液体弹珠及其研究进展

润湿性是固体表面的重要性质之一,主要由表面的化学组成和微观几何结构共同决定。不粘连表面是指具有特殊的表面形貌及性能,使得诸如尘土、水、冰以及污染物较难黏附的特殊表面。液体弹珠是被高疏水性颗粒包裹形成的不润湿的液滴,可以稳定地静置于固体及液体表面。本文介绍了液体弹珠的结构和制备方法,综述了液体弹珠的静态力学性能及其在磁场电场下的响应性能,探讨了这种新型不粘连体系用于移动和控制微量液滴的独特优势,展望了其发展趋势以及应用前景。     

浸润性梯度表面研究与应用

浸润性梯度表面是指表面浸润性随着表面位置的变化而连续变化的一种特殊梯度表面.在过去的20年间,由于浸润性梯度表面在智能涂料、微流体器件和液体自输送等方面具有广阔的应用前景,因此人们研发并制备了各种类型的浸润性梯度表面,总体而言,可分为三类:(1)化学组成类浸润性梯度表面;(2)表面形貌类浸润性梯度表面;(3)化学组成-表面形貌复合型浸润性梯度表面.重点介绍了这三大类浸润性梯度表面的分类与区别,以及近些年来这些新型浸润性梯度表面的主要制备方法,如扩散法、浸泡法、刻蚀与打印、机械拉伸法、半月板沉积法和温度梯度法等,并归纳总结了这些方法的各自优缺点.在目前的材料科学领域,虽然关于浸润性梯度的研究还属婴儿期.可是利用梯度表面研究生物蛋白或细胞吸附,液体自输送等,已经发展成为一门成熟的学科.最后综述了近期关于浸润性梯度表面在研究生物蛋白或细胞吸附,液体自输送等方面的应用进展,并展望了该课题的未来发展.     

荷叶表面纳米结构与浸润性的关系

通过烘烤、化学萃取及物理剥除等方法改变荷叶表面的纳米结构和化学组成, 在环境扫描电镜(ESEM)和全反射红外光谱(ATR)对样品的微观形貌和化学组成进行表征的基础上, 为消除其它外界因素影响样品的真实微观形貌, 进一步采用原子力显微镜(AFM)进行了表征. 通过测量不同处理方法所得样品的表观接触角表征了样品的浸润性质. 结果表明, 荷叶表面的蜡质是产生表面疏水性的根本原因, 其微米级结构放大了其疏水性, 而纳米结构是导致其表面高接触角、低滚动角, 即“荷叶效应”的关键原因.     

三种钢基疏水表面微观形貌的分形特征及其对润湿性的影响

采用化学刻蚀与低表面能物质修饰相结合的方法, 通过调控刻蚀时间在304不锈钢、 X80管线钢和45#钢表面构造不同的微观形貌; 借助扫描电子显微镜采集不同材料表面的微观形貌, 并采用接触角测量仪测量其润湿性能; 应用Matlab软件编程计算分形参数. 结果表明, 3种材料构造的疏水表面均具有分形特征, 且最佳刻蚀时间为30 min, 此时多重分形谱子集维数最大值最靠左, 对应的奇异性指数最小, 表征表面微观形貌的分形维数也达到最大值; 分形维数与接触角线性拟合效果优良, 接触角随分形维数的增大而增大.     

含氟硅丙烯酸酯乳液超疏水膜中疏水基团的梯度分布与表面微观结构研究

利用含氟疏水基团的梯度分布,结合草莓形纳米SiO2粒子提供的双重粗糙表面,制备了具有类"荷叶效应"的超疏水涂膜,水接触角达(174.2±2)°,滞后角几乎接近0°.通过原子力显微镜、扫描电镜和水接触角的测试对膜表面形貌及疏水性能进行了表征;探讨了其表面微观结构与表面疏水性能的关系.草莓形复合粒子在膜表面的无规则排列赋予涂膜表面不同等级的粗糙度,使水滴与涂膜表面接触时能够形成高的空气捕捉率,这种微观结构与疏水基团的梯度分布相结合,赋予了含氟硅丙烯酸酯乳液涂膜表面超疏水性能.     

光响应固体表面的浸润性调控

物质表面能和表面微观结构是影响物质浸润性的两大主要因素,表面能决定了平滑表面的液体接触角,而表面微观结构影响表面的浸润性。在受到外界刺激时,物质表面可发生表面能和表面微观结构的变化,从而实现表面浸润性的变化。本文综述了近年来物质表面的浸润性在光刺激下发生转变的研究进展,其中包括无机氧化物表面超疏水和超亲水之间的转换,光响应聚合物表面液滴的运动及接触角的变化,以及光响应聚合物表面黏附性的变化。     

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.     

