Abstract
The formation of bubbles in a flow-focusing (FF) junction comprising multiple rectangular sections is described. The simplest junctions comprise two sections (throat and orifice). Systematic investigation of the influence on the formation of bubbles of the flow of liquid and the geometry of the junction identifies regimes that generate monodisperse, bidisperse, and tridisperse trains of bubbles. The mechanisms by which these junctions form monodisperse and bidisperse bubbles are inferred from the shapes of the gas thread during breakup: these mechanisms differ primarily by the process in which the gas thread collapses in the throat and/or orifice. The dynamic self-assembly of bidisperse bubbles leads to unexpected groupings of bubbles during their flow along the outlet channel.
Highlights
This paper describes the stable formation of trains of mono, bi- and tri-disperse bubbles in microfluidic flow-focusing (FF) junctions
We explored the break-up of the gas thread, and the formation of bubbles, in modified FF geometries in which we replaced the simple orifice with multiple rectangular sections (Figure 1)
The streams of multidisperse bubbles generated in these junctions displayed complex interactions as they flowed downstream in the straight outlet channel; the bubbles eventually formed stable, ordered patterns via dynamic self-assembly through the patterns of flow created by the bubbles
Summary
This paper describes the stable formation of trains of mono-, bi- and tri-disperse bubbles in microfluidic flow-focusing (FF) junctions. We explored the break-up of the gas thread, and the formation of bubbles, in modified FF geometries in which we replaced the simple orifice with multiple rectangular sections (Figure 1). Each rectangular section can act as a distinct site at which bubbles can form; simple modifications of the geometry of the FF junctions made it possible to generate bior tridisperse bubbles (e.g. regular patterns of bubbles of two or three distinct sizes), and complex patterns of bubbles, reproducibly. The streams of multidisperse bubbles generated in these junctions displayed complex interactions as they flowed downstream in the straight outlet channel; the bubbles eventually formed stable, ordered patterns via dynamic self-assembly through the patterns of flow created by the bubbles
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