Triply periodic minimal surfaces for gradient impedance matching layers in ultrasonic transducers
Donato D'Aprile, Ferdinando Auricchio, Simone Morganti · Engineering Research Express · 2025
Abstract Ultrasonic transducers are widely used in various fields, including industrial non-destructive testing, underwater detection, and medical diagnostics. A key challenge in optimizing their performance is the impedance mismatch between the piezoelectric elements and the surrounding medium, which significantly affects energy transmission efficiency. Traditional matching layers, such as quarter-wavelength ( λ /4) structures, enhance transmission around a specific frequency but suffer from narrow bandwidth limitations. To address this issue, broadband matching layers with gradually varying acoustic impedance have been proposed. In this study, we introduce a new broadband matching layer design based on Triply Periodic Minimal Surfaces (TPMS), specifically utilizing primitive unit cells with a quasi-exponential density variation along the wave propagation direction. These structures can be easily designed with a continuously varying material distribution and efficiently fabricated using additive manufacturing techniques. We develop finite element models of the proposed designs, which demonstrate high efficiency in terms of energy transmission, showing a clear improvement in the transmission coefficient compared to conventional solutions. Additionally, our acoustic numerical results indicate that the number of unit cells significantly influences the presence of frequency band gaps. This characteristic could be leveraged to design matching layers that selectively block specific frequency ranges.