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Issue 46, 2013
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Neighbor-induced bubble pinch-off: novel mechanisms of in situ foam generation in microfluidic channels

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Abstract

We utilize a microfluidic constriction to demonstrate two new mechanisms of in situ foam generation in porous media. The initial foam was generated using a flow-focusing geometry with co-flowing gas and surfactant solution streams and then flowed through a microfluidic constriction. By varying the gas and surfactant solution flow rates, different types of monodisperse foams were generated in which two bubbles (2-bubble foam), three bubbles (3-bubble foam), or more than three bubbles (>3-bubble foam) spanned the channel width. It was expected that the bubbles would snap off upon passing through the constriction; however, in our system, the snap-off mechanism was observed only under unstable conditions, namely, when the foam was wet and had a large bubble size. Instead, the following behaviors were observed as stable foam passed through the constriction: no change, reorientation, and pinch-off, which included two newly observed mechanisms (neighbor–wall pinch-off and neighbor–neighbor pinch-off). Neighbor–wall pinch-off occurs as a bubble is pinched between the surfaces of a neighboring bubble and the curved wall of the constriction. Neighbor–neighbor pinch-off occurs as a bubble is pinched off between two adjacent neighboring bubbles. The width of the pinched bubble as a function of time before pinch-off was found to scale as a power law with exponents of 0.523 ± 0.06 and 1.004 ± 0.05 for neighbor–wall and neighbor–neighbor pinch-off, respectively.

Graphical abstract: Neighbor-induced bubble pinch-off: novel mechanisms of in situ foam generation in microfluidic channels

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Publication details

The article was received on 10 Jun 2013, accepted on 13 Aug 2013 and first published on 16 Sep 2013


Article type: Paper
DOI: 10.1039/C3SM51605A
Citation: Soft Matter, 2013,9, 10971-10984
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    Neighbor-induced bubble pinch-off: novel mechanisms of in situ foam generation in microfluidic channels

    R. Liontas, K. Ma, G. J. Hirasaki and S. L. Biswal, Soft Matter, 2013, 9, 10971
    DOI: 10.1039/C3SM51605A

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