Numerical investigation of submicron particle migration in Giesekus viscoelastic flows through rectangular microchannels

Viscoelastic microfluidics has emerged as an effective approach for controlling and separating submicron particles; however, the effects of particle blockage ratio, inertia, fluid elasticity, viscosity and shear-thinning behavior on submicron particle migration have not yet been understood. In this study, the migration of particles with different blockage ratios (0.008–0.15) in a shear-thinning viscoelastic fluid (Giesekus model) flowing through a rectangular microchannel with an aspect ratio of 2 is investigated numerically using direct numerical simulations (DNS). The dimensionless lift force and its inertial and elastic components are analyzed along the main vertical and horizontal axes of the channel cross-section. Particles with blockage ratios less than or equal to 0.04 are found to exhibit similar migration behavior, reaching a seven unstable focusing positions in the cross‑section. Focusing on particles with a blockage ratio of 0.04, the particle focusing position along the main vertical axis of the channel did not stabilize for the examined ranges of the Reynolds number (0.097–1), Weissenberg number (3.63–26), mobility factor (0.1–0.3), and solvent-to-solution viscosity ratio (0.3–0.5). The absence of a stable focusing position within the operating conditions examined indicates that a Giesekus fluid is not suitable for separating submicron particles. These results provide physical insight into submicron particle migration in shear thinning viscoelastic microfluidic devices and practical guidance for achieving efficient separation of submicron particles in biomedical and industrial applications.