Wetting on the Microscale: Shape of a Liquid Drop on a Microstructured Surface at Different Length Scales
Wetting on the Microscale: Shape of a Liquid Drop on a Microstructured Surface at Different Length Scales
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DOI：
10.1021/la300379u
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发表时间：
2012-06-05
期刊：
影响因子：
3.9
通讯作者：
Vollmer, Doris
中科院分区：
文献类型：
--
作者：
Papadopoulos, Periklis;Deng, Xu;Vollmer, Doris
描述液体在粗糙或结构化表面上的润湿是一个挑战，因为所涉及的长度尺度范围很广。纳米和微米尺寸的纹理导致接触线的钉扎，反映在接触角的滞后中。为了研究在不同的长度尺度的接触角，我们成像的5 μ m高的聚（二甲基硅氧烷）微柱阵列上的水滴。通过激光扫描共聚焦显微镜（LSCM）对液滴进行成像，这使我们能够同时定量分析局部和大规模液滴轮廓。液滴形状与球体的偏差在两个不同的长度尺度上衰减。靠近柱子，偏差的幅度在1-2 μ m内呈指数衰减。液滴轮廓在比柱的高度大1个数量级的长度尺度处接近球体。接触角的高度和位置依赖性可以从接触线的钉扎、由衬底的形貌设置的主曲率以及空气-水界面的最小化的相互作用来理解。
Describing wetting of a liquid on a rough or structured surface is a challenge because of the wide range of involved length scales. Nano- and micrometer-sized textures cause pinning of the contact line, reflected in a hysteresis of the contact angle. To investigate contact angles at different length scales, we imaged water drops on arrays of 5 mu m high poly(dimethylsiloxane) micropillars. The drops were imaged by laser scanning confocal microscopy (LSCM), which allowed us to quantitatively analyze the local and large-scale drop profile simultaneously. Deviations of the shape of drops from a sphere decay at two different length scales. Close to the pillars, the amplitude of deviations decays exponentially within 1-2 mu m. The drop profile approached a sphere at a length scale 1 order of magnitude larger than the pillars' height. The height and position dependence of the contact angles can be understood from the interplay of pinning of the contact line, the principal curvatures set by the topography of the substrate, and the minimization of the air-water interfaces.