Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 31: Focus Session Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation II
O 31.5: Talk
Tuesday, March 18, 2025, 11:45–12:00, H24
Friction Anisotropy in the Sliding Motion of PMMA microsphere on Rippled PVS Surface — •Ebru Cihan1, Hesam Khaksar2, Kevin Lubig3, Stephan Gräf3, Frank A. Müller3, and Enrico Gnecco1, 2 — 1TU Dresden — 2Jagiellonian University — 3Friedrich Schiller University Jena
The sliding motion of an elastically driven polymethyl methacrylate (PMMA) microsphere on a rippled polyvinyl siloxane (PVS) surface (laser-induced periodic surface structures LIPSS) was investigated for different values of normal load, scan velocity and temperature. The morphologies of the PMMA spheres and modified PVS surfaces were observed to be geometrically convoluted in AFM topographies recorded simultaneously with friction measurements. The spheres were rubbed both parallel and perpendicular to the LIPSS, and the resulting friction was found to be nearly constant, exhibiting a stick-slip behavior over time. This result differs from the reverse stick-slip observed in friction characterizations with similar PMMA microspheres on harder periodic surfaces, such as wedge-shaped silicon gratings [Trib. Lett. 67, 2019] and rippled stainless steel [Appl. Mater. Interfaces 15, 2023]. In both scanning cases, the friction force was found to increase linearly with increasing load, consistent with the increase in contact area expected from Persson contact theory. Furthermore, friction was observed to increase logarithmically with velocity, and to decrease with increasing temperature in accordance with Eyring's reaction rate theory. The stability of this sample system suggests its possible application as a basic unit for artificial tactile sensors.
Keywords: AFM; stick-slip; friction; multicontact; laser-induced periodic surface structures