Microfluidic blood cell separation based on the force balance between inertial lift and dean drag forces

Abstract

This thesis presents a novel separation principle for size separation of microparticles and cells with high throughput using inertial fluid field in a contraction-expansion array (CEA) microchannel. The CEA microchannel allows inertial size separation by a force balance between inertial lift and Dean drag forces in fluid regimes in which inertial fluid effects become significant. An abrupt change of the cross-sectional area of the channel curves fluid streams and produces a similar effect compared to Dean flows in a curved microchannel of constant cross-section, thereby inducing Dean drag forces acting on particles. In addition, the particles are influenced by inertial lift forces throughout the contraction regions. These two forces act in opposite directions each other throughout the CEA microchannel, and their force balancing determines whether the particles cross the channel, following Dean flows. To understand the inertial fluid behavior in the CEA microchannel, I firstly fabricated the CEA microchannel using soft lithography technique and numerically simulated the fluid patterns throughout the contraction and expansion regions. The CEA microchannel exploits centrifugal forces acting on fluids travelling along the contraction and expansion regions of the microchannel. Around an entrance of the contraction region, the centrifugal forces induce a secondary flow field where two counter-rotating vortices enable to envelop a sample flow with a buffer flow in three dimensions. Centrifugal effects at that region result in Dean vortices that continuously split and redirect fluid streams, thereby enabling appreciable mixing. From these inertial fluid behaviors, I presented 3D laminating mixer which provides a level of 90% mixing in the relatively large range of Reynolds number from 4.3 to 28.6. I next investigated particles migration depending on their sizes in the CEA microchannel. The particles migrate by force balance between inertial lift force throughout the...