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A molecular dynamics simulation method is used to study the translocation of a single strand DNA through nanopores opened on graphene membranes. Simulation results uncover that the translocation time for four DNA strands (20G, 20A, 20T, and 20C) is proportional to the size of the four DNA bases. However, the change of the ionic current is caused not only by the physical blockade of the DNA, but also induced by the change of the ion distribution once the negatively charged DNA enters the nanopore. An electric double layer will be formed and causes higher cation and lower anion concentration near the DNA strand surface, which makes the ionic current blockade not sensitive to the base size for a single-layer graphene nanopore. Increasing the graphene membrane thickness can enhance the DNA physical blockage effect on ionic current and improve the nanopore sensitivity to the four DNA bases. [ABSTRACT FROM AUTHOR]

We report on molecular dynamics studies of phonon (lattice vibrations) transport in bilayer silicon thin films stuck together via van der Waals interactions. Results indicate that for bilayer thin films with an atomically smooth interface, the in-plane thermal conductivity of the bilayer films is the same as that of a single layer; however, the in-plane thermal conductivity of bilayer films is higher than that of single films if roughness is introduced at the interface. These observations are explained by the effects of interfacial roughness on phonon specularity parameters for transmitted and reflected phonons. [ABSTRACT FROM AUTHOR]