Issue 8, 2013
From the journal:

Soft Matter

Non-linear and cyclical collisions between drops and bubbles: using AFM to understand droplet interactions in micro-scale flows†

Rico F. Tabor,*ab   Chu Wu,bc   Franz Grieser,bd   Derek Y. C. Chanbce  and  Raymond R. Dagastine*bfg  

* Corresponding authors

a School of Chemistry, Monash Univeristy, Clayton 3800, Australia
E-mail: rico.tabor@monash.edu
Fax: +61 3 9905 4597
Tel: +61 3 9905 4558

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

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

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

e School of Life and Social Sciences, Swinburne Univeristy of Technology, Hawthorn 3122, Australia

f Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville 3010, Australia
E-mail: rrd@unimelb.edu.au
Fax: +61 3 8344 4153
Tel: +61 3 8344 4704

g Melbourne Centre for Nanofabrication, 151 Wellington Road, Clayton 3168, Australia

Abstract

Understanding the mechanics and outcome of droplet and bubble collisions is central to a range of processes from emulsion stability to mineral flotation. The atomic force microscope has been shown to be sensitive and accurate in measuring the forces during such interactions; in combination with a suitable model framework, a powerful tool is obtained for understanding surface forces and droplet stability in dynamic systems. Here we demonstrate for the first time that this process is not limited to linear motion, and that accelerating, decelerating and cyclical droplet velocities can be used to explore the collisions between droplets and bubbles in ways that much more closely mimic real systems. In particular, the motion of droplets experiencing oscillating pumping pressures is explored, providing insight into fluid handling for microfluidics. By modelling a range of processes in which drops collide and deform, and sometimes coalesce, the validity of the theoretical model – which accounts for deformation, surface forces and dynamic lubrication – is demonstrated. Further, it is shown how this model can be used as a predictive tool to determine whether a given droplet collision will be stable or coalescent.

Graphical abstract: Non-linear and cyclical collisions between drops and bubbles: using AFM to understand droplet interactions in micro-scale flows

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Article information

DOI
https://doi.org/10.1039/C2SM27463A
Article type
Paper
Submitted
25 Oct 2012
Accepted
03 Jan 2013
First published
11 Jan 2013

Soft Matter, 2013,9, 2426-2433

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Non-linear and cyclical collisions between drops and bubbles: using AFM to understand droplet interactions in micro-scale flows

R. F. Tabor, C. Wu, F. Grieser, D. Y. C. Chan and R. R. Dagastine, Soft Matter, 2013, 9, 2426 DOI: 10.1039/C2SM27463A

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