A finite element analysis of rolling of bilayer films to cylindrical and conical tubes

With recent developments in nanotechnology, self-assembled structures are providing convenient, cheaper and more precise ways of manufacturing various patterns and shapes with less complexity. Of these self-assembled structures, rolled-up nano-tubes play a vital role in various aspects. The notion is, the utilization of strain energy developed during epitaxial growth of a bilayer thin film over a substrate, mediated by a sacrificial layer. While the sacrificial layer is etched, the bilayer film is subjected to release its own in-built strain energy in the out-of-plane direction (3D structure) due to a bending stress induced by biaxial strain through the thickness, in the bilayer. This paper proposes a new method of fabricating conical self-rolled assembly by thickness and strain variations along the width of the bilayer and, cylindrical structure of variable radius due to thickness and strain variations along the length.