Issue 6, 2012

A microfluidic method to study demulsification kinetics

Abstract

We present the results of experiments studying droplet coalescence in a dense layer of emulsion droplets using microfluidic circuits. The microfluidic structure allows direct observation of collisions and coalescence events between oil droplets dispersed in water. The coalescence rate of a flowing hexadecane-in-water emulsion was measured as a function of the droplet velocity and droplet concentration from image sequences measured with a high-speed camera. A trajectory analysis of colliding droplet pairs allows evaluation of the film drainage profile and coalescence time tc. The coalescence times obtained for thousands of droplet pairs enable us to calculate coalescence time distributions for each set of experimental parameters, which are the mean droplet approach velocity 〈v0〉, the mean dispersed phase fraction 〈ϕ〉 and the mean hydraulic diameter of a droplet pair 〈dp〉. The expected value Etc of the coalescence time distributions scales as Etc ∝ 〈v0−0.105±0.043dp0.562±0.287, but is independent of ϕ. We discuss the potential of the procedure for the prediction of emulsion stability in industrial applications.

Graphical abstract: A microfluidic method to study demulsification kinetics

Supplementary files

Article information

Article type
Paper
Submitted
26 Sep 2011
Accepted
12 Dec 2011
First published
03 Jan 2012

Lab Chip, 2012,12, 1060-1070

A microfluidic method to study demulsification kinetics

T. Krebs, K. Schroen and R. Boom, Lab Chip, 2012, 12, 1060 DOI: 10.1039/C2LC20930F

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