Generalized models for advancing and receding contact angles of fakir droplets on pillared and pored surfaces.
Generalized models for advancing and receding contact angles of fakir droplets on pillared and pored surfaces.
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DOI：
10.1016/j.jcis.2019.05.053
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发表时间：
2019-09
影响因子：
9.9
通讯作者：
Youhua Jiang;W. Xu;M. Sarshar;Chang‐Hwan Choi
中科院分区：
文献类型：
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作者：
Youhua Jiang;W. Xu;M. Sarshar;Chang‐Hwan Choi
了解表面特性如何决定fakir液滴在图案表面上的流动性（通常以接触角的增大和减小为特征），对于定制超疏水表面的设计非常重要。然而，接触角的大多数分析模型仅限于特定的运动方向和表面类型，例如，在柱状表面上后退。虽然有人提出接触角应该由液滴边界的局部结构和动力学决定，但由于缺乏详细的可视化，它们之间的联系仍然模糊。在本研究中，利用反射干涉对比显微镜观察了微柱表面和微孔表面上fakir液滴前进和后退运动的接触线动力学，并测量了接触角。根据接触线位移和接触线间液气界面变形引起的能量变化，建立了两种不同运动方向和表面类型的接触角理论模型。在此基础上，进一步建立了基于给定结构尺寸和表面固有疏水性的广义模型，作为预测接触角的有效分析模型。
Understanding how surface properties determine the mobility of a fakir droplet on patterned surfaces, which is typically characterized by advancing and receding contact angles, is important in the design of superhydrophobic surfaces for tailored applications. However, most analytical models of the contact angles are limited to a specific motion direction and surface type, e.g., receding on a pillared surface. Although it was suggested that the contact angles should be determined by the local configuration and dynamics of the droplet boundary, their link remains vague due to the lack of detailed visualizations. In this study, the contact line dynamics of a fakir droplet in both advancing and receding motions on not only micropillared but also micropored surfaces are visualized in reflection interference contrast microscopy along with the contact angle measurement. Based on the energy change induced by the displacement of a contact line and the deformation of a liquid-gas interface in between contact lines, theoretical models of the contact angles to encompass the two different motion directions and surface types are formulated. Moreover, further generalized models are established to serve as effective analytical models to predict the contact angles only based on the given structure dimensions and the inherent surface hydrophobicity.