(Dr. Levent Degertekin, advisor)
"High-Temperature, High-Pressure Acoustic Microsensor with Optical Detection"
This work is focused on the design, fabrication, and testing of a broadband acoustic microsensor capable of monitoring gas turbine engine components. The sensor consists of a movable, optically reflective membrane and optical diffraction grating on a transparent substrate. The environment of a turbine engine requires that the sensor be able to withstand temperatures up to 600°C and static pressures up to 15 ATM and the application requires that the sensor detect sound pressures as small as 10 Pa. Robust materials and the benefits of the optical detection scheme enable the sensor to operate in the volatile environment while detecting the required sound pressures. FEM and analytical models were used to determine the behavior of the membrane in the turbine environment and aided in the design of the sensor. The designed sensor was successfully fabricated in the MiRC cleanroom using surface micromachining techniques. These techniques included standard microfabrication processes such as PECVD deposition and ICP etching. Testing of the device included the study of survivability and sensitivity. Survivability testing exposed the sensor to environments with high temperature and background pressure. Sensitivity testing measured the response of the device to acoustic pressures in atmospheric and high-pressure conditions. Results suggest the device is capable of surviving the turbine engine environment as well as detecting the required Pa-level sound pressures.