Finite element method simulation, design, and fabrication of micromachined high-frequency piezoelectric composite with hexagonal pillars for intravascular ultrasound imaging

As the core component of the transducer, the property of the piezoelectric material determines the quality of the transducer. However, the traditional 1–3 piezoelectric composite is disturbed by the lateral and other spurious resonance in the application of high-frequency field, which results in the decrease of the vibration energy and acoustoelectric conversion efficiency for the ultrasound transducer. Herein, a novel 1–3 piezoelectric composite with hexagonal pillars is designed to suppress the influence of the lateral and other spurious resonance. In this paper, the finite element model of the 1–3 piezoelectric composite with hexagonal or square pillars used for 50 MHz is built. The specific design procedure and the optimum parameter of composite are exhibited by the FEM simulation. The vibration mode of the composite with hexagonal pillars is purer compared with the composite with square pillars. The effects of the side wall slope of the hexagonal pillars in composite are considered, and the value of the angle should be larger than 87° in the practical fabrication process. The composite with the hexagonal pillars is fabricated by the femtosecond laser lithography and the measured resonant impedance property agrees with the simulation results. These results provide a practicable method to design and fabricate the ultrahigh frequency ultrasonic transducer for intravascular ultrasound (IVUS) imaging.