Droplet on a regularly patterned solid. Wenzel's regime and meso-scale roughness.

The applicability of Wenzel's equation to describe a liquid droplet settled on the solid surface regularly patterned with rectangular prisms was examined by means of simulations of the droplet/surface system morphology and energetics. The droplet deposited on the meso-scale surface roughness (i.e. the droplet size was larger than the size of heterogeneities by about an order of magnitude) was considered. Several different approaches to the estimation of the contact angle were employed. The discrepancies between the results of simulated experimental measurements and the predictions based on the Wenzel equation were analyzed and discussed. The influence of three-phase contact line effects on the droplet morphology and the existence of metastable states was shown.