Microfluidic Particle Operations Based on One-Way Particle Transport in Asymmetric Traps

Utilizing micro-particles can significantly reduce the cost and time for life science and medical diagnosis with advantages including multiplexing capability, easy separation, and flexible surface modification. While research-based commercial platforms are successfully capitalizing on these benefits, portable point-of-care microdevices have showed limited processing ability of micro-particles. One possible difficulty of incorporating micro-particles into portable devices is the external devices necessary to accurately control particle positioning and transport. The development of simple, passive manipulation techniques could expand the use of particle-based devices.

In this presentation, we report on flexible, efficient particle operations. The one-way particle transport is based on hydrodynamic and steric interactions between micro-particles and an array of physical obstacles in an asymmetric trap. This technique uses asymmetric transport of particles in oscillatory flow, deterministically displacing hundreds of micro-particles across tens of array rows in a few fluid oscillations (oscillation frequency > 2 s^-1) at low Reynolds number (Re < 0.1). We found comprehensive theoretical relationships between array dimension and the trap-particle interaction dynamics by using simple mass balance equations and Finite Element Methods. Experimental validation using polystyrene microbeads (diameter = 20.3 µm) confirmed that actual asymmetric trap-particle interaction dynamics compared favorably with our theoretical predictions. The one-way particle transport could successfully isolate target particles from non-target particles. Other flexible, efficient particle operations such as particle distribution and concentration using one-way particle transport will also be presented.