Theoretical Modeling of Piezoelectric Micromachined Ultrasonic Transducers With Honeycomb Structure

In this work, we reported a theoretical model for a novel piezoelectric micromachined ultrasonic transducer (PMUT). The sensing cells with hexagonal transduction diaphragms in the PMUT array are designed and arranged in a bioinspired honeycomb structure. Based on the classical piece-wise approach commonly used for PMUT with circular diaphragm, an enhanced theoretical model is developed. In this model, the deflection of the honeycomb diaphragm is analytically determined by the volume deflection, rather than the path deflection commonly used in the previous models. The hexagonal diaphragm is converted as a circular one, whose radius is derived by correcting the characteristic size of the hexagonal diaphragm multiplied by a correction factor. The calculated parameters by the reported theoretical model of a transduction cell in the PMUT array, such as resonant frequency and static deflection, matched well with the data obtained by finite element analysis and experiment. Special investigations are made on the effects of top electrode coverage and transduction layer thickness towards PMUT’s performance. The reported theoretical model in this work is suitable not only for PMUTs with circular and hexagonal transduction cells, but also for square and other arbitrary shape diaphragms. This enhanced theoretical model provides an interesting insight on design optimizations of PMUT with various transduction cell geometries. [2022-0093]