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.

scholarly journals Non-Newtonian Droplet Generation in a Cross-Junction Microfluidic Channel

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1915
Author(s):  
Maryam Fatehifar ◽  
Alistair Revell ◽  
Masoud Jabbari
Keyword(s):  
Droplet Size ◽  
Power Law ◽  
Microfluidic Channel ◽  
Shear Thinning ◽  
Droplet Formation ◽  
Considerable Effect ◽  
Droplet Generation ◽  
Rheological Parameters ◽  
Polymeric Solutions ◽  
Detachment Time

A two-dimensional CFD model based on volume-of-fluid (VOF) is introduced to examine droplet generation in a cross-junction microfluidic using an open-source software, OpenFOAM together with an interFoam solver. Non-Newtonian power-law droplets in Newtonian liquid is numerically studied and its effect on droplet size and detachment time in three different regimes, i.e., squeezing, dripping and jetting, are investigated. To understand the droplet formation mechanism, the shear-thinning behaviour was enhanced by increasing the polymer concentrations in the dispersed phase. It is observed that by choosing a shear-dependent fluid, droplet size decreases compared to Newtonian fluids while detachment time increases due to higher apparent viscosity. Moreover, the rheological parameters—n and K in the power-law model—impose a considerable effect on the droplet size and detachment time, especially in the dripping and jetting regimes. Those parameters also have the potential to change the formation regime if the capillary number (Ca) is high enough. This work extends the understanding of non-Newtonian droplet formation in microfluidics to control the droplet characteristics in applications involving shear-thinning polymeric solutions.

Investigation on the Droplet Formation Time With Xanthan Gum Solutions at a T-Junction

2012 ◽  
Author(s):  
Zhipeng Gu ◽  
Jong-Leng Liow ◽  
Guofeng Zhu
Keyword(s):  
Flow Rate ◽  
Xanthan Gum ◽  
Critical Concentration ◽  
Droplet Diameter ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Formation Time ◽  
Drop Formation ◽  
Dispersed Phase ◽  
Phase Flow

Xanthan gum solutions with various concentrations were used as the dispersed phase to study the formation time for drop formation at a T-junction. Two critical concentrations (0.05 and 0.2 wt%) of xanthan gum solutions were observed resulting in three distinct regimes. The droplet diameter increased with increasing xanthan gum concentration within each regime but the transition through each critical concentration was accompanied by a significant reduction in the droplet size. Experimental results showed that the droplet formation time decreased exponentially with increasing continuous phase flow rate. It was also found that the formation time was reduced with increasing dispersed phase flow rate. Xanthan gum solutions with a higher concentration within each regime resulted in a longer formation time, and there was a decrease in the formation time at each critical concentration. The formation time consists of growth and breakup stages and the effect of xanthan gum concentration on each stage was examined.

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.

scholarly journals Liquid–Liquid Flows with Non-Newtonian Dispersed Phase in a T-Junction Microchannel

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 335
Author(s):  
Anna Yagodnitsyna ◽  
Alexander Kovalev ◽  
Artur Bilsky
Keyword(s):  
Flow Pattern ◽  
Dynamic Viscosity ◽  
Slug Flow ◽  
Shear Thinning ◽  
Continuous Phase ◽  
Immiscible Liquid ◽  
Dispersed Phase ◽  
Effective Dynamic ◽  
Liquid Flows ◽  
Shear Thinning Fluid

