],但由于其亲水性不高进而限制了它在纳滤膜和反渗透膜等方面的应用,因此有必要对其进行改性.目前,常用的膜及膜材料改性的方法有磺化、氯甲基化季胺化、接枝等化学改性和低温等离子体与辐射等物理改性.其…     

表面微图案化聚乳酸膜的制备及其细胞亲和性评价

利用溶剂-非溶剂法(SNS)制备表面具有微孔图案的聚乳酸(PLA)膜和聚苯乙烯(PS)膜,并以微孔PS膜为模板,构建表面具有微岛图案的PLA膜.以此为基础,对所制备的微图案表面对PLA膜亲/疏水性及成骨细胞粘附与增殖性能的影响进行研究.结果显示微图案的存在显著增强了PLA膜的表面疏水性(水接触角90°);成骨细胞在微图案表面具有良好的铺展性,其黏附数量明显高于光滑PLA膜,但细胞的生长曲线相对较平缓,显示微图案表面虽有利于细胞在PLA膜表面的粘附与铺展,但对促进细胞的增殖无贡献.     

Layer thickness of hydrophobin films leads to oscillation in wettability

In nanobiotechnology, the properties of surfaces are often key to sensor applications. If analytes possess a low tolerance or affinity regarding the sensory substrate (surface), then the setup of mediators may be indicated. Hydrophobins enable biocompatible surface functionalization without significant restrictions of the physicochemical substrate properties. Because of the imperfect formation of hydrophobin films, a high variation in surface properties is observed. In this study, we report on the relation between the film thickness of hydrophobin-coated solid surfaces and their wettability. We found that the wettability of protein-coated surfaces strictly depends on the amount of adsorbed protein, as reflected in an oscillation of the contact angles of hydrophobin-coated silicon wafers. Fusion proteins of Ccg2 and HFBI, representatives of class I and II hydrophobins, document the influence of fused peptide tags on the wettability. The orientation of the first crystal nuclei plays a decisive role in the formation of the growing hydrophobin layers. Here, a simple method of deducing the film thickness of hydrophobin assemblies on solid surfaces is presented. The determination of the static contact angle allows the prediction of which part of the protein is exposed to possible analytes.     

Wettability and surface composition of partly and fully regenerated cellulose thin films from trimethylsilyl cellulose

The wettability and surface free energy (SFE) of partly and fully regenerated cellulose model surfaces from spin coated trimethylsilyl cellulose were determined by static contact angle (SCA) measurements. In order to gain detailed insight into the desilylation reaction of the surfaces the results from SCA measurements were compared with data from other surface analytical methods, namely thickness measurements, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-IR). Additionally, the influence of ultra high vacuum treatment (UHV) during XPS measurements on the water wettability and surface morphology of regenerated cellulose thin films was investigated. The wetting of polar and non-polar liquids increased with prolonged regeneration time, which is reflected in the higher SFE values and polarities of the films. After UHV treatment the water SCA of partly regenerated films decreases, whereas fully regenerated cellulose shows a higher water SCA. Therefore it is assumed that volatile desilylation products tend to adsorb on partly regenerated films, which strongly influences their wettability.     

Fabrication of flexible gold films with periodic sub-micrometer roughness and their wettability control by modification of SAM

Flexible honeycomb gold films supported by polymer sheets are fabricated by using polystyrene particle monolayers. The surfaces of the flexible gold films are covered with self-assembled monolayers (SAMs) of hydrophobic or hydrophilic thiol compounds, and the wettability of the modified surface is evaluated by measurements of the contact angles of water droplets. The contact angle of the film covered with hydrophobic SAM is ca. 150 degrees, which is greater than the value of 112 degrees for a flat gold surface, while the values for hydrophilic SAM are below 10 degrees.     

