Advanced Micromachined Ultrasonic Transducers for High Performance Medical Imaging Systems

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Breast cancer is a leading cause of death in women that is often undetected and underdiagnosed, contributing to the significant death rate of more than 21% of all female cancer deaths [Canadian Cancer Society Statistics 2017]. Amongst all diagnostic techniques, magnetic resonance imaging provides a more accurate estimate of tumor size. However, its cost, poor accessibility and inapplicable nature for patients with some implanted medical devices restrain its usage. Therefore, there is a momentous need to develop an accurate, safe and low-cost system that makes the examination procedure more frequently available to a larger portion of women across the world. ***Advance ultrasound imaging systems are emerging as essential and practical tools in routine clinical practices due to their nonionizing and noninvasive nature and lower cost. The crucial component of these ultrasound systems is the ultrasonic transducer and a promising candidate technology to advance state-of-the-art ultrasound imaging is capacitive micromachined ultrasonic transducer, CMUT. ***These transducers bring advanced microelectromechanical system (MEMS) fabrication technology to the field of ultrasound imaging and overcome the fabrication limitations of many bulk piezoelectric transducers. They offer batch production, which reduces the cost, tight parameter specification, wide bandwidth and achievable CMOS integration. However, they fall short particularly with output acoustic pressure, performance compromise between transmitting and receiving modes and their demand for high bias voltage. ***In this research program and in contrast with traditional MEMS transducers, the focus is on an innovative micromachined transducer configuration where more than one deflectable plate is employed in the CMUT cell structure. The unifying theme is to exploit the unique opportunity given by contribution of two or more vibrating membranes in transmitting and receiving ultrasonic signals. To reach this goal comprehensive analytical and numerical model will be developed; physical properties of multiple vibrating plates will be optimized; various fabricating techniques as well as packaging will be assessed; prototype devices will be fabricated; array configurations will be probed and electrical and acoustic properties of these transducers will be analyzed. This research program is designed to address many of unique concerns of conventional CMUTs including providing dynamic switching between different modes, enhancing output pressure and lowering the driving voltage.***The wide implication of this program offers many attractive applications including diagnostic imaging and therapeutic applications that provide enhanced health care to Canadian. Training of highly qualified personnel with a diverse set of skills is the essential component of this research proposal that will benefit Canadian private and public sectors.