221f Colloidal Forces and Hydrodynamic Drainage Between Micro-Bubbles Measured Using Atomic Force Microscopy

Raymond R. Dagastine1, Ivan U. Vakarelski2, Ofer Manor3, G. W. Stevens4, Franz Grieser5, and D.Y.C. Chan3. (1) PFPC and the Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, 3010, Australia, (2) Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan, (3) PFPC and the Department of Mathematics and Statistics, The University of Melbourne, The University of Melbourne, Parkville, Australia, (4) PFPC and the Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, 3010, Australia, (5) PFPC and the School of Chemistry, The University of Melbourne, Parkville, 3010, Australia

The dynamic interactions between bubbles are highly sensitive to the nature of the adsorbed molecules at the air-water interface. We have extended the experimental and theoretical methods developed to study the dynamic interactions between droplets1. using Atomic Force Microscopy (AFM) to the interactions between two micro-bubbles2. or a micro-bubble and a flat surface in aqueous. These measurements show that bubble collisions, even at speeds comparable to Brownian motion, are dependent on a combination of equilibrium surface forces, hydrodynamic drainage forces and interfacial deformation. Bubble collisions were studied in the presence and absence of added stabilizers exhibiting extreme differences in their dynamic force behavior. Quantitative modeling, which shows excellent agreement between experiments and calculations, demonstrates that the variations in the dynamic forces arise from changes in both the equilibrium surface forces and hydrodynamic drainage boundary conditions. These results have implications in applications as wide ranging as froth floatation to micro-fluidics.

1. R. R. Dagastine, R. Manica, S.L. Carnie, D.Y.C. Chan, G.W. Stevens, and F. Grieser, Dynamic Forces between Two Deformable Oil Droplets in Water Science 313, 210-213 (2006).

2. I. U. Vakarelski, J. Lee, R. R. Dagastine, D. Y. C. Chan, G. W. Stevens, F. Grieser, Bubble Colloidal AFM Probes Formed from Ultrasonically Generated Bubbles Langmuir 24, 603-605 (2008).