Goddard Gregory, Kaduchak Gregory
Los Alamos National Laboratory, Electronic and Electrochemical Materials and Devices Group, Mail Stop D-429, P.O. Box 1663, Los Alamos, New Mexico 87545, USA.
J Acoust Soc Am. 2005 Jun;117(6):3440-7. doi: 10.1121/1.1904405.
Acoustic particle manipulation has many potential uses in flow cytometry and microfluidic array applications. Currently, most ultrasonic particle positioning devices utilize a quasi-one-dimensional geometry to set up the positioning field. A transducer fit with a quarter-wave matching layer, locally drives a cavity of width one-half wavelength. Particles within the cavity experience a time-averaged drift force that transports them to a nodal position. Present research investigates an acoustic particle-positioning device where the acoustic excitation is generated by the entire structure, as opposed to a localized transducer. The lowest-order structural modes of a long cylindrical glass tube driven by a piezoceramic with a line contact are tuned, via material properties and aspect ratio, to match resonant modes of the fluid-filled cavity. The cylindrical geometry eliminates the need for accurate alignment of a transducer/reflector system, in contrast to the case of planar or confocal fields. Experiments show that the lower energy density in the cavity, brought about through excitation of the whole cylindrical tube, results in reduced cavitation, convection, and thermal gradients. The effects of excitation and material parameters on concentration quality are theoretically evaluated, using two-dimensional elastodynamic equations describing the fluid-filled cylindrical shell with a line excitation.
声学粒子操纵在流式细胞术和微流体阵列应用中有许多潜在用途。目前，大多数超声粒子定位装置利用准一维几何结构来建立定位场。一个配有四分之一波长匹配层的换能器局部驱动一个宽度为半波长的腔体。腔内的粒子会受到一个时间平均漂移力，该力将它们传输到节点位置。目前的研究调查了一种声学粒子定位装置，其中声学激励是由整个结构产生的，而不是由局部换能器产生。通过压电陶瓷以线接触驱动的长圆柱形玻璃管的最低阶结构模式，通过材料特性和长宽比进行调整，以匹配充满流体的腔体的共振模式。与平面或共焦场的情况相比，圆柱形几何结构无需精确对准换能器/反射器系统。实验表明，通过整个圆柱形管的激励导致腔内能量密度降低，从而减少了空化、对流和热梯度。利用描述带有线激励的充满流体的圆柱形壳的二维弹性动力学方程，从理论上评估了激励和材料参数对聚集质量的影响。
