Abstract
Deterministic lateral displacement (DLD) is a passive particle separation method based on microfluidic technology, with its separation mechanism primarily relying on particle size differences. Therefore, the critical separation size is of great significance in the design of DLD devices. The geometric asymmetry of the pillar array design significantly influences fluid behavior and critical particle size variations. This study first analyzed particle motion characteristics through particle trajectory observation experiments within asymmetric microfluidic chips. Subsequently, a two-dimensional numerical simulation method was employed to investigate the effects of three different ratios of lateral gap size to downstream gap size (G(x):G(y)) on particle trajectories and flow field distribution. The results indicate that as G(x):G(y) decreases, the upward flow rate gradually reduces, accompanied by changes in the flow field velocity distribution, causing particles to favor displacement mode. This study provides new theoretical foundations for the precise regulation of particle motion behavior and introduces novel insights for optimizing DLD device design.