Abstract: Ultrathin free-standing graphene oxide (GO) films were fabricated by vacuum filtration method assisted
with Ni(OH)2 nanosheets as the sacrifice layer. The surface of the obtained GO film is very clean as the Ni(OH)2
nanosheets can be thoroughly etched by HCl. The thickness of the GO films can be well-controlled by changing
the volume of GO dispersion, and the thinnest GO film reached ~12 nm. As a novel and transparent dielectric material, the GO film has been applied as the dielectric layer for the flexible touchless capacitive sensor which can effectively distinguish the approaching of an insulator or a conductor.