Finite element analysis of CMUTs with pressurized cavities

We propose using CMUTs with pressurized cavities in environments with extreme pressure variations. By controlling the pressure inside the cavity, the pressure differential across the CMUT plate can be kept low, ensuring a stable operating point and preventing mechanical failure. In such CMUTs, a squeeze film is formed between the plate and the substrate, which provides additional damping as well as stiffening. The damping from the squeeze film helps increase the bandwidth of the CMUT. We present a new method for performing a finite element analysis for such structures using ANSYS. We fabricated a variety of vented CMUTs in the frequency range of ~100-200 kHz, which exhibited a quality factor of 25-30 in air at 1 atm pressure. Our finite element model successfully predicts the center frequency and quality factor for these devices.