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Controlling the distance of highly confined droplets in a capillary by interfacial tension for merging on-demand

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Abstract

Droplet microfluidics is a powerful technology that finds many applications in chemistry and biomedicine. Among different configurations, droplets confined in a capillary (or plugs) present a number of advantages: they allow positional identification and simplify the integration of complex multi-steps protocols. However, these protocols rely on the control of droplet speed, which is affected by a complex and still debated interplay of various physico-chemical parameters like droplet length, viscosity ratio between droplets and carrier fluid, flow rate and interfacial tension. We present here a systematic investigation of the droplet speed as a function of their length and interfacial tension, and propose a novel, simple and robust methodology to control the relative distance between consecutive droplets flowing in microfluidic channels through the addition of surfactants either into the dispersed and/or into the continuous phases. As a proof of concept application, we present the possibility to accurately trigger in space and time the merging of two confined droplets flowing in a uniform cross-section circular capillary. This approach is further validated by monitoring a conventional enzymatic reaction used to quantify the concentration of H2O2 in a biological sample, showing its potentialities in both continuous and stopped assay methods.

Graphical abstract: Controlling the distance of highly confined droplets in a capillary by interfacial tension for merging on-demand

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Publication details

The article was received on 30 Oct 2018, accepted on 21 Nov 2018 and first published on 22 Nov 2018


Article type: Paper
DOI: 10.1039/C8LC01182F
Citation: Lab Chip, 2019, Advance Article
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    Controlling the distance of highly confined droplets in a capillary by interfacial tension for merging on-demand

    D. Ferraro, M. Serra, D. Filippi, L. Zago, E. Guglielmin, M. Pierno, S. Descroix, J.-L. Viovy and G. Mistura, Lab Chip, 2019, Advance Article , DOI: 10.1039/C8LC01182F

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