Destgeer Ghulam, Ha Byunghang, Park Jinsoo, Sung Hyung Jin
Department of Mechanical Engineering, KAIST , Daejeon 34141, Korea.
Anal Chem. 2016 Apr 5;88(7):3976-81. doi: 10.1021/acs.analchem.6b00213. Epub 2016 Mar 14.
We demonstrate an acoustofluidic device using Lamb waves (LWs) to manipulate polystyrene (PS) microparticles suspended in a sessile droplet of water. The LW-based acoustofluidic platform used in this study is advantageous in that the device is actuated over a range of frequencies without changing the device structure or electrode pattern. In addition, the device is simple to operate and cheap to fabricate. The LWs, produced on a piezoelectric substrate, attenuate inside the fluid and create acoustic streaming flow (ASF) in the form of a poloidal flow with toroidal vortices. The PS particles experience direct acoustic radiation force (ARF) in addition to being influenced by the ASF, which drive the concentration of particles to form a ring. This phenomenon was previously attributed to the ASF alone, but the present experimental results confirm that the ARF plays an important role in forming the particle ring, which would not be possible in the presence of only the ASF. We used a range of actuation frequencies (45-280 MHz), PS particle diameters (1-10 μm), and droplet volumes (5, 7.5, and 10 μL) to experimentally demonstrate this phenomenon.
我们展示了一种使用兰姆波（LWs）来操控悬浮在水滴中的聚苯乙烯（PS）微粒的声流控装置。本研究中使用的基于兰姆波的声流控平台具有优势，即该装置可在一定频率范围内驱动，而无需改变装置结构或电极图案。此外，该装置操作简单且制造成本低廉。在压电基板上产生的兰姆波在流体内部衰减，并形成具有环形涡旋的极向流形式的声流（ASF）。PS微粒除了受到声流的影响外，还会受到直接声辐射力（ARF）的作用，这驱使微粒聚集形成一个环。这种现象以前仅归因于声流，但目前的实验结果证实，声辐射力在形成微粒环的过程中起着重要作用，仅存在声流的情况下是不可能形成微粒环的。我们使用了一系列驱动频率（45 - 280兆赫兹）、PS微粒直径（1 - 10微米）和液滴体积（5、7.5和10微升）来通过实验证明这一现象。
