Due to the low Reynolds number in microfluidic systems, mixing is often limited to slow diffusion, so we need to manipulate the microchannel geometry appropriately to improve mixing capabilities. In this work, we investigate the mixing efficiency of the following five microchannel geometries: a channel with moon-shaped obstacles, a zigzag channel, a sinusoidal SAR channel, a hexagonal SAR channel, and a channel with Tesla coils. In addition, we also investigate the influence of the number of mixing sections on the final mixing efficiency. The analysis is supported by an evaluation of the flow state in the channel, obtained using the PIV (Particle Image Velocimetry) method. The geometries of the microchannels are ranked according to their mixing efficiency at the end of the channel at a flow rate of 1000 μl/min as follows (from worst to best): sinusoidal SAR, channel with obstacles, hexagonal SAR, channel with Tesla coils, and zigzag. The velocity field and vorticity indicate the importance of shapes that promote vorticity and the separation and merging of both flows, especially at higher inlet flows. Microfluidic systems, whose essence is the efficient mixing of input raw materials, will play a key role in the synthesis of final active ingredients in the future of pharmaceuticals and biotechnology.
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