Quantification and modeling of anisotropic wetting of textured surfaces

This work focuses on the study of anisotropic wetting on textured surfaces. Three stripe-like textures are studied with different texture heights. These textures are realized with three different polymers. With using a lab-built goniometer, the contact angle of each surface is studied in all directions. Two different behaviors are observed on these surfaces and correlated to the wetting state according to the Extrand model. The Wenzel state is characterized by a strong anisotropy. The contact angle as a function of direction follows a Gaussian evolution. This Gaussian evolution is modeled as a function of contact angles measured experimentally in a first step. In a second step, these experimental angles are computed according to a hierarchical approach based on a roughness parameter. The Cassie-Baxter state is characterized by an absence of anisotropy, the contact angle as a function of the direction remains constant with a value close to the contact angle predicted by the Cassie-Baxter model. Thus the understanding of the phenomenon of droplet anisotropy is deepened by linking this behavior to the textures and surface chemistry. • Contact angles are measured in all directions with a new device. • Relationship between the wetting state and the spreading anisotropy. • Contact angle anisotropy modeled through the usual contact angles. • Contact angle anisotropy modeled as function of topographic parameters. • Roughness multiscale approach by Gaussian filtering.