Nanocoveyor belt systems (NCBSs) are considered key components of micro-/nanoelectromechanical systems (M/NEMS). However, it is still a tremendous challenge to find suitable NCBSs and reveal their transmission mechanism at the nano-/microscale in some special applications. Here, we report black phosphorus (BP) NCBS using molecular dynamics (MD) simulations, which consist of a drive nanowheel, a driven nanowheel, and a nanoconveyor belt. Our MD results show that the time to achieve a stable transmission ratio strongly depends on the ambient temperature, the chirality and size of the NCBS, and the velocity of the drive nanowheel. The aaa-type BP-NCBS have better transmission efficiency and stability than other types due to their greater friction and better structural stability. In particular, the friction force between the two nanowheels and the belt dominates the transmission mechanism of the NCBS, in which the logarithmic relationship between the friction force and the transmission velocity of the corresponding two BP sheets from MD simulations agrees well with that from available continuum modeling. This study provides physical insights into the transmission mechanism of different NCBSs and should be of great help for designing other more perfect NCBSs in M/NEMS.

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In this study, the thermo-breathing vibration of carbon nanoscrolls (CNSs) is studied by molecular dynamics (MD) simulations and continuum modeling. The breathing vibration strongly depends on the competition between the cohesive energy among the graphene layers of CNSs and the bending energy of CNSs, where the explicit expressions for the total cohesive energy of CNSs are derived by using Gaussian quadrature based on van der Waals interlayer interactions. In particular, the interlayer amplitudes on the breathing vibration of CNSs at different temperatures are obtained by continuum modeling with the equipartition theorem. Checking against our MD simulations shows that the present theoretical model has high accuracy. The analytical solutions show that the temperatures have no effect on the nature frequency of CNSs, but have a great effect on the vibration amplitude of CNSs. The obtained results should be of great importance for understanding the thermo-mechanical vibration of nanosized devices.

Nanoscale defects, including cracks, circular holes, and the triangularshaped defects, often occur in the growth of boron nitride nanosheets (BNNS). In this study, the fracture behavior of chiral BNNS with different crack-tip shapes and the interactions of nanoscale crack-defects are studied using molecular dynamics (MD) simulations and finite element (FE) analysis. Both MD and FE results indicate that the fracture strength of BNNS with two crack tips (t = 2) is significantly higher than that with one crack tip (t = 1), in which the difference in zigzag (ZZ) direction is more obvious than that in armchair (AC) direction, mainly due to the fact that the change of bond angles near the crack tips is more substantial in the ZZ direction than those in the AC direction. Our results show that the fracture strength of BNNS strongly depends on crack-tip shapes, chiral angles, the defect-to-crack tip spacing and deflection angles. Checking against the current MD simulations and FE analysis shows the present results are reasonable. This study should be of great importance for enhancing the fracture performance of BNNS by modulating their crack-tip shapes and the interactions of nanoscale crack-defects.