Medical imaging with capacitive micromachined ultrasound transducer (cMUT) arrays

Several groups have shown images made with capacitive micromachined ultrasound transducers (cMUTs). This new transducer technology has emerged as a leading research area because these devices are non-resonant and can be integrated with signal processing electronics. We review real time imaging performed with early silicon nitride devices. Then, we present new results from a wafer bonded cMUT probe produced and tested in our lab. These wafer bonded cMUTs show a fractional bandwidth of 130% (3-13 MHz), that covers almost the entire frequency range of interest for medical ultrasound. Further discussion outlines some of the challenges involved and potential solutions for integrating cMUT arrays with medical imagers. A review of some of the models from the literature is also given as a means to optimizing the cMUT design and impedance matching.