Y-junction Microchannel Research Articles

Analysis of magnetic field-induced breakup of ferrofluid droplets in a symmetric Y-junction microchannel

This research focuses on the analysis of the breakup of ferrofluid droplets in a symmetric microchannel with a Y-junction microchannel, utilizing computational methods. The study proposes an innovative strategy to enhance the breakup phenomenon by introducing a magnetic field within the branches of the Y-junction microchannel. To verify the obtained results, a comprehensive comparison is conducted, incorporating previous numerical and experimental investigations available in the literature. The outcomes of this comparison demonstrate a significant concurrence between the current findings and the prior studies. The results unequivocally elucidate that the presence of a magnetic field accelerates the fragmentation of the parent droplet in comparison to scenarios without a magnetic field. Furthermore, it is established that the duration required for droplet breakup decreases as the magnetic Bond number increases. Achieved results indicates \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{t}}_{breakup}^{*}$$\\end{document} decreases about 3% and 1.5% for L*=3 and L*=4, respectively. It is worth highlighting that this trend is particularly accentuated in the case of smaller non-dimensional lengths, specifically L∗=3.0.

Investigating the Performance of the Multi-Lobed Leaf-Shaped Oscillatory Obstacles in Micromixers Using Bulk Acoustic Waves (BAW): Mixing and Chemical Reaction

Proper mixing in microfluidic devices has been a concern since the early development stages. Acoustic micromixers (active micromixers) attract significant attention due to their high efficiency and ease of implementation. Finding the optimal geometries, structures, and characteristics of acoustic micromixers is still a challenging issue. In this study, we considered leaf-shaped obstacle(s) having a multi-lobed structure as the oscillatory part(s) of acoustic micromixers in a Y-junction microchannel. Four different types of leaf-shaped oscillatory obstacles, including 1, 2, 3, and 4-lobed structures, were defined, and their mixing performance for two fluid streams was evaluated numerically. The geometrical parameters of the leaf-shaped obstacle(s), including the number of lobes, lobes’ length, lobes’ inside angle, and lobes’ pitch angle, were analyzed, and their optimum operational values were discovered. Additionally, the effects of the placement of oscillatory obstacles in three configurations, i.e., at the junction center, on the side walls, and both, on the mixing performance were evaluated. It was found that by increasing the number and length of lobes, the mixing efficiency improved. Furthermore, the effect of the operational parameters, such as inlet velocity, frequency, and intensity of acoustic waves, was examined on mixing efficiency. Meanwhile, the occurrence of a bimolecular reaction in the microchannel was analyzed at different reaction rates. It was proven that the reaction rate has a prominent effect at higher inlet velocities.

Measurement of Protein-Protein Interaction Dynamics Using Microfluidics and Particle Diffusometry.

The measurement and optimization of protein-protein interactions are critical in the design of biotherapeutics, biomolecular sensing elements, and functional protein-based biomaterials among other biomolecular sciences and engineering. Current gold standard assays require specifically designed core facilities, equipment, and expertise to implement the measurement, making it inconvenient for most labs unless implemented routinely. We developed a new method aiming at measuring protein binding kinetics based on microfluidics and particle diffusometry (PD), which only needs very general lab equipment, including a fluorescence microscope, a syringe pump, and a simple microchannel fabricated on a glass slide. Protein binding pairs are immobilized on two kinds of nanoparticles with different diameters using widely available conjugation chemistries. The two diluted particle suspensions are injected using a syringe pump into a Y-junction microchannel, where they bind and form particle complexes with increasing size, thereby decreasing particles' Brownian motion amplitude and diffusivity, which can be detected by PD. By taking images at a series of specific points along the microchannel, the particle diffusivity is measured at different time points after the introduction of protein-protein binding. These data are then used to quantify the protein binding kinetic constant. This label-free particle-based method is simple to operate and as accurate as the current gold standard. We demonstrate the feasibility of this accessible method by quantifying the streptavidin-biotin association constant (1.74 ± 0.51 × 107 M-1 s-1), which compares well with previously published results.

Real-Time Tunable Optofluidic Splitter via Two Laminar Flow Streams in a Microchannel.

