Fundamental limits for Casimir repulsion between metamaterials

The Casimir force becomes increasingly important as mechanical devices are down-scaled into the micron range. We suggest here that artificial periodic materials with feature sizes in the nanometer range (meta materials) can be used to achieve Casimir repulsion at distances of a few microns. Simple analytical power laws are in good agreement with numerical calculations based on Lifshitz theory. In addition, we generalize strict upper and lower limits for the Casimir interaction to magneto-dielectric materials with in arbitrary layered structures with arbitrary (linear) response functions