While the flow of a liquid in a macroscopic channel is usually described using hydrodynamics with no-slip boundary conditions at the walls of the channel, transport phenomena in microchannels involve physics at many different scales due to the interplay between the micrometric section of the channel and the micro- or nanometric roughness of the boundaries. Roughness can have many different effects such as increasing the friction between the liquid and the walls (leading to the macroscopic no-slip boundary condition) or on the contrary reduce it thanks to the Wenzel-Cassie-Baxter wetting transition induced by capillarity. Here we detail a phase-field/dynamic density functional theory model able to account for the wetting transitions, the resulting friction between the wall and the fluid, and compressible hydrodynamics at high viscosity contrast.
© 2011 American Institute of Physics.