Flow physics of micro particles suspended in viscoelastic fluid in a microchannel

Abstract

This thesis presents a detailed numerical investigation into the behavior of microparticles in viscoelastic fluid environments within microfluidic channels of varying geometries. The study aims to understand how channel design and fluid properties influence particle migration, focusing particularly on passive manipulation strategies driven by elastic lift forces. Using COMSOL Multiphysics 6.0, a simulation model was first developed and validated by replicating results from a previously published, experimentally verified study. The replicated outcomes closely matched the reported experimental trends, establishing the reliability of the simulation framework. Following this validation, the channel geometry was systematically altered to explore the effects of various symmetric and asymmetric well configurations—such as rectangular, triangular, and curved cavities—on particle deviation and focusing efficiency. Simulations were conducted across a range of flow rates (20–40 μL/min) and PEO (polyethylene oxide) concentrations (500 ppm and 1000 ppm), with fixed particle size (4.8 μm) to mimic red blood cells. Results showed that increasing polymer concentration enhanced viscoelastic lift forces, leading to more pronounced lateral particle migration. Moreover, complex geometries, particularly those with sharp transitions like double-sided triangular wells, produced stronger elastic focusing effects compared to simpler or smoother designs.