Laboratory for Micro Systems, Department of Mechanical and Aerospace Engineering, Monash University, Clayton, Victoria 3800, Australia.
Lab Chip. 2016 Sep 21;16(18):3515-23. doi: 10.1039/c6lc00590j. Epub 2016 Jul 26.
Surface acoustic wave (SAW) based particle manipulation is contactless, versatile, non-invasive and biocompatible making it useful for biological studies and diagnostic technologies. In this work, we present a sensitive particle sorting system, termed the virtual membrane, in which a periodic acoustic field with a wavelength on the order of particle dimensions permits size-selective filtration. Polystyrene particles that are larger than approximately 0.3 times the acoustic half-wavelength experience a force repelling them from the acoustic field. If the particle size is such that, at a given acoustic power and flow velocity, this repulsive force is dominant over the drag force, these particles will be prohibited from progressing further downstream (i.e. filtered), while smaller particles will be able to pass through the force field along the pressure nodes (akin to a filter's pores). Using this mechanism, we demonstrate high size selectivity using a standing SAW generated by opposing sets of focused interdigital transducers (FIDTs). The use of FIDTs permits the generation of a highly localized standing wave field, here used for filtration in μl min(-1) order flow rates at 10s of mW of applied power. Specifically, we demonstrate the filtration of 8 μm particles from 5 μm particles and 10.36 μm particles from 7.0 μm and 5.0 μm particles, using high frequency SAW at 258 MHz, 192.5 MHz, and 129.5 MHz, respectively.
基于表面声波（SAW）的粒子操控具有非接触、多功能、非侵入性和生物兼容性，使其成为生物研究和诊断技术的有用工具。在这项工作中，我们提出了一种灵敏的粒子分选系统，称为虚拟膜，其中具有与粒子尺寸相当的波长的周期性声场允许进行尺寸选择性过滤。尺寸大于大约 0.3 倍声半波长的聚苯乙烯粒子会受到排斥力，使其远离声场。如果粒子尺寸使得在给定的声功率和流速下，这种排斥力超过阻力，那么这些粒子将被禁止进一步向下游移动（即被过滤掉），而较小的粒子将能够沿着压力节点通过力场（类似于过滤器的孔）。我们使用这种机制，通过使用 opposing sets of focused interdigital transducers (FIDTs) 产生的驻波来展示高尺寸选择性。FIDTs 的使用允许产生高度局部化的驻波场，在这里用于在 10s 的 mW 量级的施加功率下以 μl min(-1)的流速进行过滤。具体来说，我们使用 258 MHz、192.5 MHz 和 129.5 MHz 的高频 SAW 分别过滤 8 μm 粒子和 5 μm 粒子、10.36 μm 粒子和 7.0 μm 粒子、5.0 μm 粒子。
