Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 85: Poster: Tribology and Misc.

O 85.1: Poster

Wednesday, March 14, 2018, 18:15–20:30, Poster A

Frictional Behaviour of Colloidal Spheres Sliding on a Micron-Scale Periodic Substrate — •Alper Özoğul and Enrico Gnecco — Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany

The Prandtl-Tomlinson model is widely used to explain the stick-slip nature of nanoscale friction on a crystal surface. Hence, the model is commonly associated with atomic-scale interactions, even though it can be in principle applied to any periodic 'tip-surface' interaction. To study the applicability of the PT model in micron scale, friction force between colloidal spheres of different materials (PMMA, SiO2, Borosilicate glass with Ø ~10 μm) attached to an AFM cantilever and a SiO2 grating consisting of 1.5 μm high slopes with a periodici-ty of 3 μm, is measured. The lateral deflection signals, which corre-spond to the friction force experienced by the spheres, are gathered in a variety of scan conditions (normal force set point, scan speed, sample orientation). As a result, friction force was found to vary up to an order of magnitude between different materials. The stick-slip behaviour characteristic of the PT model was clearly observed only with the PMMA spheres, whereas the friction is largely dominated by the sphere roughness and the surface topography with the other materials. Interestingly, we also observed that in all cases the friction is considerably reduced by contact oscillations superimposed to the scan motion, similarly to atomic-scale friction on crystal surfaces.