Continuous elasto-inertial separation of microparticles using a co-flowing Newtonian-viscoelastic fluid system

A new method for continuous separation of microparticles in viscoelastic fluid is reported. A series of sharp corners were fabricated at one side of a microchannel, which induced the curved streamline and the asymmetric distribution of the elastic force. The Newtonian sheath flow was utilized to squeeze microparticles to the side wall with sharp corners at the inlet. Particles were subjected to inertial forces, elastic force and viscous drag force, all of which pointed to the straight wall side. Stronger forces were exerted on larger particles, leading to size-dependent migration of particles across the interface between the Newtonian and the viscoelastic fluids. The influence of the flow rate ratio on the particle separation was also studied. The results show that the sharp corners and the co-flowing fluid system significantly enhanced particle lateral migration, achieving complete particle separation at a low flow rate and in a short channel length. The particle separation efficiency was further increased at a higher flow rate ratio (sheath flow/sample flow). With a simple structure and small footprint, this device has great potential to be used in a variety of particle separation processes for lab-on-a-chip applications.