High performance large-area polymeric PMUT phased arrays in air

Airborne ultrasound applications such as mid-air vibro-tactile haptic feedback, acoustic tweezers, and touchless gesture recognition require high pressures at low ultrasonic frequencies. Current solutions for such applications include large standard bulk piezoelectric and relatively expensive and small silicon-based micromachined transducer arrays. In this study, we demonstrate the capability of flat-panel display compatible large-area thin-film polymeric PMUTs for the purposes of air-coupled high fill-factor ultrasound transducer arrays. Annular PMUT array designs were optimized via simulations and fabricated on glass wafer substrates. An optical microphone was used to perform high resolution measurements of generated acoustic focal and trap fields. Focal pressures of up to 1.1 kPa (at 30 mm) and 1.6 kPa (at 20 mm) were generated in air at 229 kHz and 390 kHz respectively demonstrating the capability of using large-area PMUTs for practical airborne applications.