scholarly journals Dripping, Jetting and Regime Transition of Droplet Formation in a Buoyancy-Assisted Microfluidic Device

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 962
Author(s):  
Chaoqun Shen ◽  
Feifan Liu ◽  
Liangyu Wu ◽  
Cheng Yu ◽  
Wei Yu
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Inertial Force ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Transitional Regime ◽  
Visualization Experiment ◽  
Lower Flow Rate ◽  
Insight Into ◽  
Comprehensive Study

Buoyancy-assisted droplet formation in a quiescent continuous phase is an effective technique to produce highly monodispersed droplets, especially millimetric droplets. A comprehensive study combining visualization experiment and numerical simulation was carried out to explore the underlying physics of single droplet generation in a buoyancy-assisted microfluidic device. Typical regimes, including dripping and jetting, were examined to gain a deep insight into the hydrodynamic difference between the regimes. Particularly, the transition from dripping regime to jetting regime was investigated to give an in-depth understanding of the transitional behaviors. The effects of interfacial tension coefficient on the droplet size and formation regimes are discussed, and a regime diagram is summarized. The results show that oscillation of the interface in dripping regimes after detachment is caused by the locally accelerated fluid during the neck pinching process. Droplet formation patterns with the characteristics of both dripping regime and jetting regime are observed and recognized as the transitional regime, and the interface oscillation lasts longer than that in dripping regime, implying intensive competition between interfacial tension and inertial force. Reducing interfacial tension coefficient results in the dripping-to-jetting transition occurring at a lower flow rate of the dispersed phase. The regime diagram indicates that only the inertial force is the indispensable condition of triggering the transition from dripping to jetting.

scholarly journals Influence on droplet formation in the presence of nanoparticles in a microfluidic T-junction

2012 ◽  
Vol 16 (5) ◽  
pp. 1429-1432
Author(s):  
Rui-Jin Wang ◽  
Zhi-Hua Li
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Liquid Interface ◽  
Dispersed Phase ◽  
Microscopic Mechanism ◽  
Formation Dynamics

The droplet formation in the presence of nanoparticles was studied in a T-shaped microfluidic device numerically. Nanoparticles in continuous phase did not influence droplet formation dynamics obviously. Contrarily, the presence of nanoparticles in dispersed phase will influence evidently droplet formation dynamics, the possible reason is that the accumulation of nanoparticles at the liquid-liquid interface would cause the variation of interfacial tension and the anisotropy of nanoparticles? movement at interface. Discussions on microscopic mechanism of droplet formation in the presence of nanoparticles were carried out.

Parametric Study of Droplet Formation and Characteristics Within Microfluidic Devices — A Case Study

2020 ◽  
Vol 12 (07) ◽  
pp. 2050077
Author(s):  
Seyedeh Sarah Salehi ◽  
Amir Shamloo ◽  
Siamak Kazemzadeh Hannani
Keyword(s):  
Interfacial Tension ◽  
Physical Properties ◽  
Flow Rate ◽  
Viscosity Ratio ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Phase Flow ◽  
Phase Density ◽  
Size And Shape ◽  
The Impact

Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a consequence of the impact of each property on fluid flow, including the viscosity ratio, density, interfacial tension, and the flow rate ratio. Based on the results, flow rate, viscosity, and interfacial tension strongly affect the droplet formation regime as well as its size and shape. Droplet diameter increases by increasing the dispersed to continuous phase flow rate as well as the interfacial tension while it decreases by increasing the viscosity ratio and the continuous phase density. Moreover, the formation of satellite droplets was modeled, and the effect of interfacial tension, the viscosity of the dispersed phase and the continuous phase density were found to be important on the conditions that the satellite droplets are suppressed. Since the formation of the satellite droplets induces polydispersity in droplet size, this phenomenon is avoided. Collectively, choosing appropriate aqueous and oil phases with proper physical properties is crucial in forming monodisperse droplets with defined size and shape.

The effect of interfacial tension on droplet formation in flow-focusing microfluidic device

2011 ◽  
Vol 13 (3) ◽  
pp. 559-564 ◽  
Author(s):  
Lu Peng ◽  
Min Yang ◽  
Shi-shang Guo ◽  
Wei Liu ◽  
Xing-zhong Zhao
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Droplet Formation ◽  
Flow Focusing

scholarly journals Numerical Simulation and Experimental Validation of Liquid Metal Droplet Formation in a Co-Flowing Capillary Microfluidic Device

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 169 ◽  
Author(s):  
Qingming Hu ◽  
Tianyi Jiang ◽  
Hongyuan Jiang
Keyword(s):  
Numerical Model ◽  
Liquid Metal ◽  
Interfacial Tension ◽  
Microfluidic Device ◽  
Droplet Diameter ◽  
Metal Droplet ◽  
Droplet Formation ◽  
Bulk Liquid ◽  
Liquid Metal Droplet ◽  
Phase Fluid

A two-phase flow axisymmetric numerical model was proposed to understand liquid metal droplet formation in a co-flowing capillary microfluidics device based on a phase field model. The droplet detachment processes were observed in the experiment and are in good agreement with the simulation method. The effects of the viscosities and flowrates of the continuous phase fluid, interfacial tension as well as the wetting property of the metallic needle against the bulk liquid metal on the droplet formation and production rate were numerically investigated. It was found that the droplet diameter decreased with the increment of the viscosities and flowrates of the outer phase carrier fluid. The dispersed phase fluid with high interfacial tension tended to prolong the time for equilibrium between the viscous drag force and interfacial tension on the liquid–liquid fluid surface, delaying the droplet to be pinched off from the capillary orifice and causing large droplet diameter. Finally, the wetting performance of the metallic needle against the liquid metal was explored. The result indicate that the droplet diameter became less dependent on the contact angle while the size distribution of the liquid metal droplet was affected by their wetting performance. A more hydrophilic wetting performance were expected to prepare liquid metal droplet with more monodispersity. The numerical model and simulation results provide the feasibility of predicting the droplet formation with a high surface tension in a glass capillary microfluidic device.

