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

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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.