The anharmonic Casimir oscillator (ACO)-the Casimir effect in a model microelectromechanical system

The Casimir effect is the attractive pressure between two flat parallel plates of solids that arises from quantum fluctuations in the ground state of the electromagnetic field. The magnitude of this pressure varies as the inverse fourth power of the separation between the plates. At a 20 nm separation between two metallic plates, the attraction is approximately 0.08 atmosphere. If one or both plates are nonconducting the pressure is smaller, roughly by an order of magnitude. As an idealized MEMS component that takes account of the Casimir effect, the anharmonic Casimir oscillator (ACO) is introduced and shown to be a bi-stable system for certain values of the dimensionless parameter, C, which characterizes the system. The phenomenon of "stiction" in MEMS is then explained as analogous to an ACO energetically descending to and settling in an equilibrium state that is very stable against perturbations for all values of C. A micromechanical switch based on the bistable ACO is proposed and modeled. The dynamics of an ACO, executing undamped periodic motion, are studied using numerical and analytical solutions of the differential equation of motion. Frequencies and amplitudes vary with C. C, in turn, is inversely proportional to the fifth power of the parallel plate separation. This extreme sensitivity makes the ACO an attractive platform for designing rather sensitive sensors and detector systems, such as submicrometer proximity sensors and microlever deflection detectors for scanning probe microscopes.