dependence stemming from the thermal change in the photon distribution [@Bostrom; @Bordag; @RodriguezW10:PRL], we find that such thermal-photon effects are negligible ($< 2$%) for the materials considered here. However, we show that substantial modifications to the objects separations occur due to Brownian motion of the micro-spheres. This effect can be reduced by lowering the temperature, limited by the freezing point of ethanol ($T \approx
159$ K ), or by increasing the sphere diameters. We propose experimentally accessible geometries consisting of hollow micro-spheres (which can be fabricated by standard methods [@Wilcox]) whose dimensions are chosen to exhibit a clear stable non-touching equilibrium in the presence of Brownian fluctuations. We believe that this work is a stepping stone to direct experimental observation of these effects.

In fluid-separated geometries the Casimir force can be repulsive, leading to experimental wetting effects [@wetting; @Capillarity; @Israelachvili] and even recent direct measurements of the repulsive force in fluids for sphere-plate geometries [@moh1; @Munday07; @Feiler]. In particular, for two dielectric/metallic materials with permittivity $\varepsilon_1$ and $\varepsilon_3$ separated by a fluid with permittivity $\varepsilon_2$, the Casimir force is repulsive when $\varepsilon_1 < \varepsilon_2 <
\varepsilon_3$ [@Dzyaloshinskii61]. More precisely, the permittivities depend on frequency $\omega$, and the sign of the 