Atoms are hold together to form different materials and devices through short range interactions such as chemical bonds and long range interactions such as the van der Waals force and electromagnetic interactions. Quantum mechanics is powerful to describe the short range interactions of materials at the nanometer scale, while molecular mechanics and dynamics based on empirical potentials are able to simulate material behaviors at much large scales, but weak in handling of processes including charge transfer and redistributions, such as mechanical-electric coupling of functional nanomaterials, plastic deformation~ fracture and phase transition of nano- materials. These issues are also challenging to quantum mechanics which needs to be extended to van der Waals distance and larger spatial as well as temporal scales. Here, we make brief review and discussions on such kind of mechanical behaviors of some important functional nanomaterials and nanostructures, to probe the frontier of nanomechanics and the trend to multiscale physical mechanics.
When material dimensions are reduced to the nanoscale,exceptional physical mechanics properties can be obtained that differ significantly from the corresponding bulk materials.Here we review the physical mechanics of the friction of low‐dimensional nanomaterials,including zero‐dimensional nanoparticles,one‐dimensional multiwalled nanotubes and nanowires,and two‐dimensional nanomaterials-such as graphene,hexagonal boron nitride(h‐BN),and transition‐metal dichalcogenides-as well as topological insulators.Nanoparticles between solid surfaces can serve as rolling and sliding lubrication,while the interlayer friction of multiwalled nanotubes can be ultralow or significantly high and sensitive to interwall spacing and chirality matching,as well as the tube materials.The interwall friction can be several orders of magnitude higher in binary polarized h‐BN tubes than in carbon nanotubes mainly because of wall buckling.Furthermore,current extensive studies on two‐dimensional nanomaterials are comprehensively reviewed herein.In contrast to their bulk materials that serve as traditional dry lubricants(e.g.,graphite,bulk h‐BN,and MoS_(2)),large‐area high‐quality monolayered two‐dimensional nanomaterials can serve as single‐atom‐thick coatings that minimize friction and wear.In addition,by appropriately tuning the surface properties,these materials have shown great promise for creating energy‐efficient self‐powered electro‐opto‐magneto‐mechanical nanosystems.State‐of‐the‐art experimental and theoretical methods to characterize friction in nanomaterials are also introduced.
