In one minute

Munday, Capasso and Parsegian measure a repulsive Casimir–Lifshitz interaction between a gold-coated sphere and a silica plate immersed in bromobenzene. Replacing the silica plate with gold changes the interaction to attraction while keeping the liquid and sphere material the same. The explanation depends on the liquid's dielectric response lying between those of the two solids across a broad frequency range. An atomic force microscope measures cantilever bending, and measurements at different approach speeds separate fluid drag from the interaction. The authors report uncertainty from material optical properties and warn that forces below 10 piconewtons cannot be measured accurately in this setup. They suggest levitation within a fluid and reduced sticking in tiny devices as possible applications, rather than demonstrated devices.

Measured long-range repulsive Casimir–Lifshitz forces