Numerical simulation of elasto-inertial focusing of particles in straight microchannels

Abstract Viscoelastic microfluidics has become a new trend for particle/cell manipulation in recent years. The coupling of fluid viscoelasticity and inertia has been proved to be effective for achieving particle elasto-inertial focusing at the channel centerline experimentally, which is important for downstream particle counting and detection. However, the mechanism of particle elasto-inertial focusing in viscoelastic flow is still unclear. This paper systematically explores particle elasto-inertial focusing in straight microchannels through using numerical simulation. The performance of particle focusing is studied under various control parameters. Numerical simulation is conducted under different Reynolds numbers Re, Weissenberg numbers Wi and particle diameters d to elucidate the force competition mechanisms. The results show that the increase of flow intensity and particle diameter d can speed up the focusing migration. Elasticity of the flow quantified by Wi can attenuate the particle rotation and thus weaken the lateral particle focusing towards the channel centerline. The separatrix for particle focusing towards the channel centerline or the channel walls is observed in the simulation. The results provide new insight into understanding particle elasto-inertial focusing in viscoelastic flows, and can be useful for guiding the design of viscoelastic microfluidics.