Townsend R J, Hill M, Harris N R, McDonnell M B
School of Engineering Sciences, University of Southampton, SO171BJ, UK.
Ultrasonics. 2008 Nov;48(6-7):515-20. doi: 10.1016/j.ultras.2008.06.005. Epub 2008 Jun 14.
A series of devices have been investigated which use acoustic radiation forces to concentrate micron sized particles. These multi-layered resonators use a quarter-wavelength resonance in order to position an acoustic pressure node close to the top surface of a fluid layer such that particles migrate towards this surface. As flow-through devices, it is then possible to collect a concentrate of particulates by drawing off the particle stream and separating it from the clarified fluid and so can operate continuously as opposed to batch processes such as centrifugation. The methods of construction are described which include a micro-fabricated, wet-etched device and a modular device fabricated using a micro-mill. These use silicon and macor, a machinable glass ceramic, as a carrier layer between the transducer and fluid channel, respectively. Simulations using an acoustic impedance transfer model are used to determine the influence of various design parameters on the acoustic energy density within the fluid layer and the nodal position. Concentration tests have shown up to 4.4-, 6.0- and 3.2-fold increases in concentration for 9, 3 and 1 microm diameter polystyrene particles, respectively. The effect of voltage and fluid flow rates on concentration performance is investigated and helps demonstrate the various factors which determine the increase in concentration possible.
已经对一系列利用声辐射力来聚集微米级颗粒的装置进行了研究。这些多层谐振器利用四分之一波长共振，以便将声压节点定位在靠近流体层顶面的位置，从而使颗粒向该表面迁移。作为流通式装置，通过排出颗粒流并将其与澄清流体分离，就有可能收集颗粒浓缩物，因此与诸如离心等分批过程不同，它可以连续运行。描述了构建方法，包括微加工、湿法蚀刻装置和使用微铣床制造的模块化装置。这些装置分别使用硅和可加工玻璃陶瓷macor作为换能器和流体通道之间的载体层。使用声阻抗传递模型进行的模拟用于确定各种设计参数对流体层内声能密度和节点位置的影响。浓缩测试表明，对于直径为9、3和1微米的聚苯乙烯颗粒，浓缩倍数分别提高了4.4倍、6.0倍和3.2倍。研究了电压和流体流速对浓缩性能的影响，并有助于证明决定可能的浓缩增加的各种因素。
