Nanotube formation from self-curling nanofilms driven by intrinsic surface-stress imbalance

Abstract

The theoretical analysis for fabricating nanotubes from self-curling of nanofilms due to intrinsic surface stress imbalance was given in this paper. A nanofilm was curled into a nanotube along tangential direction, while the other in-plane direction (cylindrical direction) was only elongated but wasn’t curled or bent. Film bending behavior is usually described by using Stoney formula, but the Poisson’s effect of cylindrical direction should be considered for describing mechanical behavior of curling up phenomenon. Stoney formula assumes that the surface stress is isotropic and the bending is also isotropic, but the shape of nanotube is anisotropic. On the other hand, surface effects and symmetry lowering effect strongly affect the mechanical properties of nonafilms. Here, we gave a more accurate curling theory by including surface stress, surface elasticity, symmetry lowering and Poisson’s effect of cylindrical direction.