Casimir repulsion though a water-based ferrofluid

Abstract

We investigate the Casimir pressure between two dissimilar plates separated by a layer of magnetic fluid. Numerical computations of the Casimir pressure are performed for Au and SiO2 plates with an intervening layer of water and water-based ferrofluid obtained on addition to water a 5% volume fraction of magnetite nanoparticles with 10 nm diameter. It is shown that an addition of nanoparticles leads to a widening of separation region, where the Casimir interaction is repulsive. This result does not depend on whether the plasma or the Drude model is used for extrapolation of the optical data of Au to low frequencies. The effect of enhanced repulsion due to the presence of ferrofluid may be useful for preventing stiction of closely spaced elements in various microdevices.