Issue 46, 2013

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

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

Article information

Article type
Paper
Submitted
10 Jun 2013
Accepted
13 Aug 2013
First published
16 Sep 2013

Soft Matter, 2013,9, 10971-10984

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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