Three-Dimensional Modeling of Circulating Cell Separation in a Y-Junction Microchannel

The migration of living cells plays an important role in immune response, cancer progression, and microfluidic technologies for cell separation and flow cytometry that often involve bifurcating (e.g., Y-or T-shaped junction) microchannels. Vessel bifurcations are among the frequent sites affected by atherosclerosis and are the focal points of drug carrier particle adhesion in vivo. Using VECAM, our custom three-dimensional computational algorithm for multiphase viscoelastic flow and mass transport, this study focuses upon the investigation of the effects of cell viscoelasticity and hydrodynamic interaction on separation of circulating cells in Y-shaped microchannels with angle ranging from 30° to 150°. In VECAM, the cell is modeled as a one-phase viscoelastic fluid material composed of a cytosol and a polymer (cytoskeletal) matrix. The cell viscoelasticity is described by the Giesekus constitutive equation. The cell-fluid interface is tracked by the volume-of-fluid (VOF) method, with the interfacial (cortical) tension force calculated by the continuous surface force (CSF) method. In the simulation, we consider single or two cells of initially spherical shape with the same or varying diameter. The separation of the cells has been investigated for different initial locations of the cells with respect to one another. The results of this study provide the critical conditions for cell separation including the critical values of cell diameter, elasticity, surface tension and initial cell-to-cell separation distances for a range of bifurcation angles. These critical conditions are important for the development of microfluidic devices to be optimized for separation and sorting of circulating cells and for understanding how circulating cells are separated in bifurcating microvessels.