疏水表面微结构设计与微铣削加工技术研究

发布时间：2019-05-06 23:33

【摘要】：疏水表面因具有自清洁、减阻和抗磨性能,给人们生产生活带来极大便利,为人类发展创造极大动力。微米结构,纳米结构组成的多阶结构和低表面能材料共同作用使得材料表面有疏水性。随着微加工机理的研究,车削,铣削加工精度的提高,铣削刀具尺寸的逐渐缩小,用微切削方法加工出微米尺寸微结构研究其疏水性成为可能。表面接触角是表征疏水性能的重要技术指标。为了研究微米尺寸微结构对水滴在其表面接触角的影响,以Young氏方程,Wenzel方程及Cassie-Baxter方程为基础,建立了二维情况下基于最小吉布斯自由能的接触角预测模型,用微铣削的方法加工出微结构,并通过理论分析与切削试验和接触角测试相结合的方法探究微结构尺寸参数对接触角的影响规律。首先,在光滑表面Young氏方程和粗糙表面Cassie-Baxter方程的基础上,建立了二维情况下基于最小吉布斯自由能的接触角预测模型,并且考虑斜壁对气-液接触线的影响对预测模型进行了修正。利用接触角预测模型及其修正研究微结构材料和尺寸参数对接触角的影响和疏水性微结构设计。研究结果表明,疏水性基底相对于亲水性基底加工出的微结构有更大的接触角提升趋势。增大微结构间隙宽度,减小凸台宽度,减小微结构斜壁角度,有利于接触角的提升。其次,设计了直壁沟槽、方柱阵列、斜壁沟槽和斜壁阵列四种类型的微结构,通过微铣削方法加工出设计的微结构,并测量水滴在微结构表面的接触角。最后,采用理论分析与试验结合的方法研究不同几何尺寸参数的直壁沟槽、方柱阵列、斜壁沟槽和斜壁阵列四种类型的微结构对水滴在其表面接触角的影响。研究结果表明,沟槽与方柱阵列微结构可以使水滴在其表面的接触角增大,接触角随着微结构间距增加而增大,随着凸台(方柱)宽度增大而减小。直壁沟槽微结构上水滴在垂直于沟槽方向和平行于沟槽方向的接触角有差异并且相互影响；水滴在直壁沟槽微结构有着更稳定的接触角变化,而在方柱阵列微结构表面有更大的接触角,并且更接近球状。相对于直壁结构,斜壁结构的存在虽然会增加水滴在微结构表面的接触角,但是增大了水滴在微结构表面的不稳定性,水滴更容易进入微结构内部呈现出Wenzel状态。此外,斜壁的存在使得微结构尺寸参数对接触角的影响减小。
[Abstract]:Because of its self-cleaning, drag-reducing and anti-wear properties, hydrophobic surface brings great convenience to people's production and life, and creates great impetus for human development. The surface hydrophobicity of micro-structure, nano-structure and low surface energy materials can be obtained by the combination of multi-order structure and low surface energy material. With the study of micro-machining mechanism, the improvement of turning and milling precision, and the gradual reduction of milling tool size, it is possible to study the hydrophobicity of micro-size microstructure by micro-cutting method. Surface contact angle is an important technical index for characterizing hydrophobic properties. In order to study the effect of micro-structure on the contact angle of water droplets on its surface, based on Young equation, Wenzel equation and Cassie-Baxter equation, a two-dimensional contact angle prediction model based on minimum Gibbs free energy was established. The micro-structure was machined by micro-milling, and the influence of micro-structure size parameters on contact angle was investigated by combining theoretical analysis with cutting test and contact angle test. Firstly, based on the Young equation of smooth surface and the Cassie-Baxter equation of rough surface, the contact angle prediction model based on minimum Gibbs free energy in two-dimensional case is established. The prediction model is modified considering the influence of inclined wall on the gas-liquid contact line. The contact angle prediction model and its modification are used to study the influence of microstructure materials and size parameters on the contact angle and the hydrophobic microstructure design. The results show that the contact angle of hydrophobic substrate is higher than that of hydrophilic substrate. Increasing the width of the microstructure gap, reducing the width of the raised platform and decreasing the angle of the inclined wall of the microstructure are beneficial to the elevation of the contact angle. Secondly, four kinds of micro-structures are designed, which are straight-wall groove, square column array, oblique-wall groove and oblique-wall array. The micro-structure is machined by micro-milling method, and the contact angle of water droplets on the microstructure surface is measured. Finally, the effects of four types of microstructure, such as straight-wall grooves, square-column arrays, oblique-wall grooves and oblique-wall arrays, on the contact angle of water droplets on the surface of the droplets are studied by means of theoretical analysis and experiment. The results show that the micro-structure of groove and square column array can increase the contact angle of water droplets on its surface, and the contact angle increases with the increase of microstructure spacing, and decreases with the increase of the width of convex platform (square column). The contact angles of the droplets perpendicular to the grooves and parallel to the grooves are different and affect each other in the microstructure of the straight-walled grooves. Water droplets have a more stable contact angle on the straight-wall grooves and larger contact angles on the surface of the square-column array, and are closer to globules. Compared with the straight wall structure, the existence of oblique wall structure can increase the contact angle of water droplets on the microstructure surface, but increase the instability of water droplets on the microstructure surface. The water droplets are more likely to enter the microstructure inside the Wenzel state. In addition, the influence of microstructure size parameters on the contact angle is reduced due to the existence of inclined wall.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG54

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