This paper reports a tunable optofluidic splitter in which the incident light is split via refraction and reflection at the interface between two laminar flows in a microchannel but with different refractive indices. A Y-junction microchannel is used to demonstrate the continuous tuning of the splitting ratio of optical power by smooth adjustment of the ratio of two flow rates. In addition, it has achieved the tuning of split angle from 5° to 19° by the control of the refractive index contrast. The dynamic response gives a fastest switching frequency of 1.67 Hz between the “wave-guiding” and “splitting” status.

A Numerical Investigation of the Mixing Performance in a Y-Junction Microchannel Induced by Acoustic Streaming.

In this study, the mixing performance in a Y-junction microchannel with acoustic streaming was investigated through numerical simulation. The acoustic streaming is created by inducing triangular structures at the junction and sidewalls regions. The numerical model utilizes Navier–Stokes equations in conjunction with the convection–diffusion equations. The parameters investigated were inlet velocities ranging from 4.46 to 55.6 µm/s, triangular structure’s vertex angles ranging from 22° to 90° oscillation amplitude ranging from 3 to 6 µm, and an oscillation frequency set to 13 kHz. The results show that at the junction region, a pair of counter-rotating streaming vortices were formed, and unsymmetrical or one-sided vortices were formed when additional triangles were added along the sidewalls. These streaming flows significantly increase the vorticity compared with the case without the acoustic stream. Mixing performances were found to have improved with the generation of the acoustic stream. The mixing performance was evaluated at various inlet velocities, the vertex angles of the triangular structure, and oscillation amplitudes. The numerical results show that adding the triangular structure at the junction region considerably improved the mixing efficiency due to the generation of acoustic streaming, and further improvements can be achieved at lower inlet velocity, sharper vertex angle, and higher oscillation amplitude. Integrating with more triangular structures at the sidewall regions also improves the mixing performance within the laminar flow regime in the Y-microchannel. At Y = 2.30 mm, oscillation amplitude of 6 µm, and flow inlet velocity of 55.6 µm/s, with all three triangles integrated and the triangles’ vertex angles fixed to , the mixing index can achieve the best results of 0.9981, which is better than 0.8355 in the case of using only the triangle at the junction, and 0.6642 in the case without acoustic streaming. This is equal to an improvement of 50.27% in the case of using both the junction and the two sidewall triangles, and 25.79% in the case of simply using a junction triangle.

Cell trapping in Y-junction microchannels: A numerical study of the bifurcation angle effect in inertial microfluidics.

The majority of microfluidic technologies for cell sorting and isolation involve bifurcating (e.g., Y- or T-shaped junction) microchannels to trap the cells of a specific type. However, the microfluidic trapping efficiency remains low, independently of whether the cells are separated by a passive or an active sorting method. Using a custom computational algorithm, we studied the migration of separated deformable cells in a Y-junction microchannel, with a bifurcation angle ranging from 30° to 180°. Single or two cells of initially spherical shape were considered under flow conditions corresponding to inertial microfluidics. Through the numerical simulation, we identified the effects of cell size, cytoplasmic viscoelasticity, cortical tension, flow rate, and bifurcation angle on the critical separation distance for cell trapping. The results of this study show that the trapping and isolation of blood cells, and circulating tumor cells in a Y-junction microchannel was most efficient and least dependent on the flow rate at the bifurcation angle of 120°. At this angle, the trapping efficiency for white blood cells and circulating tumor cells increased, respectively, by 46% and 43%, in comparison with the trapping efficiency at 60°. The efficiency to isolate invasive tumor cells from noninvasive ones increased by 32%. This numerical study provides important design criteria to optimize microfluidic technology for deformability-based cell sorting and isolation.

Extraction of samarium using a serpentine Y-junction microreactor with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl

In the modern industrialized rare earths production, solvent extraction facilities possess many problems such as long extraction time, large occupation area, high processing cost and so on. The present work attempts to extract samarium (III) from hydrochloric acid solution in a rectangular cross-section Y-junction microchannel, using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl (EHEHPA or P507). The effects of flow rate, channel length and width on the extraction efficiency, slug length and mass behavior of a liquid-liquid extraction system are assessed. The slug length decreased with increase in the flow rate, increased in channel length and channel width. The maximum extraction efficiency of 75.1% could be achieved at the longer channel length (pH = 1.5, channel width = 300 μm, flow rate = 10 μL/min). The volumetric mass transfer coefficients (kLa) of the microfluidic extractor was compared with the conventional extractor and found to be several orders of magnitude higher, authenticating the beneficial effects such as: Higher specific interfacial area and shorter diffusion length.

