  We propose a new experiment on measuring the Casimir force and its gradient
between an Au-coated sphere and two different plates made of doped
semiconductors. The concentrations of charge carriers in the plates are chosen
slightly below and above the critical density at which the Mott-Anderson
insulator-metal transition occurs. We calculate changes in the Casimir force
and the Casimir pressure due to the insulator-metal transition using the
standard Lifshitz theory and the phenomenological approach neglecting the
contribution of free charge carriers in the dielectric permittivity of
insulator materials (this approach was recently supported by the measurement
data of several experiments). It is demonstrated that for the special selection
of semiconductor materials (S- or Se-doped Si, B-doped diamond) calculation
results using both theoretical approaches differ significantly and the
predicted effects are easily detectable using the existing laboratory setups.
In the case that the prediction of the phenomenological approach is confirmed,
this would open opportunities to modify the van der Waals and Casimir forces
with almost no change of room-temperature dielectric permittivity.
