Direct 2D measurement of time-averaged forces and pressure amplitudes in acoustophoretic devices using optical trapping
Direct 2D measurement of time-averaged forces and pressure amplitudes in acoustophoretic devices using optical trapping
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DOI：
10.1039/c4lc01144a
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发表时间：
2015-01-01
期刊：
影响因子：
6.1
通讯作者：
Dual, Jurg
中科院分区：
文献类型：
--
作者：
Lakaemper, Stefan;Lamprecht, Andreas;Dual, Jurg
超声驻波越来越多地应用于微流控池中微米级颗粒的操纵和分选。为了优化这类设备的性能，必须知道粒子在声波中所受的确切力。虽然通过分析和数值模拟已经取得了很大的进展，但这些方法的可靠性很大程度上依赖于所使用的假设，例如边界条件。在这里，我们将声学流动池与光学激光陷阱相结合，直接测量二维单个球形粒子上的力。在进行超声频率扫描的同时，我们测量了单个粒子在激光陷阱通过微流体单元时所受的时间平均力。用有限元方法对含压电换能器的单元进行了建模。我们发现，实验获得的力和导出的压力场证实了理论和模型的预测。这种新的方法现在可以很容易地扩展到其他颗粒、腔和流体区域，并为研究边界、声流和非线性流体的影响打开了可能性。
Ultrasonic standing waves are increasingly applied in the manipulation and sorting of micrometer-sized particles in microfluidic cells. To optimize the performance of such devices, it is essential to know the exact forces that the particles experience in the acoustic wave. Although much progress has been made via analytical and numerical modeling, the reliability of these methods relies strongly on the assumptions used, e. g. the boundary conditions. Here, we have combined an acoustic flow cell with an optical laser trap to directly measure the force on a single spherical particle in two dimensions. While performing ultrasonic frequency scans, we measured the time-averaged forces on single particles that were moved with the laser trap through the microfluidic cell. The cell including piezoelectric transducers was modeled with finite element methods. We found that the experimentally obtained forces and the derived pressure fields confirm the predictions from theory and modeling. This novel approach can now be readily expanded to other particle, chamber, and fluid regimes and opens up the possibility of studying the effects of the presence of boundaries, acoustic streaming, and non-linear fluids.