scholarly journals Effect of Thermal Energy and Ultrasonication on Mixing Efficiency in Passive Micromixers

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 891
Author(s):  
Fahizan Mahmud ◽  
Khairul Fikri Tamrin ◽  
Shahrol Mohamaddan ◽  
Nobuo Watanabe
Keyword(s):  
Thermal Energy ◽  
Reynolds Numbers ◽  
Fluid Mixing ◽  
Structural Deformation ◽  
Energy Sources ◽  
Mixing Efficiency ◽  
Mixing Index ◽  
Mixing Performance ◽  
Lower Reynolds Number ◽  
Better Than

Micromixing is a key process in microfluidics technology. However, rapid and efficient fluid mixing is difficult to achieve inside the microchannels due to unfavourable laminar flow. Active micromixers employing ultrasound and thermal energy are effective in enhancing the micromixing process; however, integration of these energy sources within the devices is a non-trivial task. In this study, ultrasound and thermal energy have been extraneously applied at the upstream of the micromixer to significantly reduce fabrication complexity. A novel Dean micromixer was laser-fabricated to passively increase mixing performance and compared with T- and Y-micromixers at Reynolds numbers between 5 to 100. The micromixers had a relatively higher mixing index at lower Reynolds number, attributed to higher residence time. Dean micromixer exhibits higher mixing performance (about 27% better) than T- and Y-micromixers for 40 ≤ Re ≤ 100. Influence of ultrasound and heat on mixing is more significant at 5 ≤ Re ≤ 20 due to the prolonged mechanical effects. It can be observed that mixing index increases by about 6% to 10% once the temperature of the sonicated fluids increases from 30 °C to 60 °C. The proposed method is potentially useful as direct contact of the inductive energy sources may cause unwanted substrate damage and structural deformation especially for applications in biological analysis and chemical synthesis.

Numerical analysis of non-aligned inputs M-type micromixers with different shaped obstacles for biomedical applications

2021 ◽  
pp. 095440892110516
Author(s):  
Muhammad Irfan ◽  
Imran Shah ◽  
Usama M Niazi ◽  
Muhsin Ali ◽  
Sadaqat Ali ◽  
...  
Keyword(s):  
Structural Design ◽  
Biomedical Applications ◽  
Structural Changes ◽  
Nanoparticle Synthesis ◽  
Fluid Mixing ◽  
The Novel ◽  
Flow Conditions ◽  
Mixing Index ◽  
Mixing Performance ◽  
Passive Micromixer

Fluid mixing in lab-on-a-chip devices at laminar flow conditions result in a low mixing index. The reason is dominant diffusion over the convection process. The mixing index can be improved by certain changes in the micromixer structural design like introducing obstacles in the path of fluid flow. These obstacles will make dominant the advection process over the diffusion process. The main contribution of this work is based on proposing the novel hybrid type micromixer design for enhancing the mixing quality. Three non-aligned M-type and non-aligned M-type with obstacles passive type micromixers are analyzed by COMSOL5.5. These designs are hybrid types because different structural changes are combined in a single design for mixing improvement. First of all the straight non-aligned inlets, M-type passive micromixer (SMTM) is analyzed. It is observed that mixing performance is improved because of M-shaped mixing units and non-aligned inlets. This improvement is deemed to be not enough so different shaped obstacles are introduced in the micromixer design. These designs based on obstacles are named horizontal rectangular M-type micromixer, square M-type micromixer, and vertical rectangular M-type micromixer. The mixing index for SMTM, square M-type micromixer, horizontal rectangular M-type micromixer, and vertical rectangular M-type micromixer at Reynolds number Re = 60 is respectively given by 71.1%, 83.21%, 84.45%, and 89.99%. The mixing index of vertical rectangular M-type micromixer was 59.34% − 87.65% for Re = 0.5–100. Vertical rectangular M-type micromixer is concluded with the better-mixing capability design among the proposed ones. Based on these simulation results, the vertical rectangular M-type micromixer design can be utilized for mixing purposes in biomedical applications like nanoparticle synthesis and biomedical sample preparation for drug delivery.

