Electrical and Computer Engineering ETDs

Publication Date



Ultrasound covers a broad range of applications from underwater exploration and nondestructive evaluation of materials to medical diagnosis and treatment. The ultrasonic transducer plays an important role in determining the resolution, sensitivity, as well as other critical diagnostic capabilities of an ultrasonic detection or imaging system. Currently piezoelectric ultrasonic transducers dominate the market. The device performance of the piezoelectric ultrasonic transducer in medical applications is limited by the material properties and related electrical and acoustic impedance match issues. The fabrication of piezoelectric transducer array requires meticulous handcrafting. It is difficult and expensive to fabricate densely populated piezoelectric array. The Capacitive Micromachined Ultrasonic Technology (CMUT) has emerged as a promising alternative. Compared to piezoelectric technology, the MEMS based CMUT has advantages such as ease of fabrication and the potential to integrate with front-end electronic circuits. CMUT could also provide broader acoustic bandwidth and higher sensitivity over its piezoelectric counterpart, which would improve the image resolution. The main goal of this dissertation work is to develop miniature CMUT devices for minimally invasive biomedical diagnosis and treatment. A two-layer poly-silicon surface micromachining process mixed with bulk micromachining process was developed. Based on this process, three prototypes of application were developed in this research:1) a multi-looking imager, 2) a miniaturized invasive ultrasonic probe, and 3) an image-Guided Therapy (IGT) system. Primary testing results including the acoustic/electrical characterization, ultrasonic imaging and flowmetering have been obtained and are discussed. These results indicate that CMUT technology has great potential to become the next-generation transducer technology for the Intravascular Ultrasonic system, invasive blood-flow metering, and therapeutic treatment.


Transducers, Biomedical, Ultrasonic transducers, Microelectromechanical systems

Document Type




Degree Name

Electrical Engineering

Level of Degree


Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Malloy, Kevin

Second Committee Member

Shen, Yulin

Third Committee Member

Zarkesh-Ha, Payman