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Crystals
Special Issues
Anisotropic Acoustic Metamaterials
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Anisotropic Acoustic Metamaterials

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (20 April 2024) | Viewed by 3044

Special Issue Editor

Prof. Dr. Seiji Fukushima

E-Mail Website
Guest Editor
Graduate School of Science and Engineering, Kagoshima University, Korimoto 1, Kagoshima-shi, Kagoshima 890-0065, Japan
Interests: acoustic metamaterials; anisotropic media; circuit simulation; electromagnetic metamaterials; optical metamaterials

Special Issue Information

Dear Colleagues,

Following the invention of metamaterials, research trends have spread from electro-magnetic waves to other waves, including acoustic waves. Metamaterials can behave quite differently from a viewpoint of directivity, which can be partly realized by its anisotropy. We can expect both academic analysis and engineering applications when we focus on the anisotropy.

We invite researchers and engineers to contribute to this Special Issue on anisotropic acoustic metamaterials, which is intended to serve as a unique multidisciplinary forum covering broad aspects of physics, engineering, and applications of acoustic metamaterials and metasurfaces.

Potential topics include but are not limited to:

  • Physical analysis of anisotropic acoustic metamaterials;
  • Structural proposal of anisotropic acoustic metamaterials;
  • Design and simulation methods of anisotropic acoustic metamaterials;
  • Demonstrations of anisotropic acoustic metamaterials;
  • Cloak and stealth phenomena using anisotropic acoustic metamaterials;
  • New applications of anisotropic acoustic metamaterials;
  • Anisotropic supersonic metamaterials.

The metamaterials described above include metasurfaces.

Prof. Dr. Seiji Fukushima
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • anisotropy
  • acoustic(s)
  • metamaterial
  • metasurface
  • cloak, stealth
  • supersonic(s)
  • ultra-sonic(s)
  • off-diagonal element

Published Papers (2 papers)

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14 pages, 8482 KiB  
Article
A Multiband and Multifunctional Metasurface for Linear and Circular Polarization Conversion in Reflection Modes
by Saima Hafeez, Jianguo Yu, Fahim Aziz Umrani, Wang Yun and Muhammad Ishfaq
Crystals 2024, 14(3), 266; https://doi.org/10.3390/cryst14030266 - 08 Mar 2024
Viewed by 874
Abstract
Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains [...] Read more.
Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains crucial. This paper proposes a multiband and multifunctional dual reflective polarization converter surface capable of converting a linearly polarized (LP) wave into a circularly polarized (CP) wave, in frequency bands of 12.29–12.63 GHz, 16.08–24.16 GHz, 27.82–32.21 GHz, 33.75–38.74 GHz, and 39.70–39.79 GHz, with 3 dB axial ratio bandwidths of 2.7%, 40.15%, 14.6%, 13.76%, and 0.2%, respectively. Moreover, the converter is capable of achieving CPC with a polarization conversion ratio (PCR) that exceeds 95%, within the frequency ranges of 13.10–14.72 GHz, 25.43–26.00, 32.46–32.56 GHz, and 39.14–39.59 GHz. In addition, to identify the fundamental cause of the CPC and LP–CP conversion, a comprehensive theoretical investigation is provided. Furthermore, the surface current distribution patterns at different frequencies are investigated to analyze the conversion phenomena. A sample prototype consisting of 20 × 20 unit cells was fabricated and measured, verifying our design and the simulated results. The proposed structure has potential applications in satellite communications, radar, stealth technologies, and reflector antennas. Full article
(This article belongs to the Special Issue Anisotropic Acoustic Metamaterials)
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17 pages, 6491 KiB  
Article
Microstructure Design and Performance Optimization of Constant Modulus Pentamode Materials Acoustic Cloak
by Ziyin Luo, Qizheng Zhou and Peng Guo
Crystals 2022, 12(11), 1572; https://doi.org/10.3390/cryst12111572 - 04 Nov 2022
Cited by 1 | Viewed by 1139
Abstract
Underwater acoustic stealth has great scientific research value. According to acoustic coordinate transformation theory, the acoustic stealth cloak based on pentamode materials can realize underwater broadband acoustic stealth. However, due to the correlation between the density and modulus of pentamode materials and the [...] Read more.
Underwater acoustic stealth has great scientific research value. According to acoustic coordinate transformation theory, the acoustic stealth cloak based on pentamode materials can realize underwater broadband acoustic stealth. However, due to the correlation between the density and modulus of pentamode materials and the changes in the parameters of each layer of the acoustic stealth cloak, a large amount of structural optimization work is required for the pentamode material to meet the specific parameter requirements, which significantly increases the difficulty of the pentamode acoustic stealth cloak design. To simplify the design process, inspired by the calculation of equivalent modulus by representation volume element, this article proposed a pentamode material configuration with independent variation of density and modulus and designed a 1 m radius acoustic stealth cloak with a specific structure of pentamode materials matching the coordinate transformation equation of constant modal mapping. After simulation calculation and optimization design, in the range of a/λ from 0 to 1, the average total scattering cross-section of the cavity with a radius of 0.5 m covered by the acoustic stealth cloak is 0.858; the average total scattering cross-section of the cavity is 19.718 after removing the pentamode material acoustic stealth cloak. The results of the study are expected to provide some method references for simplifying the design process of the pentamode material acoustic stealth cloak and the microstructure design of the pentamode materials. Full article
(This article belongs to the Special Issue Anisotropic Acoustic Metamaterials)
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