纤毛状表面材料浸润性的分子动力学模拟研究

发布时间：2018-06-10 11:52

本文选题：超疏水 + 接触角　；参考：《吉林大学》2017年博士论文

【摘要】：对固体表面浸润性的调控一直以来受到科学界和工程界的广泛关注。通过调节材料表面的浸润性,我们能够获得具备自清洁、反生物污染等性能的材料。调整固体表面化学性质和粗糙度,能够改变固体表面的浸润性。自然界中,液滴能从某些覆盖有纤毛结构的植物叶片表面滑落,而水黾独特的纤毛状腿部结构赋予了它在水面上行走的能力。这两个不同实例的共性,就是植物叶片和昆虫腿部都覆盖有细小的纤毛。基于这些仿生学的研究,覆盖有纤毛状结构的表面材料在实验室中被制备出来。纤毛状表面粗糙度和纤毛形状、弹性与材料浸润性具有密切关系。但目前影响纤毛状表面材料浸润性的机理尚不明确,存在争议,所以明确影响纤毛状表面材料浸润性的因素,才能为设计抗浸润材料提供有效途径。研究揭示,通过改良和优化表面粗糙结构的几何形状,很多原本非疏水材料的疏水性能够得到了质的提升,甚至可以抵抗低表面张力液体(比如油类液体)的浸润。本文利用粗粒化分子动力学方法,研究了影响不同形状纤毛接枝表面浸润性的各项因素,如长度、接枝密度及硬度等,并提出了一套适用于分析纤毛状结构的计算机算法。本论文主要研究内容包括:(1)研究了影响线形纤毛接枝表面浸润性的因素。发现通过调整纤毛的接枝密度、长度和硬度等性质,纤毛接枝表面的非浸润性能够得到大幅提升。当液滴停留在纤毛顶端时,纤毛之间会自发聚集形成纤毛束来调控材料表面的浸润性。我们绘制了液滴接触角随着纤毛长度和接枝密度变化的相图。同时我们揭示了纤毛有序度和接触角的关系。不同于刚性硬固体表面和接有纯柔性链固体表面,纤毛本身硬度具有可调节性。从这个角度看,我们对纤毛状表面材料的模拟填补了柔性固体表面模拟和刚性固体表面模拟之间的空白。(2)研究了不同纤毛的几何结构对纤毛状表面材料浸润性的影响,并提出了一套适用于计算机模拟的分析表面粗糙结构的方法。我们分别对梳型、Y形和线形纤毛进行模拟。观察到不同几何形状的纤毛会自组装形成不同的表面结构,如网络状结构、纤毛束等。根据纤毛硬度不同,纤毛被分成硬纤毛和软纤毛两大类。不同硬度纤毛,影响其浸润性的主要因素差异很大。对硬纤毛而言,接触角主要依赖于表层纤毛粒子的密度;而软纤毛接触角则主要依赖于液滴下方固体表面的性质,如纤毛束或网络结构的强度、纤毛束之间的距离以及表层非浸润面积等。为了表征网络状纤毛结构,我们开发了一套计算表层网络状纤毛结构交叉点数量的算法。我们在研究中观察到,某些特定情况下,纤毛能够自发形成局部凹陷结构(re-entrant structure)。通过研究也表明,能够强烈抵抗液滴浸润的固体表面不一定具有极高的接触角。(3)研究了环状纤毛的硬度、排布方式以及多分散性对环状纤毛接枝表面材料的浸润性的影响,并利用我们提出的表征方法对纤毛结构进行分析。我们分别对规则排布、随机排布环形纤毛接枝表面,以及具备不同分散性纤毛接枝表面进行模拟。结果显示,规则排布的单分散纤毛能够在平板表面形成规则的沟槽状结构,而随机排布的单分散纤毛则形成更加无规则的结构。为研究方便,我们将环形纤毛接枝表面根据硬度不同,分为软纤毛接枝表面和硬纤毛接枝表面。研究结果发现,环形结构是提升较软纤毛状表面非浸润性的有效途径。而多分散纤毛接枝的表面,其浸润性则归因于长纤毛对液滴下表面的支撑能力。
[Abstract]:The infiltration of solid surface has been widely concerned by the scientific and engineering circles. By adjusting the wettability of the surface of the material, we can obtain materials with the properties of self cleaning and anti biological pollution. The chemical properties and roughness of the solid surface can be adjusted to change the wettability of the solid surface. In nature, the droplets can be derived from the natural surface. The surface of some plants with ciliated structure slips, and the unique ciliated leg structure of water gives it the ability to walk on the surface of the water. These two different examples are that plant leaves and insect legs are covered with fine cilia. Based on these bionics, surface materials with ciliated structure are covered. In the laboratory, the roughness and cilia shape of the fibrous surface are closely related to the wettability of the material. However, the mechanism that affects the wettability of the fibrous surface materials is not clear and controversial, so that the factors that affect the wettability of the wool like surface materials can provide an effective way for the design of anti infiltrating materials. The study reveals that by improving and optimizing the geometry of the surface roughness structure, many original non hydrophobic materials can improve the hydrophobicity and even resist the infiltration of low surface tension liquids, such as oil liquids. In this paper, the influence of the surface infiltration of different cilia grafted surfaces on the surface infiltration of different shapes of cilia was studied by using the coarse grained molecular dynamics method. Various factors, such as length, grafting density and hardness, etc., and a set of computer algorithms for the analysis of ciliate structures are proposed. The main contents of this paper are as follows: (1) the factors affecting the surface wettability of the linear cilia grafting are studied. The non wettability can be greatly enhanced. When the droplets stay at the top of the cilia, the cilia will spontaneously gather and form a cilia bundle to regulate the wettability of the material surface. We draw the phase diagram of the droplet contact angle with the length of the cilia and the grafting density. We also reveal the relationship between the order of the fiber and the contact angle. Different Yu Gang The hardness of the cilium itself is adjustable. From this point of view, our simulation of ciliated surface materials fills the gap between the flexible solid surface simulation and the rigid solid surface simulation. (2) the infiltration of the geometric structure of the cilia to the wool like surface material is studied. A set of methods for the analysis of surface roughness structure suitable for computer simulation is proposed. We simulate the comb, Y and linear cilia respectively. It is observed that the cilia of different geometries are self assembled to form different surface structures, such as network structure, cilium and so on. The cilia are divided into hard cilia according to the hardness of cilia. There are two major categories of soft cilia. The main factors affecting their wettability vary greatly. For the hard cilia, the contact angle is mainly dependent on the density of the surface ciliated particles, while the contact angles of the soft cilia are mainly dependent on the properties of the solid surface below the droplets, such as the strength of the ciliated or network structures, the distance between the fibers and the fibers. In order to characterize the network ciliated structure, we have developed a set of algorithms to calculate the number of intersections of the surface ciliated ciliated structures. In our study we have observed that the cilia can spontaneously form a local depression structure (re-entrant structure) in some specific cases. The surface of the soakage solid does not necessarily have high contact angle. (3) the hardness of the cilia, the mode of arrangement and the infiltration of the polydispersity on the surface material of the ring ciliary grafted surface are studied, and the structure of the cilium is analyzed by our method of characterization. The results show that the regular dispersed cilia can form a regular grooves on the surface of the plate, while the randomly arranged monodisperse cilia form a more irregular structure. The results show that the ring structure is an effective way to improve the non wettability of the soft ciliated surface, while the surface of the polydisperse cilia is attributed to the support capacity of the long cilia on the surface of the droplet.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O647.5

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