Ultrathin Metallic Coatings Can Induce Quantum Levitation between   Nanosurfaces
  There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5-50{\AA}) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together. 
Mathias Bostr\"om, Barry W. Ninham, Iver Brevik, Clas Persson, Drew F.   Parsons, and Bo E. Sernelius
quant-ph cond-mat.mes-hall cond-mat.mtrl-sci