scholarly journals Oscillating dispersed-phase co-flow microfluidic droplet generation: Multi-droplet size effect

2018 ◽  
Vol 12 (3) ◽  
pp. 034113 ◽  
Author(s):  
Amin Shams Khorrami ◽  
Pouya Rezai
Keyword(s):  
Size Effect ◽  
Droplet Size ◽  
Droplet Generation ◽  
Dispersed Phase

Microchannel Emulsification Devices for Generating Highly Uniform Droplets

2009 ◽  
Author(s):  
Isao Kobayashi ◽  
Mitsutoshi Nakajima
Keyword(s):  
Droplet Size ◽  
Large Scale ◽  
Continuous Phase ◽  
Droplet Generation ◽  
High Tech ◽  
Dispersed Phase ◽  
Scale Production ◽  
Crystal Silicon ◽  
Uniform Droplets ◽  
Highly Uniform

Monodisperse emulsions consisting of uniform droplets have received a great deal of attentions over the past decade due to their high-tech applications, e.g., monodisperse microparticles as spacers for electronic devices and monodisperse micro-carriers for drug delivery systems (DDS). Our group proposed microchannel (MC) emulsification, which enables generating highly uniform droplets with the smallest coefficient of variation of below 5% using MC arrays of unique geometry. The resultant droplet size can be precisely controlled by MC geometry. Droplet generation for MC emulsification is very mild and does not require any external shear stress; a dispersed phase that passed through MCs is transformed spontaneously into uniform droplets inside a continuous-phase domain. The aim of this paper is to present recent developments in MC emulsification devices, particularly focusing on straight-through MC arrays consisting of uniform straight-through holes for large-scale production of monodisperse emulsions. A straight-through MC array device of a standard 24 × 24-mm size was made of single-crystal silicon, and a straight-through MC array consisting of numerous MCs was positioned within a 10 × 10-mm central region of the device. We initially designed symmetric straight-through MCs with circular and oblong sections. Highly uniform droplets with average sizes of 4 to 100 μm were generated using oblong straight-through MCs. The simulation results using CFD (computational fluid dynamics) agreed well with the experimental results and provided useful information, such as the movement of the oil-water interface around the MC outlet during droplet generation. Below the critical value of the dispersed phase flux, monodisperse emulsions were produced via suitable oblong straight-through MCs, with droplet size and size distribution independent of the flux value. The development of asymmetric straight-through MC arrays consisting of numerous pairs of microslots and circular MCs improved the productivity of highly uniform droplets and stability during droplet generation.

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.

Effect of Shear and Water Cut on Phase Inversion and Droplet Size Distribution in Oil–Water Flow

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Mo Zhang ◽  
Ramin Dabirian ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Phase Inversion ◽  
Droplet Size Distribution ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Water Emulsion ◽  
Inversion Region ◽  
Oil Water ◽  
Water Cut

Oil–water dispersed flow occurs commonly in the petroleum industry during the production and transportation of crudes. Phase inversion occurs when the dispersed phase grows into the continuous phase and the continuous phase becomes the dispersed phase caused by changes in the composition, interfacial properties, and other factors. Production equipment, such as pumps and chokes, generates shear in oil–water mixture flow, which has a strong effect on phase inversion phenomena. The objective of this paper is to investigate the effects of shear intensity and water cut (WC) on the phase inversion region and also the droplet size distribution. A state-of-the-art closed-loop two phase (oil–water) flow facility including a multipass gear pump and a differential dielectric sensor (DDS) is used to identify the phase inversion region. Also, the facility utilizes an in-line droplet size analyzer (a high speed camera), to record real-time videos of oil–water emulsion to determine the droplet size distribution. The experimental data for phase inversion confirm that as shear intensity increases, the phase inversion occurs at relatively higher dispersed phase fractions. Also the data show that oil-in-water emulsion requires larger dispersed phase volumetric fraction for phase inversion as compared with that of water-in-oil emulsion under the same shear intensity conditions. Experiments for droplet size distribution confirm that larger droplets are obtained for the water continuous phase, and increasing the dispersed phase volume fraction leads to the creation of larger droplets.

