Friction is responsible for nearly a quarter of all irreversible energy losses in the modern world's industry. That is why scientists worldwide are trying to find better ways to reduce these losses. An international group of authors including Igor Ostanin, Assistant Professor at the department of Engineering Technology, University of Twente, investigated the fundamental question of dynamic mechanisms of structural superlubricity (a vanishingly small friction, observed between the two molecularly smooth surfaces). This research was published in Physical Review Letters.
The phenomenon occurs at relatively small scales of area – starting from hundreds of square nanometers – and features some astonishing properties, including independence of friction force on the normal load, as well as its linear dependence on the temperature.
These properties were studied both in experiment and numerical simulation for the case of two graphene-covered, molecularly smooth crystalline metal surfaces in contact. An explanation of the observed behavior was found in an elegant analytical theory of synchronic thermal fluctuations of surfaces in contact. The theory explains the dynamic origin of friction force in a superlubric system and predicts exactly the observed properties. The work contributes to our understanding of nanoscale friction, paving the way to harness structural superlubricity in practical applications.
