Development of piezoelectric micromachined ultrasonic transducer linear array including focusing function based on principle of fresnel zone plate

In this paper, we present a Fresnel zone plate piezoelectric micromachined ultrasonic transducer (FZP-pMUT) array that integrates beam-focusing functionality directly into the transducer structure. The array comprises circular and donut-shaped elements with different top-electrode geometries, which generate ultrasonic waves with opposite phases under a single drive signal. Based on Fresnel zone plate theory, this configuration enables intrinsic beam focusing without external lenses. Simulations demonstrate antiphase vibration of the elements and a significant improvement in beam convergence, including higher acoustic pressure and narrower beam width, compared with conventional linear pMUT arrays. A prototype device was fabricated, and measurements of vibration in air and acoustic pressure in liquid confirmed the predicted focusing behavior. The experimental results were in reasonable agreement with the simulation results. These results validate the feasibility of the proposed FZP-pMUT concept for compact ultrasonic transducer arrays with integrated focusing capability. • Novel pMUT array integrates Fresnel zone plate focusing function. • Circular and donut electrodes generate opposite-phase ultrasound. • FZP-based design achieves intrinsic ultrasonic beam focusing. • Simulations and experiments show excellent focusing agreement. • Promising for compact, low-cost, high-resolution ultrasonic systems.