Observation of Nanometer-Scale Rolling Motion Mediated by Commensurate   Contact
  We report, through experimental observations and computer simulations, that atomic lattice interlocking can determine whether an object rolls or slides on a surface. We have quantitatively manipulated carbon nanotubes (CNTs) on a variety of substrates with an atomic force microscope (AFM) and observe rolling to occur only on graphite. We measure the forces when the CNT is in-registry with the graphite lattice, and observe rolling only in this lock-in state. Atomistic computer simulations identify the energy barriers for sliding and rolling, elucidate atomic-scale features of slip-roll motion, and explain the details of the lateral force data in terms of the intrinsic faceting of multiwall CNTs. 
M. R. Falvo, J. Steele, A. Buldum, J. D. Schall, R. M. Taylor II, J.P.   Lu, D. W. Brenner, R. Superfine