A Review on Different Micromixers and its Micromixing within Microchannel (original) (raw)

Parametric investigation on mixing in a micromixer with two-layer crossing channels

SpringerPlus, 2016

The exponential demand for miniaturization in microfluidic applications highlights the significance of understanding the mechanism that controls mixing of fluid species at the microscale stage. The characteristic dimension of a microfluidic device is usually in a range from ten to several hundred micrometer, where the flow becomes laminar due to the low Reynolds number. Thus, the laminar behavior in the devices causes difficulty in mixing of fluids. Due to the low flow velocity, mixing primarily depends on the molecular diffusion between the fluids, which is very slow process. Diffusion mechanism is governed by the Fick's law, where the mixing mass flux is proportional to the diffusion coefficient and concentration gradient. Microfluidic devises are widely applied for many chemical and biological practices, leading to the new ideas, such as bio-chip (Schwesinger et al. 1996), bio-MEMS (Linder 2001), microreactor (Hardt et al. 2005), and lab-on-a-chip (Erickson 2005). Rapid as well as efficient mixing is very important for almost all chemical and biological analyses. In order to fulfill the demand of efficient and rapid mixing in microchannels, a variety of passive and active micromixers have been

A Survey of Microchannel Geometries for Mixing of Species in Biomicrofluidics

Microfluidics is changing the way modern biology is performed and is becoming a key technology in the field of micro arrays, DNA sequencing, and Lab on a Chip applications. Microsystems, being compact in size, disposable, and ensuring high speed of analysis using decreased sample volumes, allow to replace large-scale conventional laboratory instrumentation with miniaturized devices, reducing hardware costs, and assuring low reagent consumption and faster analysis. At the microscale mixing of species becomes crucial to i) improve the effectiveness of and ii) speed up chemical reactions, but it is often critical to be achieved, since microfluidics is characterized mainly by very low Reynolds flows, and cannot take advantage of turbulence in order to enhance mixing. Hence, given that diffusiondriven mixing in very low Reynolds number flow regimes is characterized by long time scales, methods for enhancing the rate of the mixing process are essential in microfluidics. In order to enhance mixing, several techniques have been developed. In general, mixing strategies can be classified as either active or passive, according to the operational mechanism. Active mixers employ external forces in order to perform mixing, so that actuation system must be embedded into the microchips. On the contrary, passive mixers avoid resorting to external electrical or mechanical sources by exploiting characteristics of specific flow fields in microchannel geometries to mix species, offering the advantage to be easy to be produced and integrated. In this work, a survey of the passive micromixing solutions currently adopted is presented. In detail, the most widely used microchannel geometries and the metrics used to quantify mixing effectiveness in microfluidic applications are discussed.

Mixing of liquids using obstacles in microchannels

BioMEMS and Smart Nanostructures, 2001

In general, the Reynolds number is low in microfluidic channels. This means that the viscous force plays a dominant role. As a result, the flow is most likely to be laminar under normal conditions, especially for liquids. Therefore, diffusion, rather than turbulence affects the mixing. In this work, the commercial computational fluid dynamics tool for microfluidics, known as FlumeCAD, is used to study the mixing of two liquids in a "Y" channel and the results are presented. To improve mixing, obstacles have been placed in the channel to try to disrupt flow and reduce the lamella width. Ideally, properly designed geometric parameters, such as layout and number of obstacles, improve the mixing performance without sacrificing the pressure drop too much. In addition, various liquid properties, such as viscosity, diffusion constant, are also evaluated for their effect on mixing. The results indicate that layout of the obstacle has more effect on the mixing than the number of the obstacles. Placing obstacles or textures in the microchannels is a novel method for mixing in microfluidic devices, and the results can provide useful information in the design of these devices.

Mixing of Liquids Using Obstacles In Microchannels

Proceedings …, 2001

Computational Simulation of Enhancement of Mixing Efficiency in a Micromixer

Abstract—In this paper we studied the ways to enhance the mixing performance in a microchannel. The result's analysis shows a simpler pattern on the wall(s) of the microchannel can enforce rapid mixing of fluids and reduce the mixing length. The simple pattern on walls of the microchannel is easy to fabricate when compared to prevalent staggered herringbone mixer (SHM).The proposed mixer also creates the rotation of flow within the channel, which increases the interfacial area of the fluids. Thus reduces the mixing length of a microchannel. A twofold reduction in mixing length shown by the simulations can be of importance in designing micromixers of smaller size. The computational work also reproduces the experimental results of SHM as a part of validation. In addition to quantitatively reproducing the mixing efficiency plot found from experiments, the flow structures obtained in the simulations closely resemble the same obtained through experiments.

