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Issue 8, 2012
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Experimental validation of plugging during drop formation in a T-junction

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Abstract

At low capillary number, drop formation in a T-junction is dominated by interfacial effects: as the dispersed fluid flows into the drop maker nozzle, it blocks the path of the continuous fluid; this leads to a pressure rise in the continuous fluid that, in turn, squeezes on the dispersed fluid, inducing pinch-off of a drop. While the resulting drop volume predicted by this “squeezing” mechanism has been validated for a range of systems, as of yet, the pressure rise responsible for the actual pinch-off has not been observed experimentally. This is due to the challenge of measuring the pressures in a T-junction with the requisite speed, accuracy, and localization. Here, we present an empirical study of the pressures in a T-junction during drop formation. Using Laplace sensors, pressure probes we have developed, we confirm the central ideas of the squeezing mechanism; however, we also uncover other findings, including that the pressure of the dispersed fluid is not constant but rather oscillates in anti-phase with that of the continuous fluid. In addition, even at the highest capillary number for which monodisperse drops can be formed, pressure oscillations persist, indicating that drop formation in confined geometries does not transition to an entirely shear-driven mechanism, but to a mechanism combining squeezing and shearing.

Graphical abstract: Experimental validation of plugging during drop formation in a T-junction

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Publication details

The article was received on 16 Dec 2011, accepted on 14 Feb 2012 and first published on 09 Mar 2012


Article type: Paper
DOI: 10.1039/C2LC21263C
Citation: Lab Chip, 2012,12, 1516-1521
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    Experimental validation of plugging during drop formation in a T-junction

    A. R. Abate, P. Mary, V. van Steijn and D. A. Weitz, Lab Chip, 2012, 12, 1516
    DOI: 10.1039/C2LC21263C

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