Inertial focusing patterns and equilibrium position of particles in symmetric CEA microchannels

Inertial focusing and separation of particles in symmetric contraction expansion array (CEA) channels are widely used in biomedical field. A method to calculate the equilibrium position of particles is used to explore the equilibrium mechanism of particles in symmetric CEA microchannels. The calculation results show that there were multiple focusing positions of particles in the CEA microchannel, but affected by the secondary flow with different distribution characteristics. There were two final equilibrium positions of particles in the symmetric CEA microchannel, which were located near the middle of the long wall and the short wall of the cross section, respectively. Then, the focusing patterns of particles in the CEA microchannels with different cavity length were investigated experimentally. To achieve the separation of 10 μm and 20 μm particles in CEA microchannels, the flow condition requires Re ≈40–120 and the structural condition needs to meet the cavity length–width ratio R LW ≈2–4. The equilibrium positions from the calculation method and experimental method are compared and analyzed, which provided a certain reference for the study of the inertial migration of particles in the CEA microchannel.