Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 39: Tribology

O 39.5: Talk

Wednesday, September 7, 2022, 11:30–11:45, H6

Investigating thermal and directional motion in molecular friction processes by photonic force microscopy — •Subhrokoli Ghosh and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

Friction of a moving particle is a complex process of energy dissipation to the environment, which is important on most length scales, time scales and across disciplines. Several theories approach the molecular origin of friction, but a comprehensive understanding is still missing. Usually, the relation between dynamic friction and velocity is quantified by a coefficient, which depends on various parameters. Two main routes to determine the friction coefficient can be addressed by either from a directed particle motion or from its thermal motion. In both cases, Photonic Force Microscopy (PFM) has proven to be one of the most elegant techniques that can be utilized to better understand friction on mesoscopic length scales, specially at soft (-bio) interfaces. Towards this aim, we employ PFM with high-frequency axial tracking for directed and frequency dependent measurements of different bead-surface model systems, starting from simple poly-styrene (PS) bead- glass surface. From Brownian dynamics simulations, in combination with experiments, we obtain better insights on the friction coefficient and its dependency on different system parameters. From this, we developed a theoretical model describing the microscopic origin of friction through molecular on- and off-binding processes.