One-Way Particle Transport using Oscillatory Flow in Asymmetric Traps

摘要

One challenge of integrating of passive, micro-particles manipulation techniques into multifunctional microfluidic devices is coupling the continuous-flow format of most systems with the often batch-type operation of particle separation systems. Here we present a passive fluidic technique — one-way particle transport — that can conduct micro-particle operations in a closed fluidic circuit. Exploiting pass/capture interactions between micro-particles and asymmetric traps, this technique accomplishes a net displacement of particles in an oscillatory flow field. One-way particle transport is achieved through four kinds of trap-particle interactions: mechanical capture of the particle, asymmetric interactions between the trap and the particle, physical collision of the particle with an obstacle, and lateral shift of the particle into a particle-trapping stream. The critical dimensions for those four conditions are found by numerically solving analytical mass balance equations formulated using the characteristics of the flow field in periodic obstacle arrays. Visual observation of experimental trap-particle dynamics in low Reynolds number flow (<0.01) confirms the validity of the theoretical predictions. This technique can transport hundreds of micro-particles across trap rows in only a few fluid oscillations (<500 ms per oscillation) and separate particles by their size differences.