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Continuous splitting of aqueous droplets at the interface of co-flowing immiscible oil streams in a microchannel

Abstract

We report continuous splitting of aqueous droplets at the interface between two co-flowing immiscible oil streams in a microchannel. Aqueous droplets initially present in a primary continuous stream (CP1) migrate into a secondary continuous stream (CP2) when the ratio of the non-inertial lift force and interfacial tension force exceeds a critical value (K. S. Jayaprakash et al., Langmuir, 2016, 32, 2136-2143). Here, experiments were performed to understand the droplet splitting phenomenon and demonstrate splitting of droplets encapsulating microbeads and cells. The results showed that the droplet splitting phenomena is governed by the capillary number Ca which is a function of the average shear stress (μG) @#x0305; across the channel, interfacial tension σ between the CP1 and the droplet phase and the droplet length-scale L. Irrespective of the individual values of these parameters, droplet splitting was observed when the capillary number Ca exceeds a critical value 〖Ca〗_cr, which was found to be a function of droplet to CP2 viscosity ratio λ. The 〖Ca〗_cr was found to be minimum for λ≈1 but higher for droplets of λ≫1 and λ≪1. The sizes of the primary and secondary daughter and migrated droplets (i.e. L_(p|sD) and L_(p|sM)) were found to increase linearly with increase in the size of the primary or secondary parent droplets (L_(p|sP)). Splitting of parent droplets encapsulating a single microbead or PBMC showed that after splitting, the presence of the microbead or PBMC in the daughter or migrated droplets depend on the ratio of the size of the migrated droplets to that of the parent droplet (i.e. V_M⁄V_P ). Finally, splitting of parent droplets containing two or more microbeads or cells into droplets containing a single particle or cell was demonstrated. A new paradigm of droplet splitting is reported which could find applications in soft matter and single-cell studies.

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Supplementary files

Publication details

The article was received on 19 Oct 2017, accepted on 01 Jan 2018 and first published on 02 Jan 2018


Article type: Paper
DOI: 10.1039/C7SM02068F
Citation: Soft Matter, 2018, Accepted Manuscript
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    Continuous splitting of aqueous droplets at the interface of co-flowing immiscible oil streams in a microchannel

    K. S. Jayaprakash and A. Sen, Soft Matter, 2018, Accepted Manuscript , DOI: 10.1039/C7SM02068F

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