Inertial focusing and microparticle separations in triangular cross-section microchannels

Abstract

The advantages of microfluidics include reducing expense with smaller reagents, inducing faster reactions, and precisely controlling samples with small sizes. Therefore, it has been extensively studied in biological, chemical and medical systems. Characteristics of fluids can be divided into different regions of Reynolds numbers. In Stokes flow (Re<1), flowing particles simply follow the streamlines. In the intermediate Re (~1 < Re < ~100) between Stokes and turbulent regimes, particles are affected by inertial lift forces and migrate across the streamlines. Then, particles are focused into equilibrium positions (or focusing positions). This phenomenon is called inertial focusing. Using inertial focusing, the location of particles can be manipulated within the microchannel without external forces.The number and configuration of focusing positions are affected by the channel structures. In this dissertation, we fabricated various microchannels using MEMS and investigated the relation between fluidic phenomena and channel structures. First, we elucidated the basics of inertial microfluidics in Chapter 1. In chapter 2, we investigated inertial focusing in non-rectangular cross-section channels (half-circle, triangle) and suggested the method for particle manipulation using various cross-section shapes. In chapter 3, we explained the change of focusing positions in triangular channel depending on particle size and Re, and presented the channels for size-based separation. In chapter 4, we observed the tendency of inertial focusing in accordance with particle size, Re and angles. In chapter 5, we presented the 3D curved triangular channels consisted with thin PDMS film with high flexibility. Then, we investigated the alteration of stable focusing positions by Dean flow formation and validated that curved triangular channel can be applied to both sheath-less flow cytometry and rare cell separation. In chapter 6, we suggested the novelty of research and future prospective of inertial microfluidics.