Feasibility Study of PZT Thin-Film Sensors and Actuators for Smart Microstructures and MEMS Devices

摘要

This paper demonstrates the feasibility of using PZT thin films as sensors and actuators for smart structures and MEMS applications. The feasibility study includes specimen preparation and vibration testing. The specimen consists of a substrate, a PZT thin film, and a bulk PZT. The substrate is a doped conductive silicon wafer. The PZT thin film is fabricated through sol-gel dip-coating process with added PZT nano-particles to prevent homogeneous crystallization. The thickness of the PZT thin film is about 5 urn and the capacitance varies from 90 to 130 pF. The bulk PZT, which is commercially available, serves as a reference sensor and actuator for the specimen. The dimensions of the specimen are 2.7 cm x 1.4 cm x 0.4 mm. The vibration testing consists of sensor testing and actuator testing. In the sensor testing, the PZT thin film serves as a sensor, while the bulk PZT serves as an actuator. The specimen is cantilevered, and harmonic excitations are generated from 500 Hz to 500 kHz. A laser Doppler vibrometer also monitors the specimen vibration in addition to the PZT thin-film sensor. As a sensor, the PZT thin film produces legible harmonic output voltage ranging from 0.5 mV to 200 mV. In the actuator testing, the PZT thin film serves as an actuator, while the bulk PZT serves as a sensor. Similarly, harmonic excitations are generated from 100 Hz to 1 MHz. Depending on the excitation frequency, actuation voltage of the PZT thin film ranging from 0.1 V to 100 V results in legible voltage response from the bulk PZT. Also, the PZT thin film experiences significant aging when it serves as an actuator. This might result from fatigue or accumulated defects of the PZT thin film. Finally, the PZT thin film can become nonlinear in sensing and actuation, when the excitation voltage is too high.