Design Of Micromixer Research Articles

Optimal design of micromixer for preparation of nanoliposomes

Micromixers are essential components for controlling reactions in microfluidic devices, significantly enhancing their efficiency. This paper introduces an unbalanced separation and recombination micromixer with a circulating chamber and optimizes its geometric structure. The study investigates how the width ratio of the main subchannel and secondary subchannel, as well as the position of the circulating chamber, affect the mixing index and pressure drop at the micromixer's inlet and outlet. The enhanced mixing results from the unbalanced impact generated by the micromixer's separation and recombination, combined with the synergistic effect of fluid self-circulation. Simulation results indicate that the optimized micromixer achieves a mixing index close to 100 % when the Reynolds number exceeds 30, with a pressure drop of only 30 KPa at a Reynolds number of 50 in the micromixer's inlet and outlet. A microfluidic-based micromixer was fabricated using soft lithography and molding techniques. Liposomes were synthesized in a single step using soybean phospholipids, cholesterol, ethanol, and deionized water as raw materials. The micro-mixer exhibited exceptional mixing performance, enabling faster liposome synthesis compared to conventional methods. Additionally, the resulting liposomes exhibited smaller particle sizes and narrower size distributions. By adjusting the flow rates of the organic and water phases entering the micromixer, liposomes with a small particle size of 39 nm and a concentrated particle size distribution (PDI=0.104) were successfully produced. These findings highlight the microfluidic approach as a convenient, rapid, and efficient method for liposome preparation. Furthermore, the unbalanced separation and recombination micromixer with a circulating chamber demonstrated a simple structure, high mixing efficiency, and minimal pressure drop loss. It is versatile and suitable for various microreactor applications.

Smart scale-up of micromixers for efficient continuous biodiesel synthesis: A numerical study for process intensification

This study focuses on developing continuous processes for biodiesel synthesis, overcoming limitations of conventional batch reactions, such as biphasic reaction and thermodynamic equilibrium, and reducing production costs. While microreactors are promising for enhancing mixing and transfer rates at smaller scales, scaling up to larger channels results in decreased efficiency and product yield. Microfluidic devices, useful in continuous biodiesel production, lose mixing efficiency when scaled up, affecting product yield. The present study proposes a novel microreactor design with static elements, aiming to improve fluid mixing and reaction performance at higher volumes. The smart scale-up strategy includes an optimized micromixer design, enlarged channel cross-sectional area, and an additional obstacle-free channel. Using a Fractional Design followed by a Central Compound Rotational Design, optimal values for key design variables are identified. Computational tests show a high mixing index (M > 0.77) across a wide range of Reynolds numbers (Re = 0.1–100). Numerical simulations under optimal conditions indicate high conversions (>91 %) for residence times above 60 s. This design promises advancements in industrial-scale biodiesel production, with improved flow and reactant distribution, potentially reducing the number of micro/millidevices needed.

A cost-effective and facile technique for realizing fabric based microfluidic channels using beeswax and PVC stencils.

Microfluidic channels fabricated over fabrics or papers have the potential to find substantial application in the next generation of wearable healthcare monitoring systems. The present work focuses on the fabrication procedures that can be used to obtain practically realizable fabric-based microfluidic channels (μFADs) utilizing patterning masks and wax, unlike conventional printing techniques. In this study, comparative analysis was used to differentiate channels obtained using different masking tools for channel patterning as well as different wax materials as hydrophobic barriers. Drawbacks of the conventional tape and candle wax technique were noted and a novel approach was used to create microfluidic channels through a facile and simple masking technique using PVC clear sheets as channel stencils and beeswax as the channel barriers. The resulting fabric based microfluidic channels with varying widths as well as complex microchannel, microwell, and micromixer designs were investigated and a minimum channel width resolution of 500 μm was successfully obtained over cotton based fabrics. Thereafter, the PVC clear sheet-beeswax based microwells were successfully tested to confine various organic and inorganic samples indicating vivid applicability of the technique. Finally, the microwells were used to make a simple and facile colorimetric assay for glucose detection and demonstrated effective detection of glucose levels from 10 mM to 50 mM with significant color variation using potassium iodide as the coloring agent. The above findings clearly suggest the potential of this alternative technique for making low-cost and practically realizable fabric based diagnostic devices (μFADs) in contrast to the other approaches that are currently in use.

