Robust superlubricity by strain engineering

Abstract

We demonstrate that robust superlubricity can be achieved via both biaxial and uniaxial tensile strains in a substrate using molecular dynamics simulation. Above a critical strain, the friction is no longer dependent on the relative orientation between the surfaces mainly due to the complete lattice mismatch. Importantly, the larger the size of the flake is, the smaller the critical biaxial strain is.

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

“…The different level of strain in each single layer induces a mismatch between the lattice constant (the bottom layer is under higher strain than the top and thus the lattice constant is somewhat different under increased tension) and thus, gradual incommensurable stacking occurs, leading to interfacial sliding as interlayer shear strength is overcome. The effect of lattice mismatch induced by strain has been examined by simulations which show robust superlubric behaviour when sliding a graphene on strained graphene 39,40 . As is experimentally evident, our approach provides an alternative for achieving macroscale superlubricity using two CVD graphene layers.…”

Edge length-dependent interlayer friction of graphene

“…The edge length of the inside ake increased as its number of atoms increased, increasing the friction force on the corresponding edge portion. Although the friction force on each of the inner region atoms was much smaller than that of the edge region atoms for the incommensurate case, 20,24,26,36 the friction of the interior portion dissipated moderately, which is likely due to the number of inner atoms increasing rapidly. This suggests that the friction force for the ensemble of the inside ake atoms will increase with increasing its number of atoms ( Fig.…”

“…However, the number of ake inner atoms was reduced, and hence, the friction force of the inner portion atoms deceased. In addition, although the friction dissipated on each of the inner atoms was signicantly less than that dissipated on each of the edge atoms, 20,24,26,36 the more signicant reduction rate of the number of inner portion atoms had considerable frictional variation. Therefore, when the number of the outside ake atoms decreased, the friction force on the edge portion increased, while the inner portion exhibited a corresponding reduction in the friction.…”

“…Two-dimensional materials, such as graphene, exhibit high edge-to-surface ratios, so contact edge effects are generally not negligible and must be included in the description of friction. [17][18][19][20][23][24][25][26] Contact edges provide an additional edge-related potential barrier, which leads to substantial friction energy dissipation between two contacting surfaces, indicating significant edge effects on nanoscale friction. 23 Therefore, it is essential to reveal the friction-contact area relationship and how it relates to edge effects for the design of nanometer devices with optimal mechanical performances.…”

“…14,19,25,27 In the incommensurate case, friction primarily originates from the atoms of the contact edge region, while the inside atoms contribute less to friction dissipation. 17,20,24,26 Recent studies have shown that friction is weakly dependent on the contact area in the incommensurate contact (i.e., lattice mismatch) because friction is dominated primarily by the contact edge. 17,21,28,29 For example, molecular dynamics simulations of incommensurate double-walled carbon nanotube oscillators showed that friction is independent of the tube length (i.e., area).…”