Effect of surface hydrophobicity on interaction between particle and flat plate at final stage of wet coating process

When a droplet of a colloidal suspension on a flat plate with low contact angle was observed during drying process, the edge of the droplet did not recede towards the center, and the highly ordered structure of particles was obtained on the plate. Increasing hydrophobicity or decreasing ionic strength in the solution, however, the edge of the droplet receded during drying process and the particle structure became disordered. erstand the influence of surface hydrophobicity on the final stage of drying process, adhesion force between solid surfaces was measured by using an atomic force microscope as a function of relative humidity. The observed adhesion force between the glass particle and the hydrophilic plate increased with relative humidity due to strong capillary condensation. In contrast, the adhesion force between the glass particle and the hydrophobic plate was weaker than that using a hydrophilic plate and almost independent of relative humidity due to weak capillary condensation. This difference of surface hydrophobicity on adhesion force could be important role to make the ordered structure.