2022-09-07 ワシントン大学セントルイス
ワシントン大学セントルイス校の研究者たちは、このほど、虹のように自己湾曲する超音波を発生させる技術を発明した。
水中でエアリービームを発生させるには大型で高価な装置が必要なため、超音波診断への幅広い応用には限界があったが、研究達は、超音波ビーム操作のためのエアリービーム対応バイナリー音響メタサーフェス（AB-BAM）と呼ばれる柔軟で汎用性のあるツールを設計し3Dプリントした。そして、水中でAB-BAMの能力を実証した。
＜関連情報＞
- https://source.wustl.edu/2022/09/new-practical-method-of-producing-airy-beams-could-enhance-ultrasound/
- https://engineering.wustl.edu/news/2022/New-practical-method-of-producing-Airy-beams-could-enhance-ultrasound.html
- https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.18.024070
水中超音波ビームマニピュレーションのためのエアリービーム対応二次元音響メタサーフェス Airy-Beam-Enabled Binary Acoustic Metasurfaces for Underwater Ultrasound-Beam Manipulation
Zhongtao Hu, Yaoheng Yang, Lu Xu, Yun Jing, and Hong Chen
Physical Review Applied Published 26 August 2022
DOI:https://doi.org/10.1103/PhysRevApplied.18.024070
ABSTRACT
Airy beams are peculiar beams that are nondiffracting, self-accelerating, and self-healing, and they have offered great opportunities for ultrasound-beam manipulation. However, one critical barrier that limits the broad applications of Airy beams in ultrasound is the lack of simply built devices to generate Airy beams in water. This work presents a family of Airy-beam-enabled binary acoustic metasurfaces (AB BAMs) to generate Airy beams for underwater ultrasound-beam manipulation. AB BAMs are designed and fabricated by three-dimensional (3D) printing with two coding bits: a polylactic acid (which is the commonly used 3D printing material) unit acting as a bit “1” and a water unit acting as a bit “0.” The distribution of the binary units on the metasurface is determined by the pattern of Airy beam. To showcase the wave-front engineering capability of the AB BAMs, several examples of AB BAMs are designed, 3D printed, and coupled with a planar single-element ultrasound transducer for experimental validation. We demonstrate the capability of AB BAMs in flexibly tuning the focal region size and beam focusing in 3D space by changing the design of the AB BAMs. The focal depth of AB BAMs can be continuous and electronical tuned by adjusting the operating frequency of the planar transducer without replacing the AB BAMs. The superimposing method is leveraged to enable the generation of complex acoustic fields, e.g., multifoci and letter patterns (e.g., “W” and “U”). The more complex focal patterns are shown to be also continuously steerable by simply adjusting the operating frequency. Furthermore, the proposed 3D-printed AB BAMs are simple to design, easy to fabricate, and low cost to produce with the capabilities to achieve tunable focal size, flexible 3D beam focusing, arbitrary multipoint focusing, and continuous steerability, which creates unprecedented potential for ultrasound-beam manipulation.
