Polymer-based piezoelectric ultrasound transducer arrays on glass demonstrating mid-air applications

Glass backed ultrasound transducer arrays enable the possibility of exciting new ultrasound applications that require larger surface areas and scaling beyond traditional CMOS fabricated devices. In this work, we describe the modeling and design of our fabricated large area polymer-based P(VDF-TrFE) piezoelectric micromachined ultrasound transducers (PMUTs). In addition, we demonstrate the capabilities of the technology using a fabricated large area annular array driven with phased input signals yielding focused acoustic waves in mid-air. Theoretical electromechanical modeling and simulations of individual PMUTs were conducted and the nominated PMUT design was incorporated into an annular array for use in mid-air ultrasound focusing. Array performance was characterized using a Polytec laser Doppler vibrometer and a Xarion optical microphone and was subsequently compared with expected results. The PMUTs were driven at 256 kHz and the input phase delay was configured to produce a focal point at 10 mm above the center of the annular array. The pressure at the focal point was found to have a pressure exceeding 300 Pa and good linearity w.r.t. input voltage. Reasonable agreement is observed between the expected and measured fields demonstrating the future capability of using large-area PMUTs for ultrasonic applications in air.