Laser scanning confocal microscope with fluorescence correlation spectroscopy

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A device for fluorescence correlation spectroscopy (FCS) and confocal microscopy is applied for. The aim is the investigation of flow and transport phenomena in close vicinity of surfaces and interfaces. By geometric or chemical structuring on the micro- or nanometer scale, surfaces and interfaces can be designed such that they possess certain desired properties, such as a reduced flow resistance or enhanced or reduced wettability. Such properties are keys to controlling and enhancing the efficiency of processes in fluid transport or process engineering. To be able to investigate the physical mechanisms underlying these processes and thereby to be able to design such surfaces in a targeted manner, a measurement technique is required that can resolve the flow over the surface on the same scale as the structuring of the surface, i.e. on the micro- and sub-micrometer range. This also includes the necessity to measure within this range close to a surface. FCS fulfills both of these criteria. In contrast to FCS, particle-based measurement techniques are limited, e.g. because of the particle size which has to be optically accessible, but should not influence the flow while the particle size is often of the same order of magnitude as the surface structures. Technically, FCS always builds upon a confocal microscope, such that microscopic imaging is another key property of the device. Beyond FCS, this property is required for the investigation of fluids on surfaces, especially to visualize processes in wettability or phase change on functionalized surfaces. First, the device is supposed to provide a basis to build up a research group that investigates flow and transport processes close to surfaces. Specifically, this proposal is connected to a proposal in the Emmy Noether program „Marangoni propulsion in microscale systems – principle and potential of transferring surface tension gradients into motion“. This proposal aims at the investigation of new types of optically and thermally driven flows close to microstructured interfaces and their applicability. Second, further research groups in process engineering are involved. For their research, FCS and confocal imaging are excellently suited and needed both in the short and long term. Overall, multiphysical questions are at the heart of all investigations, such as coupled heat transfer and flow processes that are essential for the development of efficient heat transfer technologies or local influence factors on processes in bioreactors and their optimization.