Design and characterization of high-throughput deterministic lateral displacement (DLD) devices

Brian Michael Dincau

The advancement of biosensors is dependent on the simultaneous advancement of biosample preparation techniques. Well-developed techniques such as centrifugation and filtration are excellent methods for bulk sample processing, but require significant equipment and resources, and are not suited for rapid processing of individual samples. Microfluidic techniques have risen in popularity over the last decade, due to their reduced resource requirements and faster process times. These techniques utilize a variety of different kinetic principles such as diffusion, electromagnetism, and viscous or inertial flow forces, in order to separate or concentrate a species in a biosample. Deterministic lateral displacement (DLD) is a microfluidic separation technique that uses an array of pillars to separate particles based on their size. Particles larger than the critical diameter (Dc) are displaced laterally, while particles smaller than Dc undergo no net displacement through the pillar array. DLD has received significant attention since its first demonstration in 2004, but most of this focus has been on pillar shape, operational efficiency, and reducing the operational scale. While each of these factors will be essential in the commercialization and implementation of DLD, the topic of throughput has not been well-developed. Most previous DLD devices report flow rates in the µL/min range, which may not be sufficient to meet the demand for rapid process times. As this flow rate increases, so does the average fluid velocity, and consequently the Reynolds number (Re). With this climb in Re, streamlines evolve and microvortices emerge in the wake of the pillars, which can dramatically alter device functionality. This thesis investigation lays the groundwork for high throughput high-Re DLD performance, which was done using several DLD devices in order to better understand the high-Re effects. These devices include two traditional DLD devices with circular pillars, a near-nano DLD for investigating non-spherical particle (E. coli) trajectories, and a set of devices with airfoil-shaped pillars to control microvortex emergence. The most notable finding is that the effective Dc for any given DLD will decrease with a rising Re, and this effect must be accounted for in high throughput DLD design.

Design and characterization of high-throughput deterministic lateral displacement (DLD) devices

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