Investigation of mixing characteristics in a novel SAR micromixer with locally overlapping V-shaped flow channels

Micromixers have been widely used in chemical reactions, drug testing, bio-analysis, and various other fields where achieving effective mixing is crucial for system performance. To enhance mixing efficiency, this study presents a novel micromixer design based on principles of separation diffusion and chaotic convection. It features a double-layer V-shaped channel and mixing chamber structure, along with an innovative approach of locally overlapping flow channels. The results demonstrate that this design induces fluid split and recombination within the flow channel, increasing contact areas between fluids. Furthermore, under the identical conditions, the overlapping of flow channels induces secondary flow separation, further enhancing mixing. Specifically, we observed a 9.39 % improvement in the mixing index when comparing before and after overlapping (when Re = 10). Moreover, when the Reynolds number exceeds 20, the mixing index at the outlet consistently surpasses 99 %, which is superior to most existing micromixers. These novel models significantly improve mixing efficiency at low Reynolds numbers and introduce a promising method for future research.

Numerical simulation and coupling mechanism study of acoustic-inertial micromixer

Acoustic-inertial micromixers exhibit a wider operating range and higher mixing efficiency than conventional mixers. We have carried out experimental studies and numerical simulations of acoustic-inertial micromixers. It is found that the acoustic streaming will be changed in morphology and intensity by the background flow, and the coupling mechanism between them is obtained. Specifically, we developed the numerical model of acoustic-inertial micromixer by using perturbation theory and the Generalized Lagrangian Mean (GLM) theory. By dividing the flow variables into zero-order, first-order and second-order variables, we obtained the control equations representing background flow, acoustic response and time-averaged streaming flow. Then realized the decoupling analysis of the acoustic-inertial coupling phenomenon. It is found that in terms of acoustic streaming flow, the intensity extreme of it increases as the background flow rate increases. The flow velocity at 5Vpp can reach 0.46 m/s under 500 μL/min, which is 30 times for the same condition under 10 μL/min. However, the streaming morphology no longer behaves as a symmetric vortex distributed on both sides of the sharp edge, which is stretched and twisted by the background flow and structure at a high flow rate. The percentage of acoustic contribution at different working conditions is also investigated quantitatively, and the acoustic contribution index (ACI) will generally decrease to less than 0.5 after the background flow dominates the flow field. The results of the study can provide a reference for the design of acoustic-inertial micromixers with larger flow ranges and higher efficiencies.

Design and scale-up of a superb micromixer with fan-shaped obstacles for synthesis of Dolutegravir intermediate

Micromixer have received significant attention for fluid mixing enhancement, while traditional micromixers have long mixing times and unstable mixing effects, which has discouraged their commercial development. Herein, we report a methodology for the design, optimization, scale-up fabrication and performance evaluation of a novel micromixer. A combination of Solidworks modeling, Design of Experiments and Computational Fluid Dynamics numerical simulation is used to optimize the configuration of micromixer. Analysis and optimization of experimental results from CFD numerical simulations revealed the channel width had the greatest impact on the performance of the micromixer. Based on the DoE results, two optimized micromixers (FOM-A and FOM-B) were developed and subjected to a series of numerical simulations at Reynolds number 0.5 ≤ Re ≤ 100. Both micromixers had a high mixing index (> 94%) and maintained a low pressure drop. Next, the FOM-B was scaled up and used as a microreactor for the synthesis of Dolutegravir intermediate. A 98% yield was obtained at a residence time of 4 min. Furthermore, the mass transfer performance of the FOM-B microreactor was measured and a mass transfer coefficient of 0.5012 s−1 was obtained at liquid flow rate of 20 mL/min, which is double the value of other commercial microreactors.

