Analysis And Simulation Of RBCs Flow Morphology In DLD Device

DLD is a technology that achieves efficient and continuous separation of particles based on their size.It has the advantages of less analysis reagents,short detection cycle,and high accurateness,providing the possibility for microfluidic chip diagnosis to replace the traditional blood detection.Due to RBCs move in the microchannel with complex dynamic behavior,which is subject to many restrictions in RBCs sorting and application.The DLD technology only implements in rigid spherical particles.However,the deformation and sorting of biological cells have extremely high research value for the analysis of human circulation processes,the treatment of blood diseases,and the application of medical devices.This requires researchers to conduct detailed research and accurate model on the deformability of biological cells.And then,make comprehensive analysis on the movement and deformation of the RBCs during the sorting process.This paper sets up RBCs two-dimensional simulation model,and simulates rigid RBCs and soft RBCs flow morphology in the DLD with triangular micropillar array based on the fluid-structure interaction method,providing reference for sorting biological cells.The research mainly includes the following parts.First,regarding biological RBCs as rigid RBCs with small deformation and soft RBCs with multiphase flow.Then,establish linear elastic model for RBCs and Non-Newtonian elastic model for soft RBCs.The simulation results consistent with the theory are obtained through numerical calculation.Second,designing DLD with Sx=10?m?Sy=8?m for rigid RBCs and Sx=6?m?Sy=6?m for soft RBCs.After that,changing the column travel distance,RBCs initial movement position,initial fluid velocity,fluid density and cell viscosity,to analyze the factors that affect RBCs flow morphology.At last,the movement rules of biological cells in the DLD device are summarized as follows.The RBCs initial velocity is close to initial fluid velocity,about 120-140?m/s.The RBCs velocity reaches the maximum when passing through the center of the column gap,and shows a downward trend at the exit,eventually reaching zero.The stress on the RBC increases with its moving speed decreases.Besides,it reaches maximum when the cell occurs shape rolls or displacement under the flow field force.The arrangement of the triangular micropillar array in DLD will affect the RBCs motion traj ectory.When ???2.5?m,the RBCs move in a "displacement" mode;when ???3 ?m,the RBC moves in a "zigzag" mode.But as ?? is fixed,the RBCs have completely different traj ectories when their initial movement position is different.When the fluid density and initial velocity increase,the RBCs will suffer more shear force and large deformation.While the cell viscosity increases,the RBC deformability decreases.As?=0.2Pa·s,the soft RBCs deformation is extremely small,and its shape is almost maintained.Observing the flow morphology of the soft RBCs in the triangular column array,it is found that the cells have "disappeared pits","cell body folding",and a stretched "long strip".Besides,the movement of cells in the microchannel is the same as in the shear flow.When RBCs collide with the triangular column,it will produce large deformations,or has displacement deflection,which shows it is expected that the DLD device with sharp-edged microcolumns can be used to improve the sorting effect by changing the degree of cell deformation.