Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Langmuir. 2010 Jun 1;26(11):8704-8. doi: 10.1021/la9044495.
Sliding behaviors of liquid droplets on solid surfaces are among the fundamental results of wettability. To remedy the lack of quantitative correlation between sliding angle and roughness of the surface, which is known to be effective at enhancing wettability, we report in this paper the observation that the onset of water droplets sliding under gravity on inclined micropillar-structured hydrophobic surfaces always starts with detachment of the rear contact lines of the droplets from the pillar tops. We also establish an explicit analytical model, based on the observed mechanism, by which the sliding angle is fully determined by the fraction of water-solid interface area, droplet volume, and Young's contact angle. This model gives predictions of sliding angles that agree well with experimental measurements.
液滴在固体表面上的滑动行为是润湿性的基本结果之一。为了弥补已知能有效提高润湿性的滑动角与表面粗糙度之间缺乏定量相关性的问题，本文报道了在重力作用下液滴在倾斜微柱结构疏水性表面上滑动的起始点总是从液滴的后接触线从柱顶开始脱离这一观察结果。我们还基于观察到的机制建立了一个显式分析模型，通过该模型，滑动角完全由水-固界面面积、液滴体积和杨氏接触角的分数决定。该模型对滑动角的预测与实验测量吻合较好。
