Macroscopic orientation control of graphene flakes by magnetic field and broad device applications

We demonstrate the orientation control of graphene flakes by a weak static magnetic field and subsequently achieve high order parameter alignment by rotating magnetic field. The orientation control is made by weak static magnetic field for large diamagnetic susceptibility of exfoliated graphene. Viewed as a non-magnetic material, a liquid suspension of graphene flakes is firstly used for magnetic field sensing with high sensitivity and spatial resolution. The graphene suspension is then packaged as a writing and/or display board that can be controlled by magnets or magnetic field. Graphene liquid suspension was firstly aligned with high order parameter of 0.8 by rotating magnetic field. Macroscopic optical properties of aligned graphene flakes such as birefringence and diffraction were investigated. After mixing with UV cured resin, graphene flakes suspension was aligned as high performance polarizer. By combination lithography process with rotating magnetic field alignment, graphene flakes were assembled into patterns of different orientations with lithography mask. 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.