Design and characterization of an acoustic composite lens with high-intensity and directionally controllable focusing

Hongyu Sun,Wei Zhao,Shen Wang,Qing Wang,Lisha Peng,Songling Huang

doi:10.1038/s41598-020-58092-6

Hongyu Sun, Wei Zhao + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-58092-6

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Journal: Scientific Reports	Publication Date: Jan 30, 2020
Citations: 7	License type: open-access

Affiliation: Tsinghua University, Durham University

Abstract

Acoustic orientation and bunching methods, which include the radiation surface expansion, ultrasonic demodulation, multiunit coherence, phased arrays and acoustic lenses, can be used to manipulate and focus sound waves. Recently, focusing systems composed of acoustic lenses have been found to offer high controllability and focusing intensity. In this paper, a newly designed composite acoustic lens that can achieve wave convergence is proposed by assembling a lattice array of concave hexagonal (CH)-shaped rods. In comparison with the latest published work, the new CH structure improves upon the focusing capability of traditional acoustic lenses while retaining their advantages in terms of 3-D underwater focusing. Simulated and experimental results show that a lens with the CH structure has good focusing intensity and can focus acoustic waves over a wide range of incidence angles without losing its functionality. With its good focusing capabilities, this new composite lens may open the door to a broad range of applications, including high-precision nondestructive testing (NDT), high-efficiency medical treatment and multidirectional underwater focusing.

Highlights

Acoustic orientation and bunching methods, which include the radiation surface expansion, ultrasonic demodulation, multiunit coherence, phased arrays and acoustic lenses, can be used to manipulate and focus sound waves
In contrast to metamaterial-based negative refractive index devices with deep-subwavelength resolution[8,9,10,11,12,13], periodic crystal structures introduce acoustic waves into phononic crystals resulting from Bragg scattering and occurring in passbands with a negative group velocity[14,15]
To overcome the limitations of such materials for these potential applications, the focusing of acoustic waves using phononic crystals has been systematically studied in both air and water[17,18], and a broad variety of applications for acoustic focusing have been demonstrated

Summary

Introduction

Acoustic orientation and bunching methods, which include the radiation surface expansion, ultrasonic demodulation, multiunit coherence, phased arrays and acoustic lenses, can be used to manipulate and focus sound waves. In the field of acoustic focusing with composite lens structures, resonant units for convergent lenses have been designed and developed with various shapes, such as rigid cylinders[19,20,21,22], Helmholtz resonators[23,24], cross structures[25,26,27], and concentric rings[28], or with the use of multiphase materials to reduce impedance mismatch[29]. We develop a composite acoustic lens with an improved focusing capability by changing the shape of the unit cell from the traditional CS structure to the new concave hexagonal (CH) structure, which enables smaller gaps and a smaller volume fraction. The results show that the newly designed CH unit cell structure for composite lenses improves the 3-D focusing intensity for underwater acoustic waves and enables multidirectional focusing over a wide range of bias angles

Methods

Results

Conclusion