Fourier reconstruction of the force signal using a microelectromechanical oscillator in the Casimir regime

Harmonics of the force between an engineered sample and a sphere mounted on high quality factor microelectromechanical oscillator have been measured. The sample consists of regions with deep trenches and flat regions. Both the sample and the sphere are coated with a thick layer of gold. The sample is sequentially rotated at selected frequencies yielding the Casimir interaction between the sphere and the sample, disentangled from the electrostatic contribution. The approach is promising and it should yield a Casimir measurement between 0.2 and 8 microns.