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BP: Fachverband Biologische Physik

BP 14: Poster Session II

BP 14.82: Poster

Dienstag, 10. März 2026, 18:00–21:00, P2

Thermal noise particle tracking and interaction measurements at interfaces under minimal external force — •Nils le Coutre and Alexander Rohrbach — Bio- and Nano-Photonics, IMTEK, University of Freiburg, Germany

Forces play a vital role in experimental biophysics. From receptor-binding studies to flow-drag analysis, understanding the magnitude, direction, and origin of these forces is essential for uncovering underlying mechanisms. Optical tweezers are widely used in this context because they not only enable the measurement of biophysical interactions, but also deliberately manipulate a biological system to trigger and observe otherwise highly unlikely yet relevant interactions between the system's individuals.

To leverage this advantage for studying specific interaction processes, a robust understanding of the probe position distributions, defined by both the trapping and the surface potential and the interferometric tracking response is required, especially near interfaces and surfaces such as cell membranes. We discuss the question how far an optical trap has to approach an interface such that a natural interaction process between two binding partners is enabled (e.g. receptor on surface and ligand in optical trap).

In this presentation, I expound experiments by exploring the underlying theory and by conducting benchmark measurements in electrolyte-controlled systems, characterizing the behavior of trapped probes as their microscopic environment is altered.

Keywords: Particulate Matter; Optical Tweezers; Thermal position fluctuations; Interface effects; Receptor-ligand interactions