Molecular Desorption by a Moving Contact Line

The interaction of the contact line with topographical or chemical defects at the nanometer scale sets the macroscopic wetting properties of a liquid on a solid substrate. Based on specific atomic force microscopy (AFM) experiments, we demonstrate that molecules physically sorbed on a surface are removed by a dynamic contact line. The mechanism of molecules desorption is directly determined by the capillary force exerted at the contact line on the molecules. We also emphasize the potential of AFM to clearly decorrelate the effects of topographical and chemical defects and monitor, with a subsecond time resolution, the dynamics of molecules adsorption on a surface.