Résumé
The Casimir force arises from the quantum fluctuations of the electromagnetic field. It leads to an attraction between electrically neutral bodies with a vacuum gap that be- comes measureable at nanoscale separations. Under the trend of miniaturization, such quantum electrodynamical effects are expected to play an important role in nanomechanical devices. One remarkable property of the Casimir force is its non-trivial dependence on the shape of the in- teracting bodies. Experiments using the corrugated surface of gratings have demonstrated the deviation of the Casimir force from the proximity force approximation. In these experiments, it was necessary to choose one of the bodies to be a sphere to circumvent alignment difficulties.Here, we present measurement of the Casimir force gradient between two microfabricated silicon beams, both of which contain rectangular corrugations. One of the beams acts as the forcesensing element. As it vibrates in a perpendicular magnetic field, a back electromotive force is generated and the corresponding change in the current is measured. The force gradient exerted on this beam is measured from the resonance frequency shift. The distance to the other beam is controlled using a comb actuator integrated on the same substrate, where electrostatic forces push the second beam towards the force-sensing beam. By using lithography to define the structures, they are aligned to allow the two gratings to interpenetrate when the separation between them is reduced. Our data shows a number of novel features, including strong deviations of the force gradient from the proximity force approximation and a non-zero, distance-independent Casimir force over certain range of displacement.We will also discuss the design of a bridge to measure the difference in Casimir forces on two types of surfaces. By fabricating an additional sensing beam next to the original one and measuring their resonant frequency shifts simultaneously in the same experimental run, the difference in the Casimir force gradient of two different geometries can be compared.