Lateral migration of particles suspended in viscoelastic fluids in a microchannel flow

In this work, we investigated the lateral migration of microparticles suspended in two different viscoelastic fluids with or without the second normal stress difference. For the viscoelastic fluid without the second normal stress difference, competing forces existed between microfluidic inertia and the first normal stress difference (N₁), which resulted in a synergetic effect of particle focusing. For the fluid with the second normal stress difference (N₂), particles were greatly affected by a N₂-induced secondary flow, and the competition among the inertia, N₁, and N₂ determined the lateral migration trajectories of the particles. The obtained results were delineated with the blockage ratio, which showed good agreement with the results of a recent numerical study (Villone et al. in J Non Newton Fluid Mech 195:1–8, 2013). The present study also examined the possibility of particle separation in a size-dependent manner using the N₂-induced secondary flow in microchannel flow.