Modelling of 3D-Printed Air-Coupled PLA-Based Ultrasonic Transducers

Additive manufacturing enables low-cost fabrication of ultrasonic transducers in small quantities. However, their design is challenging due to fabrication tolerances and multiple dependent parameters. Thus, we present a finite element model for optimizing a PLA-based 3D-printed capacitive film transducer to analyze the different behavior. The model, implemented in COMSOL Multiphysics, combines solid mechanics, electrostatics, pressure acoustics, and thermoviscous acoustics in a 2D-axisymmetric configuration. Validation is carried out using a commercial reference transducer, showing that the main lobe width is 10°, with a loss of -10dB between the simulated and measured directivity. Based on this validated numerical model, an additively manufactured custom PLA-based transducer is analyzed. The simulation model can accurately represent the mechanical prestress in the membrane. The results confirm that the model captures the influence of mechanical prestress on resonance frequency, sound pressure level, and membrane displacement. Reduced prestress results in a resonance frequency shift of up to 26.4% and a decrease in sound pressure of 2.1%. The directivity patterns further demonstrate agreement in the main lobe between simulation and measurement. The study proves that the model presented reliably captures the coupled electromechanical and acoustic behavior of 3D-printed ultrasonic transducers, thereby reducing prototyping effort and supporting future improvements in transducer design.