Lateral migration of deformable particles in microfluidic channel flow of Newtonian and viscoelastic media: a computational study

The dynamics of an initially spherical elastic particle in pressure-driven flow of Newtonian and viscoelastic fluids in a square-cross-section microfluidic channel is studied in 3D by the finite element method. Two viscoelastic constitutive equations are considered, i.e., the Oldroyd-B and Giesekus models. The dependence of particle deformation and cross-stream migration on geometric confinement, particle deformability, and fluid rheology is investigated. If its initial position is not on the center line of the channel, the bead attains an asymmetric shape and migrates transversally to the stream direction. In an inertialess Newtonian liquid, the migration is always directed towards the channel center line and its velocity depends on geometric confinement and particle deformability, whereas, in a viscoelastic liquid, the migration direction and velocity depend on the complex interplay among geometric confinement, particle deformability, fluid elasticity, shear-thinning, and secondary flows.