Friction and Slip at Simple Fluid-Solid Interfaces: The Roles of the Molecular Shape and the Solid-Liquid Interaction

Using total internal reflection-fluorescence recovery after photobleaching, the local velocity, averaged over distances of 50 nm from the solid wall, has been measured for two different simple liquids, squalane and hexadecane, sheared on three smooth surfaces with similar roughness but with gradually decreasing fluid-solid interactions. We show that not only the strength of the fluid-solid interactions, but also the shape of the molecules of the fluid deeply affect the friction and the degree of slip at the wall.