Directional Roll-up of Nanomembranes Mediated by Wrinkling

TL;DR

This paper explores how strain gradients and wrinkle geometry influence the direction of nanomembrane rolling, revealing a regime where rolling occurs parallel to the long edge, supported by theory, experiments, and simulations.

Contribution

It introduces a new understanding of directional roll-up behavior in nanomembranes influenced by wrinkling and strain gradients, expanding beyond traditional perpendicular rolling models.

Findings

Preferential rolling direction depends on wrinkle geometry and strain gradient

Experimental verification of parallel rolling regime

Finite element simulations match elasticity theory predictions

Abstract

We investigate the relaxation of rectangular wrinkled thin films intrinsically containing an initial strain gradient. A preferential rolling direction, depending on wrinkle geometry and strain gradient, is theoretically predicted and experimentally verified. In contrast to typical rolled-up nanomembranes, which bend perpendicular to the longer edge of rectangular patterns, we find a regime where rolling parallel to the long edge of the wrinkled film is favorable. A non-uniform radius of the rolled-up film is well reproduced by elasticity theory and simulations of the film relaxation using a finite element method.