Superelasticity and wrinkles controlled by twisting circular graphene

Controllable wrinkles in terms of amplitude, wavenumber and onset torsional angle are realized by using a twisting way of circular graphene sheets. A parametric study is carried out to investigate several factors, i.e., graphene size (inner radius rI and outer radius Ro) and torsional angle, on the wrinkle formation of graphene. The effects of both wavenumber and amplitude are investigated in detail, because they are the most critical parameters in tuning the surface morphology that is finally reflected on the electrical properties of graphene. It is found that the onset torsional angle on the formation of wrinkles decreases as the graphene size increases. When the torsional angle increases continuously, the amplitude will abruptly jump due to a sudden change in the wrinkle pattern. The wrinkle wavenumber of graphene can also be controlled by changing the ratio of the inner and outer radii (i.e., rI∕Ro). The variation of the strain energy shows that the structural transformation is reversible, this is mainly caused by the superelastic property of graphene. Hence, the formation of recyclable wrinkles can be realized by loading and unloading processes.