When working in the grand canonical ensemble we write the grand potential as $\Omega = \Omega (T,V,\mu)$. In this case we are taking the chemical potential $\mu$ to be an independent variable. This would imply that this ensemble is best suited to situations in which the chemical potential is an experimentally controlled parameter.
If this is the case, then what are some ways in which the chemical potential can be controlled experimentally?
Specifically I am interested in a solid state system which is being modeled as electrons on a lattice. In theory, by adjusting the chemical potential we could control the filling fraction of electrons for this system, taking it from band insulator to conductor or from Mott insulator to conductor. Is this type of tuning possible with real systems? If so, what are some realistic applications and/or specific limitations of these techniques.