Formation of photochromic spiropyran polymer brushes via surface-initiated, ring-opening metathesis polymerization: reversible photocontrol of wetting behavior and solvent dependent morphology changes

In this article, we described a method for the formation of photochromic polymer brushes grafted from oxide surfaces using surface-initiated ring-opening metathesis polymerization of spiropyran-based monomers in the presence of second generation Grubbs catalyst. The growth of the polymer film, as monitored by ellipsometry and atomic force microscopy (AFM), is strongly influenced by the initial concentrations of the catalyst and monomer, as well as reaction time. These densely packed and highly smooth polymer films were successfully used as surfaces with switchable color and wettability using light as the external stimulus. The relatively nonpolar spiropyran can be switched to a polar, zwitterionic merocyanine isomer (with a larger dipole moment) using light of the appropriate wavelength. This process is reversible and can be switched back using visible light. The spiropyran-merocyanine photoinduced isomerization gives a reversible contact angle change up to 15 degrees for smooth Si/SiO 2 substrate under sequential irradiation cycles with UV and visible light. This contact angle change can be amplified by complexing the merocyanine form with metal ions through the phenolate oxygen, which enhances the switching of wettability with these polymer brushes. Irradiation in the presence of cobalt(II) ions gives rise to a contact angle variation as high as 35 degrees . This is the largest change in photoinduced surface wettability observed for a flat substrate. Photoisomerization in spiropyrans also yields a change in the refractive index of the film, which we have investigated using ellipsometric imaging. Lastly, morphological changes accompanying photochromism were investigated using atomic force microscopy. Significant morphological changes can only be induced in the films by irradiating in polar solvents that help to stabilize the merocyanine ring open form.     

Characterization of maleic acid/anhydride copolymer films by low-rate dynamic liquid-fluid contact angle measurements using axisymmetric drop shape analysis

Thin films of alternating maleic acid/anhydride copolymers (poly(octadecene-alt-maleic acid/anhydride), POMA; poly(propene-alt-maleic acid/anhydride), PPMA; poly(styrene-alt-maleic acid/anhydride), PSMA) were studied to unravel the influence of the comonomer characteristics in the backbone on the surface-energetic properties of the copolymer films in the dry state and in contact with aqueous solutions. Water contact angle measurements revealed a graduation of the wettability of the dry hydrolyzed and annealed copolymer films that was dependent on the comonomer unit. It ranged from moderately hydrophilic (PPMA, annealed gamma(sv) = 39.9 mJ/m2) to very hydrophobic (POMA, annealed, gamma(sv) = 18.4 mJ/m2) surfaces. Liquid-fluid contact angle measurements using captive air bubbles were performed in different aqueous media (pure water, phosphate-buffered saline, and 10(-)(3) M KCl of two different pH values (pH = 3 and pH = 10) to study the copolymer films in their hydrated states relevant for biointerfacial phenomena. It was found that the graduation of the wettability of the copolymer films in the dry state is overall maintained upon immersion in aqueous solutions. The dependence of the wettability on the pH value of the aqueous medium could be related to the (de)protonation of the carboxylic groups.     

Cleaning of Starchy Soils in Clean-in-Place (CIP) Systems: Relationship Between Contact Angle and Detergency

The cleaning of hard surfaces soiled with starch films using nonionic (alkylpolyglucosides and polyoxyethylene alkyl ethers) and zwitterionic (lauramine oxide) surfactant solutions has been investigated. Response surface methodology was applied to determine the effect of the composition of the cleaning solution on detergency, as well as the relationship between the contact angle of surfactant solutions on starch films and the removal efficacy of such films. The surfactants with a higher capacity for the removal of starch films were lauramine oxide and alkylpolyglucosides, and their mixtures. The effect of polyoxyethylene alkyl ethers was also statistically significant; however, their contribution to soil removal was very low. A correlation between contact angle and detergency for starchy soils was found, and the importance of the hydration process of the starch film on its removal was established.     

