Self-Folding Mechanics of Surface Wettability Patterned Graphene Nanoribbons by Liquid Evaporation

The control of geometric shapes is well acknowledged as one of the facile routes to regulate properties of graphene. Here, we conduct a theoretical study on the evaporation-driven self-folding of a single piece of graphene nanoribbon that is immersed inside a liquid droplet prior, and demonstrate the folded pattern, which is significantly affected by the surface wettability gradient of the graphene nanoribbon. On the basis of energy competition among elastic bending deformation, liquid-graphene interaction and van der Waals force interaction of folded nanoribbons, we propose a theoretical mechanics model to quantitatively probe the relationship among self-folding, surface wettability gradient, and pattern and size of ultimate folded graphene. Full-scale molecular dynamics (MD) simulations are performed to validate the energy competition and the self-folded patterns, and the results show good agreement with theoretical analyses. This study sheds novel insight on folding graphene nanoribbons by leveraging surface wettability and will serve as a theoretical guidance for the controllable shape design of graphene nanoribbons.