Direct Numerical Simulation of particle migration in microfluidic channels

The separation and sorting of living cells play an important role for medical, biological and industrial applications. Current research focuses on the inertial migration mechanism for a label-free, passive and continuous separation of neutrally buoyant particles. The physical effects and different particle behaviours, however, are not completely understood. To elucidate the migration and focusing of particles in a microfluidic channel direct numerical simulations of geometrically resolved particles using the Immersed-Boundary Method are presented. The analysis in this work is structured based on the geometry of the channel. In straight channels, particle focusing is dominated by the inertial migration. In spirals the curvature introduces a new phenomenon which increases the complexity of the flow. The numerical simulation of particles in curved channels, however, still presents a challenge. To allow such simulations at a reasonable computational cost, a coordinate transformation is implemented and validated against experimental results. The simulation results provide another insight on the migration process concerning migration time, particle positioning in the cross-section, streamwise particle spacing, and the surrounding fluid flow. Focus is given to the migration of no-spherical particles.