表面修饰引发的ZnO纳米棒阵列膜的超疏水性

润湿性是固体表面的重要性质之一 ,它受控于固体表面自由能和表面粗糙度的大小 ,一般可用液体在固体表面接触角的大小来衡量 .由于水与超疏水表面 (水与固体表面的接触角大于 1 5 0°的表面 )的接触面积很小 ,通过水所发生的化学发应和化学键的形成受到限制 ,使这种表面具有防水、防污染和防氧化等多种功能 ,因而备受人们的关注 [1～ 6 ] .作为宽禁带半导体材料 ,Zn O以其独特的光电和催化等性质在短波激光器、气体传感器、高效催化剂、太阳能电池等方面具有广阔的应用前景 .表面润湿性的研究对于将 Zn O用于各种器件非常重要 .Pesika等 […     

Contact angles on spherical surfaces

In this paper, we explore the influence of curved surfaces on contact angles. Small liquid drops were deposited at the apex of spheres. Liquid was added to advance the contact line (or withdrawn to cause recession). As drop volume increased, the contact line advanced outward and downward. With the addition of each increment of liquid, the contact line encountered a steeper slope and showed progressively larger apparent advancing contact angles. Observed apparent contact angles could be explained in terms of intrinsic contact angles and surface orientation. We found that if curvature and geometry were correctly accounted for, the classic Gibbs relation held. The experimental approach and analysis used here for estimating intrinsic wettability from curved surfaces could easily be integrated into automated contact angle measurement systems.     

Study on the wettability of polyethylene film fabricated at lower temperature

Polyethylene films were prepared with phase separation at lower temperatures. The wettability of such films varied from hydrophobicity to superhydrophobicity as the processing temperature decreased owing to the increase of surface roughness. Storing the as-prepared films at subzero temperature (-15 °C), it was found that the water contact angle of the film decreased obviously, and the decrease depended on the corresponding roughness. Further keeping the as-prepared films at room temperature for 30 min, the water contact angle would return to the normal value, which indicated that the reversible switching of surface wettability can be controlled by the environmental temperature.     

Superhydrofobic effect of hybrid organo-inorganic materials

Superhydrophobic films were obtained on the basis of sol–gel-derived titania or alumina/dodecylamine hybrid materials. It has been shown that wettability of surfaces of the inorganic oxides changes from superhydrophilic to superhydrophobic. For superhydrophobic materials, the surface roughness of the hybrid films on the basis of titania and alumina is 39 and 55 μm, respectively, and water contact angle is about 150°.     

A modified Cassie–Baxter relationship to explain contact angle hysteresis and anisotropy on non-wetting textured surfaces

The Cassie–Baxter model is widely used to predict the apparent contact angles obtained on composite (solid–liquid–air) superhydrophobic interfaces. However, the validity of this model has been repeatedly challenged by various research groups because of its inherent inability to predict contact angle hysteresis. In our recent work, we have developed robust omniphobic surfaces which repel a wide range of liquids. An interesting corollary of constructing such surfaces is that it becomes possible to directly image the solid–liquid–air triple-phase contact line on a composite interface, using an electron microscope with non-volatile organic liquids or curable polymers. Here, we fabricate a range of model superoleophobic surfaces with controlled surface topography in order to correlate the details of the local texture with the experimentally observed apparent contact angles. Based on these experiments, in conjunction with numerical simulations, we modify the classical Cassie–Baxter relation to include a local differential texture parameter which enables us to quantitatively predict the apparent advancing and receding contact angles, as well as contact angle hysteresis. This quantitative prediction also allows us to provide an a priori estimation of roll-off angles for a given textured substrate. Using this understanding we design model substrates that display extremely small or extremely large roll-off angles, as well as surfaces that demonstrate direction-dependent wettability, through a systematic control of surface topography and connectivity.     

纳米结构表面浸润性质的分子动力学研究

采用分子动力学方法研究了氩纳米液滴在铂金属及其模型固体表面的浸润现象,获得了液滴在平滑表面和三角纳米结构阵列表面的接触角和展布特性.研究表明,液滴与壁面的势能作用较强时,液滴与纳米结构表面为均匀浸润,但是由于迟滞效应,接触角受表面纳米结构的影响不明显;势能作用较弱时,纳米结构间隙中存在类似蒸汽的低密度相,液滴与纳米结构表面为非均匀浸润,接触角受纳米结构的影响而增大;表面纳米结构可以使表面具有超疏水性.