Membrane sandwich squeeze film pressure sensors.

Squeeze film pressure sensors exploit the dynamical modification of the mechanical properties of oscillating elements due to the compression of a fluid in a small gap region and allow for direct and absolute pressure measurements. This Tutorial article discusses the working principles of membrane sandwich squeeze film pressure sensors—i.e., sensors comprised of a parallel arrangement of two large-area, ultrathin suspended films forming a few-micrometer gap, and immersed in a fluid—and focuses on their operation in the free molecular flow regime. The effects of gas pressure on the vibrations of the membrane resonators and their coupled dynamics are discussed in general terms before recent experimental implementations using high tensile stress silicon nitride membranes are presented. [ABSTRACT FROM AUTHOR]