Mixing performance improvement of T-shaped micromixer using novel structural design of channel and obstacles

Micromixers play a crucial role in mixing different fluids within microfluidic systems. Therefore, it is essential to analyze parameters, such as dimensional characteristics, mixing length, micromixer efficiency, and the mixing process, to enhance their performance. In this study, we examine various T-shaped micromixer designs, including triangular, rectangular, and trapezius configurations, to evaluate their mixing performance and compare them with a corresponding circular micromixer. Additionally, we investigate the effects of obstacles, varying their angles and distances, in the circular micromixer to determine trends in mixing improvement across cases. The micromixers have minimal dimensions, resulting in laminar flow. By comparing the outcomes of the proposed cases with those without obstacles, we find that the triangular micromixer exhibits the highest mixing performance with 8.3% improvement with respect to the circular case. Furthermore, while the rectangular case initially displayed the weakest performance at lower Reynolds numbers, a discernible enhancement was observed as Reynolds numbers increased. This improvement was attributed to the emergence of vortices at Re = 20. The performance showed a substantial increase, reaching a coefficient of 0.98 at Re = 40, a value closely approaching that of the triangular case. Among the three obstacles, one obstacle is varied at four different angles (0°, 60°, 90°, and 120°), while the other two obstacles remain fixed at distances of 150 and 200 μm. In cases involving obstacles, a noteworthy enhancement was evident when compared to cases without obstacles. In these cases, the introduction of obstacles resulted in a remarkable 34% improvement in the mixing index compared to obstacle-free scenarios. This improvement can be attributed to the observed flow behavior, where the formation of vortices, even at low Reynolds numbers, emerges as a key factor contributing to this enhancement. In addition, we assess the mixing enhancement to identify the most efficient arrangement of obstacles. The results indicate angles of 90° and 120° are more effective than others in improving mixing proficiency.

AC Electrothermal Effect Promotes Enhanced Solute Mixing in a Wavy Microchannel.

For liquids used in biological applications, a smaller diffusion coefficient results in a longer mixing time. We discuss, in this endeavor, the promising potential of the AC electrothermal (ACET) effect toward modulating enhanced mixing of electrolytic liquids with higher convective strength in a novel wavy micromixer. To this end, we develop a modeling framework and numerically solve the pertinent transport equations in a three-dimensional (3D) configuration numerically. By benchmarking the developed modeling framework with the experimental results available in this paradigm, we aptly demonstrate the maximum temperature rise, flow topology, species concentration field, and mixing efficiency in the proposed configuration for a set of parameters pertinent to this analysis. We find that the maximum temperature increase in the wavy micromixer, owing to the electrothermal effect, is less than 10 K even for the higher strength of the applied voltage, implying nondegradation of biological substances within the liquid sample. We report that the formation of significant lateral flow closer to the electrodes leads to a highly three-dimensional ACET flow field, which has a significant impact on the mixing efficiency for the range of diffusive Peclet numbers considered. We also report that the wave amplitude of the mixer, when intervening with the diffusive Peclet number, strongly impacts the mixing efficiency. As witnessed in this endeavor, for the smaller diffusive Peclet number, the mixing efficiency increases with amplitude, while the effect becomes the opposite for the higher Peclet number. The results of this study seem to provide an adequate basis for the design of a novel micromixer intended for enhanced solute mixing in realistic microfluidic applications.

Enhanced Microfluidics Mixing Performance in a Grooved Serpentine Microchannel at Different Flow Rates

Reliable and efficient mixing in microfluidic systems is crucial for various applications such as molecular diagnostics, DNA hybridization, microreactors and nanoparticle synthesis. However, achieving adequate mixing at the microscale is challenging due to the fact that flow regime in microfluidics is laminar that is characterized by low Reynolds numbers. In an attempt to tackle this challenge, active and passive strategies have been utilized to enhance mixing. Passive techniques mainly rely on the interaction between fluid and channel geometry in order to extend the interface between the components of the fluid by inducing transversal flows. Passive methods have shown their simplicity over the active methods in microfluidics by simply controlling the channel geometry and flow configurations without involving any complex external forces and components. Based on this, our work presents a passive micromixer design with trapezoidal grooves placed at the bottom of the serpentine channels. The grooves induce periodic pressure drops along the channel which create staggered transversal vortices in orthogonal directions which disturbs the symmetries in the flow that results in stirring. These combined effects result in an enhanced mixing performance especially at higher flow rates. The results suggest that the design could be integrated into lab-on-a-chip systems to achieve enhanced mixing of biological or chemical components with reduced footprint, complexity and cost.