scholarly journals Droplet Formation in a T-Junction Microfluidic Device in the Presence of an Electric Field

2015 ◽  
Author(s):  
Zeeshan Ahmad ◽  
Rattandeep Singh ◽  
Supreet Singh Bahga ◽  
Amit Gupta
Keyword(s):  
Electric Field ◽  
Microfluidic Device ◽  
Lattice Boltzmann ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Immiscible Fluids ◽  
Multiphase Model ◽  
Dispersed Phases ◽  
Rate Ratios ◽  
Boltzmann Method

In this work, the effect of applying an electric field on droplet formation in a T-junction microfluidic device is examined by simulations based on a recent technique known as lattice Boltzmann method (LBM). The electric field is applied in the main channel just beyond the confluence of the continuous and dispersed phases. A combined electrohydrodynamics-multiphase model that can simulate the flow of immiscible fluids in the presence of an electric field is developed and validated. The same model is then applied to study the droplet formation process in a T-junction microfluidic device at a capillary number of 0.01 and at different dispersed to continuous phase flow rate ratios. Results show that there is a decrease in the droplet size and an increase in formation frequency as the electric field is increased. The interplay of the electric and interfacial forces on droplet formation is investigated.

Phase Inversion in Two-Phase Liquid Systems

1992 ◽  
Vol 57 (7) ◽  
pp. 1419-1423
Author(s):  
Jindřich Weiss
Keyword(s):  
Interfacial Tension ◽  
Phase Inversion ◽  
Continuous Phase ◽  
Considerable Effect ◽  
Weak Dependence ◽  
Dispersed Phase ◽  
Two Phase ◽  
Liquid Systems ◽  
Phase Liquid

New data on critical holdups of dispersed phase were measured at which the phase inversion took place. The systems studied differed in the ratio of phase viscosities and interfacial tension. A weak dependence was found of critical holdups on the impeller revolutions and on the material contactor; on the contrary, a considerable effect of viscosity was found out as far as the viscosity of continuous phase exceeded that of dispersed phase.

scholarly journals Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 272
Author(s):  
Doojin Lee ◽  
Amy Q. Shen
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Extensional Flow ◽  
Immiscible Fluids ◽  
Droplet Microfluidics ◽  
Channel Height ◽  
Deformation Model ◽  
Droplet Deformation ◽  
Extensional Flows ◽  
2D Model

Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.

scholarly journals Study on the Effect of Nanoparticle Used in Nano-Fluid Flooding on Droplet–Interface Electro-Coalescence

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1764
Author(s):  
Donghai Yang ◽  
Huayao Sun ◽  
Qing Chang ◽  
Yongxiang Sun ◽  
Limin He
Keyword(s):  
Interfacial Tension ◽  
Oil Recovery ◽  
Liquid Bridge ◽  
High Speed ◽  
Droplet Formation ◽  
Force Balance ◽  
Secondary Droplet ◽  
Droplet Deformation ◽  
Deformation Degree ◽  
Nano Fluid

Nano-fluid flooding is a new method capable of improving oil recovery; however, nanoparticles (NPs) significantly affect electric dehydration, which has rarely been investigated. The effect of silica (SiO2) NPs on the droplet–interface coalescence was investigated using a high-speed digital camera under an electric field. The droplet experienced a fall, coalescence, and secondary droplet formation. The results revealed that the oil–water interfacial tension and water conductivity changed because of the SiO2 NPs. The decrease of interfacial tension facilitated droplet deformation during the falling process. However, with the increase of particle concentration, the formed particle film inhibited the droplet deformation degree. Droplet and interface are connected by a liquid bridge during coalescence, and the NP concentration also resulted in the shape of this liquid bridge changing. The increase of NP concentration inhibited the horizontal contraction of the liquid bridge while promoting vertical collapse. As a result, it did not facilitate secondary droplet formation. Moreover, the droplet falling velocity decreased, while the rising velocity of the secondary droplet increased. Additionally, the inverse calculation of the force balance equation showed that the charge of the secondary droplet also increased. This is attributed to nanoparticle accumulation, which resulted in charge accumulation on the top of the droplet.

scholarly journals Interfacial Tension Sensor for Low Dosage Surfactant Detection

2021 ◽  
Vol 5 (1) ◽  
pp. 9
Author(s):  
Piotr Pawliszak ◽  
Bronwyn H. Bradshaw-Hajek ◽  
Christopher Greet ◽  
William Skinner ◽  
David A. Beattie ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Profile Analysis ◽  
Simple Method ◽  
Bubble Generation ◽  
Flotation Process ◽  
Line Measurement ◽  
Tension Sensor ◽  
Low Dosage

Currently there are no available methods for in-line measurement of gas-liquid interfacial tension during the flotation process. Microfluidic devices have the potential to be deployed in such settings to allow for a rapid in-line determination of the interfacial tension, and hence provide information on frother concentration. This paper presents the development of a simple method for interfacial tension determination based on a microfluidic device with a flow-focusing geometry. The bubble generation frequency in such a microfluidic device is correlated with the concentration of two flotation frothers (characterized by very different adsorption kinetic behavior). The results are compared with the equilibrium interfacial tension values determined using classical profile analysis tensiometry.

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