Multi-train elasto-inertial particle focusing in straight microfluidic channels

Herein, we reported a multi-train focusing in viscoelastic flows where the fluid inertia effect is comparable with the elastic effect. Different from their behaviors in inertia- or elasticity-dominating flows, particles in the current elasto-inertial flow were found to equilibrate at two symmetrical positions in the vertical center plane under the balance of the shear-induced inertial lift force and the elastic force. With further increasing flow rate, a third focusing position was observed at the channel center due to the fast-increasing elastic force. Based on these findings, we experimentally explored the particle focusing behaviors over various influential factors to better understand the underlying mechanics. The sheathless and high-throughput focusing of particles into multiplex deterministic trains at the same plane provides a potential method for image-based particle/cell detection.