Design and Mixing Analysis of a Passive Micromixer Based on Curly Baffles.

A novel passive micromixer based on curly baffles is proposed and optimized through the signal-to-noise analysis of various design parameters. The mixing performance of the proposed design was evaluated across a wide Reynolds number range, from 0.1 to 80. Through the analysis, the most influential parameter was identified, and its value was found to be constant regardless of the mixing mechanism. The optimized design, refined using the signal-to-noise analysis, demonstrated a significant enhancement of mixing performance, particularly in the low Reynolds number range (Re< 10). The design set obtained at the diffusion dominance range shows the highest degree of mixing (DOM) in the low Reynolds number range of Re< 10, while the design set optimized for the convection dominance range exhibited the least pressure drop across the entire Reynolds number spectrum (Re< 80). The present design approach proved to be a practical tool for identifying the most influential design parameter and achieving excellent mixing and pressure drop characteristics. The enhancement is mainly due to the curvature of the most influential design parameter.

A novel micromixer for efficient mixing and nano‐TATB preparation

AbstractPassive micromixers are widely used in the preparation of ultrafine explosives because of their efficient mixing and necessary safety. A novel passive micromixer was designed to prepare nano‐TATB. Computational fluid dynamics (CFD) is used to simulate the opening width (K), fluid velocity and mixing performance of the micromixer. The results show that the proposed micromixer has good mixing performance in the Reynolds number (Re) range of 0.1~100, and its pressure drop less than 28204 Pa at Re=100. A microfluidic recrystallization system was established and nano‐TATB was prepared by a new micromixer. The results show that the average particle size of the prepared TATB is 93.12 nm, and the particle size distribution ranges from 43 nm to 151.4 nm. The SEM test shows that TATB has better morphological characteristics. XRD results show that the crystal structure of TATB is consistent with that of raw materials. This study proves that the new micromixer has good mixing effect and the feasibility of preparing nano TATB. It also provides reference for the design of micromixer and refinement of other energetic materials.

Topology-Optimized Micromixer Design with Enhanced Reverse Flow to Increase Mixing Efficiency.

In this work, a serpentine mixing unit model based on topology optimization is proposed to enhance the reverse flow in both horizontal and vertical directions. The increase in reverse flow in both directions can enhance the chaotic advection phenomenon, leading to a rapid increase in the mixing index. The proposed mixing unit model is applied in a T-shaped micromixer to create a new micromixer design, named TOD. Numerical simulations of TOD are performed using Comsol Multiphysics software to analyze the characteristics of the liquid flow, mixing surface, and pressure drop. The simulation results confirm that TOD has an outstanding mixing performance. By widening the surface area of contact and enhancing the chaotic advection phenomenon, TOD shows an excellent mixing performance at both a high and low Reynolds number, making it a promising micromixer design. For Re > 5, the mixing indexes of TOD are all beyond 90%.

Constructal design of passive micromixers with multiple obstacles via computational fluid dynamics

Passive micromixers have applications mainly in the chemical, pharmaceutical, and materials industries. Two or more fluids mix while flowing through microchannels in these devices. Due to the small dimensions and low flow rates, the flow is essentially laminar, and mixing takes place mainly by mass diffusion. One way to increase the mixing rate in micromixers is the addition of obstacles that increase the advective effects. This work aimed to introduce high-performance designs of passive micromixers with multiple obstacles. These designs were obtained by combining the Constructal Design method with the Response Surface Optimization method and Computational Fluid Dynamics (CFD). The micromixers were Y-shaped tubes with grooves and circular obstacles in cells that repeated along the device. From the first design inspired by a high-performance design from the literature, the evolutionary design of the system was achieved by increasing the number of obstacles and finding the best configuration for each evolution level (number of obstacles per cell, from three to seven). The effects on mixing percentage, pressure difference, and mixing energy cost (MEC) of obstacles’ vertical and horizontal distances were investigated with CFD simulations. Increasing the number of obstacles made it possible to increase the mixture percentage of the micromixer. At the same time, the total pressure drop rises faster than the mixing percentage. However, analyzing the pressure locally, it was shown that the lower the number of obstacles, the greater the local pressure drop, which could cause flow obstructions. The vertical distance of the obstacles had a more significant impact on the mixing than their horizontal distance. Both vertical and horizontal distances had a substantial effect on the pressure drop. As the number of obstacles increased, the effect of the horizontal distance became weaker as its variation was limited. The three-obstacles design presented a MEC equal to 2.47 and a mixing percentage equal to 67.12% mixing index. The latest design evolution (i.e., seven obstacles) achieved the best mixing percentage, 70.30%, with MEC equal to 2.97. By modifying the degrees of freedom, it was possible to understand and propose a path to the evolutionary design of the system to increase its performance while still using simple designs.

