Study on the shape and deformability of red blood cells on the critical diameter of deterministic lateral displacement for cell sorting

Deterministic lateral displacement (DLD) is a size-based microfluidic technology that allows for the continuous separation of suspended particles. Nevertheless, the shape and deformability affect the critical diameter, especially in terms of bio-samples. In this study, the influence of the shape and deformability of red blood cells (RBCs) on the critical diameter was investigated in DLD devices, leading to the design of microfluidic chips with multiple critical diameters to separate the blood samples. A biconcave disk-shaped RBC model was constructed in the simulation of the sorting process, and the Neo-Hookean model was applied to describe the deformability. According to the simulation results, polystyrene particles, spherocytes, and normal RBCs were employed, and the effectiveness of the design was confirmed by the experiments. Results indicated that increased deformability corresponded to an increase in critical diameter. Because of the increased rigidity of the membrane structure, spherocytes flowed out of the desired outlet in a typical zig-zag pattern with a sorting purity of 92.97%, while the removal rate of the healthy RBCs was 95.58%, which achieves the separation of healthy RBCs and spherocytes in the whole blood samples.