<p>Separating particles with large fluxes, high precision, and small equipment footprints remains an important industrial separations challenge.&nbsp; Microfluidic bump arrays, also called microfluidic deterministic lateral displacement devices have been used to separate a wide variety of biological and non-biological particles ranging from polystyrene and polymethylmethacrylate spheres to biconcave red blood cells, rod-shaped bacteria, decidedly non-spherical parasites, coiled up chromosomes, and cancer cells.&nbsp; Nearly all separations using the bump arrays reported in a vast literature have been performed at very small Reynolds numbers under laminar flow conditions based on the conventional wisdom that laminar flow conditions are essential for separation.&nbsp; The key to particle separation in these arrays is the interaction between the pin array and the fluid.&nbsp; Stagnation streamlines create flow channels.&nbsp; Particles small enough to remain within the flow channels (i.e., smaller than a cutoff diameter) as the particles approach pins simply pass from entrance to exit.&nbsp; Particles too large to remain within a flow channel as they approach pins (i.e., larger than the cutoff diameter) “bump” (often without direct pin contact) into a neighboring channel.&nbsp; With enough pins and “bumps” larger particles may be directed toward one side of the flow where they may be collected separately.&nbsp; Low flowrates may suffice for microfluidic medical applications where smaller blood volumes are preferential, for example.&nbsp; Yet, many if not most full-scale industrial applications require much larger flowrates (e.g., tens to thousands of gallons per minute), because low flowrates lead to untenably large equipment.&nbsp;</p><p>In this paper, we evaluate the hypothesis that bump arrays can be used to separate particles from turbulent flows entering the array.&nbsp; Microfluidic bump arrays are known for separating particles by size from laminar inlet flows.&nbsp; However, turbulent inlet flows have not been explored but become important as microfluidic bump arrays are scaled up to microfluidic bump arrays.&nbsp; We find experimentally that particle separation is indeed effective at higher Reynolds numbers.&nbsp; These experimental findings portend industrial scale particle separation due to the higher flow rates they facilitate.</p>

Can Bump Arrays Separate Particles From Turbulent Flows?

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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