A three-dimensional numerical simulation study of size-based particle separation in a deterministic lateral displacement array with different inlet flow angles

This study uses a three-dimensional (3D) model of a deterministic lateral displacement microfluidic system to investigate the effect of velocity deflection angle on the separation of microparticles of different sizes. Using the numerical model, we investigated the effect of flow direction on the fluid flow pattern and particle migration angle by using the immersed boundary method and a numerical solver developed based on the open-source OpenFOAM. The immersed boundary method is used for simulations of fluid–structure interaction in OpenFOAM because of its simple meshing process, and we modify pisoFOAM, a transient solver in OpenFOAM for incompressible fluid, to solve the Navier–Stokes equations. These results from multiple cases conducted for different flow directions and different particle sizes demonstrate the efficiency of convergence and separation of microparticles of different sizes in deterministic lateral displacement arrays of the same size with different flow directions. The detailed numerical model results clarify the trajectories of particles in different 3D cases, demonstrating improved agreement compared to the two-dimensional simulation model. The transition from locked to zigzag mode occurs when the direction of the driving force reaches a critical angle with respect to the particle size, which allows us to classify particles of different sizes. In addition, I also compared the results obtained with previous experimental and theoretical studies to ensure the correctness of the research method solver.