Nonlinear Analysis of Physicochemically Driven Dewetting – Statics and Dynamics

An initially homogeneous film of a partially wetting liquid covering a solid substrate undergoes various types of dynamics depending on the film height. Assuming the liquid layer to be relatively thin, infinitesimal perturbations will eventually lead to spinodal dewetting which induces a breakup of the film into multiple droplets of small volume. Driven by pressure differences, these structures will successively merge into larger drops resulting in fewer drops of larger volumes. For substrates with specific modulations of their chemical properties, e.g., prepatterns in wettability, coalescence may be suppressed to stabilize the corresponding drop patterns. By inclining the solid surface, lateral components of the gravitational force will cause both a translation and possibly a breakup of drops. Analogously to the process of coalescence, the dynamics of sliding drops may be affected or even suppressed by chemical prepatterns of the substrate. This thesis deals with liquids on solid substrates by employing a thin film model extended by physicochemical driving forces as well as condensation. To this end, the influence of the fundamental control parameters of the system, i.e., drop volume, inclination angle and wettability contrast, is quantified in bifurcation diagrams by combining numerical continuation techniques and direct numerical simulations. These analyses of single drops lead to predictive phase diagrams which are finally confirmed by statistical evaluation of ensembles involving hundreds of individual interacting droplets.