Deterministic separation of suspended particles in a reconfigurable obstacle array

TL;DR

This study investigates size-based particle separation in a reconfigurable microfluidic system using a deterministic lateral displacement model, revealing a linear relationship between particle size and critical transition angles.

Contribution

It introduces a reconfigurable DLD model system and a simple theoretical model explaining particle migration behavior based on irreversible interactions.

Findings

Larger particles transition at higher forcing angles.

A linear correlation exists between particle size and critical angle.

The model accurately predicts the migration angle dependence.

Abstract

We use a macromodel of a flow-driven deterministic lateral displacement (DLD) microfluidic system to investigate conditions leading to size-separation of suspended particles. This model system can be easily reconfigured to establish an arbitrary orientation between the average flow field and the array of obstacles comprising the stationary phase (forcing angle). We also investigate the effect of obstacle size using two arrays with different obstacles but same surface-to-surface distance between them. In all cases, we observe the presence of a locked mode at small forcing angles, in which particles move along a principal direction in the lattice until a locked-to-zigzag transition takes place when the driving force reaches a critical angle. We show that the transition occurs at increasing angles for larger particles, thus enabling particle separation at specific forcing angles. Moreover, we observe a linear correlation between the critical angle and the size of the particles that could be used in the design of microfluidic systems with a fixed orientation of the flow field. Finally, we present a simple model, based on the presence of irreversible interactions between the suspended particles and the obstacles, which describes the observed dependence of the migration angle on the orientation of the average flow.