A NOVEL 3D MICROMIXER WITH QUARTIC KOCH CURVE FRACTAL

2021 ◽  
pp. 2150049
Author(s):  
SIYUE XIONG ◽  
XUEYE CHEN
Keyword(s):  
Numerical Simulation ◽  
Deflection Angle ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Flow State ◽  
Koch Curve ◽  
Mixing Performance ◽  
Chaotic Convection ◽  
The Deflection Angle ◽  
High Application

In this paper, we mainly study the mixing performance of the micromixer with quartic Koch curve fractal (MQKCF) by numerical simulation. Changing the structure of the microchannel based on the fractal principle can significantly improve the fluid flow state in the microchannel and improve the mixing efficiency of the micromixer. This paper discussed the effects of different fractal deflection angles, microchannel heights and different fractal times on the mixing efficiency under four different Reynolds numbers (Re). It is found that changing the deflection angle of the fractal can bring extremely high benefits, which makes the fluid deflect and fold in the microchannel, enhancing the chaotic convection in the microchannel, and improve the mixing efficiency of the fluid. Under the reasonable arrangement of the quartic Koch curve fractal principle, it can give the micro-mixture more than 99% mixing efficiency. Based on the excellent mixing performance of MQKCF, it also has extremely high application value in the biochemical neighborhood.

scholarly journals A Computational Study on Mixing of Two-Phase Flow in Microchannels

2003 ◽  
Author(s):  
Farshid Bondar ◽  
Francine Battaglia
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Mixing Index ◽  
Wave Type ◽  
Two Phase ◽  
Chaotic Flows ◽  
Two Fluids ◽  
Passive Mixing ◽  
Better Than

The passive mixing of water and alcohol, as two fluids with different densities, is carried out computationally in three-dimensional microchannels. Four designs of microchannels are considered to investigate the efficiency of mixing for Reynolds numbers ranging between 6 and 96. In a straight-type microchannel, mixing is very poor. In a square-wave-type microchannel, mixing is marginally better than the straight one. Mixing in the serpentine-type and twisted-type microchannels develops considerable better than the first two microchannels, especially at higher Reynolds numbers. However, in the twisted microchannel, the mixing index is substantially larger compared to the serpentine microchannel for the Reynolds number of 35. The higher mixing index implies the occurrence of spatially chaotic flows with a higher degree of chaos compared to the case of the serpentine microchannel. The results are compared quantitatively and qualitatively in Eulerian and Lagrangian frameworks and a correlation between Lagrangian chaos and Eulerian chaos is concluded.

A Microfluidic Mixer Fabricated From Compliant Thermoplastic Films

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
N. Paya ◽  
T. Dankovic ◽  
A. Feinerman
Keyword(s):  
Reynolds Number ◽  
Lab On A Chip ◽  
Microfluidic Devices ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Minimal Amount ◽  
Microfluidic Mixer ◽  
Mixing Performance ◽  
Rapid Mixing ◽  
Microfluidic Flows

Mixing is often crucial to the operation of various microfluidic devices. And the most common objective is rapid mixing between two initially segregated fluid streams in a minimal amount of space. In microfluidic flows characterized by incompressibility and low Reynolds number, however, turbulence is almost entirely absent and mixing generally relies on diffusion. Therefore, based on the properties of the fluids involved, it can take impractically long to achieve high mixing efficiency in some cases. To resolve this problem, this paper demonstrates a novel compliant micromixer made of thermoplastic films for lab-on-a-chip applications. The microfluidic mixer utilizes self-rotation effects to achieve high mixing efficiency at Reynolds numbers below 100. In addition, a possible design is suggested for a thermoplastic voltage-actuated micromixer which can lead to even better mixing performance at Reynolds numbers below 1.

scholarly journals Numerical Investigation of Liquid–Liquid Mixing in Modified T Mixer with 3D Obstacles

2021 ◽  
pp. 25-32
Author(s):  
Md. Readul Mahmud
Keyword(s):  
Numerical Investigation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Mixing Performance ◽  
Wide Range

