Iran, Islamic Republic of
Keywords: graphene, self-assembly
Summary:I discuss the large-scale self-assembly of graphene ribbons we recently discovered for surface adhered sheets exfoliated onto silicon oxide substrates (Fig. 1)1. Directed folding of flap-like structures seeds growth of long ribbons that spontaneously peel and tear the sheet as they slide in superlubricous fashion. We observe ribbon growth up to 20 micrometers in size in ambient conditions. Measurement of ribbon velocity versus width in a slow growth regime reveals a logarithmic dependence consistent with thermally-activated bond dissociation. Our analysis inidcates this form of self-assembly may be a general phenomenon common to a large class of 2D materials. We present a theoretical treatment of the dynamics of the phenomena based on fracture mechanics. Our simple model predicts ribbon length and taper angle based on a balance of forces acting on two crack tips. The analysis predicts a driving force proportional to ribbon width based on self-affinity of the graphene relative to the substrate, and suggests the phenome may be general for any thermally activated sheet. 1. Annett, J. & Cross, G. L. W. Self-assembly of graphene ribbons by spontaneous self-tearing and peeling from a substrate. Nature 535, 271-275, doi:10.1038/nature18304 (2016).