Pre-charged CMUTs with efficient low-bias voltage operation for medical applications

Traditionally dielectric charging has been viewed as an undesirable feature of Capacitive Micromachined Ultrasound Transducers (CMUTs) because charging can alter performance of devices and lead to permanent collapse. We introduce a beneficial aspect of dielectric charging in CMUTs. We demonstrate CMUTs that may be pre-charged with a shift in collapse voltage so that at zero applied bias voltage they experience an electrostatic deflection due to trapped dielectric charge. We demonstrate efficient pre-collapse operation at zero applied bias voltage with exceptional long-term reliability. Similar existing strategies for pre-charging CMUTs were not implemented for diagnostic frequencies for immersion or tissue-coupled applications.