(444d) Dynamics of Viscous Droplets Falling Towards a Micro-Patterned Substrate

The interaction between droplets and solid substrate is of great importance in industrial applications, biochemical processes, and fundamental materials research. In this study, a three-dimensional spectral boundary element method has been employed to investigate the dynamics of a viscous droplet falling under gravity influence to a micro-patterned solid surface. The substrate pattern is created by rectangular pillars. The droplet dynamics is investigated under the influence of the Bond number, droplet size, viscosity and the topological features of the substrate. Out of all influencing factors, the effect of the substrate pattern is most intriguing and hence the focus of this study. We found that the dimensions of the pillars on the substrate strongly affect the droplet shape, deformation, and velocity as it approaches the substrate. For large Bond numbers, the droplets are found to either hover above the pillar structures or protrude between pillars, depending on the height and the gap width of the pillars. Critical values are determined for the afore-mentioned dimensions, which would help to predict the droplet behavior as it falls towards micro-patterned substrates.