scholarly journals Microfluidic Magnetic Mixing at Low Reynolds Numbers and in Stagnant Fluids

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 731 ◽  
Author(s):  
Eriola-Sophia Shanko ◽  
Yoeri van de Burgt ◽  
Patrick D. Anderson ◽  
Jaap M. J. den Toonder
Keyword(s):  
Magnetic Beads ◽  
External Source ◽  
Magnetic Bead ◽  
Mixing Efficiency ◽  
Microfluidic Mixing ◽  
Low Reynolds Number Flows ◽  
Passive Mixing ◽  
Magnetic Mixing ◽  
Low Reynolds ◽  
Active Mixing

Microfluidic mixing becomes a necessity when thorough sample homogenization is required in small volumes of fluid, such as in lab-on-a-chip devices. For example, efficient mixing is extraordinarily challenging in capillary-filling microfluidic devices and in microchambers with stagnant fluids. To address this issue, specifically designed geometrical features can enhance the effect of diffusion and provide efficient mixing by inducing chaotic fluid flow. This scheme is known as “passive” mixing. In addition, when rapid and global mixing is essential, “active” mixing can be applied by exploiting an external source. In particular, magnetic mixing (where a magnetic field acts to stimulate mixing) shows great potential for high mixing efficiency. This method generally involves magnetic beads and external (or integrated) magnets for the creation of chaotic motion in the device. However, there is still plenty of room for exploiting the potential of magnetic beads for mixing applications. Therefore, this review article focuses on the advantages of magnetic bead mixing along with recommendations on improving mixing in low Reynolds number flows (Re ≤ 1) and in stagnant fluids.

scholarly journals Microspinning: Local Surface Mixing via Rotation of Magnetic Microparticles for Efficient Small-Volume Bioassays

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 175
Author(s):  
Su Deok Kim ◽  
Seo Woo Song ◽  
Dong Yoon Oh ◽  
Amos Chungwon Lee ◽  
Jeong Woo Koo ◽  
...  
Keyword(s):  
High Throughput Screening ◽  
Magnetic Nanoparticle ◽  
Inertial Force ◽  
Rotating Magnetic Field ◽  
Mixing Efficiency ◽  
Small Scale ◽  
Simple Diffusion ◽  
Passive Mixing ◽  
Active Mixing ◽  
Nanoparticle Chains

The need for high-throughput screening has led to the miniaturization of the reaction volume of the chamber in bioassays. As the reactor gets smaller, surface tension dominates the gravitational or inertial force, and mixing efficiency decreases in small-scale reactions. Because passive mixing by simple diffusion in tens of microliter-scale volumes takes a long time, active mixing is needed. Here, we report an efficient micromixing method using magnetically rotating microparticles with patterned magnetization induced by magnetic nanoparticle chains. Because the microparticles have magnetization patterning due to fabrication with magnetic nanoparticle chains, the microparticles can rotate along the external rotating magnetic field, causing micromixing. We validated the reaction efficiency by comparing this micromixing method with other mixing methods such as simple diffusion and the use of a rocking shaker at various working volumes. This method has the potential to be widely utilized in suspension assay technology as an efficient mixing strategy.

scholarly journals Versatile Microfluidic Mixing Platform for High- and Low-Viscosity Liquids via Acoustic and Chemical Microbubbles

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 854
Author(s):  
Yanfang Guan ◽  
Baichuan Sun
Keyword(s):  
Point Of Care ◽  
Mixing Time ◽  
High Viscosity ◽  
Mixing Efficiency ◽  
Chemical Research ◽  
Microfluidic Mixing ◽  
Mixing Effect ◽  
Low Viscosity ◽  
Passive Mixing ◽  
The Relationship

