We report a novel experimental technique using total internal reflection -
fluorescence recovery after photobleaching (TIR-FRAP) to probe the velocity
of a liquid near a wall with a resolution of the order of 100 nm. As an ex
ample of use, we have investigated the boundary condition of the liquid vel
ocity during lubricated friction and studied the influence of a classical a
dditive (stearic acid) in a base oil (hexadecane), and demonstrate that sim
ple Newtonian fluids can develop slip at the wall.