Vortex-free high-Reynolds deterministic lateral displacement (DLD) via airfoil pillars

Abstract

One essential step in biosample analysis is the purification, separation, or fractionation of a biofluid prior to transport to the biosensor. Deterministic lateral displacement (DLD) has demonstrated the potential for continuous size-based separation of numerous medically relevant particles and organisms, such as circulating tumor cells, red blood cells, and even viral particles. Recently, high-throughput DLD separation has been demonstrated by utilizing higher flow rates, but this also results in changing separation dynamics as the Reynolds number (Re) increases. It has been observed that the critical diameter (Dc) for a DLD device decreases as Re climbs, and theorized that both streamline compression and vortex emergence may contribute to this phenomenon. The precise mechanism for this shift has been difficult to isolate, however, due to the coupled nature of vortex emergence and streamline compression in high-Re DLD devices with circular pillars. To decouple these effects, we have characterized the performance of a DLD device with symmetric airfoil pillars that do not produce vortices up to Re = 100. In demonstrating a complete particle trajectory shift at Re = 51, we have shown that vortex effects are not a predominant contributor to this Dc shift, thus streamline evolution is likely to be the primary mechanism. Furthermore, we have compared the performance of this device to a similar device with rotated pillars having a negative 15° angle of attack, and found that separation effectiveness declines as streamlines become highly asymmetric and small particles exhibit significant variation in their trajectories.