Issue 19, 2011
From the journal:

Soft Matter

Homo- and hetero-interactions between air bubbles and oil droplets measured by atomic force microscopy†

Rico F. Tabor,ab   Chu Wu,bc   Hannah Lockie,ab   Rogerio Manica,d   Derek Y. C. Chan,bce   Franz Grieserbf  and  Raymond R. Dagastine*ab  

* Corresponding authors

a Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville 3010, Australia
E-mail: rrd@unimelb.edu.au

b Particulate Fluids Processing Centre, University of Melbourne, Parkville 3010, Australia

c Department of Mathematics and Statistics, University of Melbourne, Parkville 3010, Australia

d Institute of High Performance Computing, Singapore

e Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn 3122, Australia

f School of Chemistry, University of Melbourne, Parkville 3010, Australia

Abstract

The atomic force microscope was used to analyse the interactions between bubbles and oil droplets in surfactant-free aqueous solutions. Both homo- (bubble-bubble and drop-drop) and hetero- (bubble-drop) interactions were examined to elucidate the role of colloidal and hydrodynamic forces which, together with interfacial deformations dictate the stability in these systems. It is shown that electrical double-layer forces can be rendered attractive within a small pH range, and that the Van der Waals force can be switched from attractive to repulsive by material choice and ionic strength through salt effects on the so-called ‘zero-frequency’ term of the Lifshitz theory. By measuring interaction events between bubbles and drops at higher velocities, it is seen that deformation of the bodies and lubrication in the film generated between them can be predicted with a continuum hydrodynamic theory. These results suggest that solution pH and droplet material choice can be used to enhance or inhibit coalescence in such multi-component and multi-phase systems, and this may prove useful in controlling the behaviour of systems in microfluidics, as well as dispersion and formulation science.

Graphical abstract: Homo- and hetero-interactions between air bubbles and oil droplets measured by atomic force microscopy

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Article information

DOI
https://doi.org/10.1039/C1SM06006F
Article type
Paper
Submitted
31 May 2011
Accepted
12 Jul 2011
First published
10 Aug 2011

Soft Matter, 2011,7, 8977-8983

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Homo- and hetero-interactions between air bubbles and oil droplets measured by atomic force microscopy

R. F. Tabor, C. Wu, H. Lockie, R. Manica, D. Y. C. Chan, F. Grieser and R. R. Dagastine, Soft Matter, 2011, 7, 8977 DOI: 10.1039/C1SM06006F

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