Frictional Duality Observed during Nanoparticle Sliding

Abstract

One of the most fundamental questions in tribology concerns the area dependence of friction at the nanoscale. Here, experiments are presented where the frictional resistance of nanoparticles is measured by pushing them with the tip of an atomic force microscope. We find two coexisting frictional states: While some particles show finite friction increasing linearly with the interface areas of up to 310,000 nm 2 , other particles assume a state of frictionless sliding. The results further suggest a link between the degree of surface contamination and the occurrence of this duality.

Study of Friction of Ag and Ni Nanoparticles: An Atomistic Approach

“…While in Ref. 9 the coexistence of the two frictional states is ascribed to the presence of contamination molecules and structure of the nanoparticles is not considered as a crucial factor defining the observed behavior.…”

Microscale Motion Control through Ferromagnetic Films

“…Specifically at the nanoscale, peculiar means to control friction would be available, for instance the commensurability of the crystal lattices of the sliding nano-objects and the onset of a superlubric state [25]. However, once the materials have been chosen, it is hard to modify the contact geometry and no efficient friction control can be achieved [12,13]. One possibility to circumvent this difficulty is to tune the material properties through some external parameter.…”

Current trends in the physics of nanoscale friction

“…The macroscopic Da Vinci-Amontons law -friction independent of area -is not confirmed at the microscopic scale. In most nanoscale investigations the friction of a single contact is found to increase linearly with the contact area [27][28][29]. In contrast, structurally mismatched atomically flat and hard crystalline or amorphous surfaces are expected to produce a sublinear increase of friction with contact area.…”

“…Superlubricity is experimentally rare. Until recently, it has been demonstrated or implied in a relatively small number of cases [29,[42][43][44][45][46]. There are now more evidences of superlubric behavior in cluster nanomanipulation [32,33,47], sliding colloidal layers [48][49][50], and inertially driven rare-gas adsorbates [51,52] (see Fig.…”