Oil droplet generation in PDMS microchannel using an amphiphilic continuous phase

Lab on a Chip ◽  
2009 ◽  
Vol 9 (13) ◽  
pp. 1957 ◽  
Author(s):  
Su-Kyoung Chae ◽  
Chang-Ha Lee ◽  
Soo Hyun Lee ◽  
Tae-Song Kim ◽  
Ji Yoon Kang
Keyword(s):  
Continuous Phase ◽  
Droplet Generation ◽  
Oil Droplet ◽  
Pdms Microchannel

Effect of Geometry on Droplet Generation in a Microfluidic T-Junction

2013 ◽  
Author(s):  
Katerina Loizou ◽  
Wim Thielemans ◽  
Buddhika N. Hewakandamby
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Main Channel ◽  
Superficial Velocity ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Aspect Ratios ◽  
The Cross

The main aim of this study is to examine how the droplet formation in microfluidic T-junctions is influenced by the cross-section and aspect ratio of the microchannels. Several studies focusing on droplet formation in microfluidic devices have investigated the effect of geometry on droplet generation in terms of the ratio between the width of the main channel and the width of the side arm of the T-junction. However, the contribution of the aspect ratio and thus that of the cross-section on the mechanism of break up has not been examined thoroughly with most of the existing work performed in the squeezing regime. Two different microchannel geometries of varying aspect ratios are employed in an attempt to quantify the effect of the ratio between the width of the main channel and the height of the channel on droplet formation. As both height and width of microchannels affect the area on which shear stress acts deforming the dispersed phase fluid thread up to the limit of detaching a droplet, it is postulated that geometry and specifically cross-section of the main channel contribute on the droplet break-up mechanisms and should not be neglected. The above hypothesis is examined in detail, comparing the volume of generated microdroplets at constant flowrate ratios and superficial velocities of continuous phase in two microchannel systems of two different aspect ratios operating at dripping regime. High-speed imaging has been utilised to visualise and measure droplets formed at different flowrates corresponding to constant superficial velocities. Comparing volumes of generated droplets in the two geometries of area ratio near 1.5, a significant increase in volume is reported for the larger aspect ratio utilised, at all superficial velocities tested. As both superficial velocity of continuous phase and flowrate ratio are fixed, superficial velocity of dispersed phase varies. However this variation is not considered to be large enough to justify the significant increase in the droplet volume. Therefore it can be concluded that droplet generation is influenced by the aspect ratio and thus the cross-section of the main channel and its effect should not be depreciated. The paper will present supporting evidence in detail and a comparison of the findings with the existing theories which are mainly focused on the squeezing regime.

Electrowetting Induced Droplet Generation in T-junctions

2021 ◽  
Author(s):  
Arshia Merdasi ◽  
Ali Moosavi
Keyword(s):  
Shear Stress ◽  
Continuous Phase ◽  
Droplet Breakup ◽  
Droplet Generation ◽  
The Finite Element Method ◽  
Fluidic Channel ◽  
Generation Frequency ◽  
Two Phases ◽  
Breakup Time ◽  
Good Agreement

Abstract In the current study, droplet generation in a T-junction fluidic channel device was studied through using electrowetting actuation with the consideration of different droplet forming regimes. For this purpose, the finite element method (FEM) was used to solve the unsteady Naiver-Stokes equation. In addition, the level set method was applied to capture the interface between two phases. It was shown that there was a good agreement between obtained data and other work during the process of droplet generation in the absence of electrowetting actuation which results in decrease in the size of droplet with increasing the velocity ratios. In shearing regime, the effectiveness of electrowetting on the droplet generation frequency as well as droplet size is visible in a T-junction fluidic channel since after applying voltages, specified with non-dimensional electrowetting numbers of ?=0.5 and 1.2, dispersed phase is pulled out into the oil phase. In fact, with applying the voltage on the top wall, the droplet breakup time was decreased and smaller droplets were produced. Finally, different important parameters such as pressure difference across the interface as well as Shear Stress exerted from the continuous phase shear stress were examined in a detail.

