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micromixer
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Modeling active micromixers with multiple microstirrers using smoothed particle hydrodynamics
, Article Scientia Iranica ; Vol. 21, issue. 4 , 2014 , pp. 1390-1402 ; ISSN: 10263098 ; Pishevar, A ; Saidi, M. S ; Sharif University of Technology
Abstract
The smoothed particle hydrodynamics method is used to explore the effects of design parameters on the mixing efficiency of two types of active micromixer. First, the complex flow field and the mixing process of two separated fluids in a square mixing chamber with nine symmetric microstirrers are simulated. The influence of design parameters, such as the microstirrer rotation arrangement and the angular velocity of the microstirrer, on the mixing performance, is investigated. The mixing index parameter on ten control points is calculated and the average mixing index is compared for different cases. Simulations illustrate that the rotation arrangement of microstirrers is a key parameter in the...
A new scheme for improving the mixing efficiency in micro scale
, Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011 ; Volume 1 , 2011 , Pages 183-191 ; 9780791844632 (ISBN) ; Haroutunian, A ; Saidi, M. S ; Shafii, M. B ; Sharif University of Technology
2011
Abstract
Generally speaking, most micro-fluidic mixing systems are limited to the low Reynolds number regime in which diffusion dominates convection, and consequently the mixing process tends to be slow and it takes a relatively long time to have two fluids completely mixed. Therefore, rapid mixing is essential in micro-fluidic systems. In order to hasten the mixing process in micro scale, in this study we come up with a novel scheme for a two dimensional micro-fluidic mixer which encompasses three pairs of electrodes, one pair embedded in the mixing chamber and two pairs located in the micro-channels before and after the mixing chamber. The width of the middle pair is assumed to be twice of the...
A depthwise averaging solution for cross-stream diffusion in a Y-micromixer by considering thick electrical double layers and nonlinear rheology
, Article Microfluidics and Nanofluidics ; Volume 19, Issue 6 , 2015 , Pages 1297-1308 ; 16134982 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Springer Verlag
2015
Abstract
Both nonlinear rheology and finite EDL thickness effects on the mixing process in an electroosmotically actuated Y-sensor are being investigated in this paper, utilizing a depthwise averaging method based on the Taylor dispersion theory. The fluid rheological behavior is assumed to obey the power-law viscosity model. Analytical solutions are obtained assuming a large channel width to depth ratio for which a 1-D profile can efficiently describe the velocity distribution. Full numerical simulations are also performed to determine the applicability range of the analytical model, revealing that it is able to provide accurate results for channel aspect ratios of ten and higher and quite...
Computational Simulation of Micromixing, Using LBM
, M.Sc. Thesis Sharif University of Technology ; Taeibi-Rahni, Mohammad (Supervisor)
Abstract
Nowadays, microfluidic flow appears in many applications, such as medical, biological, and chemical industries. Where as, micromixing, which deals with mixing of microfluidic flow in micro channels, appears to be an important issue to many researchers. In such systems, molecular diffusion plays an important role. On the other hand, lattice Boltzmann method is a relatively new simulation technique for complex fluid systems and has become interesting to many researchers in computational physics. In this study, computational simulation of such mixing process, using LBM is the main objective. Different obstacle layouts inside a microchannel have been investigated. Chaotic advection and jet...
Numerical and Analytical Study of Mixing in Y-shaped Micromixers: Electroosmotic and Poiseuille Flow of PTT Fluids
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
Abstract
Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors...
Electrokinetic mixing at high zeta potentials: Ionic size effects on cross stream diffusion
, Article Journal of Colloid and Interface Science ; Volume 442 , 2015 , Pages 8-14 ; 00219797 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Academic Press Inc
2015
Abstract
The electrokinetic phenomena at high zeta potentials may show several unique features which are not normally observed. One of these features is the ionic size (steric) effect associated with the solutions of high ionic concentration. In the present work, attention is given to the influences of finite ionic size on the cross stream diffusion process in an electrokinetically actuated Y-shaped micromixer. The method consists of a finite difference based numerical approach for non-uniform grid which is applied to the dimensionless form of the governing equations, including the modified Poisson-Boltzmann equation. The results reveal that, neglecting the ionic size at high zeta potentials gives...
Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation
, Article Chemical Engineering and Processing: Process Intensification ; 2017 ; 02552701 (ISSN) ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
Elsevier B.V
Abstract
The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over...
Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with villermaux/dushman test reaction
, Article Microsystem Technologies ; 2016 , Pages 1-14 ; 09467076 (ISSN) ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
Springer Verlag
2016
Abstract
This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a...
Numerical simulation of centrifugal serpentine micromixers and analyzing mixing quality parameters
, Article Chemical Engineering and Processing: Process Intensification ; Volume 104 , 2016 , Pages 243-252 ; 02552701 (ISSN) ; Madadelahi, M ; Akbari, A ; Sharif University of Technology
Elsevier, B.V
2016
Abstract
Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular...
Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with Villermaux/Dushman test reaction
, Article Microsystem Technologies ; Volume 23, Issue 8 , 2017 , Pages 3117-3130 ; 09467076 (ISSN) ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
Springer Verlag
2017
Abstract
This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a...
Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation
, Article Chemical Engineering and Processing: Process Intensification ; Volume 116 , 2017 , Pages 9-16 ; 02552701 (ISSN) ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over...
