Kim Minji, Bayly Philip V, Meacham J Mark
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
Lab Chip. 2021 Feb 9;21(3):521-533. doi: 10.1039/d0lc01025a.
Acoustic microfluidics has emerged as a versatile solution for particle manipulation in medicine and biology. However, current technologies are largely confined to specialized research laboratories. The translation of acoustofluidics from research to clinical and industrial settings requires improved consistency and repeatability across different platforms. Performance comparisons will require straightforward experimental assessment tools that are not yet available. We introduce a method for characterizing acoustofluidic devices in real-time by exploiting the capacity of swimming microorganisms to respond to changes in their environment. The unicellular alga, Chlamydomonas reinhardtii, is used as an active probe to visualize the evolving acoustic pressure field within microfluidic channels and chambers. In contrast to more familiar mammalian cells, C. reinhardtii are simple to prepare and maintain, and exhibit a relatively uniform size distribution that more closely resembles calibration particles; however, unlike passive particles, these motile cells naturally fill complex chamber geometries and redistribute when the acoustic field changes or is turned off. In this way, C. reinhardtii cells offer greater flexibility than conventional polymer or glass calibration beads for in situ determination of device operating characteristics. To illustrate the technique, the varying spatial density and distribution of swimming cells are correlated to the acoustic potential to automatically locate device resonances within a specified frequency range. Peaks in the correlation coefficient of successive images not only identify the resonant frequencies for various geometries, but the peak shape can be related to the relative strength of the resonances. Qualitative mapping of the acoustic field strength with increasing voltage amplitude is also shown. Thus, we demonstrate that dynamically responsive C. reinhardtii enable real-time measurement and continuous monitoring of acoustofluidic device performance.
声学微流体技术已成为医学和生物学中用于粒子操控的通用解决方案。然而，目前的技术主要局限于专业研究实验室。将声流体技术从研究转化到临床和工业环境需要提高不同平台间的一致性和可重复性。性能比较将需要尚未可用的直接实验评估工具。我们介绍一种通过利用游动微生物对其环境变化作出反应的能力来实时表征声流体装置的方法。单细胞藻类莱茵衣藻被用作活性探针，以可视化微流体通道和腔室内不断变化的声压场。与更常见的哺乳动物细胞不同，莱茵衣藻易于制备和维持，并且呈现出相对均匀的尺寸分布，更类似于校准粒子；然而，与被动粒子不同，这些活动细胞会自然填充复杂的腔室几何形状，并在声场变化或关闭时重新分布。通过这种方式，莱茵衣藻细胞在原位确定装置操作特性方面比传统的聚合物或玻璃校准珠提供了更大的灵活性。为了说明该技术，游动细胞变化的空间密度和分布与声势相关，以自动定位指定频率范围内的装置共振。连续图像的相关系数峰值不仅能识别各种几何形状的共振频率，而且峰值形状可与共振的相对强度相关。还展示了随着电压幅度增加对声场强度的定性映射。因此，我们证明动态响应的莱茵衣藻能够实时测量和连续监测声流体装置的性能。
