Journal Article

Self-assembly of graphene ribbons by spontaneous self-tearing and peeling from a substrate

Annett, James, Cross, Graham L. W.

2016

Overview

The controllable self-assembly of graphene ribbons on a substrate is shown, demonstrating an effect which could be applied to patterning and actuating devices made from two-dimensional materials. Adding a new dimension to monolayer graphene More than twenty years ago it was envisioned that graphene could be folded and cut into useful forms as a kind of nanoscale origami. In this issue James Annett and Graham Cross describe a system in which single-layer graphene can reorganize itself into three dimensions by a process of folding, sliding and tearing. When a small flap of graphene sheet is folded over to touch itself, it spontaneously starts to slide, tearing into a ribbon-like strip in the process. On removal of a kinetic barrier, the two-dimensional material can coalesce into its more familiar three-dimensional, layered form. The driver for this peeling phenomenon is a thermodynamic mechanism that is robust enough to work over large areas even in air at room temperature. The findings hold promise as a novel mechanism to mechanically actuate two-dimensional materials as well as a new way of assembling them into complex three-dimensional architectures. Graphene and related two-dimensional materials have shown unusual and exceptional mechanical properties 1 , 2 , 3 , with similarities to origami-like paper folding 4 , 5 and kirigami-like cutting 6 , 7 demonstrated. For paper analogues, a critical difference between macroscopic sheets and a two-dimensional solid is the molecular scale of the thin dimension of the latter, allowing the thermal activation of considerable out-of-plane motion. So far thermal activity has been shown to produce local wrinkles in a free graphene sheet that help in theoretically understanding its stability 8 , for example, and give rise to unexpected long-range bending stiffness 6 . Here we show that thermal activation can have a more marked effect on the behaviour of two-dimensional solids, leading to spontaneous and self-driven sliding, tearing and peeling from a substrate on scales approaching the macroscopic. We demonstrate that scalable nanoimprint-style contact techniques can nucleate and direct the parallel self-assembly of graphene ribbons of controlled shape in ambient conditions. We interpret our observations through a simple fracture-mechanics model that shows how thermodynamic forces drive the formation of the graphene–graphene interface in lieu of substrate contact with sufficient strength to peel and tear multilayer graphene sheets. Our results show how weak physical surface forces can be harnessed and focused by simple folded configurations of graphene to tear the strongest covalent bond. This effect may hold promise for the patterning and mechanical actuating of devices based on two-dimensional materials.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 140/133 / 639/301/119/544 / 639/301/357/1018 / 639/301/357/918/1053 / Bond strength / Carbon / Graphene / Humanities and Social Sciences / letter / Mechanical properties / multidisciplinary / Ribbons / Science / Thermal properties