Mixing Performance In Microchannels Research Articles

Facile microfabrication of three dimensional-patterned micromixers using additive manufacturing technology

This study investigates the manufacturing method of oblique patterns in microchannels and the effect of these patterns on mixing performance in microchannels. To fabricate three-dimensional (3D) and oblique patterns in microchannels, 3D printing and replica methods were utilized to mold patterns and microchannels, respectively. The angle and size of the patterns were controlled by the printing angle and resolution, respectively. The mixing efficiency was experimentally characterized, and the mixing principle was analyzed using computational fluid dynamics simulation. The analysis showed that the mixing channel cast from the mold printed with a printing angle of 30° and resolution of 300 μm exhibited the best mixing efficiency with a segregation index of approximately 0.05 at a Reynolds number of 5.4. This was because, as the patterns inside the microchannel were more oblique, “split” and “recombine” behaviors between two fluids were enhanced owing to the geometrical effect. This study supports the use of the 3D printing method to create unique patterns inside microchannels and improve the mixing performance of two laminar flows for various applications such as point-of-care diagnostics, lab-on-a-chip, and chemical synthesis.

3D micromixers based on Koch fractal principle

In this paper, we mainly study the effect of the Koch fractal microchannel on the mixing efficiency. Using the Koch fractal principle can effectively change the geometric shape of the microchannel, and increase the convective contact area of the microfluid, enhance chaotic convection. Changing the geometric shape of the microchannel is an effective way to improve the mixing efficiency of the micromixer. So, it is of great significance to study the influence of fractal principle on the mixing performance of microchannel. This paper introduces the design process of the fractal microchannel. The effects of different microchannel heights and different Reynolds (Res) on the mixing efficiency are studied, we also compared the mixing efficiency of the Primary fractal and secondary fractal with different Res. When the microchannel height is 0.5 mm, the mixing efficiency exceeds 90%. In the main section of the Koch fractal channel, the vortex region produced by the fractal microchannel is an important factor to improve the mixing efficiency of the micromixer. As its excellent mixing performance, the micromixers based on the fractal principle will have great potential in chemical engineering and bioengineering.

A Numerical Study on Liquid Mixing in Multichannel Micromixers

Single microchannels and their arrangements for liquid mixing are investigated numerically. A smaller lateral inlet diameter and the zigzag form of the channels are found to be beneficial for the mixing performance in microchannels. Under proper operational conditions, the mixing process can be almost completed. Furthermore, some constructal distributor designs for the arrangement of microchannels are proposed and analyzed with regard to the fluid distribution. For the optimized distributor, the standard deviation from perfectly even distribution does not exceed 4% while keeping the pressure drop low. Two multichannel micromixer designs are suggested, with accordingly optimized microchannels and distributors, and their mixing performance is very close to that of a single microchannel. The specific energy dissipation in the multichannel micromixer is in the range of 0.016–93 W/kg, which is similar to batch reactors. Finally, the design procedure for multichannel micromixers is proposed.

Crosswise ridge micromixers with split and recombination helical flows

This study presents a novel crosswise ridge micromixer (CRM) with a series of microstructures placed on the top and bottom floors of channels. Passive micromixers fabricated by Micro Electro-Mechanical Systems (MEMS) technologies with slanted ridges are investigated. Numerical simulations and experimental investigations are undertaken to determine the effects of various microstructure patterns on mixing efficiency with Reynolds numbers ( Re) of 0.05–50. The confocal images at the cross-sections along the channel with ridges on both the channel top and bottom are first investigated in our study. A significant amount of split and recombination (SAR) helical flows is produced by the slanted ridges embedded on the two floors of the channels. The effects of non-dimensional parameters, such as the Re, as well as geometrical parameters on mixing performance are presented in terms of the mixing index. When the Re exceeds 1, the mixing index of the micromixer with slanted ridges increases as the Re increases further. Simulation results are presented and compared with experimental data. The trends of the experimental results and numerical data are very similar. Finally, various numbers of slanted ridges in the same orientation in one channel cycle are investigated to determine mixing performance in microchannels. The mixing performance achieves an optimum value in case where the number of ridges per cycle is equal to 8.