Piezoelectric micromachined acoustic emission sensors for early stage damage detection in structures

Acoustic emission (AE) is a passive nondestructive evaluation (NDE) method that relies on the energy release of active flaws. The passive nature of this NDE method requires highly sensitive transducers in addition to low power and lightweight characteristics. With the advancement of micro-electro-mechanical systems (MEMS), acoustic emission (AE) transducers can be developed in low power and miniaturized. In this paper, the AE transducers operating in plate flexural mode driven piezoelectrically known as Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are presented. The AE PMUTs are manufactured using PiezoMUMPS process by MEMSCAP and tuned to 46 kHz and 200 kHz. The PiezoMUMPs is a 5-mask level SOI (silicon-on-insulator) patterning and etching process followed by deposition of 0.5 micron Aluminum Nitride (AlN) to form piezoelectric layer to form the transducers. The AE transducers are numerically modeled using COMSOL Multiphysics software in order to optimize the performance before manufacturing. The electrometrical characterization experiments are presented. The efficiency of the proposed AE PMUTs compared to the conventional AE transducers in terms of power consumption, weight and sensitivity is presented.