Friction between two weakly adhering boundary lubricated surfaces in water.

The sliding of adhesive surfactant-bearing surfaces was studied with a surface forces apparatus nanotribometer. When the surfaces are fully immersed in an aqueous solution, the dynamic behavior is drastically different and more varied than under dry conditions. In solution, the shear stress exhibits at least five different velocity regimes. In particular, the sliding may proceed by an "inverted" stick-slip over a large range of driving velocities, this regime being bounded by smooth (kinetic) sliding at both lower and higher driving velocities. The general behavior of the system was studied in detail, i.e., over a large range of experimental conditions, and theoretically accounted for in terms of a general model based on the kinetics of formation and rupture of adhesive links (bonds) between the two shearing surfaces with an additional viscous term.