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BP: Fachverband Biologische Physik

BP 7: Poster 1

BP 7.43: Poster

Montag, 5. September 2022, 18:00–20:00, P1

Multiple thermophoretic particle trapping at single molecule resolution — •Benjamin Fanselow, Tobias Thalheim, and Frank Cichos — Peter-Debye Institute for Soft Matter Physics, Leipzig University, Germany

Achieving single molecule resolution for microscopy enabled to gain valuable insight into processes, that otherwise would be hidden in the ensemble, such as amyloid fibril fragmentation, volume exclusion of DNA molecules, or localization of proteins within a cell. One technique is the combination of fluorescence microscopy with thermophoretic trapping. It utilizes thermophoresis for confining freely diffusing single molecules within a liquid into a region of interest and allows observing these molecules without surface immobilization, over a time period of several minutes. The required temperature fields are generated via optical heating using a focused laser beam steered on a thin chromium layer. So far, only one trap at a time could be used, entailing multiple time-consuming measurements to achieve a reasonable statistics. We present the realization and characterization of up to four thermophoretic traps, which can be controlled simultaneously while preserving the single molecule resolution. This mode is characterized by a model system of 200-nm polystyrene particles in water, trapped with a feedback assisted mode. Analyzing the molecule displacement framewise, the trap stiffness and temperature induced velocities can be calculated. While it could be shown, that the stiffness is scalable with the laser power and the number of used traps, it also revealed an upper limit caused by the feedback loop frequency.