Leibniz Institute for Solid State and Materials Research Dresden, SAWLab Saxony, Helmholtzstr. 20, 01069 Dresden, Germany.
Leibniz Institute for Solid State and Materials Research Dresden, SAWLab Saxony, Helmholtzstr. 20, 01069 Dresden, Germany.
Ultrasonics. 2020 Aug;106:106160. doi: 10.1016/j.ultras.2020.106160. Epub 2020 Apr 14.
Using surface acoustic waves (SAW) for the agitation and manipulation of fluids and immersed particles or cells in lab-on-a-chip systems has been state of the art for several years. Basic tasks comprise fluid mixing, atomization of liquids as well as sorting and separation (or trapping) of particles and cells, e.g. in so-called acoustic tweezers. Even though the fundamental principles governing SAW excitation and propagation on anisotropic, piezoelectric substrates are well-investigated, the complexity of wave field effects including SAW diffraction, refraction and interference cannot be comprehensively simulated at this point of time with sufficient accuracy. However, the design of microfluidic actuators relies on a profound knowledge of SAW propagation, including superposition of multiple SAWs, to achieve the predestined functionality of the devices. Here, we present extensive experimental results of high-resolution analysis of the lateral distribution of the complex displacement amplitude, i.e. the wave field, alongside with the electrical S-parameters of the generating transducers. These measurements were carried out and are compared in setups utilizing travelling SAW (tSAW) excited by single interdigital transducer (IDT), standing SAW generated between two IDTs (1DsSAW, 1D acoustic tweezers) and between two pairs of IDTs (2DsSAW, 2D acoustic tweezers) with different angular alignment in respect to pure Rayleigh mode propagation directions and other practically relevant orientations. For these basic configurations, typically used to drive SAW-based microfluidics, the influence of common SAW phenomena including beam steering, coupling coefficient dispersion and diffraction on the resultant wave field is investigated. The results show how tailoring of the acoustic conditions, based on profound knowledge of the physical effects, can be achieved to finally realize a desired behavior of a SAW-based microacoustic-fluidic system.
利用表面声波（SAW）在微流控系统中搅拌和操纵流体以及浸入的颗粒或细胞已经成为多年来的技术热点。基本任务包括流体混合、液体雾化以及颗粒和细胞的分类和分离（或捕获），例如在所谓的声镊中。尽管用于各向异性、压电衬底上的 SAW 激励和传播的基本原理已经得到了很好的研究，但包括 SAW 衍射、折射和干涉在内的复杂波场效应目前还无法用足够的精度进行全面模拟。然而，微流控执行器的设计依赖于对 SAW 传播的深入了解，包括多个 SAW 的叠加，以实现器件预定的功能。在这里，我们展示了对复杂位移幅度（即波场）的横向分布以及产生换能器的电 S 参数的高分辨率分析的广泛实验结果。这些测量是在利用 traveling SAW（tSAW）的设置中进行的，该 tSAW 由单个叉指换能器（IDT）激发，standing SAW 是在两个 IDT 之间（1DsSAW，1D 声镊）和两对 IDT 之间产生的（2DsSAW，2D 声镊），它们的角度排列相对于纯瑞利模式传播方向和其他实际相关方向不同。对于这些通常用于驱动基于 SAW 的微流控的基本配置，研究了常见的 SAW 现象，包括光束转向、耦合系数色散和衍射对所得波场的影响。结果表明，如何基于对物理效应的深刻了解来调整声学条件，最终实现基于 SAW 的微声流系统的期望行为。
