Recent Advances in Active Acoustic Metamaterials

2019 ◽  
Vol 11 (08) ◽  
pp. 1950081 ◽  
Author(s):  
Sanjay Kumar ◽  
Heow Pueh Lee
Keyword(s):  
Sound Wave ◽  
Dynamic Responses ◽  
Acoustic Metamaterials ◽  
Design Strategies ◽  
Acoustic Characteristics ◽  
Early 21St Century ◽  
Active Metamaterials ◽  
Potential Applications ◽  
Restricted Use ◽  
Active Acoustic Metamaterials

Since its first demonstration of an acoustic metamaterial in the early 21st century, it is widely used for sound wave manipulation purposes in many applications such as aerospace, automotive, defense, marine, etc. However, the traditional acoustic metamaterials display acoustic characteristics for restricted use because of their fixed structures. For real-world applications, the active sound wave manipulation is desirable. In recent years, active acoustic metamaterials (AAMs) have garnered attention owing to their unique design and material characteristics, which result in various dynamic responses against the incoming sound wave. This paper aims to provide an overview of the fundamental concept of active metamaterials, describing the multiple tuning mechanisms and design strategies, and highlighting their potential applications. The current fabrication challenges and future outlook in this promising field are also discussed.

An Active Acoustic Metamaterial With Tunable Effective Density

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Amr M. Baz
Keyword(s):  
Material Properties ◽  
Control Strategies ◽  
Natural Extension ◽  
Effective Density ◽  
Acoustic Metamaterials ◽  
Active Metamaterials ◽  
Theoretical Predictions ◽  
Material Volume ◽  
The Individual ◽  
Active Acoustic Metamaterials

Extensive efforts are being exerted to develop various types of acoustic metamaterials to effectively control the flow of acoustical energy through these materials. However, all these efforts are focused on passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a class of one-dimensional acoustic metamaterials with tunable effective densities in an attempt to enable the adaptation to varying external environment. More importantly, the active metamaterials can be tailored to have increasing or decreasing variation of the material properties along and across the material volume. With such unique capabilities, physically realizable acoustic cloaks can be achieved and objects treated with these active metamaterials can become acoustically invisible. The theoretical analysis of this class of active acoustic metamaterials is presented and the theoretical predictions are determined for an array of fluid cavities separated by piezoelectric boundaries. These boundaries control the stiffness of the individual cavity and in turn its dynamical density. Various control strategies are considered to achieve different spectral and spatial control of the density of this class of acoustic metamaterials. A natural extension of this work is to include active control capabilities to tailor the bulk modulus distribution of the metamaterial in order to build practical configurations of acoustic cloaks.

scholarly journals Demultiplexing Infrasound Phonons With Tunable Magnetic Lattices

2020 ◽  
Vol 7 ◽  
Author(s):  
Audrey A. Watkins ◽  
Osama R. Bilal
Keyword(s):  
Self Assembly ◽  
Small Volume ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Propagation Characteristics ◽  
Low Frequencies ◽  
Experimental Realization ◽  
Nonlinear Properties ◽  
Potential Applications ◽  
Low Frequency Waves

Controlling infrasound signals is crucial to many processes ranging from predicting atmospheric events and seismic activities to sensing nuclear detonations. These waves can be manipulated through phononic crystals and acoustic metamaterials. However, at such ultra-low frequencies, the size (usually on the order of meters) and the mass (usually on the order of many kilograms) of these materials can hinder its potential applications in the infrasonic domain. Here, we utilize tunable lattices of repelling magnets to guide and sort infrasound waves into different channels based on their frequencies. We construct our lattices by confining meta-atoms (free-floating macroscopic disks with embedded magnets) within a magnetic boundary. By changing the confining boundary, we control the meta-atoms’ spacing and therefore the intensity of their coupling potentials and wave propagation characteristics. As a demonstration of principle, we present the first experimental realization of an infrasound phonon demultiplexer (i.e., guiding ultra-low frequency waves into different channels based on their frequencies). The realized platform can be utilized to manipulate ultra-low frequency waves, within a relatively small volume, while utilizing negligible mass. In addition, the self-assembly nature of the meta-atoms can be key in creating re-programmable materials with exceptional nonlinear properties.

