Stereolithography for Tailoring the Dynamics of Flexural Ultrasonic Transducers

The flexural ultrasonic transducer (FUT) is a sensor primarily composed of a circular metallic plate, to which a piezoelectric ceramic disk is bonded. The vibrations generated from the piezoelectric ceramic stimulate vibration modes in the plate, thereby generating ultrasound waves. FUTs are typically utilized for industrial and proximity measurement and are narrowband in their nature. This means that driving even marginally off-resonance can significantly reduce their amplitude performance. In this study, additive manufacturing (AM) is explored to broaden the bandwidth of the FUT beyond what is possible using metallic variants. Here, stereolithography apparatus (SLA) printing is used to design FUT plates, thereby demonstrating how operational bandwidth can be tailored. Through using SLA resins, the achievable resonance frequencies are lower than those for metallic FUTs due to the significantly lower levels of Young’s modulus. Here, SLA resin-based FUTs are also demonstrated with comparable resonance frequencies to commercial metallic FUTs, showing their potential for industrial applications. There are opportunities for tailoring the dynamics of the transducer via the use of nonmetallic materials, which will enable for rapid and low-cost FUT manufacture. Using finite element analysis, electrical impedance measurement, laser Doppler vibrometry, and acoustic microphone measurement, this study shows how low-cost photopolymer resin-based air-coupled FUTs can be designed and fabricated, with enhanced bandwidth compared to metallic equivalents, in addition to wider beamwidth radiation patterns.