The ability to control the flow of fluids is crucial in biological analysis, chemical synthesis, and medical diagnostics. Microfluidic technology has achieved promising progress in fluid manipulation due to the application of secondary flows. However, no matter if it is in the straight or curved channels, there is often a compromise between throughput and effectivity. To have a high-throughput system, the general choice is to enlarge the channel dimension. The fabrication procedure for high aspect ratio microchannels is challenging and expensive. However, the channels with a low aspect ratio are not very powerful in generating strong counter-rotating vortex to promote efficient fluid manipulation.
Recently, some researchers have introduced novel curved channels with a trapezoidal cross-section that generates stronger Dean vortices in order to enhance the performance of the low aspect ratio microchannels in fluidic applications. However, such systems suffer from the complicated fabrication process.
Jinyi Wang and colleagues (from Shanxi Agricultural University and Northwest A&F University, China) demonstrated a novel microfluidic strategy to regulate the secondary flow by geometric confinement in ultra-low aspect ratio microchannels, in their paper published in Advanced Theory and Simulations. By using a series of micro-obstacles in semicircular microchannels, the acceleration of Dean-like secondary flow and helical vortices can be applied to achieve fluid manipulation in an efficient manner. The ultra-low aspect ratio microchannel results in an easy-to-fabricate system, a high and broad flow capacity (2–20 mL min−1), and efficient operation in a smaller channel path (only using a semicircular microchannel).
This work offers an insight into the phenomenon of development of ultra-low aspect ratio microfluidic channels and improves the understanding of the concept of secondary flow control in curved devices. Additionally, this study paves the way to understand the reason behind the need for a high (and wide range of) flow rates for fluidic applications. The strategy to engineer secondary flow used in this work should be further improved to address the need for an easy-to-use, efficient, flexible microfluidic device for fluid manipulations.
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Kindly contributed by the Authors.