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Issue 16, 2012
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Use of electrowetting to measure dynamic interfacial tensions of a microdrop

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Abstract

The adsorption of surface active species to liquid–liquid and to solid–liquid interfaces can have dramatic effects in microfluidics. In this paper we show how electrowetting on dielectric can be used to monitor a dynamic liquid–liquid interfacial tension (IFT) with a time resolution of O(1 s) using amplitude modulation of the AC voltage. This straightforward method, which requires less than a microlitre of sample, is demonstrated for aqueous drops containing Triton X-100 surfactant on a Teflon AF-coated substrate and with heptane as the immiscible oil ambient. Under these conditions, next to extracting the oil–water IFT (γow), also the effective water–substrate IFT difference (Δγws) can be obtained from the oil–water IFT and the Young's angle. Both γow and γws decrease over time due to adsorption. The measured dynamic oil–water IFT compares well to results of pendant drop experiments.

Graphical abstract: Use of electrowetting to measure dynamic interfacial tensions of a microdrop

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Article information


Submitted
28 Jan 2012
Accepted
30 Apr 2012
First published
30 May 2012

Lab Chip, 2012,12, 2832-2836
Article type
Paper

Use of electrowetting to measure dynamic interfacial tensions of a microdrop

R. de Ruiter, P. Wennink, A. G. Banpurkar, M. H. G. Duits and F. Mugele, Lab Chip, 2012, 12, 2832
DOI: 10.1039/C2LC21036C

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