Behavior of rigid and deformable particles in deterministic lateral displacement devices with different post shapes.

Deterministic lateral displacement (DLD) devices have great potential for the separation and sorting of various suspended particles based on their size, shape, deformability, and other intrinsic properties. Currently, the basic idea for the separation mechanism is that the structure and geometry of DLDs uniquely determine the flow field, which in turn defines a critical particle size and the particle lateral displacement within a device. We employ numerical simulations using coarse-grained mesoscopic methods and two-dimensional models to elucidate the dynamics of both rigid spherical particles and deformable red blood cells (RBCs) in different DLD geometries. Several shapes of pillars, including circular, diamond, square, and triangular structures, and a few particle sizes are considered. The simulation results show that a critical particle size can be well defined for rigid spherical particles and depends on the details of the DLD structure and the corresponding flow field within the device. However, non-isotropic and deformable particles such as RBCs exhibit much more complex dynamics within a DLD device, which cannot properly be described by a single parameter such as the critical size. The dynamics and deformation of soft particles within a DLD device become also important, indicating that not only size sorting, but additional sorting targets (e.g., shape, deformability, internal viscosity) are possible.