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Comparison of surfactant mass transfer with drop formation times from dynamic interfacial tension measurements in microchannels

Kalli, M; Chagot, L; Angeli, P; (2022) Comparison of surfactant mass transfer with drop formation times from dynamic interfacial tension measurements in microchannels. Journal of Colloid and Interface Science , 605 pp. 204-213. 10.1016/j.jcis.2021.06.178. Green open access

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Abstract

Dynamic interfacial tension was studied experimentally during drop formation in a flow-focusing microchannel. A low viscosity silicone oil (4.6 mPa s) was the continuous phase and a mixture of 48% w/w water and 52% w/w glycerol was the dispersed phase. An anionic (sodium dodecylsulfate, SDS), a cationic (dodecyltrimethylammonium bromide, DTAB) and a non-ionic (Triton™ X-100, TX100) surfactant were added in the dispersed phase, at concentrations below and above the critical micelle concentration (CMC). For SDS and DTAB the drop size against continuous phase flowrate curves initially decreased with surfactant concentration and then collapsed to a single curve at concentrations above CMC. For TX100 the curves only collapsed at surfactant concentrations 8.6 times the CMC. From the collapsed curves a correlation of drop size with capillary number was derived, which was used to calculate the dynamic interfacial tension at times as low as 3 ms. The comparison of the surfactant mass transport and adsorption times to the interface against the drop formation times indicated that surfactant adsorption also contributes to the time required to reach equilibrium interfacial tension. Criteria were proposed for drop formation times to ensure that equilibrium interfacial tension has been reached and does not affect the drop formation.

Type: Article
Title: Comparison of surfactant mass transfer with drop formation times from dynamic interfacial tension measurements in microchannels
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jcis.2021.06.178
Publisher version: https://doi.org/10.1016/j.jcis.2021.06.178
Language: English
Additional information: Copyright © 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Droplet formation, Surfactants, Dynamic interfacial tension, Flow-focusing microchannel
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10133051
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