Switchable friction enabled by nanoscale self-assembly on graphene

Abstract

Graphene monolayers are known to display domains of anisotropic friction with twofold symmetry and anisotropy exceeding 200%. This anisotropy has been thought to originate from periodic nanoscale ripples in the graphene sheet, which enhance puckering around a sliding asperity to a degree determined by the sliding direction. Here we demonstrate that these frictional domains derive not from structural features in the graphene but from self-assembly of environmental adsorbates into a highly regular superlattice of stripes with period 4–6 nm. The stripes and resulting frictional domains appear on monolayer and multilayer graphene on a variety of substrates, as well as on exfoliated flakes of hexagonal boron nitride. We show that the stripe-superlattices can be reproducibly and reversibly manipulated with submicrometre precision using a scanning probe microscope, allowing us to create arbitrary arrangements of frictional domains within a single flake. Our results suggest a revised understanding of the anisotropic friction observed on graphene and bulk graphite in terms of adsorbates.

Switchable Friction across Insulator–Metal Transition in VO2

“…The COF, μ is calculated by assuming lateral force, F L is proportional to normal force, F N according to Equation (2). The COF, μ is calculated by assuming lateral force, F L is proportional to normal force, F N according to Equation (2).…”

“…[1][2][3] At the atomic level, in the absence of wear, this mechanical energy dissipation is the result of lattice and electronic excitations. The underlying energy dissipation mechanisms are actively being explored for a variety of materials for critical engineering applications such as brakes, clutches, tires, skating, friction cutting, magnetic disks, etc.…”

Ambient atomic resolution atomic force microscopy with qPlus sensors: Part 1

“…This system was theoretically shown to enable a strong gas enhancement, at the hydrophobic solid–liquid interface (Dammer & Lohse, ). Experimentally a gas enhancement on the surface, the formation of solid like gas domains was shown on hydrophobic surfaces like mono‐ and bilayer graphene and highly oriented pyrolytic graphite surfaces (Gallagher et al, ; Lu et al, ; Wastl et al, , ). The nature of these solid like gas domains, enabled due to the presence of moisture in air and therefore an condensation layer on hydrophobic surfaces, is not yet totally clarified (Gallagher et al, ; Lu et al, ; Wastl et al, , ).…”

“…Experimentally a gas enhancement on the surface, the formation of solid like gas domains was shown on hydrophobic surfaces like mono‐ and bilayer graphene and highly oriented pyrolytic graphite surfaces (Gallagher et al, ; Lu et al, ; Wastl et al, , ). The nature of these solid like gas domains, enabled due to the presence of moisture in air and therefore an condensation layer on hydrophobic surfaces, is not yet totally clarified (Gallagher et al, ; Lu et al, ; Wastl et al, , ). However, recently it was shown that the stripe like domains formed on hydrophobic surfaces (Lu et al, ; Wastl et al, , ) have important influences on the surface properties of graphene (Gallagher et al, ).…”

Optical-assistant characterization of friction anisotropy properties of single-crystal graphene domains

“…At the atomic scale, most of the researchers think that the friction anisotropy should be caused by the lattice orientations [38]. Gallagher et al demonstrate the frictional domains caused by self-assembly of environmental adsorbates [39]. Almeida et al found that the friction force in graphene was highly dependent on the scanning direction, and the energy dissipated along the armchair direction could be 80% higher than the zigzag direction [40].…”