Influence of contact angle on droplet parameters in ellipsoidal wettability model

Abstract

Contact angle is one of the most important indexes to evaluate the hydrophobicity of solid surface. In order to explore the wetting characteristics of droplets on anisotropic solid surfaces, including contact angle, droplet radius, droplet height, contact radius, contact area and projected area, an ellipsoidal droplet contact angle model was established. Different from the ordinary plane ellipsoidal cap model, the major axis and minor axis of the elliptical cap shape in this model are not exactly the same in different planes. This model studied the relationship between contact angle and interface parameters in different planes. By collecting the droplet size parameters of fluororubber (FKM) prepared by template method, the correctness of the theoretical model was verified. Among them, the maximum error between the theoretical value of droplet radius and the actual measured value was 4.3%, and the maximum error of droplet projected area was 2.1%. It was found that the contact angle was inversely proportional to the droplet-solid contact radius and contact area, and directly proportional to the projected area of the droplet. In addition, for the same droplet on the surface of the same solid material, it was observed that the contact radius between the droplet and the solid was small in the direction of large contact angle. This discovery is helpful to explain the hydrophobic mechanism of the material surface with anisotropic contact angle.