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We study the effect of atomic scale surface-lubricant interactions on nanoscale boundary-lubricated friction, by considering two example surfaces - hydrophilic mica and hydrophobic graphene - confining thin layers of water in molecular…
The increase of sliding friction upon increasing load is a classic in the macroscopic world. Here we discuss the possibility that friction rise might sometimes turn into a drop when, at the mesoscale and nanoscale, a confined lubricant film…
Hydrocarbon films confined between smooth mica surfaces have long provided an experimental playground for model studies of structure and dynamics of confined liquids. However fundamental questions regarding the phase behavior and shear…
We report measurements of the normal surface forces and friction forces between two mica surfaces separated by a nano-film of dicationic ionic liquid using a Surface Force Balance. The dicationic ionic liquid…
Recent highly idealized model studies of lubricated nanofriction for two crystalline sliding surfaces with an interposed thin solid crystalline lubricant layer showed that the overall relative velocity of the lubricant $v_{\rm lub} / v_{\rm…
Despite the extensive research that has been conducted for decades on the behavior of confined liquids, detailed knowledge of this phenomenon, particularly in the mixed/boundary lubrication regime, remains limited. This can be attributed to…
Using molecular dynamics based on Langevin equations with a coordinate- and velocity-dependent damping coefficient, we study the frictional properties of a thin layer of "soft" lubricant (where the interaction within the lubricant is weaker…
Stability of lubricating fluid infused slippery surfaces is a concern for scientists and engineers and attempts are being made for its improvement. Lubricating oil coated slippery surface for aqueous drops is one of the important candidates…
We experimentally study the surface roughness and the lateral friction force in single-layer MoS2 crystals deposited on different substrates: SiO2, mica and hexagonal boron nitride (h-BN). Roughness and sliding friction measurements are…
Structural lubricity arises typically at incommensurate, well-defined dry contacts where short-range elastic instability is significantly mitigated. However, under ambient conditions, airborne molecules adsorb onto solid surfaces, forming…
Ionic liquids, salts in the liquid state under ambient conditions, are of great interest as precision lubricants. Ionic liquids form layered structures at surfaces, yet it is not clear how this nano-structure relates to their lubrication…
The sliding of three-dimensional clusters and two-dimensional islands adsorbed on crystal surfaces represent an important test case to understand friction. Even for the same material, monoatomic islands and thick clusters will not as a rule…
We explore the nematic ordering of the rod-like liquid crystals 5CB and 6CB, embedded into parallel-aligned nanochannels in mesoporous silicon and silica membranes as a function of mean channel radius (4.7<=R <=8.3 nm), and thus geometrical…
This paper examines friction as a function of the sliding velocity and applied normal load from air to UHV in a scanning force microscope (SFM) experiment in which a sharp silicon tip slides against a flat Si(100) sample. Under ambient…
The contribution of sliding-induced, atomic-scale instabilities to the kinetic friction force is investigated by molecular dynamics. For this purpose, we derive a relationship between the kinetic friction force $F_{\rm k}$ and the…
Liquids play an important role in adhesion and sliding friction. They behave as lubricants in human bodies especially in the joints. However, in many biological attachment systems they acts like adhesives, e.g. facilitating insects to move…
This paper reports on the frictional properties of smooth rubber substrates sliding against rigid surfaces covered with various densities of colloidal nano-particles (average diameter 77 nm). Friction experiments were carried out using a…
Lubricated contacts in soft materials are important in various engineering systems and natural settings. Three major lubrication regimes are boundary (BL), mixed (ML), and elasto-hydrodynamic (EHL) lubrication, where the contact region is…
Two-dimensional MXenes are promising solid lubricants, but the roles of compositional complexity and surface chemistry in governing interfacial friction remain unclear. Here, we systematically investigate the adhesion and friction behaviors…
Friction between ordered, atomically smooth surfaces at the nanoscale (nanofriction) is often governed by stick-slip processes. To test long-standing atomistic models of such processes, we implement a synthetic nanofriction interface…