Planar ultrasonic transducer based on a metasurface piezoelectric ring array for subwavelength acoustic focusing in water

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.

Design and micromanufacturing technologies of focused piezoelectric ultrasound transducers for biomedical applications

“…The multi-element self-focusing transducer makes a special structure on the surface of the piezoelectric material, so that each region of the piezoelectric material emits different phases of ultrasonic waves, so as to realize the regulation of sound waves [117]. This method is very similar to acoustic lenses, especially through the special structural design of the material to achieve focusing [118].…”

Investigation of an Active Focusing Planar Piezoelectric Ultrasonic Transducer

“…Curved piezoelectric structures [23], on the other hand, face challenges in adapting to optimal acoustic matching layers. Some studies develop acoustic metamaterials [24,25] or introduce phased array methods [26,27] to avoid these problems mentioned above. However, these solutions also present challenges in terms of fabrication complexity and cost-effectiveness.…”

Distinct thermal effect on biological tissues using subwavelength ultrasound metalens at megahertz

“…Rapid development of acoustic metamaterial/metasurface has made a significant breakthrough in sound-wave manipulation and provided new opportunities for higher-precision acoustic focusing with the passive and compact metalens. 24 , 25 , 26 It is expected that the metalens-based focusing could provide promising potential in precision medical treatment, whereas several key technical issues should be figured out before the actual implementation. On the one hand, most of current researches on acoustic metamaterial/metasurface are restricted to airborne sound, which cannot be directly translated to the underwater ultrasound due to its shorter wavelength, stronger microstructural viscosity, and insufficient acoustic impedance contrast between the natural materials and water.…”