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Open AccessArticle

Examining the Effect of Flow Rate Ratio on Droplet Generation and Regime Transition in a Microfluidic T-Junction at Constant Capillary Numbers

1
Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham NG7 2RD, UK
2
Department of Chemical and Environmental Engineering, University of Nottingham Malaysia Campus, Semenyih 43500, Malaysia
*
Author to whom correspondence should be addressed.
Current address: Department of Chemical Engineering, University College London, London WC1E 7JE, UK.
Current address: School of Engineering and Physical Sciences, Heriot-Watt University Malaysia Campus, Putrajaya Wilayah Persekutuan 62200, Malaysia.
Inventions 2018, 3(3), 54; https://doi.org/10.3390/inventions3030054
Received: 16 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 10 August 2018
(This article belongs to the Special Issue Microfluidics and Nanofluidics)
The focus of this work is to examine the effect of flow rate ratio (quotient of the dispersed phase flow rate over the continuous phase flow rate) on a regime transition from squeezing to dripping at constant capillary numbers. The effect of the flow rate ratio on the volume of droplets generated in a microfluidic T-junction is discussed, and a new scaling law to estimate their volume is proposed. Existing work on a regime transition reported by several researchers focuses on the effect of the capillary number on regime transition, and the results that are presented in this paper advance the current understanding by indicating that the flow rate ratio is another parameter that dictates regime transition. In this paper, the transition between squeezing and dripping regimes is reported at constant capillary numbers, with a transition region identified between squeezing and dripping regimes. Dripping is observed at lower flow rate ratios and squeezing at higher flow rate ratios, with a transition region between the two regimes at flow rate ratios between 1 and 2. This is presented in a flow regime map that is constructed based on the observed mechanism. A scaling model is proposed to characterise droplet volume in terms of flow rate ratio and capillary number. The effect of flow rate ratio on the non-dimensional droplet volume is presented, and lastly, the droplet volume is expressed in terms of a range of parameters, such as the viscosity ratio between the dispersed and the continuous phase, capillary number, and the geometrical characteristics of the channels. View Full-Text
Keywords: microfluidics; T-junction; microdroplet generation; regime transition; squeezing; dripping microfluidics; T-junction; microdroplet generation; regime transition; squeezing; dripping
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MDPI and ACS Style

Loizou, K.; Wong, V.-L.; Hewakandamby, B. Examining the Effect of Flow Rate Ratio on Droplet Generation and Regime Transition in a Microfluidic T-Junction at Constant Capillary Numbers. Inventions 2018, 3, 54.

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