Numerical analysis of separation of blood cells by microchip using Dielectrophoresis (DEP) technique

This study numerically investigates a dielectrophoresis (DEP)-based microfluidic chip for separating red blood cells (RBCs) and platelets (PLTs) based on differences in size and dielectric properties. COMSOL Multiphysics was used to analyze electric field distributions and particle trajectories for different electrode designs. The numerical method was verified by modeling a square-electrode device and comparing its predictions with published numerical results. At 5 V and 100 kHz, both cell types experience negative DEP, but the larger RBCs undergo a considerably greater dielectrophoretic force and move towards Outlet 2, whereas PLTs, dominated by fluid drag, exit through Outlet 1. Two rounded-corner electrode designs (Type-1 and Type-2) are proposed. Under the same operating conditions, both achieve separation within 6--7 s, comparable to the square-electrode reference ($\approx$6.7 s), while increasing RBC/PLT recovery from 89.2/90.5\% to 98.7/99.1\% (Type-1) and 97.9/98.8\% (Type-2), and separation efficiency from 90.4\% to 99.1\% and 98.7\%, respectively. Platelet purity at Outlet 1 reached $\approx$99.8--99.9\%, and RBC purity at Outlet 2 reached $\approx$89--92\%, compared with 98.8\% and 48.4\% for the square design. These findings suggest that electrode geometry optimization can significantly improve recovery, purity and separation efficiency in low-voltage DEP devices without increasing voltage. These two-dimensional numerical predictions require experimental confirmation.