Atomic force microscope study of boundary layer lubrication

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Abstract
An atomic force microscope is used to investigate the lubrication properties of a simple surfactant (n-dodecanol) on mica at 24 °C. The liquid becomes strongly layered as it is confined between the tip and the mica and a bilayer structure was often observed. The lubrication properties of the adsorbed molecules are clearly evident in the very low friction forces observed at appreciable applied loads (∼100 MPa). It is only when the last layer of molecules is removed that a significant friction signal is observed. It appears that the tip-mica interaction is dominated by adhesive forces and hence the measured friction and normal forces are strongly influenced by the effective contact area of the tip.