We present the basic principles of non-local optics in connection with the calculation of the Casimir force between half-spaces and thin films. At currently accessible distances L, non-local corrections amount to about half a per cent, but they increase roughly as 1/L at smaller separations. Self-consistent models lead to corrections with the opposite sign as models with abrupt surfaces.
Esquivel-Sirvent, R., Villarreal, C., Mochan, W. L., Contreras-Reyes, A. M., & Svetovoy, V. (2006). Spatial dispersion in Casimir forces: a brief review. Journal of physics A: mathematical and general, 39(Technical), 6323-6331. [10.1088/0305-4470/39/21/S24]. https://doi.org/10.1088/0305-4470/39/21/S24