Effect of Fluid Properties on Droplet Generation in a Microfluidic T-Junction

2014 ◽  
Author(s):  
Katerina Loizou ◽  
Voon-Loong Wong ◽  
Wim Thielemans ◽  
Buddhika Hewakandamby
Keyword(s):  
Interfacial Tension ◽  
Scaling Laws ◽  
Viscosity Ratio ◽  
Continuous Phase ◽  
Generation Mechanism ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Supporting Evidence ◽  
Fluid Properties ◽  
Break Up

Over the last decade, significant work has been performed in an attempt to quantify the effect of different parameters such as flowrate, geometrical and fluid characteristics on the droplet break up mechanism in microfluidic T-Junctions. This demand is dictated by the need of tight control of the size and dispersity of the droplets generated in such geometries. Even though several researchers have investigated the effect of viscosity ratio on both the droplet break up mechanism as well as on the regime transition, fluid properties have not been included in most scaling laws. It is therefore evident that the contribution of fluid properties has not been quantified thoroughly. In the present work, the effect of fluid properties on the volume of droplets generated in a microfluidic T-junction is investigated. The main aim of this work is to examine the influence of viscosity of both the dispersed and continuous phase as well as the effect of interfacial tension on the size of droplet generated along with the break up mechanism. Three different oils have been utilised as continuous phase in this work to enable investigation of the effect of viscosity of the continuous phase with experiments performed at constant Capillary numbers. Various glycerol weight percentages have been employed to vary the viscosity of the dispersed phase fluid (water). Lastly, the effect of interfacial tension has been explored using two of the oils at constant μcUc (viscous force term). High speed imaging has been utilised to visualise and measure the volume of the resulting droplets. The viscosity ratio (viscosity of dispersed phase over viscosity of continuous phase) between the two phases appears to affect the droplet generation mechanism, especially for the highest viscosity ratio employed (mineral oil-water system) where the system behaves in a noticeably different way. Influence of interfacial tension is also noticeable even though less evident. In terms of the effect of viscosity of dispersed phase on the droplet generation a small difference on the volume of the droplets generated in olive oil glycerol systems is also reported. In an attempt to enumerate the effect of fluid properties on the droplet generation mechanism in a microfluidic T-junction, this paper will present supporting evidence in detail on the above and a comparison of the findings with the existing theories.

Lattice Boltzmann Simulation of Droplet Formation in Non-Newtonian Fluids

2015 ◽  
Vol 17 (4) ◽  
pp. 1056-1072 ◽  
Author(s):  
Y. Shi ◽  
G. H. Tang
Keyword(s):  
Newtonian Fluid ◽  
Power Law ◽  
Lattice Boltzmann ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Droplet Generation ◽  
Bgk Model ◽  
Lattice Boltzmann Simulation ◽  
Power Law Exponent ◽  
Boltzmann Method

AbstractNewtonian and non-Newtonian dispersed phase droplet formation in non-Newtonian continuous phase in T-junction and cross junction microchannels are investigated by the immiscible lattice BGK model. The effects of the non-Newtonian fluid power-law exponent, viscosity and interfacial tension on the generation of the droplet are studied. The final droplet size, droplet generation frequency, and detachment point of the droplet change with the power-law exponent. The results reveal that it is necessary to take into account the non-Newtonian rheology instead of simple Newtonian fluid assumption in numerical simulations. The present analysis also demonstrates that the lattice Boltzmann method is of potential to investigate the non-Newtonian droplet generation in multiphase flow.

scholarly journals Droplet Formation in a Cross-Junction Microfluidic Channel with Non-Newtonian Dispersed Phase

2021 ◽  
Vol 4 (1) ◽  
pp. 21
Author(s):  
Maryam Fatehifar ◽  
Alistair Revell ◽  
Masoud Jabbari
Keyword(s):  
Power Law ◽  
Flow Rate ◽  
Xanthan Gum ◽  
Real Life ◽  
Microfluidic Channel ◽  
Shear Thinning ◽  
Continuous Phase ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Generating Series

Microfluidics enables generating series of isolated droplets for high-throughput screening. As many biological/chemical solutions are of shear thinning non-Newtonian nature, we studied non-Newtonian droplet generation to improve the reliability of simulation results in real-life assays. We considered non-Newtonian power-law behaviour for Xanthan gum aqueous solution as the dispersed phase, and Newtonian canola oil as the continuous phase. Simulations were performed in OpenFOAM, using the inter foam solver and volume of fluid (VOF) method. A cross-junction geometry with each inlet and outlet channel height (H) and width (W) equal to 50 micrometers with slight contractions in the conjunctions was used to gain a better monodispersity. Following validation of the numerical setup, we conducted a series of tests to provide novel insight into this configuration. With a capillary number, of 0.01, dispersed phase to continuous phase flow-rate ratio of 0.05, and contact angle of 160°, simulations revealed that, by increasing the Xanthan gum concentration (0, 800, 1500, 2500 ppm) or, in other words, decreasing the n-flow behaviour index from 1 to 0.491, 0.389, and 0.302 in power-law model, (a) breakup of the dispersed phase thread occurred at 0.0365, 0.0430, 0.0440, and 0.0450 s; (b) the dimensionless width of the thread at the main channel entrance increased from 0 to 0.066, 0.096, and 0.16; and (c) the dimensionless droplet diameter decreased from 0.76 to 0.72, 0.68, and 0.67, respectively. Our next plan is to study effect of shear-thinning behaviour on droplet generation in different Ca and flow-rate ratios.

