Combined Effects of Surface Roughness and Wetting Characteristics on the Moving Contact Line in Microchannel Flows

The present study investigates moving contact lines in microfluidic confinements with rough topographies modeled with random generating functions. Using matched asymptotic expansion, the description of the whole contact line is obtained and the dynamic contact angle is extracted by extrapolating the bulk meniscus to the channel wall. Significant variations are observed in the contact angle because of the heterogeneities of the confining walls of the microfluidic channel. The effects of the surface wetting condition also play a crucial role in altering the description of the contact line bearing particular nontrivial interactions with the topological features of the solid boundaries. In an effort to assess the underlying consequences, two different surface wetting conditions are studied; namely, complete wetting substrate and partial wetting substrate. Our studies reveal that the consequent wetting characteristics are strongly influenced by action of intermolecular forces in presence of surface roughness. The effect of slip, correlation length, and roughness parameters on the dynamic contact angle have been also investigated.