氧化锌薄膜的可控浸润性研究

采用一步电沉积的方法在导电玻璃基底上制备了具有粗糙表面的氧 化锌薄膜．用SEM和XPS表征了薄膜的表面形貌和化学组成,用接触角测定仪 测定接触角以评估薄膜的浸润性．结果显示,薄膜表面布满了无序生长的花瓣状 的微晶,形成疏松的结构．薄膜与水的接触角为133．2°,呈现了疏水的性质．通 过紫外光照射的方法可以使其由疏水性薄膜转化为亲水性薄膜,接触角降低到 4．8°。     

非离子表面活性剂Triton X-100溶液在不同生长期小麦叶片表面的润湿行为

选择不同生长期小麦叶片,利用座滴法研究了非离子表面活性剂Triton X-100在小麦叶片表面接触角,考察浓度对接触角、粘附张力、固-液界面张力及润湿状态的影响。研究表明,在低浓度下,表面活性剂分子在气-液界面吸附量(ΓLV)和固-液界面吸附量(Γ'SL)相似,但吸附量较少形成了不饱和吸附层,接触角保持不变,其润湿状态为Cassie-Baxter状态;当浓度进一步增加,液滴突破叶片表面三维立体结构中存在的钉扎效应,取代空气层而处于Wenzel状态,接触角陡降,同时Γ'SL/ΓLV远大于1;当浓度超过临界胶束浓度(CMC)时,表面活性剂分子在气-液界面和固-液界面形成饱和吸附层,并产生毛细管效应,使溶液在小麦叶片三维立体结构中产生半渗透过程,此时接触角保持不变。     

吐温-60对钢在Cl2CHCOOH溶液中的缓蚀性能

通过失重法、动电位极化曲线和电化学阻抗谱(EIS)研究了非离子表面活性剂吐温-60在0.10 mol·L^-1二氯乙酸(Cl₂CHCOOH)溶液中对冷轧钢的缓蚀性能，并且采用扫描电子显微镜(SEM)、原子力显微镜(AFM)和接触角测试对冷轧钢表面的微观形貌和亲水/疏水性进行了表征分析。结果表明：20℃时100 mg·L^-1吐温-60的缓蚀率可达89.6%,6～48 h内缓蚀效果稳定；20～50℃时吐温-60在冷轧钢表面的吸附符合Langmuir吸附等温式，标准吸附Gibbs自由能为-42.92～-47.41 kJ·mol^-1,吸附过程中伴随着熵增加。动电位极化曲线表明吐温-60为“几何覆盖效应”的混合抑制型缓蚀剂；随着吐温-60浓度的增大，Nyquist图的容抗弧半径增大，电荷转移电阻增大，而界面双电层电容值下降。SEM和AFM的微观表面形貌进一步证实了吐温-60能有效减缓钢表面的腐蚀程度；缓蚀后钢表面接触角增大，表面疏水性增强，可有效屏蔽酸介质对钢表面的腐蚀。     

A topography/chemical composition gradient polystyrene surface: toward the investigation of the relationship between surface wettability and surface structure and chemical composition

In this paper, we have prepared of a topography/chemical composition gradient polystyrene (PS) surface, i.e., an orthogonal gradient surface, to investigate the relationship between surface wettability and surface structure and chemical composition. The prepared surface shows a one-dimensional gradient in wettability in the x, y, and diagonal directions, including hydrophobic to hydrophilic, superhydrophobic to hydrophobic, superhydrophobic to superhydrophilic gradients, and so forth. These one-dimensional gradients have different gradient values, gradient range, and contact angle hysteresis, which lie on both the surface roughness and the surface compositions. From the trend of variation of contact angle hysteresis, it can be concluded that the transition from the Cassie's model to the Wenzel's model occurs both by decreasing surface roughness and by increasing surface hydrophilic compositions. Moreover, the transition is more effective via changing surface chemical composition than changing surface roughness herein.     

The effect of surface wettability on induction and growth of neurites from the PC-12 cell on a polymer surface

Surface properties of polymeric devices that are used to regenerate nervous damage are a point to be considered for axon regeneration in nerve system. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using a corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces were oxidized gradually with increasing power. The effect of surface wettability on the different types of cells has an important role for cell adhesion and proliferation. The purpose of this study is to investigate neurite formation on polymer surfaces with different wettability. Induction and growth of neurites from the rat pheochromocytoma (PC-12) cells attached on the polymer surfaces with different hydrophilicity were investigated using the wettability gradient PE surfaces prepared by a corona discharge treatment. Neurites were investigated for number and length of neurites in terms of surface wettability. It was observed that neurite formation of PC-12 cells was increased more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. From those results, it could be assumed that initial adhesion of PC-12 cells was caused by more calf serum (CS) protein than nerve growth factor (NGF), whereas the neurite formation of PC-12 cells was caused by more NGF than CS protein. It follows from what has been said thus far that PC-12 cells are a differentiated neuronal phenotype with a long neurite at around the position 2.5 cm (water contact angle of about 55 deg). In conclusion, surface wettability plays an important role for neurite formation on the polymer surfaces for axon regeneration.     

