(142h) Asymmetric Trap Array for Particle Transport

Flexible spatial control of particles is important for many particle-based systems.  Active manipulation techniques can be used to achieve particle placement, separation, and sorting by introducing external force fields.  The operational requirements of such systems including external power and the need for specifically designed particles (e.g., magnetically susceptible) limit their usefulness. As an alternative, passive manipulation techniques such as deterministic lateral displacement and inertial microfluidics can solve these problems although their use has been limited to predominantly particle separation in continuous flow. Widening the functionality of passive particle manipulations can be helpful for achieving both simplicity and versatility in fluidic operations.

In this presentation, we describe a group of passive fluidic elements, termed an asymmetric trap array, for particle manipulation based on obstacle/particle steric interactions. The asymmetric behavior of the array — capturing particles during forward flow and not capturing particles during reverse flow — was achieved by carefully designing the physical dimensions of the array. The conditions of the asymmetric behavior were theoretically formulated based on the continuity equation. Five different regimes ⎯ symmetric passage, asymmetric passage, symmetric capturing, asymmetric capturing, and channel clogging ⎯ of trap/particle interaction were predicted via streamline analysis utilizing FEM simulation, and these regimes were experimentally validated for micro-sized particle (10-30μm) at low Reynolds number flow (Re<0.1). This asymmetric trap array can be used for variety of applications including cell capture, particle separation, and size-based multiplexed operation.