Mixing characterisation for a serpentine microchannel equipped with embedded barriers

Biomedical Applications of Micro- and Nanoengineering IV and Complex Systems, 2008

This paper describes the design, simulation, fabrication and experimental analysis of a passive micromixer for the mixing of biological solvents. The mixer consists of a T-junction, followed by a serpentine microchannel. The serpentine has three arcs, each equipped with circular barriers that are patterned as two opposing triangles. The barriers are engineered to induce periodic perturbations in the flow field and enhance the mixing. CFD (Computational Fluid Dynamics) method is applied to optimise the geometric variables of the mixer before fabrication. The mixer is made from PDMS (Polydimethylsiloxane) using photo-and soft-lithography techniques. Experimental measurements are performed using yellow and blue food dyes as the mixing fluids. The mixing is measured by analysing the composition of the flow's colour across the outlet channel. The performance of the mixer is examined in a wide range of flow rates from 0.5 to 10 μl/min. Mixing efficiencies of higher than 99.4% are obtained in the experiments confirming the results of numerical simulations. The proposed mixer can be employed as a part of lab-on-a-chip for biomedical applications.

Mixing Behavior and Pressure Drop Analysis of Micromixer with Different Geometric Conditions

International Journal for Research in Applied Science and Engineering Technology, 2021

A 3-D design of and analysis of fluid flow in the micromixer with different configurations is carried out in this dissertation. The main purpose of this research is to obtain minimum mixing length as rapid mixing is essential in many of the micro-fluidic systems used in biochemistry analysis, drug delivery, sequencing, or synthesis of nucleic acids. Also effect on various parameters such as mixing behavior, volume arrow, mixing length, maximum velocity, maximum pressure, pressure drop, and velocity distribution were analyzed by changing the mixing angle between inlets. Micromixers with square cross-section rectangular mixing chamber with various types of obstacle place in fluid flow paths such as rectangular obstacles, elliptical obstacle, and circular obstacle in split and recombination manner were designed for the analysis. The micromixer has 3 inlets and 1 outlet. Water and ethanol were used as working fluids. For computational fluid dynamics analysis, COMSOL Multiphysics 5.0 is ...

Passive mixing in microchannels by applying geometric variations

Passive mixing by applying geometric variations were studied in this research. In respect to the nature of laminar flow in a microchannel, the geometric variations were designed to try to improve the lateral convection. By doing this, the dispersion of solute was not only contributed by diffusion, but also, and more importantly, the convection in the lateral direction. Geometric parameters versus the mixing performance were investigated systematically in T-type channels, by applying a known computational fluidic dynamic (CFD) solver for microfluidics. Various obstacle shapes, sizes and layouts were studied. As the ratio of the height of obstacles to the depth of channel became negative, it was the special case that obstacles became grooves. The mechanism for obstacles to enhance mixing was to create convective effects. However, the asymmetric arrangement of grooves applied a different mechanism to enhance mixing by create helical shaped recirculation of fluids. The stretching and folding of fluids of this mixing mechanism provided a efficient way to reduce the diffusion path in microchannels. The mixing performance of mixers with obstacles were evaluated by mass fraction, and mixers with grooved surfaces were evaluated by particle tracing techniques. The results illustrated that both of the strategies provided potential solutions to microfluidic mixing.

On Optimization of Mixing Process of Liquids in Microchannels

2010

A method for simulating fluid flows in microchannels is proposed. The method is tested using available experimental data obtained in micro-PIV studies of microchannel flows. Flow regimes in Y-, T- and S-types micromixers are studied. Passive and active mixers are considered. The dependence of the mixing efficiency on the Peclet number and the Reynolds number is examined, and the possibility of using hydrophobic and ultrahydrophobic coatings is analyzed.

A Review on Different Micromixers and its Micromixing within Microchannel (original) (raw)

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