Microfluidic mixers have been extensively studied due to their wide application in various fields, including clinical diagnosis and chemical research. In this paper, we demonstrate a mixing platform that can be used for low- and high-viscosity liquid mixing by integrating passive (utilizing the special circulating crossflow characteristics of a zigzag microstructure and cavitation surfaces at the zigzag corners) and active (adding an acoustic field to produce oscillating microbubbles) mixing methods. By exploring the relationship between the active and passive mixing methods, it was found that the microbubbles were more likely generated at the corners of the zigzag microchannel and achieved the best mixing efficiency with the acoustically generated microbubbles (compared with the straight channel). In addition, a higher mixing effect was achieved when the microchannel corner angle and frequency were 60° and 75 kHz, respectively. Meanwhile, the device also achieved an excellent mixing effect for high-viscosity fluids, such as glycerol (its viscosity was approximately 1000 times that of deionized (DI) water at 25 °C). The mixing time was less than 1 s, and the mixing efficiency was 0.95 in the experiment. Furthermore, a new microbubble generation method was demonstrated based on chemical reactions. A higher mixing efficiency (0.97) was achieved by combining the chemical and acoustic microbubble methods, which provides a new direction for future applications and is suitable for the needs of lab-on-a-chip (LOC) systems and point-of-care testing (POCT).

Optimized design of obstacle sequences for microfluidic mixing in an inertial regime

Lab on a Chip ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 3910-3923
Author(s):  
Matteo Antognoli ◽  
Daniel Stoecklein ◽  
Chiara Galletti ◽  
Elisabetta Brunazzi ◽  
Dino Di Carlo
Keyword(s):  
Optimized Design ◽  
Fast Method ◽  
Microfluidic Mixing ◽  
Passive Mixing ◽  
Contact Surfaces ◽  
Inertial Regime

A fast method for designing optimal sequences of passive mixing units is provided for inertial flows. Intense mixing is achieved through highly-controlled stretching of the fluid contact surfaces.

scholarly journals High Mixing Efficiency by Modulating Inlet Frequency of Viscoelastic Fluid in Simplified Pore Structure

Processes ◽  
2018 ◽  
Vol 6 (11) ◽  
pp. 210 ◽  
Author(s):  
Meng Zhang ◽  
Yunfeng Cui ◽  
Weihua Cai ◽  
Zhengwei Wu ◽  
Yongyao Li ◽  
...  
Keyword(s):  
Viscoelastic Fluid ◽  
Essential Role ◽  
Fluid Flows ◽  
Fluid Mixing ◽  
Modulation Method ◽  
Mixing Efficiency ◽  
Microscale Flow ◽  
Pressure Modulation ◽  
Active Mixing ◽  
Junction Structure

Fluid mixing plays an essential role in microscale flow systems. Here, we propose an active mixing approach which enhances the mixing of viscoelastic fluid flow in a simplified pore T-junction structure. Mixing is actively controlled by modulating the driving pressure with a sinusoidal signal at the two inlets of the T-junction. The mixing effect is numerically investigated for both Newtonian and viscoelastic fluid flows under different pressure modulation conditions. The result shows that a degree of mixing as high as 0.9 is achieved in viscoelastic fluid flows through the T-junction mixer when the phase difference between the modulated pressures at the two inlets is 180°. This modulation method can also be used in other fluid mixing devices.

The Research of a New Method for Manipulating Magnetic Beads through Multi-Layered Flat Micro-Coils Coupled with Permanent Magnet

2013 ◽  
Vol 753-755 ◽  
pp. 1571-1575
Author(s):  
Zhi Hua Liu ◽  
Yu Feng Huang ◽  
Jian Peng Li ◽  
Xin Wei Xu
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Flow Velocity ◽  
Magnetic Beads ◽  
Magnetic Bead ◽  
New Method ◽  
Viscous Resistance ◽  
Main Factors ◽  
The Magnetic Field

Magnetic bead droplet's non-contacted manipulation can be realized in Electromagnetic MEMS, but how to achieve magnetic beads manipulation is the major problem. A new method of multi-layered flat coils coupled with permanent magnet was proposed. Firstly, the theory of magnetic bead manipulation was analyzed and the main factors affected the magnetic beads manipulation was identified; then the magnetic field of multi-layered flat coils and Stokes viscous resistance of magnetic beads were analyzed and simulated quantificationally; finally the magnetic bead capture area was got under different flow velocity. Consequently the feasibility and correctness of this method was verified.

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