Fabrication of Ultrasonic Sensors Using Micro Cantilevers and Characteristic Measurement in Vacuum for Acoustic Emission Sensing

Acoustic emission AE sensors are attractive for the detection of machine fracture in real time. We fabricated AE sensors using the MEMS technology. The AE sensors consisted of silicon cantilevers resonating at frequencies of 50, 100, and 150i¾?kHz. Silicon piezoresistors were installed close to the cantilevers. In order to obtain an ambient pressure appropriate for the operation of the cantilevers, the Q factor of the cantilevers was calculated by analytical models as a function of pressure. The properties of the fabricated sensors were measured in a vacuum chamber. We also tentatively packaged the AE sensor and an amplifier in a vacuum to decrease the influences of air damping and noise.