▎ 摘　　要

Graphene folding is an essential process in the design and manufacturing of graphene origami. Here we report the nanomechanical z-shape (accordion) folding of single graphene sheets on flat substrates by using atomic force microscopy techniques. The quantitative nanomechanical measurements in conjunction with nonlinear mechanics modeling and molecular dynamics simulations reveal that a reversible out-of-plane buckling delamination of graphene occurs in its early-stage folding process, which enables graphene to deform into a stable self-folded z-shape conformation. The research findings are useful to the study of active and controllable folding of graphene and in the pursuit of graphene origami with intricate geometries. (C) 2016 Published by Elsevier Ltd.