Ultrathin layers of single-wall carbon nanotubes (SWCNTs) show considerable promise for applications ranging from fuel-cell membranes and biochemical sensors to bioactive films and transparent electrodes. The high conductivity and extreme anisotropy of SWCNTs enable the formation of conductive quasi-2D networks at remarkably low surface density, and the mechanical properties of the individual nanotubes can be outstanding. Recent advances in the separation of SWCNTs by length and type allow for the production of nanotube membranes with precisely tunable properties, and the tremendous potential of these films for flexible-electronics based applications demands a deeper understanding of the coupling between mechanical deformation and film conductivity. Compressive wrinkling is a powerful tool for measuring thin film elasticity and we use this approach here to study the nonlinear mechanical response of length-purified SWCNT membranes. Our measurements reveal a material that is remarkably stiff under infinitesimal deformation, but that softens dramatically just beyond this. We explain this strongly non-linear behavior in terms of a stress-induced rupturing of the network junctions that give the film its mechanical integrity, an effect correspondingly apparent as an anisotropic decrease in electrical conductivity.
Citation: Physical Review Letters
Pub Type: Journals
buckling, wrinkling, nanotubes, elasticity, conductivity, deformation