Interaction of a microsphere with a solid-supported liquid film.

The interaction between particles with thin liquid films on solid surfaces was studied by sintering polystyrene microspheres of 4 to 5 microm diameter to the end of atomic force microscope cantilevers. Films of three silicone oils (viscosity 4.6, 9.2, and 9700 mPa s) and water of thickness 0.2-1.8 microm were formed on glass. The interaction between a particle and the film was measured at different particle approach/retraction velocities. The interaction is dominated by capillary and hydrodynamic forces. It depends on the surface tension and the viscosity of the liquid. The film thickness can be determined from the force curves. In addition, the meniscus formation of a film wetting a particle was demonstrated experimentally by solidifying a liquid polystyrene film as it wetted glass particles.