Influence of groove location in pillar geometries on particle separation in deterministic lateral displacement arrays

Deterministic lateral displacement (DLD) microfluidic devices enable size-based particle separation through flow partitioning in periodic pillar arrays. Introducing asymmetric features such as grooves in pillar geometries offers a potential route to tune separation performance, yet the hydrodynamic mechanisms associated with groove placement remain insufficiently understood. In this study, dissipative particle dynamics simulations were performed to investigate particle separation in DLD arrays with grooved pillars. Four pillar geometries were examined by varying the groove location relative to the streamwise and row-shift directions. The results show that introducing grooves generally increases the critical separation diameter compared with the square pillar geometry and that the separation behavior depends strongly on the groove location relative to the row-shift direction. Flow-field analysis further indicates that the classical estimate of the first flow lane width based on the one-dimensional velocity profile across the lateral gap cannot fully describe separation behavior in asymmetric geometries. Instead, two distinct hydrodynamic mechanisms are identified depending on groove location: transverse-flow deflection associated with L-type geometries and stall-line reshaping associated with Γ-type geometries. These findings clarify the hydrodynamic origin of groove-dependent separation and provide physical insight into how groove placement may be used to tune separation behavior in DLD arrays with grooved pillars.