The fluids inside passive micromixers are laminar in nature and mixing depends primarily on diffusion. Hence mixing efficiency is generally low, and requires a long channel length and longtime compare to active mixers. Various designs of complex channel structures with/without obstacles and three-dimensional geometries have been investigated in the past to obtain an efficient mixing in passive mixers. This work presents a design of a modified T mixer. To enhance the mixing performance, circular and hexagonal obstacles are introduced inside the modified T mixer. Numerical investigation on mixing and flow characteristics in microchannels is carried out using the computational fluid dynamics (CFD) software ANSYS 15. Mixing in the channels has been analyzed by using Navier–Stokes equations with water-water for a wide range of the Reynolds numbers from 1 to 500. The results show that the modified T mixer with circular obstacles has far better mixing performance than the modified T mixer without obstacles. The reason is that fluids' path length becomes longer due to the presence of obstacles which gives fluids more time to diffuse. For all cases, the modified T mixer with circular obstacle yields the best mixing efficiency (more than 60%) at all examined Reynolds numbers. It is also clear that efficiency increase with axial length. Efficiency can be simply improved by adding extra mixing units to provide adequate mixing. The value of the pressure drop is the lowest for the modified T mixer because there is no obstacle inside the channel. Modified T mixer and modified T mixer with circular obstacle have the lowest and highest mixing cost, respectively. Therefore, the current design of modified T with circular obstacles can act as an effective and simple passive mixing device for various micromixing applications.

Structure optimization of plough blades in a ploughshare mixer using the DEM simulations

2020 ◽  
Vol 37 (9) ◽  
pp. 3455-3475
Author(s):  
Ziqiang Fang ◽  
Songlin Peng ◽  
Jiangang Yi ◽  
Jun Du
Keyword(s):  
Structural Parameters ◽  
Structure Optimization ◽  
Mixing Efficiency ◽  
Asymmetric Distribution ◽  
Sweep Angle ◽  
Content Type ◽  
Mixing Performance ◽  
Dem Simulations ◽  
Dem Model ◽  
Better Than

Purpose The purpose of this paper is to optimize the structure of plough blades in a ploughshare mixer using the discrete element method (DEM) simulations. Design/methodology/approach Using the validated DEM model, three numerical tests are conducted to determine how the mixing performance evolves as structural parameters of blades change. Results from the analysis provide basis for structure optimization of blades. The structural parameters include sweep angle of blade γ, regular axial pitch p and regular circumferential angular offset α. The parameters to evaluate mixing performance include mass flow rate and Lacey index. Findings The DEM results show that the mixing performance at γ of 35° is better than 15°, 25° and 45°. The mixer which has a p of less than or equal to 1.11 · b is more efficient than the mixer which has a p greater than 1.11 · b, where b is tail width of blade. The circumferential symmetric distribution of blades (α = 180°) is more beneficial to improve the mixing performance in comparison with the circumferential asymmetric distribution (α < 180°). Based on the results, an optimized mixer with a γ of 35°, a p of 0.61 · b and an α of 180° is proposed, which has a better mixing performance compared to all mixers listed. Originality/value The structural parameters of blades, including γ, p and α, are found to be critical for good mixing. From the view angle of structure optimization of plough blades, a new ploughshare mixer with a γ of 35°, a p of 0.61 · b and an α of 180° is investigated and recommended for improving mixing efficiency.

scholarly journals Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 637 ◽  
Author(s):  
Mahmut Burak Okuducu ◽  
Mustafa M. Aral
Keyword(s):  
Fluid Flow ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Flow Profile ◽  
Complex Flow ◽  
Mixing Index ◽  
Micro Channels ◽  
Mixing Dynamics ◽  
Passive Micromixer ◽  
Novel Design

