Abstract The Casimir force caused by the electromagnetic fluctuations
is computed in the configurations of micro- and nanoelectromechanical pressure
sensors using Si membranes and either Si or Au-coated Si substrates. It is
shown that if, under the influence of external pressure, the membrane-substrate
separation drops to below 100 nm, the Casimir force makes a profound effect on
the sensor functioning. There exists the maximum value of external pressure
depending on the sensor parameters such that it finds itself in a state of
unstable equilibrium. For this and larger pressures, the Casimir force leads
to a collapse of the sensor, which loses its functionality. For any smaller
external pressures, there exist two equilibrium positions, one of which is
unstable and another one is stable, at smaller and larger membrane-substrate
separations, respectively. The latter can be safely used for the pressure
measurements. Possible applications of the ontained results in the design of
micro and nano pressure sensors of next generations with further decreased
dimensions are discussed.