Department of Biomedical Engineering, Duke University , Durham, North Carolina 27708, USA.
Center for Biomedical Engineering and Department of Chemical and Biological Engineering, University of New Mexico , Albuquerque, New Mexico 87131, USA.
Biomicrofluidics. 2015 Jan 20;9(1):014105. doi: 10.1063/1.4905875. eCollection 2015 Jan.
We report a modeling and experimental study of techniques to acoustically focus particles flowing through a microfluidic channel. Our theoretical model differs from prior works in that we solve an approximate 2-D wave transmission model that accounts for wave propagation in both the solid and fluid phases. Our simulations indicate that particles can be effectively focused at driving frequencies as high as 10% off of the resonant condition. This conclusion is supported by experiments on the acoustic focusing of particles in nearly square microchannels, which are studied for different flow rates, driving frequencies and placements of the lead zirconate titanate transducer, either underneath the microchannel or underneath a parallel trough. The relative acoustic potential energy and the resultant velocity fields for particles with positive acoustic contrast coefficients are estimated in the 2-D limit. Confocal microscopy was used to observe the spatial distribution of the flowing microparticles in three dimensions. Through these studies, we show that a single driving frequency from a single piezoelectric actuator can induce the 2-D concentration of particles in a microchannel with a nearly square cross section, and we correlate these behaviors with theoretical predictions. We also show that it is possible to control the extent of focusing of the microparticles, and that it is possible to decouple the focusing of microparticles in the vertical direction from the lateral direction in rectangular channels with anisotropic cross sections. This study provides guidelines to design and operate microchip-based acoustofluidic devices for precise control over the spatial arrangement of microparticles for applications such as flow cytometry and cellular sorting.
我们报告了一项关于通过微流道对流动颗粒进行声聚焦技术的建模和实验研究。我们的理论模型与之前的工作有所不同，因为我们解决了一个近似的 2-D 波传播模型，该模型考虑了在固相与流体相中的波传播。我们的模拟表明，在偏离共振条件高达 10%的驱动频率下，颗粒可以有效地聚焦。这一结论得到了在几乎方形微通道中进行的颗粒声聚焦实验的支持，这些实验研究了不同的流速、驱动频率以及在微通道下方或平行槽下方的锆钛酸铅换能器的位置对颗粒的影响。在 2-D 极限下，估计了具有正声对比系数的颗粒的相对声势能和相应的速度场。共聚焦显微镜用于观察三维流动微颗粒的空间分布。通过这些研究，我们表明，单个压电致动器的单个驱动频率可以在具有近乎方形横截面的微通道中诱导颗粒的 2-D 浓度，并且我们将这些行为与理论预测相关联。我们还表明，可以控制微颗粒的聚焦程度，并且可以在具有各向异性横截面的矩形通道中，将微颗粒在垂直方向上的聚焦与侧向方向上的聚焦分离。这项研究为设计和操作基于微芯片的声流控装置提供了指导，以便对微颗粒的空间排列进行精确控制，例如在流式细胞术和细胞分选等应用中。