Lanthanide Doped Complexes and Organometallic Clusters: Design Strategies and their Applications in Biology and Photonics

2019 ◽  
Vol 9 (3) ◽  
pp. 166-217 ◽  
Author(s):  
Gangadharan A. Kumar
Keyword(s):  
Nanostructured Materials ◽  
Rational Design ◽  
Near Infrared ◽  
Organic Ligand ◽  
Central Core ◽  
Design Strategies ◽  
Ceramic Core ◽  
Light Emitting ◽  
Potential Applications ◽  
Lanthanide Atoms

In this review, we discuss the rational design of a new class of lanthanide-doped organometallic nanostructured materials called `molecular minerals`. Molecular minerals are nanostructured materials with a ceramic core made from chalcogenide groups and other heavy metals. Part of the central core atoms is replaced by suitable lanthanide atoms to impart fluorescent spectral properties. The ceramic core is surrounded by various types of organic networks thus making the structure partly ceramic and organic. The central core has superior optical properties and the surrounding organic ligand makes it easy to dissolve several kinds of organic solvents and fluoropolymers to make several kinds of active and passive photonic devices. This chapter starts with elaborate design strategies of lanthanidebased near-infrared emitting materials followed by the experimental results of selected near-infrared emitting lanthanide clusters. Finally, their potential applications in telecommunication, light-emitting diodes and medical imaging are discussed.

Characteristics of Band Gap and Low-frequency Wave Propagation of Mechanically Tunable Phononic Crystals with Scatterers in Periodic Porous Elastomeric Matrices

2021 ◽  
pp. 1-34
Author(s):  
Shaowu Ning ◽  
Dongyang Chu ◽  
Fengyuan Yang ◽  
Heng Jiang ◽  
Zhanli Liu ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Coupling Effect ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Dynamic Responses ◽  
Acoustic Metamaterials ◽  
Frequency Wave ◽  
Strong Coupling Effect ◽  
The Matrix

Abstract The characteristics of passive responses and fixed band gaps of phononic crystals (PnCs) limit their possible applications. For overcoming this shortcoming, a class of tunable PnCs comprised of multiple scatterers and soft periodic porous elastomeric matrices are designed to manipulate the band structures and directionality of wave propagation through the applied deformation. During deformation, some tunable factors such as the coupling effect of scatterer and hole in the matrix, geometric and material nonlinearities, and the rearrangement of scatterer are activated by deformation to tune the dynamic responses of PnCs. The roles of these tunable factors in the manipulation of dynamic responses of PnCs are investigated in detail. The numerical results indicate that the tunability of the dynamic characteristic of PnCs is the result of the comprehensive function of these tunable factors mentioned above. The strong coupling effect between the hole in the matrix and the scatterer contributes to the formation of band gaps. The geometric nonlinearity of matrix and rearrangement of scatterer induced by deformation can simultaneously tune the band gaps and the directionality of wave propagation. However, the matrix's material nonlinearity only adjusts the band gaps of PnCs and does not affect the directionality of wave propagation in them. The research extends our understanding of the formation mechanism of band gaps of PnCs and provides an excellent opportunity for the design of the optimized tunable PnCs and acoustic metamaterials.

scholarly journals Mechanoresponsive scatterers for high-contrast optical modulation

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Donghwi Cho ◽  
Haomin Chen ◽  
Jonghwa Shin ◽  
Seokwoo Jeon
Keyword(s):  
Energy Consumption ◽  
Electric Fields ◽  
Structural Parameters ◽  
Future Research ◽  
Great Promise ◽  
Design Strategies ◽  
Smart Windows ◽  
Advantages And Disadvantages ◽  
Potential Applications ◽  
External Stimuli

