Ultrasonic transducers are widely used in various applications including medical imaging, nondestructive evaluation, object/gesture recognition, automotive, and range-finding. Compared to conventional capacitive micromachined ultrasonic transducers (CMUTs), piezoelectric micromachined ultrasonic transducers (PMUTs) have an advantage that they can be utilized without high bias voltages, resulting in simpler electronic interfaces. This project targets air-coupled PMUTs with wide bandwidth to achieve high axial resolution in pulse-echo imaging, where air-coupled transducers typically operate in the frequency range of 40 kHz to 80 kHz. In this project, we design the below 100kHz resonance frequency to achieve long-range detection. Two major piezoelectric materials are PZT and AlN; PZT is well known to have high piezoelectric coefficient e31,f related to the transmitting efficiency, where AlN has low e31,f but its low dielectric constant results in much better receive sensitivity. Another emerging material Scandium-doped AlN exhibits significantly increased piezoelectric properties retaining the features of AlN. In this project, we design, model, and characterize ScAlN PMUTs with a large displacement amplitude for an in-air operation to realize long-range object detection system.
Project end date: 08/07/19