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Microdroplet formation in rounded flow-focusing junctions

Microdroplet formation in rounded flow-focusing junctions
Microdroplet formation in rounded flow-focusing junctions
Herein we report microfluidic droplet formation in flow-focusing geometries possessing varying degrees of rounding. Rounding is incorporated in all four corners (symmetric) or only in the two exit corners (asymmetric). The ratios of the radius of curvature, R, to channel width, w, are varied where R/w = 0, 0.5 and 1. In all cases, monodisperse droplets are produced, with the largest droplets being produced at the junctions with the largest rounding. Junctions without rounding are shown to produce droplets at higher frequencies than those with rounding. Droplet pinch-off position is found to be dependent on both geometry and volumetric flow rates; the location shifts toward the interior of the rounded junctions with increasing oil-to-water flow rate ratios. Accordingly, we find that rounding within microfluidic flow-focusing junctions strongly influences droplet formation. Junction rounding may be deliberate due to the selected fabrication method or occur as an unintended result of microfabrication processes not held to strict tolerances. Indeed, understanding droplet characteristics for those formed in such structures is critical for microfluidic applications where droplet volume or reagent mass must be well controlled. Thus, rounding can be a valuable design parameter when tuning the size and production frequency for emulsion collection or ensuing downstream operations such as chemical reactions.
droplet production, microfluidics, flow focusing, flow instabilities
1613-4982
1-9
Gulati, Shelly
eee1de2e-7519-4998-91cd-d59015690ba7
Vijayakumar, Kalpana
dc5367b5-8783-4dd0-a14d-a0e80207e4fc
Good, Wilson W.
2582c118-3ff5-48c9-9f40-68c0bffbe405
Tamayo, Warren L.
403e240d-50d6-42d7-a744-4f012c085381
Patel, Akhil R.
04651291-5275-4332-9039-6c3d8907108b
Niu, Xize
f3d964fb-23b4-45db-92fe-02426e4e76fa
Gulati, Shelly
eee1de2e-7519-4998-91cd-d59015690ba7
Vijayakumar, Kalpana
dc5367b5-8783-4dd0-a14d-a0e80207e4fc
Good, Wilson W.
2582c118-3ff5-48c9-9f40-68c0bffbe405
Tamayo, Warren L.
403e240d-50d6-42d7-a744-4f012c085381
Patel, Akhil R.
04651291-5275-4332-9039-6c3d8907108b
Niu, Xize
f3d964fb-23b4-45db-92fe-02426e4e76fa

Gulati, Shelly, Vijayakumar, Kalpana, Good, Wilson W., Tamayo, Warren L., Patel, Akhil R. and Niu, Xize (2016) Microdroplet formation in rounded flow-focusing junctions. Microfluidics and Nanofluidics, 20 (2), 1-9. (doi:10.1007/s10404-015-1680-3).

Record type: Article

Abstract

Herein we report microfluidic droplet formation in flow-focusing geometries possessing varying degrees of rounding. Rounding is incorporated in all four corners (symmetric) or only in the two exit corners (asymmetric). The ratios of the radius of curvature, R, to channel width, w, are varied where R/w = 0, 0.5 and 1. In all cases, monodisperse droplets are produced, with the largest droplets being produced at the junctions with the largest rounding. Junctions without rounding are shown to produce droplets at higher frequencies than those with rounding. Droplet pinch-off position is found to be dependent on both geometry and volumetric flow rates; the location shifts toward the interior of the rounded junctions with increasing oil-to-water flow rate ratios. Accordingly, we find that rounding within microfluidic flow-focusing junctions strongly influences droplet formation. Junction rounding may be deliberate due to the selected fabrication method or occur as an unintended result of microfabrication processes not held to strict tolerances. Indeed, understanding droplet characteristics for those formed in such structures is critical for microfluidic applications where droplet volume or reagent mass must be well controlled. Thus, rounding can be a valuable design parameter when tuning the size and production frequency for emulsion collection or ensuing downstream operations such as chemical reactions.

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More information

Accepted/In Press date: 15 November 2015
Published date: January 2016
Keywords: droplet production, microfluidics, flow focusing, flow instabilities
Organisations: Mechatronics

Identifiers

Local EPrints ID: 385863
URI: http://eprints.soton.ac.uk/id/eprint/385863
ISSN: 1613-4982
PURE UUID: 45a60780-bc82-431e-ad7e-569ecaa1e5b3

Catalogue record

Date deposited: 25 Jan 2016 14:06
Last modified: 15 Jul 2019 20:51

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