A Molecular-Kinetic Scaling Relation for Fluid Slip at Solid Boundaries*

Fluid slip at solid boundaries is perhaps the most well known nanoscale-related phenomenon associated with fluid flow. Despite the attention it has received, predictive models of slip based on ab-initio (molecular) considerations have yet to be fully developed.  Using the observation that slip in simple fluids at low to moderate shear rates is a thermally activated process driven by the shear stress in the fluid close to the solid boundary, we use kinetic arguments to develop a model for fluid slip at solid boundaries in the form of a universal scaling relation that connects fluid slip and shear rate. The proposed model reduces to the well known Navier-slip condition under low shear conditions, providing a direct connection between molecular parameters and the slip length. Molecular-dynamics simulations strongly support the predicted dependence of slip on system properties, including the temperature and fluid-solid interaction strength. Finally, we explore the connections between our model and previous theories, simulation results, and experiments studying fluid-solid slip.