Laminar fluid flow and advection-dominant transport produce ineffective mixing conditions in micromixers. In these systems, a desirable fluid mixing over a short distance may be achieved using special geometries in which complex flow paths are generated. In this paper, a novel design, utilizing semi-circular ridges, is proposed to improve mixing in micro channels. Fluid flow and scalar transport are investigated employing Computational Fluid Dynamics (CFD) tool. Mixing dynamics are investigated in detail for alternative designs, injection, and diffusivity conditions. Results indicate that the convex alignment of semi-circular elements yields a specific, helicoidal-shaped fluid flow along the mixing channel which in turn enhances fluid mixing. In all cases examined, homogenous concentration distributions with mixing index values over 80% are obtained. When it is compared to the classical T-shaped micromixer, the novel design increases mixing index and mixing performance values by the factors of 8.7 and 3.3, respectively. It is also shown that different orientations of ridges adversely affect the mixing efficiency by disturbing the formation of helicoidal-shaped flow profile.

Numerical Investigation and Geometric Parameterization of Lamination Inlet of Passive Micromixer

2010 ◽  
Author(s):  
Yanfeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Straight Channel ◽  
Interface Area ◽  
Mixing Performance ◽  
Passive Micromixer ◽  
Two Parameters ◽  
Parallel Type

A lamination inlet is proposed and optimized in this paper. The perpendicular incoming fluids are applied instead of parallel type. The total mixing length is fixed at 3.2 mm and the depth of channel is fixed at 0.1 mm. The tested Reynolds number is calculated at the entrance of downstream straight channel. The tested Reynolds numbers range from 5 to 200. The perpendicular incoming type enhances the mass-convection and enlarges the interface area. Two parameters, the radius of holes (R) and the distance between two holes (D1), are selected to achieve the optimization. Numerical simulation is used to estimate the mixing performance and flow characteristics. The results show that the vortices are generated in the microchannel. The interface becomes irregular. In order to evaluate the mixing improvement, the parallel lamination is also simulated. The comparison shows that the perpendicular inlet type has better mixing efficiency than the parallel lamination type. This inlet type could be connected with certain mixing element to achieve the applications in biochemistry.

Parametric Study of Obstacle Geometry Effect on Mixing Performance in a Convergent-Divergent Micromixer with Sinusoidal Walls

2017 ◽  
Vol 12 (1) ◽  
Author(s):  
Fazlollah Heshmatnezhad ◽  
Halimeh Aghaei ◽  
Ali Reza Solaimany Nazar
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Molecular Diffusion ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Mixing Efficiency ◽  
Main Concept ◽  
Mixing Index ◽  
Operational Parameter

Abstract This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases.

scholarly journals Enhancement of Fluid Mixing with U-Shaped Channels on a Rotating Disc

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1110
Author(s):  
Chi-Wei Hsu ◽  
Po-Tin Shih ◽  
Jerry M. Chen
Keyword(s):  
Secondary Flow ◽  
Rotational Speed ◽  
Fluid Mixing ◽  
Maximum Efficiency ◽  
Mixing Efficiency ◽  
Rotating Disc ◽  
Mixing Performance ◽  
Simple Geometry ◽  
Visualization Experiments ◽  
Good Agreement

In this study, centrifugal microfluidics with a simple geometry of U-shaped structure was designed, fabricated and analyzed to attain rapid and efficient fluid mixing. Visualization experiments together with numerical simulations were carried out to investigate the mixing behavior for the microfluidics with single, double and triple U-shaped structures, where each of the U-structures consisted of four consecutive 90° bends. It is found that the U-shaped structure markedly enhances mixing by transverse secondary flow that is originated from the Coriolis-induced vortices and further intensified by the Dean force generated as the stream turns along the 90° bends. The secondary flow becomes stronger with increasing rotational speed and with more U-shaped structures, hence higher mixing performance. The mixing efficiency measured for the three types of mixers shows a sharp increase with increasing rotational speed in the lower range. As the rotational speed further increases, nearly complete mixing can be achieved at 600 rpm for the triple-U mixer and at 720 rpm for the double-U mixer, while a maximum efficiency level of 83–86% is reached for the single-U mixer. The simulation results that reveal detailed characteristics of the flow and concentration fields are in good agreement with the experiments.

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