Surprisingly, the friction between the idea of an atomic force microscopic lense and the Moiré superstructures depends on the speed at which the idea is crossed the surface area. Credit: Department of Physics, University of Basel and Scixel
Scientists from Basel and Tel Aviv discovered that friction varies with speed in particular graphene structures on platinum surfaces, defying Coulombs law which specifies that friction is speed-independent in the macro world.
Products made from single atomic layers are extremely valued for their low-friction qualities, useful in lowering friction in hard drives or moving parts of satellites or space telescopes. Graphene, including a single layer of carbon atoms organized like a honeycomb, is a prime example and is under assessment for its possible as a lubricating layer. Earlier studies showed that a graphene ribbon can glide nearly friction-free throughout a gold surface
Surprising outcomes with a rough surface area.
If graphene is used to a platinum surface, it has a considerable effect on the measurable friction forces. Now, physicists from the University of Basel and Tel Aviv University have actually reported in the journal Nano Letters that, in this instance, the friction depends on the speed at which the tip of an atomic force microscope (AFM; see box) is crossed the surface area. This finding is unexpected because friction does not depend on speed according to Coulombs law, which uses in the macro world.
Now, physicists from the University of Basel and Tel Aviv University have reported in the journal Nano Letters that, in this instance, the friction depends on the speed at which the idea of an atomic force microscopic lense (AFM; see box) is moved across the surface area.” If we move the AFM idea throughout this a little corrugated surface area at low speed, we determine a weak and almost constant frictional force,” discusses Professor Ernst Meyer from the Swiss Nanoscience Institute and the Department of Physics at Basel University. “Above a certain threshold, however, the friction then increases with the speed of the AFM idea,” includes first author Dr. Yiming Song.
In combination with the platinum substrate, graphene no longer forms just the hexagonal honeycomb pattern of carbon atoms and instead forms superstructures called Moiré superlattices. The surface area is then no longer entirely flat and exhibits a specific degree of roughness.
” If we move the AFM pointer across this slightly corrugated surface at low speed, we determine a practically constant and weak frictional force,” explains Professor Ernst Meyer from the Swiss Nanoscience Institute and the Department of Physics at Basel University. “Above a certain threshold, however, the friction then increases with the speed of the AFM suggestion,” includes first author Dr. Yiming Song. “The bigger the Moiré superstructure, the lower the threshold at which the friction ends up being speed-dependent.”
The scientists found that there is higher resistance at the ridges of the Moiré superstructures throughout the motion of the pointer. These ridges go through flexible contortion due to the pushing idea before unwinding once again when the pressure is adequately high. This effect results in higher frictional forces that increase with the speed of the suggestion. Simulations and an analytical model verify the experimental findings acquired by this global group of researchers.
Recommendation: “Velocity Dependence of Moiré Friction” by Yiming Song, Xiang Gao, Antoine Hinaut, Sebastian Scherb, Shuyu Huang, Thilo Glatzel, Oded Hod, Michael Urbakh and Ernst Meyer, 30 November 2022, Nano Letters.DOI: 10.1021/ acs.nanolett.2 c03667.