Particle separation based on poly (ethylene oxide) concentration gradient in a microchannel with rhombic cross-section

Much attention has been focused on viscoelastic microfluidics which can be widely used for the focusing and separation of particles/cells in continuous flows without any external force or energy. In this study, we demonstrate that microparticles can be separated by the elasto-inertial focusing and the concentration gradient of viscoelastic fluid in a microchannel with a rhombic cross-sectional shape. We have already presented a simple and robust fabrication method for microchannel with the rhombic cross-section, which was used for particle focusing in viscoelastic polyethylene oxide (PEO) solution. Using the fabricated microfluidic device, we observed the behavior of particles by size in viscoelastic fluids with various concentration gradients and presented their focusing and separation. Separation experiments were performed on 12, 5.0, and 2.1 µm particles, and the optimal separation conditions were sought according to flow rate, sample-to-sheath flow rate ratio, and PEO concentration gradient.