The Effect of Rarefaction on Lubricated Microfluidic Flows

The no-slip boundary condition for fluid flow along a wall is applicable in nearly all macroscopic and microscopic flows, with the only significant exception being for rarefied gas flow. Many experimental and theoretical studies of microfluidic flows over ‘superhydrophobic’ surfaces, however, have shown evidence of apparent slip, or slip-like behavior. This behavior is often attributed to nanobubbles or a thin gaseous film. In analyzing these flows, however, the real slip of a rarefied gas in this film is often neglected. Here we will present the effect of rarefaction of the gas in microfluidic flows with a gaseous lubricating film.