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. Author manuscript; available in PMC: 2014 Sep 19.
Published in final edited form as: Nature. 2009 Jan 8;457(7226):170–173. doi: 10.1038/nature07610

Figure 1. Repulsive quantum electrodynamical forces can exist for two materials separated by a fluid.

Figure 1

a, The interaction between material 1 and material 2 immersed in a fluid (material 3) is repulsive when ε1(iξ) > ε3(iξ) > ε2(iξ), where the ε(iξ) terms are the dielectric functions at imaginary frequency (see Supplementary Information for details about the definition of ε(iξ)). b, The optical properties of gold, bromobenzene and silica are such that εgold(iξ) > εbromobenzene(iξ) > εsilica(iξ) and lead to a repulsive force between the gold and silica surfaces.