Experimental investigation and process intensification of barium sulfate nanoparticles synthesis via a new double coaxial spinning disks reactor
, Article Chemical Engineering and Processing: Process Intensification ; Volume 115 , 2017 , Pages 11-22 ; 02552701 (ISSN) ; Shahrokhi, M ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
In this article, a new double spinning disks reactor (DSDR) has been proposed and tested successfully for the synthesis of barium sulfate nanoparticles by means of the reactive precipitation. The proposed DSDR consists of two coaxial rotating disks placed horizontally in a cylindrical chamber. Continuous precipitation of barium sulfate nanoparticles as a chemical test system was carried out using this new contacting device and the effects of operating and design parameters such as the disk rotational speed, distance between the disks, feed concentration, feed flow rate, free ion ratio, feed location, and feed distribution pattern on the mean size, size distribution, and morphology of the...
Three-dimensional numerical simulation of a novel electroosmotic micromixer
, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the...
Experimental Investigation and Modeling of Nanoparticles Synthesis by Reactive Precipitation and Using a Spinning Disk Reactor
, Ph.D. Dissertation Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor) ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
In this research work, to enhance the performance of the conventional spinning disk reactors, a novel type of spinning disk reactor has been proposed and tested successfully through the synthesis of barium sulfate nanoparticles by means of the reactive precipitation. This reactor consists of two coaxial rotating disks placed horizontally in a cylindrical chamber. The experimental results clearly indicate the capability of the proposed reactor in the synthesis of nanoparticles with the smaller mean particle size and the narrower particle size distribution compared to those obtained in various process intensification devices such that barium sulfate nanoparticles with a mean particle size of...
Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection
, Article Analytica Chimica Acta ; Volume 1022 , 2018 , Pages 96-105 ; 00032670 (ISSN) ; Shamloo, A ; Sharif University of Technology
Abstract
Recent advances in the field of microfabrication have made the application of high-throughput microfluidics feasible. Mixing which is an essential part of any miniaturized standalone system remains the key challenge. This paper proposes a geometrically simple micromixer for efficient mixing for high-throughput microfluidic devices. The proposed micromixer utilizes a curved microchannel (spiral microchannel) to induce chaotic advection and enhance the mixing process. It is shown that the spiral microchannel is more efficient in comparison to a straight microchannel, mixing wise. The pressure drop in the spiral microchannel is only slightly higher than that in the straight microchannel. It is...
Investigation of the Geometry Effect on Electrokinetic Instability in Microflows
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Hassan (Supervisor)
Abstract
Lab-on-a-chip devices have gained a lot of attention in chemical and biomedical analyses during the past two decades. These devices employ microfluidics basics and fundamentals to combine multifold laboratory processes in one single portable chip. The electric field has been often used in most microfluidics applications for the ease of sample control as well as become easily integrated to other chip components. Instabilities in microflows would occur when two fluids of different electric properties are exposed to an adequately strong electric field. Studying these electrokinetic instabilities is not only important for the fundamental studies but also for practical applications in micromixers...
Numerical Simulation and Characterization of a Micro-mixer with Moving Walls
, M.Sc. Thesis Sharif University of Technology ; Saeedi , Mohammad Saeed (Supervisor) ; Sani, Mahdi (Supervisor)
Abstract
Recent advances in micro-technology are finding important applications especially in chemical and biological processes. In these applications, mixing has a profound importance. Due to the inherent low Reynold’s number flow in micro systems, diffusion mixing is the dominant mixing mechanism at these scales. This is in contrary to the high Reynold’s number ordinary applications where turbulent mixing plays the major role. There are two major classes of micro-mixers: passive and active. Passive micro-mixers rely on geometric features to enhance mixing. Active micro-mixers on the other hand, use external excitation to promote and control the rate of mixing. In this work, using numerical tools,...
Numerical Simulation and Analysis of Active Electro-Kinetic Micro-Mixer
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor) ; Sani, Mahdi (Supervisor)
Abstract
The “Lab-on-a-Chip” is a micro-scale device which uses fluids as working medium and can handle number of functions such as sample preparation and transfer, separation, bio-sensing and detection. One of the important parts of these devices is micro-mixer, that should blend two fluid species in a short time with desirable mixing quality. Micro-mixers are classified as passive and active. By considering the micro-scale of mixers, turbulence phenomena cannot occur due to dominance of viscous forces, therefore the mixing only depends on molecular diffusion. This thesis consists of two main parts, in the first part algebraic multigrid has been studied and implemented in Rayan (in-house CFD code)....
Ionic Size and Rheology Effects on the Mixing Process of Electroosmotic Flows
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
Abstract
In recent years, there have been huge advancements in fabrication of micron-sized devices such that they enabled engineers to create a wide range of miniaturized systems, each of which is utilized in mechanical, electrical, and thermal applications. Micromixers are one of these devices with the role of mixing various micro flows. These devices are broadly used for chemical, biological, and biomedical assays. Among variety of micromixers, one that employs electrokinetic transport phenomenon is of great popularity. For instance, mixing under electroosmotic flow enables accurate process control and eliminates the need for moving components inside micromixer. The very complex nature of electric...
Analysis and Design of an Electrokinetically-driven Micro-Mixer
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor) ; Saeedi, Mohammad Saeed (Supervisor)
Abstract
A Lab-On-A-Chip is a micro-scale system whic h utilizes some micro-scale components in order to implement detection tests on samples. One of the most important components of a lab-on-a-chip device is the micro-mixer, which is responsible for appropriately mixing of samples in a short period of time. The biggest problem relevant to mixing in micro scales is that since as the viscous forces are dominant in micro scale and dimensions are small, it is impractical to mix fluids via turbulence, and consequently mixing process is performed by diffusion mechanism. Two major strategies are being used in order to improve the mixing performance and two groups of micro-mixers, passive and active types,...