Application of Flexible Piezoelectric Micromachined Ultrasonic Transducer Array for Object Detection

This paper presents the design, fabrication, and characterization of a reconfigurable flexible piezoelectric micromachined ultrasonic transducer (PMUT) array for object detection applications. The developed 3×3 PMUT array, operating at 230 kHz, can dynamically switch between flat, concave, and convex configurations to achieve both wide field-of-view scanning and high-resolution localization. The array is divided into four independent channels to enable beamforming and improve spatial coverage and detection accuracy. A key limitation of air-coupled PMUTs—long ringdown and inter-element crosstalk—was mitigated by coating the devices with a 5 µm parylene-C polymer layer, which reduced ringdown time by up to 40% without significant sensitivity degradation. Experimental results show that the ringdown was reduced from 500 µs to <300 µs, enabling a minimum detection range of 5 cm, while maintaining a maximum detection distance of ~1 m. Finite element method (FEM) simulations and pulse-echo measurements confirmed that the flexible array can successfully detect and localize small objects (2 cm diameter) with high accuracy using time-of-flight (ToF) and signal strength analysis of the A-scan signals. The array’s adaptable configuration facilitates efficient transition between scanning and precise localization modes, making it a promising candidate for compact ultrasonic object detection systems in applications such as robotics and augmented/virtual reality (AR/VR).