Measuring the Casimir force gradient from graphene on a SiO2 substrate

The gradient of the Casimir force between a Si-SiO2-graphene substrate and an Au-coated sphere is measured by means of a dynamic atomic force microscope operated in the frequency shift technique. It is shown that the presence of graphene leads to up to a 9% increase in the force gradient at the shortest separation considered. This is in qualitative agreement with the predictions of Lifshitz theory using the dielectric permittivities of Si and SiO2 and the Dirac model of graphene.