Multiphysics Simulation of Acoustic Hologram-Lensed Piezoelectric Ultrasound Transducers

Traditional design methods for acoustic hologram (AH) lenses primarily rely on simulations of acoustic wave propagation, often using the iterative angular spectrum approach (IASA) and machine learning-assisted iterative algorithms. However, these methods typically omit practical factors such as the resonance characteristics of the source and the assembly conditions of transducer frontends, which are critical to optimizing multifocal focusing performance and minimizing experimental errors. To address this gap, we explored the use of multiphysics finite element analysis (FEA) to account for both harmonic wave propagation and the structural vibration of transducer components. In this preliminary study, we assessed the viability of an AH lens designed via FEA. An acoustic hologram lens for 450 kHz was modeled to generate a 'U'-shaped pressure pattern using the conventional IASA. This model was then imported into an FEA program for analysis. After volume wrapping and meshing, the wave propagation through the hologram lens was simulated at 450 kHz. Two models were compared: 1) an AH lens-only model and 2) an AH-lensed piezo-resonator model, both in full 3D and half-symmetric configurations. The full model contained 1.8 million tetrahedral elements and 2.5 million nodes, with the single-frequency harmonic analysis completed in 1 hour and 50 minutes, utilizing 13.25 GB of memory. The comparison revealed that the piezoelectric vibrator effects reduced image correlation by ~20% compared to the IASA result, indicating that multiphysics FEA provides more realistic simulations by incorporating structural vibrations, leading to more accurate design outcomes.