Oscillating dispersed-phase co-flow microfluidic droplet generation: jet length reduction effect

Soft Matter ◽  
2018 ◽  
Vol 14 (48) ◽  
pp. 9870-9876 ◽  
Author(s):  
Amin Shams Khorrami ◽  
Pouya Rezai
Keyword(s):  
High Throughput ◽  
Droplet Generation ◽  
Dispersed Phase ◽  
Jet Length ◽  
Reduction Effect ◽  
Length Reduction

An oscillating-needle co-flow technique for jet length reduction and production of multi-size droplets at high throughput in a channel.

Study on Propylene Recovery in a Dispersed Absorption System-(Water-in-Oil) Emulsion System

2011 ◽  
Vol 383-390 ◽  
pp. 6151-6155
Author(s):  
Hong Jing Liu ◽  
Ying Zhang ◽  
Hui Yao ◽  
Wei Zhao
Keyword(s):  
Droplet Size ◽  
Absorption Rate ◽  
Volume Fraction ◽  
Dispersed Phase ◽  
Emulsion System ◽  
Absorption System ◽  
Oil Emulsion ◽  
Stirring Rate ◽  
Water In Oil Emulsion ◽  
System Water

The purpose of the paper is to investigate propylene recovery by a new absorption system, namely water-in-oil emulsion absorbent. Water in oil emulsion, in which kerosene used as oil phase with dispersed water droplet, is prepared to be as absorbent to absorb propylene. The effect of volume fraction dispersed phase, dispersed droplet size, and the stirring rate on propylene absorption rate are researched. Experimental results indicate that the absorption rate of propylene can increase 20% compared with traditional absorption method. The volume fraction dispersed phase should be appropriate, otherwise the enhancement absorption can not be attained. The appropriate number is 0.05 for this dispersion. The smaller droplet size of dispersed phase as well as the faster stirring rate can increase the propylene absorption rate. The mechanism of enhancement propylene absorption is attributed to the intensive turbulence in boundary layer between gas and liquid due to the movement of dispersed water droplets.

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.

scholarly journals The Effect of Oil Viscosity on Droplet Generation Rate and Droplet Size in a T-Junction Microfluidic Droplet Generator

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 808 ◽  
Author(s):  
Junyi Yao ◽  
Fan Lin ◽  
Hyun Kim ◽  
Jaewon Park
Keyword(s):  
Water Flow ◽  
Droplet Size ◽  
Droplet Generation ◽  
Generation Rate ◽  
Droplet Generator ◽  
Oil Viscosity ◽  
High Throughput Analysis ◽  
Oil Emulsion ◽  
Oil Flow ◽  
Flow Pressure

There have been growing interests in droplet-based microfluidics due to its capability to outperform conventional biological assays by providing various advantages, such as precise handling of liquid/cell samples, fast reaction time, and extremely high-throughput analysis/screening. The droplet-based microfluidics utilizes the interaction between the interfacial tension and the fluidic shear force to break continuous fluids into uniform-sized segments within a microchannel. In this paper, the effect of different viscosities of carrier oil on water-in-oil emulsion, particularly how droplet size and droplet generation rate are affected, has been investigated using a commonly used T-junction microfluidic droplet generator design connected to a pressure-controlled pump. We have tested mineral oils with four different viscosities (5, 7, 10, and 15 cSt) to compare the droplet generation under five different flow pressure conditions (i.e., water flow pressure of 30–150 mbar and oil flow pressure of 40–200 mbar). The results showed that regardless of the flow pressure levels, the droplet size decreased as the oil viscosity increased. Average size of the droplets decreased by approximately 32% when the viscosity of the oil changed from 5 to 15 cSt at the flow pressure of 30 mbar for water and 40 mbar for oil. Interestingly, a similar trend was observed in the droplet generation rate. Droplet generation rate and the oil viscosity showed high linear correlation (R2 = 0.9979) at the water flow pressure 30 mbar and oil flow pressure 40 mbar.

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.

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