Department of Biomedical Engineering, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana, 70118, USA.
Lab Chip. 2022 Aug 9;22(16):3067-3079. doi: 10.1039/d2lc00356b.
Knowledge of rheological properties, such as viscosity and elasticity, is necessary for efficient material processing and transportation as well as biological analysis. Existing rheometers operate with large sample volume and induce sample contact with container or device walls, which are inadequate for rheological analysis of sensitive fluids limited in availability. In this work, we introduce acoustic tweezing spectroscopy (ATS), a novel noncontact rheological technique that operates with a single 4-6 μl drop of fluid sample. In ATS, a sample drop is acoustically levitated and then exposed to a modulated acoustic signal to induce its forced oscillation. The time-dependent sample viscosity and elasticity are measured from the resulting drop response. The ATS measurements of polymeric solutions (dextran, xanthan gum, gelatin) agree well with previously reported data. The ATS predicts that the shear viscosity of blood plasma increases from 1.5 cP at 1.5 min of coagulation onset to 3.35 cP at 9 min, while its shear elastic modulus grows from a negligible value to 10.7 Pa between 3.5 min and 6.5 min. Coagulation increases whole blood viscosity from 5.4 cP to 20.7 cP and elasticity from 0.1 Pa to 19.2 Pa at 15 min. In summary, ATS provides the opportunity for sensitive small-volume rheological analysis in biomedical research and medical, pharmaceutical, and chemical industries.
流变学性质（如粘度和弹性）的知识对于高效的材料加工和输送以及生物分析是必要的。现有的流变仪需要较大的样品体积，并使样品与容器或设备壁接触，这对于有限可用性的敏感流体的流变分析是不够的。在这项工作中，我们介绍了声学镊子光谱（ATS），这是一种新颖的非接触流变技术，只需使用 4-6 μl 的单个液滴样品即可操作。在 ATS 中，样品液滴被声学悬浮，并随后暴露于调制的声信号以诱导其强制振荡。从产生的液滴响应中测量随时间变化的样品粘度和弹性。ATS 对聚合物溶液（葡聚糖、黄原胶、明胶）的测量与先前报道的数据吻合良好。ATS 预测，血浆的剪切粘度从凝固开始后 1.5 分钟的 1.5 cP 增加到 9 分钟时的 3.35 cP，而其剪切弹性模量从 3.5 分钟到 6.5 分钟之间的可忽略值增加到 10.7 Pa。在 15 分钟时，凝血会使全血粘度从 5.4 cP 增加到 20.7 cP，弹性从 0.1 Pa 增加到 19.2 Pa。总之，ATS 为生物医学研究以及医疗、制药和化学工业中的敏感小体积流变分析提供了机会。