Immiscible liquid–liquid flows in microchannels are used extensively in various chemical and biological lab-on-a-chip systems when it is very important to predict the expected flow pattern for a variety of fluids and channel geometries. Commonly, biological and other complex liquids express non-Newtonian properties in a dispersed phase. Features and behavior of such systems are not clear to date. In this paper, immiscible liquid–liquid flow in a T-shaped microchannel was studied by means of high-speed visualization, with an aim to reveal the shear-thinning effect on the flow patterns and slug-flow features. Three shear-thinning and three Newtonian fluids were used as dispersed phases, while Newtonian castor oil was a continuous phase. For the first time, the influence of the non-Newtonian dispersed phase on the transition from segmented to continuous flow is shown and quantitatively described. Flow-pattern maps were constructed using nondimensional complex We0.4·Oh0.6 depicting similarity in the continuous-to-segmented flow transition line. Using available experimental data, the proposed nondimensional complex is shown to be effectively applied for flow-pattern map construction when the continuous phase exhibits non-Newtonian properties as well. The models to evaluate an effective dynamic viscosity of a shear-thinning fluid are discussed. The most appropriate model of average-shear-rate estimation based on bulk velocity was chosen and applied to evaluate an effective dynamic viscosity of a shear-thinning fluid. For a slug flow, it was found that in the case of shear-thinning dispersed phase at low flow rates of both phases, a jetting regime of slug formation was established, leading to a dramatic increase in slug length.

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 Formation of Microdroplet in T-junction Microfluidic System: Experiment and Simulation

2018 ◽  
Vol 28 (3) ◽  
pp. 225
Author(s):  
Nguyen Thi Thai ◽  
Chu Thi Xuan ◽  
Pham Duc Thanh ◽  
Mai Anh Tuan ◽  
Nguyen Phuong Nhung
Keyword(s):  
Flow Rate ◽  
Experimental Methods ◽  
Continuous Phase ◽  
Microfluidic System ◽  
Dispersed Phase ◽  
Immiscible Liquids ◽  
Lateral Channel ◽  
System Experiment ◽  
System Geometry ◽  
Lithography Technique

The purpose of this study is to investigate the formation of the water droplet in oil using T-junction microfluidic device. Both numerical and experimental methods have been developed to explore the dependence of droplet size on the flow rate of two immiscible liquids as well as the system geometry. The velocity of droplet in channel is also considered. The microfluidic system was fabricated with lithography technique. The 3D simulation was performed based on COMSOL software using level set method. The size of droplet is inversely proportional to the flow rate of continuous phase according to exponential function, increases linearly with the flow rate of dispersed phase, and decreases as the width of lateral channel decreases.  While the decreasing of the width of the lateral channel gives rise to the increasing of droplet velocity, the velocity of droplet depends linearly on the flow rate of disperse phase. A good consistence was observed between the theory and the experiment.

scholarly journals Dinamika tetes ekstraksi cair-cair sistem air-metil etil keton (mek)-heksan dalam kolom isian

2018 ◽  
Vol 9 (3) ◽  
pp. 99
Author(s):  
Agus Mirwan ◽  
Danu Ariono
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Transfer Process ◽  
Mass Transfer Process ◽  
Continuous Phase ◽  
Column Height ◽  
Dispersed Phase ◽  
Drop Diameter ◽  
Raschig Ring ◽  
Drop Dynamics

Mass transfer process occurs as effect of contact between continuous phase from above and dispersed phase from underside column. With existence of size and type of packing in column, that caused interfacial area to become bigger and residence time more and older so that improvement of mass transfer process. The aim of this research is to observe drop dynamics or movement behavior of drop in which the drop diameter size grouped based on current regime deputizing with Reynolds Number (Re) and to study mass transfer liquid-liquid extraction in packed column based on drop diameter size influenced by flow rate and packing type. Observation of drop behavior is done by using length square column transparent so that visually drop dynamics can be observed and recorded at every segment of column height using digital camera. This research will be done by varying packing type and flow rate of the dispersed phase and continuous phase to know behavior of drop. The research will be done by using water–MEK (methyl ethyl ketone)–n-hexane system. The result of this research for packing type of sphere and raschig ring show that more and more big dispersed phase flow rate and height from under side column (distributor), hence drop is more and more small with number of which more and more many. This caused significant increase on overall mass transfer coefficient.Keywords: drop distribution, sphere, raschig ring, drop diameter Abstrak Proses perpindahan massa ekstraksi cair-cair dalam kolom isian terjadi akibat adanya kontak antara fase kontinu dan fase dispersi yang dialirkan secara berlawanan. Berbagai macam ukuran dan jenis isian yang digunakan dalam kolom, menyebabkan luas permukaan kontak menjadi lebih besar dan waktu kontak makin lama sehingga terjadi peningkatan proses perpindahan massa. Penelitian ini bertujuan mengamati dinamika pergerakan tetesan dengan cara mengelompokkan ukuran diameter tetesan berdasarkan pada rezim aliran yang diwakilkan dengan Bilangan Reynold (Re) dan mempelajari perpindahan massa pada ekstrasi cair-cair dalam kolom isian yang didasarkan ukuran diameter tetesan yang dipengaruhi laju alir dan jenis isian. Pengamatan perilaku tetesan dilakukan dengan menggunakan kolom persegi panjang yang transparan sehingga secara visual dinamikanya dapat diamati dan direkam pada tiap segmen ketinggian kolom menggunakan kamera digital. Percobaan dilakukan dengan menggunakan sistem air-MEK (metil etil keton)-n-heksan. Hasil penelitian untuk jenis isian bola padat dan raschig ring menunjukkan bahwa makin besar laju alir fase dispersi dan ketinggian dari bagian bawah (distributor), maka tetesannya makin kecil dengan jumlah yang makin banyak. Hal ini menyebabkan kenaikan yang signifikan terhadap koefisien perpindahan massa keseluruhan.Kata kunci: distribusi tetesan, bola, raschig ring, diameter tetesan.