Three-Dimensional Modeling of Circulating Cell Separation in a Y-Junction Microchannel

The migration of living cells plays an important role in immune response, cancer progression, and microfluidic technologies for cell separation and flow cytometry that often involve bifurcating (e.g., Y-or T-shaped junction) microchannels. Vessel bifurcations are among the frequent sites affected by atherosclerosis and are the focal points of drug carrier particle adhesion in vivo. Using VECAM, our custom three-dimensional computational algorithm for multiphase viscoelastic flow and mass transport, this study focuses upon the investigation of the effects of cell viscoelasticity and hydrodynamic interaction on separation of circulating cells in Y-shaped microchannels with angle ranging from 30° to 150°. In VECAM, the cell is modeled as a one-phase viscoelastic fluid material composed of a cytosol and a polymer (cytoskeletal) matrix. The cell viscoelasticity is described by the Giesekus constitutive equation. The cell-fluid interface is tracked by the volume-of-fluid (VOF) method, with the interfacial (cortical) tension force calculated by the continuous surface force (CSF) method. In the simulation, we consider single or two cells of initially spherical shape with the same or varying diameter. The separation of the cells has been investigated for different initial locations of the cells with respect to one another. The results of this study provide the critical conditions for cell separation including the critical values of cell diameter, elasticity, surface tension and initial cell-to-cell separation distances for a range of bifurcation angles. These critical conditions are important for the development of microfluidic devices to be optimized for separation and sorting of circulating cells and for understanding how circulating cells are separated in bifurcating microvessels.

Numerical study of droplet formation in a Y-junction microchannel

This study investigates the formation process of droplets in a Y-junction microchannel using two immiscible fluids: water as the continuous fluid and oil as the dispersed phase. We have examined the influence of the capillary number, flow rate ratio and viscosity ratio between the two fluids; parameters which determine the length and generation frequency of the droplets. Numerical simulations have been performed using the software Ansys Fluent with the interface capture method Volume of Fluid (VOF) for solving the governing equations. Three different algorithms have been tested for the pressure-velocity coupling: SIMPLE, SIMPLEC and PISO. The results are quite similar for SIMPLE and SIMPLEC, however it turned out that PISO is a better algorithm to solve the two-phase flow. Additionally, another Y-junction is coupled in the initial geometry to observe a symmetric breakup of the droplets and their formation is explained using the pressure field and the velocity field.

SIMULATIONS OF DROPLET FORMATION IN A T-JUNCTION MICRO-CHANNEL USING THE PHASE FIELD METHOD

Micro-fabrication techniques are developed rapidly because they offer numerous benefits for chemical and biological industries. Numerical simulations (based on incompressible Navier–Stokes equations) are presented of the two-phase flow in a cross-flowing T-junction micro-channel using the phase field method and the results are in agreement with experimental measurements. The leakage rate in the gap between the droplet and lower wall decreases during the droplet formation, the relationship between the leakage rate and the derivative of the up-stream droplet size is obtained, which is applicable when the droplet contacts with the lower wall on the wetted conditions or expands to the up-stream in the main channel. The droplet formation is related to several factors, including the capillary number, the contact angle, the flow rate ratio, and the micro-channel shape. The critical capillary number could distinguish between the squeezing and dripping regimes for the generation of different kinds of droplets. The simulations show that the critical capillary number is 0.012. Influence of those factors on the droplet length is related to the leakage rate. The leakage rate of the continuous phase decreases slowly as the flow rate ratio decreases or contact angle increases. In the squeezing regime, the leakage rate is weakly influenced by the contact angle at the small flow rate ratio and is different in three type micro-channels, the droplet length increases with the increase in contact angle which intensifies growth at the big flow rate ratio, and the longest droplet is obtained in the Y-junction micro-channel. In the dripping regime, at the big flow rate ratio the leakage rate is almost independent to the contact angle and micro-channel shape, and the droplet length also is same.

