Anomalous time effect on particle-bubble interactions studied by atomic force microscopy.

The atomic force microscope was employed to investigate the time effect on normal interactions between a hydrophilic silica particle and an air bubble deposited onto a hydrophobic Teflon surface in pure water and 10 mM methyl isobutyl carbinol solutions. The force versus separation distance curves taken at different times after bubble generation were qualitatively compared. It has been found that the penetration distance, jump-in force, contact angle, rupture distance, force required for the film to rupture, interfacial spring constant, and bubble shape were time-dependent. The results were explained by the change of the air-water interface shape with time due to water droplet growth on the Teflon surface inside the air bubbles.