Direct experimental evidence of slip in hexadecane: Solid interfaces

The boundary condition for the flow velocity of a Newtonian fluid near a so lid wall has been probed experimentally with a novel setup using total inte rnal reflection-fluorescence recovery after photobleaching leading to a res olution from the wall of the order of 80 nm. For hexadecane flowing on a hy drocarbon/lyophobic smooth surface, we give what we think to be the first d irect experimental evidence of noticeable slip at the wall. We show that th e surface roughness and the strength of the fluid-surface interactions both act on wall slip, in antagonist ways.