Methods of Manipulation of Acoustic Radiation Using Metamaterials with a Focus on Polymers: Design and Mechanism Insights

Abstract

The manipulation of acoustic waves is becoming increasingly crucial in research and practical applications. The coordinate transformation methods and acoustic metamaterials represent two significant areas of study that offer innovative strategies for precise acoustic wave control. This review highlights the applications of these methods in acoustic wave manipulation and examines their synergistic effects. We present the fundamental concepts of the coordinate transformation methods and their primary techniques for modulating electromagnetic and acoustic waves. Following this, we deeply study the principle of acoustic metamaterials, with particular emphasis on the superior acoustic properties of polymers. Moreover, the polymers have the characteristics of design flexibility and a light weight, which shows significant advantages in the preparation of acoustic metamaterials. The current research on the manipulation of various acoustic characteristics is reviewed. Furthermore, the paper discusses the combined use of the coordinate transformation methods and polymer acoustic metamaterials, emphasizing their complementary nature. Finally, this article envisions future research directions and challenges in acoustic wave manipulation, considering further technological progress and polymers' application potential. These efforts aim to unlock new possibilities and foster innovative ideas in the field.

Keywords: acoustic manipulation; acoustic metamaterials; coordinate transformation methods; polymers.

Figure 1

A coordinate transformation method is proposed for regulating electromagnetic waves. Based on a geometric coordinate transformation method (a), an ellipsoidal electromagnetic cloak (b) and an arbitrary geometric cloak (c) are designed. Reproduced with permission from [58]. Copyright © 2021, Elsevier. The electromagnetic wave concentrator is designed based on a coordinate transformation process (d) and the simulation results (e,f). Reproduced with permission from [59]. Copyright © 2019, Wiley. An electromagnetic cloak designed based on a coordinate change method (g) and a preset electric field and power trend (h), and radar detection results (i). Reproduced with permission from [60]. Copyright © 2019, AIP Publishing.

Figure 2

(a) The coordinate transformation method of elliptical acoustic cloak. The sound pressure scattering effect of the acoustic cloak when the sound wave is incident in the x-axis (b) and y-axis (c) directions. Reproduced with permission from [64]. Copyright © 2022, Springer Nature. Based on the multi-region segmentation coordinate transformation (d), the scattering pressure field (e) and cosine similarity simulation (f) of the acoustic cloak are designed. Reproduced with permission from [65]. Copyright © 2019, IOP Publishing.

Figure 3

(a) Model diagram. Two layering methods: constant thickness layering (b) and constant impedance layering (c). The absorption coefficient (d) and reflection coefficient (e) simulated by the two methods. Reproduced with permission from [67]. Copyright © 2021, Elsevier. An acoustic cloak is designed based on a coordinate transformation method (f), which has good stealth performance (g) and high transmission efficiency (h). Reproduced with permission from [68]. Copyright © 2021, Springer Nature.

Figure 4

(a) Experimental device diagram. (b) The schematic diagram of the acoustic waveguide based on the coordinate transformation. (c) The experimental results of the acoustic waveguide at 20 kHz. Reproduced with permission from [75]. Copyright © 2022, Frontiers. (d) Acoustic cloak structure. (e) Simulation and experimental results of acoustic cloak stealth performance at 9–15 kHz. Reproduced with permission from [76]. Copyright © 2017, APS Publishing. (f) A coordinate transformation method. (g) Design the parameters of acoustic cloak materials by changing the density and modulus. (h) Stealth performance. Reproduced with permission from [77]. Copyright © 2022, MDPI Publishing.

Figure 5

(a) A coordinate transformation method. (b) Layered structure with different density and bulk modulus. (c) Scattering results of acoustic waves under different layers. Reproduced with permission from [78]. Copyright © 2021, Springer Nature. (d,e) The design process of the acoustic cloak. Reproduced with permission from [79]. Copyright © 2019, Elsevier.

Figure 6

(a) Structure of electromagnetic acoustic metamaterials. (b) Free-space microwave absorption (A) properties. (c) Water acoustic wave absorption (A), reflection (R), and transmission (T) properties. Reproduced with permission from [6]. Copyright © 2020, Wiley. (d) Metamaterials’ structures based on steel and rubber. (e) The variation in absorption (A) coefficient and reflection (R) coefficient with frequency in single-layer metamaterials. (f) The variation in absorption (A) coefficient and reflection (R) coefficient of multilayer metamaterials with frequency. Reproduced with permission from [82]. Copyright © 2021, AIP Publishing.

Figure 7

(a) The structure of pumping water into the metamaterials. (b) The relationship between the change in water depth and the phase shift in the structure, and (c) the reflection effect of the metamaterials on the sound wave at different water depths. Reproduced with permission from [83]. Copyright © 2020, IOP Publishing. (d) Metamaterials with helical structure. The acoustic phase changes with the spiral depth at 2.2 kHz (e) and 6.1 kHz (f). Reproduced with permission from [84]. Copyright © 2020, APS Publishing.

Figure 8

(a) Metamaterials based on structural movement. (b) The relationship between the change in h1 in the structure and the phase shift and the transmission ratio. Reproduced with permission from [85]. Copyright © 2019, IOP Publishing. (c) Metamaterials based on surface micropillars. (d) The relationship between the change in the micropillar and the phase shift in the structure. (e) The height of the micropillar decreases with the increase in frequency and metamaterials’ velocity. Reproduced with permission from [86]. Copyright © 2023, Wiley. (f) Metamaterials’ structure under magnetic force. (g) The effect of film spacing on frequency and phase changes in the structure. (h) Phase distribution and transmission coefficient at different membrane tensions. Reproduced with permission from [87]. Copyright © 2020, AIP Publishing.

Figure 9

(a) The structure of the coding metasurface. The relationship between the reflection phase, the reflection coefficient, and the neck width w₁ (b) and w₂ (c) of the two subunits at f₁ and f₂. Reproduced with permission from [88]. Copyright © 2021, Elsevier. (d) The structure of the coding metasurface unit. The reflection phase (e) and reflection coefficient (f) change with the length d of the neck side in the structure. Reproduced with permission from [89]. Copyright © 2019, AIP Publishing.

Figure 10

(a) The schematic of the experimental device. (b) The sound field real shot of sound wave through the Nefer lens. Reproduced with permission from [92]. Copyright © 2020, IOP Publishing. (c) The structure of bubble-based modulator, and imaging results (d,e). Reproduced with permission from [93]. Copyright © 2020, Springer Nature.

Figure 11

(a) Metagel filled with different media. (b) Filling different media proportionally in parallel channels. (c) The acoustic transmission coefficient of the metagel when filled with water, air, and liquid metal. The acoustic transmission coefficient (d) of the metagel when filled with water and air in different proportions. Experiment: (e). Simulation: (f). Adjusting the filling medium, the acoustic impedance of the metagel can achieve a wide range of matching. Reproduced with permission from [20].