Marcali Merve, Chen Xiaoming, Aucoin Marc G, Ren Carolyn L
Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Phys Rev E. 2022 Feb;105(2-2):025105. doi: 10.1103/PhysRevE.105.025105.
The extension of microfluidics to many bioassay applications requires the ability to work with non-Newtonian fluids. One case in point is the use of microfluidics with blood having different hematocrit levels. This work is the first part of a two-part study and presents the formation dynamics of blood droplets in a T-junction generator under the squeezing regime. In this regime, droplet formation with Newtonian fluids depends on T-junction geometry; however, we found that in the presence of the non-Newtonian fluid such as red blood cells, the formation depends on not only to the channel geometry, but also the flow rate ratio of fluids, and the viscosity of the phases. In addition, we analyzed the impact of the red blood cell concentration on the formation cycle. In this study, we presented the experimental data of the blood droplet evolution through the analysis of videos that are captured by a high-speed camera. During this analysis, we tracked several parameters such as droplet volume, spacing between droplets, droplet generation frequency, flow conditions, and geometrical designs of the T junction. Our analysis revealed that, unlike other non-Newtonian fluids, where the fourth stage exists (stretching stage), the formation cycle consists of only three stages: lag, filling, and necking stages. Because of the detailed analysis of each stage, a mathematical model can be generated to predict the final volume of the blood droplet and can be utilized as a guide in the operation of the microfluidic device for biochemical assay applications; this is the focus of the second part of this study [Phys. Rev. E 105, 025106 (2022)10.1103/PhysRevE.105.025106].
将微流控技术扩展到许多生物测定应用中需要能够处理非牛顿流体。一个典型的例子是将微流控技术用于具有不同血细胞比容水平的血液。这项工作是一项分为两部分的研究的第一部分，展示了在挤压模式下T型结发生器中血滴的形成动力学。在这种模式下，牛顿流体的液滴形成取决于T型结的几何形状；然而，我们发现，在存在诸如红细胞等非牛顿流体的情况下，形成不仅取决于通道几何形状，还取决于流体的流速比以及各相的粘度。此外，我们分析了红细胞浓度对形成周期的影响。在本研究中，我们通过分析高速摄像机拍摄的视频，展示了血滴演变的实验数据。在该分析过程中，我们跟踪了几个参数，如液滴体积、液滴间距、液滴产生频率、流动条件以及T型结的几何设计。我们的分析表明，与存在第四阶段（拉伸阶段）的其他非牛顿流体不同，形成周期仅由三个阶段组成：滞后、填充和颈缩阶段。由于对每个阶段进行了详细分析，因此可以生成一个数学模型来预测血滴的最终体积，并可作为微流控装置用于生化测定应用操作的指南；这是本研究第二部分的重点[《物理评论E》105, 025106 (2022)10.1103/PhysRevE.105.025106]。