Machine learning-augmented fluid dynamics simulations for micromixer educational module.

Micromixers play an imperative role in chemical and biomedical systems. Designing compact micromixers for laminar flows owning a low Reynolds number is more challenging than flows with higher turbulence. Machine learning models can enable the optimization of the designs and capabilities of microfluidic systems by receiving input from a training library and producing algorithms that can predict the outcomes prior to the fabrication process to minimize development cost and time. Here, an educational interactive microfluidic module is developed to enable the design of compact and efficient micromixers at low Reynolds regimes for Newtonian and non-Newtonian fluids. The optimization of Newtonian fluids designs was based on a machine learning model, which was trained by simulating and calculating the mixing index of 1890 different micromixer designs. This approach utilized a combination of six design parameters and the results as an input data set to a two-layer deep neural network with 100 nodes in each hidden layer. A trained model was achieved with R2 = 0.9543 that can be used to predict the mixing index and find the optimal parameters needed to design micromixers. Non-Newtonian fluid cases were also optimized using 56700 simulated designs with eight varying input parameters, reduced to 1890 designs, and then trained using the same deep neural network used for Newtonian fluids to obtain R2 = 0.9063. The framework was subsequently used as an interactive educational module, demonstrating a well-structured integration of technology-based modules such as using artificial intelligence in the engineering curriculum, which can highly contribute to engineering education.

Numerical and experimental investigations of spiral and serpentine micromixers over a wide Reynolds number range

Micromixers are important components in microfluidic systems and play a pivotal role in chemical processes. In this work, numerical simulation and experimental studies were used to investigate the mixing efficiencies of spiral (S-M) and serpentine (C-S-M) micromixers in a wide Reynolds number (Re) range. We found that the structure of the Dean vortex played a crucial role in the mass transfer of the mixing process. The two structures produced Dean vortices with double vortex structures at the Re of 1 and 300, the mixing efficiency of C-S-M was lower than S-M. A Dean vortex with a four-vortex structure was produced in the two micromixers at the Re of 300 and 500, and the mixing efficiency of C-S-M was higher than S-M. Finally, the running cost (RC) concept was proposed to evaluate the comprehensive efficiencies of the two micromixers, which showed that the RC of S-M was lower at the Re of 50 and 100, and the RC of C-S-M was lower at the Re of 300 and 500. Our research may provide theoretical guidance for the design and application of micromixers.

Cost‐effective fast prototyping using a dry film photoresist for micromixers towards point‐of‐care devices

AbstractThis paper deals with a novel structure of serpentine micromixer with its high mixing efficiency and its fabrication of soft photolithography molds using dry film photoresist as an alternative to the conventional liquid photoresist, such as SU‐8. This method provides simplification, significant time‐savings, low cost due to non‐cleanroom setting and less toxic developer solution. In this paper, the design, simulation, fabrication and experimental analysis of the passive micromixers have been presented. The mixing efficiency of the chip was implemented by using of micro‐barrier structure along its meander microchannel. The serpentine structures with and without embedded grooves on their micro sidewalls were designed and compared together in order to prove good mixing performance. Experimental measurements were introduced using white and green food dyes as the mixing fluids. The mixing efficiencies of micromixers were determined and compared in the analytical model and the mixing test. It was found that grooved structures significantly enhanced the performance of the serpentine micromixers due to induce perturbations in the flow field. By optimizing the design of the serpentine micromixers equipped with embedded grooves under its simple fabrication method making this study a promising solution for a wide variety of application.

