Effects of bubble size and approach velocity on bubble-particle interaction - a theoretical study

A theoretical analysis of the atomic force microscopy (AFM) approach-retract dynamic interaction between an air bubble and a hydrophilic silica plane was carried out based on the well-established Stokes-Reynolds-Young-Laplace model. An air bubble with different radii attached to the end of a cantilever approached the silica surface with different approach velocities in a 10(-3)M KCl solution. Results showed that with increasing approach velocity (0.1, 1, and 10 mu m/s), the repulsive force, flattened area of the film, and hydrodynamic suction force between the 100-mu m bubble and the silica plane increased. The film continued thinning at the initial stages of bubble retraction because of the attractive hydrodynamic pressure. When the bubble size decreased, the influence of hydrodynamic pressure was less evident. The final film thickness before bubble retraction was similar to the theoretical equilibrium thickness when the Laplace pressure was equal to the disjoining pressure. [GRAPHICS] .