Friction and Molecular Deformation in the Tensile Regime

Recent molecular level studies of energy dissipation in sliding friction have suggested a contribution from adhesive forces. In order to observe this directly, we have constructed a scanning force microscope with decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and attractive forces. Measurements made on self-assembling alkanethiol films with chemically different tail groups show that friction can increase with stronger adhesive intermolecular forces and from the associated tensile deformation and collective motion of the thiol chains.