Effects of sample rheology on the equilibrium position of particles and cells within a spiral microfluidic channel

Elasto-inertial migration in non-Newtonian fluids is a rapidly growing field with tremendous potentials for manipulating micron to submicron particles. Previous research attempts were mainly carried out in straight channels due to the complexity of particle migration, solution tuning, and data analysis in elasto-inertial microfluidics. Consequently, the combined effects of Dean drag force and solution rheology on coupled Dean drag elasto-inertial focusing phenomena have not been carefully analyzed. This study delved thoroughly into the combined effects of solution rheology and Dean drag force on elasto-inertial focusing of particles and cells within a spiral microchannel. Polyethylene oxide (PEO) of 1MDa, 2MDa, and 4MDa molecular weights were used to prepare 250, 500, and 1000 ppm non-Newtonian solutions to investigate the focusing behavior of particles and cells over a wide range of flow rates and solution rheologies. Dean coupled elasto-inertial effects were systematically investigated to demonstrate its potentials for position-adjustable and size-tunable particle and cell focusing phenomenon. Various cells and microbeads with diameters ranging from 1 to 17 μm were employed to carefully study the equilibrium position, focusing band, and migration behavior under different elastic, inertial, and Dean conditions. Following the focusing, cell viability, morphology, and growth rate were evaluated which showed cells remained undamaged from viscosity, shear rate, and chemical properties of PEO solutions. We are of the opinion that the current study can provide scientists with a better understanding of focusing phenomena in viscoelastic fluids within spiral microfluidic channels.