Simultaneous, volumetric temperature and velocity field measurements within and around micro-droplets for the analysis and characterization of disperse multiphase flows in microfluidic Lab-on-a-Chip systems

近年来，微流控分析系统在医疗技术、制药、化学、生物、过程工程等科学和工业领域引起了人们的极大兴趣。尤其是基于所谓的液滴微流体的微流控平台的应用激增。在这些系统中，样品被引入到体积从几微升到飞升的液滴中，这些液滴被不可溶的相包围，并在微通道中进行分析。这大大减少了所需的样品或反应物的数量和处理时间，这可以节省很大一部分相关成本。这些程序中的一个基本步骤是对各种液滴的操纵和分选，因此对液滴动力学的精确控制对于分析平台的有效性至关重要。一种有效且经常使用的方法是使用Marangoni力，这种力通常是由于在液滴界面产生温度梯度而引起的，例如利用聚焦的激光束。然而，目前，决定微通道中液滴行为的流体力学现象还没有得到充分的了解。为此，本研究项目将对微通道中液滴操纵产生的三维和瞬变流动现象进行详细的实验分析和表征。为此，将利用先进的光学测量方法，以高分辨率和高精度同时测量单个液滴内部和周围的三维流场和三维温度场。这些结果将有助于更好地理解控制液滴行为的基本流体力学，从而有助于进一步提高这些芯片实验室系统的效率和分布。

In recent years, microfluidic analysis systems have gained considerable interest in various scientific and industrial fields such as medical technology, pharmacy, chemistry, biology, process engineering, etc.. Particularly microfluidic platforms based on so-called droplet microfluidics have experienced a surge in applications. In these systems, samples are introduced into liquid droplets with volumes ranging from a few microliters to femtoliters, which are surrounded by an insoluble phase and analyzed in the microchannel. This results in considerable reductions in the amount of samples or reactants required and in process time, which can save a large part of the associated costs. An essential step in these procedures is the manipulation and sorting of the various droplets, whereby precise control of the droplet dynamics is crucial for the effectiveness of the analysis platform. An efficient and frequently applied method is the use of Marangoni-forces, which are often induced by producing temperature gradients at the droplet interface, for example with of a focused laser beam. At present, however, the fluid mechanical phenomena that determine the droplet behavior in the microchannel are not yet sufficiently understood. For this reason, a detailed experimental analysis and characterization of the three-dimensional and transient flow phenomena arising from the manipulation of a droplet in a microchannel will be performed within this research project. For this purpose, advanced optical measurement methods will be utilized which enable the simultaneous measurement of the three-dimensional flow field and the three-dimensional temperature field in and around individual droplets with high resolution an accuracy. The results will lead to an improved understanding of the fundamental fluid mechanics that control the droplet behavior and thus contribute to a further increase in efficiency and distribution of these lab-on-a-chip systems.