Role of the Casimir force in micro- and nanoelectromechanical pressure sensors

The Casimir force caused by the electromagnetic fluctuations is computed in the configurations of micro- and nanoelectromechanical pressuresensors 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 onthe 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 obtained results in the design of micro- and nanoelectromechanical pressure sensors of next generations with further decreased dimensions are discussed.