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.