Orateur
Description
The physical parameter quantifying the wetting behaviour of a droplet on solid surfaces is the contact angle. Several types of contact angles can be defined, mainly the apparent (or macroscopic) contact angle at the scale of the droplet, and the local (or microscopic) contact angle locally estimated at a given point of the contact line between the surface, the droplet, and the air surrounding it. This latter contact angle is difficult to measure experimentally, hence, many studies focus on the apparent contact angle. This work aims to determine how the apparent and the local contact angles can be related. To that end, we conducted numerical experiments on three-dimensional droplets at rest on flat heterogeneous surfaces consisting of a hydrophilic base patterned with hydrophobic square-shaped defects. The simulations were performed with our in-house multiphase code implementing a phase-field lattice-Boltzmann method. For a fixed value of drop diameter to pattern period ratio, we investigated the influence of the defect size to pattern period ratio on both the apparent and local contact angles. It was shown that a connection indeed exists between these two types of contact angles.
