Doubly Negative Acoustic Metamaterials with Air-Coupled Diaphragms

近年来，声学超材料（AMM）已成为一种新兴的工具，用于制造具有天然材料中没有的奇异特性的材料。本研究项目的核心思想是实现双负质量密度和体积模量（即负折射率材料），这是设计许多具有新功能的AMM器件的关键。这种材料对电磁波的折射率在某些频率范围内呈负值。这项研究支持了创造一种新型双负极AMM的基本进展，其单位电池由隔膜直接与一个空腔耦合组成。凭借这种简单而创新的配置，单元电池可以很容易地缩放成1D， 2D和3D AMM，为从超分辨率成像，隐身到完美吸收器等许多应用的转变铺平了道路。这项研究的结果将被整合到新的课程中，作为一种催化剂，激励学生，特别是少数民族和女性，追求科学和工程领域的高级学位和职业。本研究项目支持一种新型双负性AMM的基础研究。本研究将采用综合的方法，包括分析、数值和实验方法来研究这些材料的特性。该研究项目的总体目标是实现对空气耦合膜片的AMM的基本理解，开发用于原位压力和位移测量的光纤传感器，并利用获得的理解和开发的新工具来创建双负极性的AMM。通过简单的空气耦合隔膜配置，单元格可以缩放成1D， 2D和3D AMM，这有可能改变许多需要双负性（例如亚波长成像和变换声学）和复杂几何形状（例如声学超表面）的应用。新开发的光纤传感器将用于绘制AMM内外的压力和位移场。这项工作还补充了理论和数值研究与经过深思熟虑的实验，使用高性能光纤探针来绘制声波。这项工作为AMM波浪操纵的研究提供了一个新的范例，在成像、隐身等领域有着广泛的应用。

In recent years, Acoustic Metamaterials (AMM) have become an emerging tool to create materials with exotic properties that are not found in natural materials. A central idea in this research project is the realization of doubly negative mass density and bulk modulus (a.k.a. negative index material), which is the key to designing many AMM devices with novel functionalities. Such material's refractive index for an electromagnetic wave has a negative value over some frequency range. This research supports fundamental advances on the creation of a new type of AMM with double negativity, whose unit cell consists of diaphragms directly coupled by an air cavity. With this simple yet innovative configuration, the unit cell can be easily scaled to form 1D, 2D, and 3D AMM, paving the ways for transforming many applications ranging from super-resolution imaging, cloaking, to perfect absorbers. The outcome from the this research will be integrated into new course that will serve as a catalyst to motivate students, particularly minority and women, to pursue advanced degrees and careers in science and engineering.This research project supports fundamental research on a new type of AMM with double negativity. The research will investigate characteristics of such materials using a comprehensive approach including analytical, numerical, and experimental methods. The overall objective of the awarded research program is to achieve a fundamental understanding of the AMM with air-coupled diaphragms, develop fiber optic sensors for in situ pressure and displacement measurements, and use the gained understanding and the developed new tools to create AMM with double negativity. With a simple configuration of air-coupled diaphragms, the unit cells can be scaled to form 1D, 2D, and 3D AMM that has the potential to transform many applications requiring double negativity (e.g. sub-wavelength imaging and transformation acoustics) and complex geometry (e.g. acoustic metasurface). Newly developed fiber optic sensors will be used for mapping the pressure and displacement fields inside and outside the AMM. The work also complements theoretical and numerical studies with the well-thought out experiments that use high-performance fiber optic probes to map the acoustic wave. This work provides a new paradigm to the study of wave manipulation by AMM and has wide spread applications in fields such as imaging, cloaking, and several others.