Institute of Chemical Engineering, Dalian University of Technology, Dalian 116012, China.
Langmuir. 2010 Apr 6;26(7):4831-8. doi: 10.1021/la903603z.
We have fabricated a series of textured silicon surfaces decorated by square arrays of pillars whose radius and pitch can be adjusted independently. These surfaces possessed a hydrophobic/superhydrophobic property after silanization. The dynamic behavior of water droplets impacting these structured surfaces was examined using a high-speed camera. Experimental results validated that the remaining liquid film on the pillars' tops gave rise to a wet surface instead of a dry surface as the water droplet began to recede away from the textured surfaces. Also, experimental results demonstrated that the difference in the contact time was subjected to the solid fraction referred to as the ratio of the actual area contacting with the liquid to its projected area on the textured surface. Because the mechanism by which the residual liquid film emerges on the pillars' tops can essentially be ascribed to the pinch-off of the liquid threads, we further addressed the changes in the contact time in terms of the characteristic time of pinch-off of an imaginary liquid cylinder whose radius is related to the solid fraction and the maximum contact area. The match of the theoretical analysis and the experimental results substantiates the assumption aforementioned.
我们制造了一系列由方阵阵列修饰的纹理化硅表面，其半径和间距可以独立调节。这些表面经过硅烷化处理后具有疏水/超疏水性质。使用高速摄像机研究了水滴冲击这些结构化表面的动态行为。实验结果验证了，当液滴开始从纹理表面退去时，在柱子顶部残留的液膜导致了一个湿表面，而不是一个干表面。此外，实验结果表明，接触时间的差异取决于固体分数，即实际与液体接触的面积与在纹理表面上的投影面积之比。由于在柱子顶部出现残留液膜的机制本质上可以归因于液体线的收缩，我们进一步根据与固体分数和最大接触面积有关的假想液体圆柱的收缩特征时间来描述接触时间的变化。理论分析与实验结果的吻合证实了上述假设。
