Curved micromachined ultrasonic transducers

Capacitive micromachined ultrasonic transducers (cMUTs) have recently emerged as an alternative to traditional piezoelectric ultrasonic transducers. They have demonstrated competitive image quality, increased bandwidth and the potential for integrated on-chip electronics. For a variety of reasons, the cMUT fabrication process has limited initial cMUT array prototypes to high frequency, flat linear or phased array designs. However, Sensant has developed a straightforward method for the manufacture of curvilinear cMUT probes. This paper outlines the modeling and cMUT design strategies, describes relevant process steps, and details the manufacturing challenges associated with the curving and packaging of a cMUT. The paper concludes with measured results, including time and frequency domain impulse response plots and phantom and in vivo images from a fully packaged cMUT array with a center frequency of 4 MHz and a radius of curvature of 40 mm, parameters typical of an abdominal imaging probe.