Microchannel Emulsification Using Stainless-Steel Chips: Oil Droplet Generation Characteristics

2012 ◽  
Vol 35 (10) ◽  
pp. 1865-1871 ◽  
Author(s):  
I. Kobayashi ◽  
Y. Wada ◽  
Y. Hori ◽  
M. A. Neves ◽  
K. Uemura ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Droplet Generation ◽  
Oil Droplet ◽  
Microchannel Emulsification

scholarly journals Controlling the Internal Structures of Polymeric Microspheres via the Introduction of a Water-Soluble Organic Solvent

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 789 ◽  
Author(s):  
Yanping He ◽  
Xin Li ◽  
Tianci Zhu ◽  
Mengxing Shan ◽  
Linhua Zhu ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Evaporation Rate ◽  
Continuous Phase ◽  
Water Soluble ◽  
Polymeric Microspheres ◽  
Oil Droplet ◽  
Internal Structures ◽  
Solvent Molecules ◽  
Continuous Use ◽  
Solvent Layer

Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale.

Non-Newtonian Droplet Generation in a Flow-Focusing Microchannel

2019 ◽  
Author(s):  
C. D. Xue ◽  
Z. P. Sun ◽  
Y. J. Li ◽  
K. R. Qin
Keyword(s):  
Polyethylene Oxide ◽  
Food Production ◽  
Continuous Phase ◽  
Droplet Microfluidics ◽  
Droplet Generation ◽  
Flow Focusing ◽  
Complete Understanding ◽  
Practical Applications ◽  
Primary Droplet ◽  
Newtonian Behavior

Abstract The emergence of microfluidic droplets offers new opportunities to advance biomedical engineering, food production, and energy storage applications. These applications always involve complex fluids exhibiting obvious non-Newtonian behavior. Droplet generation has been extensively addressed, while the complete understanding of droplet generation in non-Newtonian fluid system is still nascent. Here, we present the study of non-Newtonian droplet generation in a flow-focusing microchannel. Polyethylene oxide aqueous solutions are used as the dispersed phase, while olive oil serves as the continuous phase to induce the generation. The molecular weight of polymer is constant while the concentrations are varied from dilute to semi-dilute regimes that are rarely explored in existing studies. The main features of non-Newtonian droplet generation are first identified, after which the concentration-dependent dripping to jetting transitions are clarified. The effects of shear thinning and elasticity on droplet generation are then separately investigated. We finally propose a scaling relation to predict the primary droplet size with the satellite droplets neglected. These results can not only extend the fundamental theory of droplet microfluidics but also facilitate the practical applications.

scholarly journals Development of Microdroplet Generation Method for Organic Solvents Used in Chemical Synthesis

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5360
Author(s):  
Shohei Hattori ◽  
Chenghe Tang ◽  
Daiki Tanaka ◽  
Dong Hyun Yoon ◽  
Yoshito Nozaki ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Organic Solvents ◽  
Chemical Reactions ◽  
Microfluidic Device ◽  
Microfluidic Devices ◽  
Continuous Phase ◽  
Immiscible Liquid ◽  
Droplet Generation ◽  
Scaling Effects ◽  
Reaction Field

Recently, chemical operations with microfluidic devices, especially droplet-based operations, have attracted considerable attention because they can provide an isolated small-volume reaction field. However, analysis of these operations has been limited mostly to aqueous-phase reactions in water droplets due to device material restrictions. In this study, we have successfully demonstrated droplet formation of five common organic solvents frequently used in chemical synthesis by using a simple silicon/glass-based microfluidic device. When an immiscible liquid with surfactant was used as the continuous phase, the organic solvent formed droplets similar to water-in-oil droplets in the device. In contrast to conventional microfluidic devices composed of resins, which are susceptible to swelling in organic solvents, the developed microfluidic device did not undergo swelling owing to the high chemical resistance of the constituent materials. Therefore, the device has potential applications for various chemical reactions involving organic solvents. Furthermore, this droplet generation device enabled control of droplet size by adjusting the liquid flow rate. The droplet generation method proposed in this work will contribute to the study of organic reactions in microdroplets and will be useful for evaluating scaling effects in various chemical reactions.

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