Several surfaces with special wettability: Influence on spreading and motion of W/O emulsion droplets

Physical and chemical modifications were made on the surface of the aluminum sheet to change the surface properties and superhydrophobic–hydrophilic wettability gradient surface was made on the perspex surface by using microstructure-pattering technique and self-assembled-monolayer method. By using high-speed video camera system and optical tensiometer, this paper discusses the influence of special surfaces with different wettability on spreading and motion of water, oil, and W/O emulsion droplets both experimentally and theoretically. In addition, the paper also discusses the influence of the superhydrophobic–hydrophilic wettability gradient on fluidity of W/O emulsion droplets and the coalescence process of droplets. The results showed that the contact angle of W/O emulsion droplets on the modified surfaces was related to the water and oil distribution at the three-phase line. On the wettability gradient surface, the droplet moved spontaneously when the droplet was located at the junction of the gradient. A quasi-steady theoretical model was used to analyze the driving and resistant forces acting on a droplet to improve the understanding of the self-transport behavior of the droplets.     

Surface study of sintered alumina substrates using solution‐processed ZnO nanorods as a microscopic wettability indicator

Wettability and its distribution are crucial factors that indicate the surface conditions of substrates. We report a surface study of sintered alumina substrates using solution‐processed ZnO nanorods as a microscopic wettability indicator. The alumina substrates comprising of micrometer‐sized sintered grains were treated separately with ultraviolet/ozone (dry process) or ozone water (wet process), and their surface conditions were characterized by conventional surface analysis methods, such as water contact angle, X‐ray photoelectron spectroscopy and grazing angle attenuated total reflection Fourier transform infrared spectroscopy. The results showed that the alumina substrates treated with ultraviolet/ozone and ozone water had distinct clean surfaces compared to those without treatments, but no significant differences were noted between these two ozone‐based treatments. Then, as a wettability‐sensitive deposition technique, Pd‐catalyzed chemical deposition of ZnO nanorods was performed on the alumina substrates, which involved dip coating of Pd nanoparticles on the substrates in aqueous solutions, followed by the chemical solution growth of ZnO. Vertically aligned ZnO nanorods of ~85 nm in diameter were densely formed along a rough surface of the substrates. Morphological uniformity of the nanorods varied depending on the treatment condition; local surfaces with sufficient wettability provided uniform nanorods but those with insufficient wettability gave irregular nanorods, making the visualization of the microscopic surface wettability possible. Copyright © 2016 John Wiley & Sons, Ltd.     

Recent research progress in wettability of colloidal crystals

The wettability of solid surfaces has attracted extensive interest in both theoretical research and industrial applications. This paper reviews recent research progress in the fabrication and applications of the colloidal crystals with special wettability. Based on the modified equation of Wenzel and Cassie, the colloidal crystals with special wettability have been obtained by either application of the intrinsic rough structure or modification of the surface chemical composition. Some typical applications o...     

仿生多微纳米梯度界面的液滴动态行为调控

对液滴在界面上动态行为的研究是化学和材料领域的一个重要方向,许多先进的表面和界面技术,比如集水、防覆冰、防雾、微流体控制和传热等,均属于这一范畴.通过模仿自然界中具有特殊微纳米结构和特定化学组成的生物表面,设计并构筑相应具有特殊浸润性的仿生界面,对仿生界面材料的技术应用起到了良好的先导与示范作用.本文结合本课题组的研究...     

静电纺丝制备具有浸润性梯度的聚酰亚胺纳米纤维膜

采用高压静电纺丝技术, 在非对称异型电极上制备得到放射状聚酰亚胺(PI)纳米纤维膜. 采用环境扫描电子显微镜(ESEM)观察了PI膜的微观形貌以及纳米纤维的排列状态; 采用接触角测量仪研究了水滴浸润性的变化; 采用高敏感性力学微电力学天平测量了水滴的黏附力, 分析了微观形貌变化与水滴浸润性质和黏附性质的关系. 结果表明, 该PI纳米纤维膜沿着非对称异型电极三角电极至弧型电极方向纤维排列由密到疏, 呈放射状, 具有独特的微结构梯度; 整个纤维膜上的PI纳米纤维直径均一且具有光滑均匀表面, 纤维与纤维之间的距离约为几微米到几十微米. 由于PI纳米纤维膜所具有的独特的微结构梯度, 致使沿着微结构梯度方向水滴的接触角(从超疏水到疏水)和黏附力(从低黏附到高黏附)均表现出梯度变化的特征.     

Controlled Directional Water‐Droplet Spreading on a High‐Adhesion Surface

Controlled directional spreading of a droplet on a smart high‐adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm^?1 by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V‐ or inverse‐V‐shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.     

Fabrication and Characterization of an Organic‐Inorganic Gradient Surface made by Polymethylsilsesquioxane (PMSQ)

Summary: A simple method for the fabrication of a chemical composition gradient from organic to inorganic by the pyrolysis of a polymethylsilsesquioxane (PMSQ) thin film in a gradient temperature field is reported. The resultant chemical gradient surface demonstrates gradual changes in wettability, and slight microstructural changes are observed along the substrate.

FT‐IR spectra of gradient PMSQ surface along the length from the unheated side to the heated side.