The effect of sharp solid edges on the droplet wettability.

Affiliation

State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: [Email]

Abstract

Understanding the role of pinning force in droplet dynamic wetting is of critical importance for surface science studies. Generally, the pinning force is only related to the surface tension and the change of contact angle. However, there is an obvious correlation between the pinning force and the surface geometry. In this paper, the relation between the surface geometry and contact line pinning was studied with systematical experiments and theoretical analysis. We compared the samples with different edge angles and carried out plenty experiments with different liquids. Meanwhile, the theoretical analysis and molecular simulation were carried out. The results show that the sharp edge has a strong pinning effect on the contact line and can significantly change the contact angle and wetting state of droplets. The maximum contact angle of droplet has a linear relation with the edge angle of substrate. The formula of pinning force was revised to consider the impact of surface topography. According to the relationship between surface defect and contact line, we proposed a model to classify the cases of contact line pinning for the first time. Our research will deepen the understanding of contact line pinning and provide help for potentially industrial production designs.

Keywords

Contact angle,Contact line pinning,Droplet wettability,Sharp edge,

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