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Particle Migration and Focusing in Inertial Microfluidic Flows

Abstract

The behavior of confined particles in microchannels at moderate Reynolds number has received much attention in recent years and has developed into a new area of research named “inertial microfluidics". This interest has been motivated by the development of high-throughput tools for the manipulation of bioparticles as a precursor for bio-analytic assays. However, a crucial first step towards developing these tools is understanding how particles are transported and localized in confined channels. Here I discuss how the interplay between axial and lateral flow in both a porous and curved microchannel results in non-trivial lateral migration and focusing of finite sized particles. To understand this behavior, I numerically explore this interplay by computing the lateral forces on a neutrally buoyant spherical particle that is subject to both inertial and secondary forces over a range of experimentally relevant particle sizes and channel Reynolds numbers. Interestingly, the lateral forces on the particles in both cases are well represented across a wide range of flow configurations using a simple perturbation based model. The representation of forces in this manner significantly reduces the complexity and time required to predict the migration of inertial particles in microfluidic channels. Finally, I experimentally validate this model and demonstrate how these moderate Reynolds number flows can be used to selectively enrich rare cells in a heterogeneous suspension.

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