Department of Chemical Engineering, University of Michigan at Ann Arbor, 3074 H. H. Dow, 2300 Hayward St, Ann Arbor, MI, 48109, USA.
Department of Biomedical Engineering, University of Michigan, 1107 Carl A. Gerstacker, 2200 Bonisteel Blvd, Ann Arbor, MI, 48109, USA.
Small. 2018 Mar;14(9). doi: 10.1002/smll.201702724. Epub 2018 Jan 29.
One challenge of integrating of passive, microparticles 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, a passive fluidic technique-one-way particle transport-that can conduct microparticle operations in a closed fluidic circuit is presented. Exploiting pass/capture interactions between microparticles 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 microparticles across trap rows in only a few fluid oscillations (<500 ms per oscillation) and separate particles by their size differences.
将被动式、微粒子操控技术整合到多功能微流控装置中面临的一个挑战是，要将大多数系统的连续流格式与粒子分离系统的批量操作相匹配。这里，提出了一种被动式流体技术——单向微粒子输运，它可以在封闭的流体回路中进行微粒子操作。利用微粒子和非对称捕获物之间的通过/捕获相互作用，该技术在振荡流场中实现了微粒子的净位移。单向微粒子输运是通过四种捕获物-微粒子相互作用来实现的：微粒子的机械捕获、捕获物与微粒子之间的非对称相互作用、微粒子与障碍物的物理碰撞以及微粒子横向进入微粒子捕获流。这四个条件的临界尺寸是通过数值求解用周期性障碍物阵列中的流场特性来制定的解析质量平衡方程来找到的。在低雷诺数(<0.01)下观察到的实验捕获物动力学证实了理论预测的有效性。该技术仅需几个流体振荡（每个振荡<500 毫秒）即可将数百个微粒子输送过捕获物行，并且可以根据尺寸差异来分离微粒子。