Design and Simulation of the Spiral Micromixer with Chaotic Advection

In recent years, the microfluidics technique has screwed up rising attention and be in progress a fascinating topic. Species mixing is a compelling part of any microfluidic system that abides by the major challenge. In this research, a relative explication of mixing quality of microchannels of two cross-sections square and circular in spiral form is presented by numerical simulation. To perform the visitation, geometric parameters like axial length of microchannels and hydraulic diameter are taken equal for both cases. Computational Fluid Dynamics codes unriddle the Continuity equation, Navier-Stokes equation, and Convection-Diffusion equation. Explication of fluid flow and mixing have been gone through with an extensive limit of Reynolds numbers 1 to 125. The results explicate that the circular section spiral microchannel affords a higher mixing quality admixed to the square section spiral microchannel. Furthermore, in the circumstance of circular section spiral micromixer, mixing index esteem has attained 92% at Re =125. For both section micromixer, the esteem of mixing index enhancement be contingent on Reynolds numbers. For both cases, pressure downfall has been computed for microchannels of similar lengths. The esteem of pressure downfall in square section spiral mixer is excess than circular section spiral mixer. The simulation outcomes exhibited that the circular section spiral micromixer is an effective design for microfluidic devices like Lab on a chip (LOC).

Topology optimization design of a passive two-dimensional micromixer

In this study, a novel two-dimensional micromixer design is proposed using the topology optimization method. The pressure drop constraint is introduced to achieve a limited pressure drop. The mixing performance of the proposed micromixer is evaluated over a broad range of Reynolds numbers (Re) through numerical simulations and experiments. The results showed that the mixing efficiency of the one-period and multi-period micromixers could reach 96% and 99%, respectively, while still maintaining a relatively low pressure drop. In addition, the experiment on the preparation of silver nanoparticles demonstrate the applicability and practicality of using topology optimization in the design of micromixers.

Recent Advances of the Development and Optimization Design of Passive Microfluidic Mixers

In recent decades, the micromixers are developing very fast. They have wide application in biology and chemistry. Also, micromixers are widely used in both industry and academia situations. Many research are conducted to find novel design of micromixers. The existing micromixers can be classfied into two categories: active and passive micromixer. Active micromixers need external energy supply whereas passive mixers only use geometric structures to finish mixing. In passive micromixer, the diffusion is the main way to mix fluids. Researching the active micromixer is much more complicated because there are many variables to control. This paper mainly discuss the recent advances of of the development and design principles of passive micromixers. Several types of passive micromixers are studied, such as serpentine mixers and trapezoidal-zigzag mixers. Ways to obtain and measure those passive micromixers are studied, such as the layout optimization method. The main findingas include that the non-rectangular micromixer and the trapezoidal-zigzag mixers shows great mixing performance, and many design of micromixers are obtained by the layout optimization method.

Vortex-assisted electroosmotic mixing of Carreau fluid in a microchannel.

Pertaining to the mixing of the non-Newtonian Carreau fluid under electrokinetic actuation inside a plane microchannel, we propose a new design of micromixer that involves inserting a two-part cylinder bearing zeta potential of the same sign but different magnitude in the upstream and downstream directions. We numerically solve the transport equations to predict the underlying mixing characteristics. We demonstrate that a substantial momentum difference between the microchannel's plane wall and cylinder leads to the development of a vortex in the flow pathway, which in turn, enhances mixing substantially. As shown, for a fluid having a highly shear-thinning nature, the vortex-assisted convection mixing strength increases with diffusivity of the candidate fluids. Moreover, it is shown that for the higher shear-thinning nature of the candidate fluid, an increase in cylinder radius enhances mixing efficiency and flow rate simultaneously, resulting in a "quick and efficient" mixing condition. Additionally, the fluid rheology significantly alters the kinetics of shear-induced binary aggregation. Our findings show that the shear-induced aggregation characteristic time sharply increases with increasing shear-thinning behavior of the fluid.