scholarly journals Extraction of heavy metals from aqueous solutions in a modified rotating disc extractor

2016 ◽  
Vol 7 (2) ◽  
pp. 187-196
Author(s):  
B. A. Amer ◽  
M. H. Abdel-Aziz ◽  
E.-S. Z. El-Ashtoukhy ◽  
N. K. Amin
Keyword(s):  
Aqueous Solutions ◽  
Flow Rate ◽  
Rotational Speed ◽  
Cation Exchanger ◽  
Naphthenic Acid ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Mass Transfer Equation ◽  
Rotating Disc ◽  
Rate Of Extraction

Extraction of Cu+2 from dilute aqueous solutions as a case study by liquid cation exchanger in a modified rotating disc extractor was studied. The liquid cation exchanger consisted of naphthenic acid dissolved in an inert carrier kerosene. Variables studied were: initial concentration of Cu+2, disc rotational speed, concentration of naphthenic acid, flow rates of continuous and dispersed phase, degree of roughness, and number of rotating discs. The rate of extraction increased with increasing rotational speed, concentration of naphthenic acid, flow rate of dispersed phase, degree of roughness and number of discs to a certain number, while increasing Cu+2 concentration and flow rate of continuous phase decreased the rate of extraction. All variables were correlated by the dimensionless mass transfer equation. Possible practical applications of the present data in treating aqueous waste from different sources such as petrochemical industries, electroplating, and hydrometallurgical processes was highlighted.

scholarly journals Experimental Studies of Droplet Formation Process and Length for Liquid–Liquid Two-Phase Flows in a Microchannel

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1341
Author(s):  
Li Lei ◽  
Yuting Zhao ◽  
Wukai Chen ◽  
Huiling Li ◽  
Xinyu Wang ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Scaling Law ◽  
Experimental Studies ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Volume Flow ◽  
Dispersed Phase ◽  
Two Phase

In this study, changes in the droplet formation mechanism and the law of droplet length in a two-phase liquid–liquid system in 400 × 400 μm standard T-junction microchannels were experimentally studied using a high-speed camera. The study investigated the effects of various dispersed phase viscosities, various continuous phase viscosities, and two-phase flow parameters on droplet length. Two basic flow patterns were observed: slug flow dominated by the squeezing mechanism, and droplet flow dominated by the shear mechanism. The dispersed phase viscosity had almost no effect on droplet length. However, the droplet length decreased with increasing continuous phase viscosity, increasing volume flow rate in the continuous phase, and the continuous-phase capillary number Cac. Droplet length also increased with increasing volume flow rate in the dispersed phase and with the volume flow rate ratio. Based on the droplet formation mechanism, a scaling law governing slug and droplet length was proposed and achieved a good fit with experimental data.

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