Orientation control of graphene flakes by magnetic field: broad device applications of macroscopically aligned graphene.

We demonstrate the orientation control of graphene flakes by a weak magnetic field and subsequently show two examples of novel device applications of macroscopically aligned graphene. The control is made possible by a large diamagnetic susceptibility of exfoliated graphene. A liquid suspension of graphene flakes is first used for magnetic field sensing and display with sensitivity and spatial resolution higher than traditional iron filings or particles. The graphene suspension is then packaged as a writing and/or display board that can be controlled by magnets or magnetic field. Both applications require no external lighting or polarizing optics because they utilize macroscopic alignment and anisotropic optical properties of graphene. The macroscopic control and alignment of graphene can not only transfer unique properties of graphene from microscopic to macroscopic scale, but also be used to align other nanomaterials..