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A theoretical description of the convection-diffusion process in a homogeneous system enabling estimation of diffusion coefficients employing commercially available Y-junction microchannel is presented. A detailed numerical analysis based on finite volumes and finite differences, namely the explicit, implicit and Crank-Nicolson method, was performed and analyzed on the same domain in order to verify the proposed models. All numerical approaches provided stable solutions with certain numerical variations depending on the number of iterations defined by the mesh density. In addition, the method was validated with measurements of diffusion coefficients of some selected components in the short Y-junction microchannel. Benefits and possible pitfalls of this estimation method are discussed.

Numerical Analysis of Junction Point Pressure during Droplet Formation in Y-Junction Microchannel

Junction point pressure changes during droplet formation in Y-junction microchannels with differed Y-angles, wetting property and capillary number of the liquid by using a three dimensional numerical simulation. The pressure of the junction point fluctuates throughout the droplet formation process, and it can be used to depict exactly and directly different stages of droplet in microchannels. And the pressure of junctions with different Y-angles of microchannel, different contact angles of dispersed phase with the surface, and different capillary numbers of continuous phase could thus be investigated via the droplet formation mechanism.

Experimental Investigation of Inertial Mixing in Colliding Droplets

Achieving the increasingly fast mixing requirements posed by the chemical, biological, and life science community for confined microchannel droplet flows remains an engineering challenge. The viscous and surface tension forces that often dominate microflows undermine fast, efficient mixing. A novel mixing arrangement based on droplet collisions has been developed that significantly improves mixing rates by utilizing inertia to rapidly rearrange fluid contents. This article experimentally investigates inertial droplet mixing in micro-flows following high-speed droplet pair collisions. The technique utilizes a gaseous flow for liquid droplet generation and transport with collisions occurring in Y-junction microchannel geometries. Mixing rates are quantified using differential fluorescent optical diagnostics, custom image processing algorithms, and statistical analysis. Measured droplet mixing times are compared to the characteristic time scales for mass and viscous diffusion and bulk convective transport. Results show that mixing times are decreased as the droplet pair collision inertia is increased, indicating the potential benefit for inertial collision mixing.

Microfluidic synthesis of amorphous cefuroxime axetil nanoparticles with size-dependent and enhanced dissolution rate

In this work, size-controllable nanoparticles of amorphous cefuroxime axetil (CFA), a poorly water-soluble drug, have been prepared in a Y-junction microchannel reactor (YMCR) by nanoprecipitation for enhancing dissolution rate of CFA. The effects of the operation parameters, such as flow rate of CFA acetone solution, antisolvent flow rate, overall flow rate, CFA concentration and precipitation temperature, on particle size and size distribution were experimentally investigated. The results indicated that the particle size obviously decreased from 1100 to 630 nm with decreasing the CFA solution flow rate from 16 to 2 mL/min, and decreased from 450 to 350 nm with the decreased temperature from 50 to 5 °C. However, with the increase of the antisolvent flow rate at a fixed CFA solution flow rate of 4 mL/min, the particle size obviously decreased from 1229 nm (20 mL/min) to 581 nm (60 mL/min), and then increased to 698 nm (80 mL/min). Also, the particle size firstly decreased and then increased with the increase of the overall flow rate and CFA solution concentration. The as-prepared CFA nanoparticles displayed a size-dependent and significantly enhanced dissolution property when compared to raw CFA and commercial spray-dried CFA. This work suggests that the continuous synthesis in a microfluidic reactor is a simple and economic way to prepare pharmaceutical nanoparticles with tunable sizes.

Micro-PIV를 이용한 마이크로 튜브/채널 내에서의 혈장유동측정

In this paper, flow characteristics of plasma flow in a micro-tube were investigated experimentally using micro particle image velocimetry(micro-PIV). For comparison, the experiments were repeated for deionized(DI) wale. instead of plasma. Both velocity profiles of plasma and do-ionized water are well agreed with the theoretical velocity distribution of newtonian fluid. We also carried out generating plasma-in-oil droplet formation at a Y-junction microchannel. In order to clarify the hydrodynamic aspects involved in plasma droplet formation, Rhodamine-B were mixed with plasma only for visualization of plasma droplet. With oil as the continuous phase and plasma as the dispersed phase, plasma droplet can be generated in a continuous phase flow at a Y-junction. For given experimental parameters, regular-sized droplets are reproducibly formed at a uniform flow conditions.