Regensburg 2025 – scientific programme

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BP: Fachverband Biologische Physik

BP 17: Poster Session II

BP 17.49: Poster

Tuesday, March 18, 2025, 18:00–20:30, P4

Revealing minimal cell particle interactions by thermal noise frequency decomposition — •Max Wechlin, Felix Jünger, and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

Nearly every interaction process in nano-scale soft materials, especially in living cells is governed by thermal noise. However, it is hardly known or often disregarded that many interaction processes take place only on specific timescales. This means that observing or measuring on the wrong timescale, can lead to wrong results or even no results. While interactions can be visible on one timescale, they can be completely invisible on another. Therefore, it is not only necessary to measure on a much broader frequency range than usually, but also to decompose the broadband fluctuation data with appropriate mathematical models. This way minimal or even hidden interactions can be revealed. We use optical tweezers based Photonic Force Microscopy with MHz-rate interferometric 3D particle tracking to approach 1*m-sized polystyrene beads to functional gels or to living cells. We demonstrate that interactions between particles and cells change in stiffness or friction over time and distance only on certain frequency bands, but not over the average fluctuations in energy and position.

Keywords: particle fluctuations; frequency decomposition; cell-surface; optical trapping; interferometric tracking