Kelvin probe force microscopy at normal pressure was performed on the
Au-coated planar sample used to measure the Casimir interaction in a
sphere-plane geometry. The obtained voltage distribution was used to
calculate the electrostatic pressure P(D) in the configuration of the
Casimir experiments (D being the separation). In the calculation it was
assumed that the potential on the sphere had the same statistical
properties as that measured on the palne, and that there were no
correlation effects on the potentials due to the presence of the other
surface. Within this framework, and assuming that the potential
distribution does not vary significantly at low pressure, the calculated
P(D) does not explain the magnitude or the separation dependence of the
difference Delta P(D) between the measured Casimir pressure and the one
calculated using a Drude model for the electromagnetic response of Au.

Référence:
Kelvin probe force microscopy of metallic surfaces used in Casimir force
measurements
R.O. Behunin, D.A.R. Dalvit, R.S. Decca, C. Genet, I.W. Jung, A. Lambrecht,
A. Liscio, D. Lopez, S. Reynaud, G. Schnoering, G. Voisin, and Y. Zeng
http://arxiv.org/abs/1407.3741