Abstract
The development of a new ultrasonic transducer capable of improved focusing performance has become a necessity to overcome the limitations of conventional ultrasonic transducer technology. In this study, we designed and optimized a metasurface piezoelectric ring device, and using multiphysics finite element analysis, we examined the performance of a planar ultrasonic transducer consisting of this device, a matching layer, a backing layer, and housing in producing a needle-like subwavelength focusing beam in water. For practical experiments, a metasurface piezoelectric ring device was fabricated using a laser ablation process. Subsequently, using a pulse-echo test, we found that the − 6 dB bandwidth of a planar ultrasonic transducer with a center frequency of 1.0 MHz was 37.5%. In addition, the results of an ultrasonic-focusing performance test showed that the full width at half-maximum of the axial subwavelength focusing beam was 0.78λ, and the full lateral width at half-maximum of the subwavelength lateral focusing beam was 7.03λ at a distance of 10.89λ. The needle-like focused ultrasonic beam technology implemented with a piezoelectric ring array based new planar ultrasound transducer is expected to be used in high-resolution imaging devices or medical ultrasound focusing devices in the future.
Highlights
The development of a new ultrasonic transducer capable of improved focusing performance has become a necessity to overcome the limitations of conventional ultrasonic transducer technology
We developed a method for optimizing metasurface piezoelectric ring array(MPRA) capable of forming a needle-like subwavelength ultrasonic-focusing beam and prepared a detailed structural design for a planar ultrasonic transducer (PUT) consisting of a matching layer, MPRA layer, backing layer, and housing using multiphysics finite element analysis
When a 5-cycle tone-burst signal excitation is performed on the PUT, the − 6 dB bandwidth is approximately 37.5% based on 1.0 MHz
Summary
The development of a new ultrasonic transducer capable of improved focusing performance has become a necessity to overcome the limitations of conventional ultrasonic transducer technology. The needlelike focused ultrasonic beam technology implemented with a piezoelectric ring array based new planar ultrasound transducer is expected to be used in high-resolution imaging devices or medical ultrasound focusing devices in the future. Beyond investigation of planar metasurfaces for ultrasonic transducer technology, studies focusing on engineering piezoelectric materials have been conducted, from which several ultrasonic devices have been developed These include an annular interdigital transducer that concentrates acoustic waves on the surface of lithium niobate to a single point[26]; an ultrathin helical 3D piezoelectric element for generating arbitrarily complicated ultrasonic fields[27]; and active acoustic metasurface consisting of 16 × 16 square lattice elements of subwavelength thickness in which each element is a supercell with a 4 × 4 piezoelectric sheet embedded in a matrix of epoxy resin[28] capable of eliminating the grating lobes caused by structural diffraction and steering the ultrasonic focus. A planar PUT integrating such an MPRA realizes a subwavelength ultrasonic focused b eam[30]
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