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Issue 10, 2012
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Selective droplet coalescence using microfluidic systems

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Abstract

We report a microfluidic approach, which allows selective and controlled 1 : 1, 2 : 1 or 3 : 1 droplet fusion. A surfactant-stabilized droplet with an interfacial surfactant coverage, Γ, of >98% will fuse spontaneously with a second droplet when Γ of the latter droplet is <16%. However, when Γ of the second droplet is ∼66%, the two droplets will not fuse, unless they have previously been brought into contact for critical time τ. Therefore, controlling the number of droplets in contact for time τ allows precise control over the number of fused droplets. We have demonstrated efficient (proportion of droplets coalesced p(c) = 1.0, n > 1000) and selective 1 : 1, 2 : 1 or 3 : 1 droplet fusion (proportion of correctly fused droplets p(s) > 0.99, n > 1000). Coalescence in this regime is induced by hydrodynamic flow causing interface separation and is efficient at different Ca numbers and using different dispersed phases, continuous phases and surfactants. However, when Γ of the second droplet is ∼96% coalescence is no longer observed. Droplet-based microfluidic systems, in which each droplet functions as an independent microreactor, are proving a promising tool for a wide range of ultrahigh-throughput applications in biology and chemistry. The addition of new reagents to pre-formed droplets is critical to many of these applications and we believe the system described here is a simple and flexible method to do so, as well as a new tool to study interfacial stability phenomena.

Graphical abstract: Selective droplet coalescence using microfluidic systems

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Publication details

The article was received on 03 Feb 2012, accepted on 27 Feb 2012 and first published on 06 Mar 2012


Article type: Paper
DOI: 10.1039/C2LC40121E
Citation: Lab Chip, 2012,12, 1800-1806
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    Selective droplet coalescence using microfluidic systems

    L. Mazutis and A. D. Griffiths, Lab Chip, 2012, 12, 1800
    DOI: 10.1039/C2LC40121E

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