Abstract Smart chromatic materials with optical transmittances that can be modified by light scattering upon external stimuli are attracting extensive interest because of their appealing applications in smart windows, privacy protection, electronic displays, etc. However, the development of these scatterers, which are mostly activated by electric fields, is hindered by their intrinsic energy consumption, slow responses, and poor stability. Recently, mechanoresponsive scatterers based on a strain-driven reconfiguration of the surface or internal structure have emerged, featuring fast responses and a simple composition/fabrication. Because there is no energy consumption to maintain the transparency/opacity, this novel scheme for scatterers holds great promise to break the existing bottleneck. This article presents recent advances in the development of mechanoresponsive scatterers and compares different structural design strategies. The scatterers are categorized into 2D, 3D, and other types according to the dimensions of their functioning structures. The fabrication methods, mechanisms, and relationships between the structural parameters and optical modulating performances are discussed for each category. Next, the potential applications of these scatterers are outlined. Finally, the advantages and disadvantages of the mainstream 2D and 3D categories are summarized, followed by a perspective on future research directions.

scholarly journals A Review on Breathing Behaviors of Metal-Organic-Frameworks (MOFs) for Gas Adsorption

2021 ◽  
Author(s):  
Mays Alhamami ◽  
Huu Doan ◽  
Chil-Hung Cheng
Keyword(s):  
Molecular Sieves ◽  
Gas Adsorption ◽  
Metal Organic Frameworks ◽  
Design Strategies ◽  
Surface Areas ◽  
Host Materials ◽  
Potential Applications ◽  
Metal Organic ◽  
Definition Of ◽  
Dynamics Simulations

Metal-organic frameworks (MOFs) are a new class of microporous materials that possess framework flexibility, large surface areas, “tailor-made” framework functionalities, and tunable pore sizes. These features empower MOFs superior performances and broader application spectra than those of zeolites and phosphine-based molecular sieves. In parallel with designing new structures and new chemistry of MOFs, the observation of unique breathing behaviors upon adsorption of gases or solvents stimulates their potential applications as host materials in gas storage for renewable energy. This has attracted intense research energy to understand the causes at the atomic level, using in situ X-ray diffraction, calorimetry, Fourier transform infrared spectroscopy, and molecular dynamics simulations. This article is developed in the following order: first to introduce the definition of MOFs and the observation of their framework flexibility. Second, synthesis routes of MOFs are summarized with the emphasis on the hydrothermal synthesis, owing to the environmental-benign and economically availability of water. Third, MOFs exhibiting breathing behaviors are summarized, followed by rationales from thermodynamic viewpoint. Subsequently, effects of various functionalities on breathing behaviors are appraised, including using post-synthetic modification routes. Finally, possible framework spatial requirements of MOFs for yielding breathing behaviors are highlighted as the design strategies for new syntheses.

scholarly journals Research Progress of Locally Resonance Acoustic Metamaterials

2021 ◽  
Vol 248 ◽  
pp. 01041
Author(s):  
Du Zhehua
Keyword(s):  
Sound Wave ◽  
Negative Refraction ◽  
Low Frequency ◽  
Research Progress ◽  
Frequency Noise ◽  
Bragg Scattering ◽  
Acoustic Metamaterials ◽  
Low Frequency Noise ◽  
Phonon Crystal ◽  
Developed Surface

Bragg scattering phonon crystal and locally resonant acoustic metamaterials were introduced. In order to generate noise reduction, the lattice constant of Bragg scattering phonon crystal should be of the same order of magnitude as the wave length of the sound wave, therefore, its application field is limited. Locally resonant acoustic metamaterials consume sound energy by coupling its own resonant frequencies with those of sound waves at close range. Its size is two orders of magnitude smaller than the wavelength of sound wave; thus, the control of low-frequency noise by small-size acoustic metamaterials is realized. Locally resonant acoustic metamaterials have some extraordinary physical characteristic in the conventional medium for their special acoustic structural units, such as negative refraction and negative mass density. Especially in low frequency band, they have acoustic forbidden band in which the sound wave transmission is prohibited. Acoustic structural unit having resonant characteristics has been developed. Surface-mounted resonant element plate structures and thin film acoustic metamaterials are the normal types of locally resonant acoustic metamaterials. Their research and development provide a new method for low-frequency noise control.

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