Numerical Study of Multivortex Regulation in Curved Microchannels with Ultra-Low-Aspect-Ratio

Abstract

The field of inertial microfluidics has been significantly advanced in terms of application to fluid manipulation for biological analysis, materials synthesis, and chemical process control. Because of their superior benefits such as high-throughput, simplicity, and accurate manipulation, inertial microfluidics designs incorporating channel geometries generating Dean vortexes and helical vortexes have been studied extensively. However, existing technologies have not been studied by designing low-aspect-ratio microchannels to produce multi-vortexes. In this study, an inertial microfluidic device was developed, allowing the generation and regulation of the Dean vortex and helical vortex through the introduction of micro-obstacles in a semicircular microchannel with ultra-low aspect ratio. Multi-vortex formations in the vertical and horizontal planes of four dimension-confined curved channels were analyzed at different flow rates. Moreover, the regulation mechanisms of the multi-vortex were studied systematically by altering the micro-obstacle length and channel height. Through numerical simulation, the regulation of dimensional confinement in the microchannel is verified to induce the Dean vortex and helical vortex with different magnitudes and distributions. The results provide insights into the geometry-induced secondary flow mechanism, which can inspire simple and easily built planar 2D microchannel systems with low-aspect-ratio design with application in fluid manipulations for chemical engineering and bioengineering.

Multi-Vortex Regulation for Efficient Fluid and Particle Manipulation in Ultra-Low Aspect Ratio Curved Microchannels

“…The computational results demonstrated that the mixing effect appeared improved, accompanied by the increase in micro-obstacles, especially for the consequence in D3 and D4 which are superior to that in D1 and D2. As previously demonstrated, since the D4 has the lowest magnitude of helical vortex and Dean vortex [ 32 ], the maximum number of multi-vortex productions generated by dimensional confinement indeed advanced the effect of fluid mixing. Similar results can be more noticeably found by the quantitative comparison of coefficient of variation (CoV) values in four D-channels ( Figure 2 B).…”

“…Our group has systematically investigated the regulation mechanism of the Dean vortex and helical vortex in the ultra-low AR-curved microchannels [ 30 , 31 , 32 ]. The Dean vortex could be elevated through the decline of channel height in semicircular channels.…”

“…Accordingly, the present study developed a simple single-layer microchannel by introducing a sequence of order micro-obstacles for simultaneously producing a helical vortex and Dean vortex to achieve the manipulation of fluid and particles with high efficiency [ 30 , 31 , 32 ]. The unique semicircular channel design with ultra-low aspect ratio (AR = 1:9) mitigated the challenge of production-technology and fabricating-cost increase by employing standard soft lithography and stereolithography technology.…”

Editorial for the Special Issue on Inertial Microfluidics

“…About half of the articles in this Special Issue present theoretical and experimental investigations on the fundamentals of inertial microfluidics [ 1 , 2 , 3 , 4 ]. Gao et al [ 1 ] report a comprehensive study on inertial focusing and ordering in a square channel.…”

“…Variation of Reynolds number, Re, from 5 to 280 in a square channel smaller than 100 µm reveals an optimal Re for focusing, and the inertial ordering is found from corner focusing positions. Shen et al [ 2 ] report the result of numerical simulations on low-aspect-ratio semicircular channels with obstacles, which results in the formation of vortices. They show that the magnitude and distributions of Dean vortices and helical vortices can be regulated by the number of obstacles and flow rate, which can help us to understand geometry-induced secondary flow formation mechanism, thereby leading to useful applications for manipulation of microfluidic flows.…”