Extracellular flow patterns of Red Blood Cells in microchannels under time-dependent shear rates*

Red Blood Cell (RBC) is highly flexible with convoluted morphological deformations. These characteristics can be used to provide valuable insights into their membranes' mechanical properties and facilitate the identification of pathological changes. This study explores the dynamics of RBC, which is subjected to oscillatory flows in microchannels. To achieve this, we employed numerical simulations with a hybrid continuum-particle approach. The Dissipative Particle Dynamics (DPD) method is used to model the cell membrane and cytosol fluid. The Immersed Boundary Method (IBM) is employed to represent the interaction between the membrane surface and the blood plasma (an incompressible fluid). Our results demonstrate the controllability of the morphological modes of the RBC membrane by the transient shear rates. In particular, adjusting the oscillatory flow waveform at the channel inlet can control the transient dynamics of the RBC and induce the axial and lateral migration of the cell. Our findings suggest that flow oscillation can serve as a viable method for cell manipulation, potentially offering significant implications for cell separation and sorting.