Deployment of Piezoelectric Disks in Sensing Applications

Abstract

Micro-electromechanical Systems (MEMS) have revolutionized the way we approach sensing and actuation, offering benefits like low power usage, high sensitivity, and cost efficiency. These systems rely on various sensing mechanisms such as electrostatic, piezoresistive, thermal, electromagnetic, and piezoelectric principles. This thesis focuses on piezoelectric sensors, which stand out due to their ability to generate electrical signals without needing an external power source. Their compact size and remarkable sensitivity make them highly attractive. However, they’re not without challenges—their performance can be affected by temperature changes, and they can’t measure static forces. These limitations call for advanced signal processing and compensation techniques. Piezoelectric sensors, which operate based on the direct and inverse piezoelectric effects, find use in a wide range of applications, from measuring force and acceleration to detecting gases. This research zooms in on two key applications of piezoelectric sensors: force sensing and gas detection. For force sensing, the study focuses on developing smart shims that measure forces between mechanical components, which helps prevent structural failures. The experimental setup includes an electrodynamic shaker, a controller, and custom components like a glass wafer read-out circuit and a 3D-printed shim holder. During tests, the system underwent a frequency sweep from 10 Hz to 500 Hz, and a resonance was detected at about 360 Hz, matching the structural resonance. Some inconsistencies in the sensor’s output were traced back to uneven machining of the shim’s holes and variations in circuit attachment. To address these issues, the study suggests improving the machining process and redesigning the shim holder for better circuit alignment. Future work will include testing for bending moments, shear forces, and introducing a universal joint in the design to study moment applications more effectively. On the gas sensing side, the research examines a piezoelectric disk with a Silver- Palladium electrode for detecting methane. Using the inverse piezoelectric effect, the sensor’s natural frequency was found to be around 445 kHz. When coated with a sensitive material—PANI doped with ZnO—the disk exhibited a frequency shift of 2.538 kHz, indicating successful methane detection. The setup for this experiment included a gas chamber with precise control over gas flow and displacement measurements. Interestingly, after methane was replaced with nitrogen, the natural frequency returned to its original value, demonstrating the sensor’s reversible detection capability. Future research will expand to test other gases and sensitive materials, broadening the scope of applications. In summary, this thesis pushes the boundaries of piezoelectric MEMS sensors by tackling key design and performance challenges. Through detailed experimental methods, results, and suggested improvements, it lays a solid foundation for further research aimed at enhancing the reliability and versatility of piezoelectric sensors in real-world applications.