左手材料设计与制备的研究进展

左手材料是一种介电常数ε和磁导率μ同时为负值的超材料,具有许多非常奇异的电磁学性质.阐述了左手材料的基本概念和性质,介绍了能够同时实现负介电常数和负磁导率的Ω形、S形和树枝等单一结构,综述了利用机械加工法和化学制备法制备的高频段负磁导率材料,以及基于耦合作用的电磁波垂直入射条件下左手材料的设计与制备方法,阐述了超材料负磁导率或左手行为的验证方法,最后展望了左手材料的应用前景.     

左手材料的研究进展与应用前景

左手材料是一种介电常数ε和磁导率μ同时为负的人工复合材料,具有许多反常的物理性质,是材料、电磁、光学等领域的热门研究方向.在结合国内外研究现状的基础上综述了左手材料的理论、结构特征、制备工艺、性能测试等,最后探讨了左手材料的发展趋势、应用前景和亟需解决的问题,以期获得对左手材料更为深刻和全面的理解.     

左手材料研究进展及应用前景

详细介绍了左手材料(同时拥有负磁导率和负介电常数)存在的理论依据、实现方法和基本电磁特性,针对其出现的新颖电磁特性介绍了它在隐身、光学和微波等领域的潜在应用,及其需进一步加强的工作和发展方向.     

左手材料的研究进展

左手材料是一种介电常数ε和磁导率μ同时为负值的电磁材料.介绍了左手材料的基本原理,阐述了微波段、红外和可见光波段左手材料的实现方式,展望了左手材料的应用前景.     

负折射率材料的研究进展

负折射率材料由于其独特的性质引起了人们极大的兴趣。介绍了负折射产生的原理及其奇特性质，着重阐述了实现负折射材料的3种主要方法：双负介质实现负折射、左手介质实现负折射和光子晶体实现负折射。分析了各种方法在实现光频段低损耗负折射材料中的可行性及纳米技术发挥的重大作用。     

左手材料设计的研究进展

阐述了左手材料的基本概念和性质,介绍了目前几种常见金属基元左手材料的结构、基本原理及特点,综述了左手材料近年来的研究动态及发展前景,指出左手材料要得到应用必须向低损耗和宽带宽方向发展。     

负折射现象的研究进展

负折射现象是一种崭新的现象,是上个世纪60年代理论预言,直到一年前被实验证明微波照射在左手化媒质(LHM)上,折射方向不同于Snell定律所描述的.介绍了这种负折射现象研究的最新发展.着重于LHM的人工合成,理论解释以及负折射率的实验证明等几个方面,以便进一步开展这方面的工作.     

“王”字型左手材料结构的设计与仿真

针对目前由金属开口谐振环与金属杆构成的左手材料结构存在构造比较复杂、工艺实现较难的缺点,设计实现了一种基于金属条的改进结构-"王"字型结构。通过理论分析和电磁仿真软件Ansoft HFSS 10模拟仿真,利用散射参量法提取参数结果表明该结构可以在X波段实现介电常数和磁导率同时为负。讨论研究了该左手结构的金属条宽度、中间缺口宽度、中间条宽度三个结构尺寸参数变化对谐振频率和透射峰幅值的影响,结果表明三个参数的变化都会对二者产生影响,其中金属条宽度改变对透射峰值影响幅度相对较大,缺口宽度改变对谐振频率影响幅度相对较大。     

负折射材料实验验证的研究进展

负折射材料已成为近几年来物理学,材料科学,电子科学等交叉学科领域的研究热点。首先介绍负折射材料的基本原理,并详细介绍近年来这类材料的仿真与实验研究。     

新型负热膨胀材料的研究

介绍了近几年负热膨胀材料的研究成果及其主要发展,分析了此类材料的负热膨胀性能、结构特点、制备技术、应用中存在的主要问题及发展趋势,探计了负热膨胀材料在今后研究中所面临的问题.     

Magnetoactive Acoustic Metamaterials

Acoustic metamaterials with negative constitutive parameters (modulus and/or mass density) have shown great potential in diverse applications ranging from sonic cloaking, abnormal refraction and superlensing, to noise canceling. In conventional acoustic metamaterials, the negative constitutive parameters are engineered via tailored structures with fixed geometries; therefore, the relationships between constitutive parameters and acoustic frequencies are typically fixed to form a 2D phase space once the structures are fabricated. Here, by means of a model system of magnetoactive lattice structures, stimuli‐responsive acoustic metamaterials are demonstrated to be able to extend the 2D phase space to 3D through rapidly and repeatedly switching signs of constitutive parameters with remote magnetic fields. It is shown for the first time that effective modulus can be reversibly switched between positive and negative within controlled frequency regimes through lattice buckling modulated by theoretically predicted magnetic fields. The magnetically triggered negative‐modulus and cavity‐induced negative density are integrated to achieve flexible switching between single‐negative and double‐negative. This strategy opens promising avenues for remote, rapid, and reversible modulation of acoustic transportation, refraction, imaging, and focusing in subwavelength regimes.     

Ultrasonic metamaterials with negative modulus

The emergence of artificially designed subwavelength electromagnetic materials, denoted metamaterials, has significantly broadened the range of material responses found in nature. However, the acoustic analogue to electromagnetic metamaterials has, so far, not been investigated. We report a new class of ultrasonic metamaterials consisting of an array of subwavelength Helmholtz resonators with designed acoustic inductance and capacitance. These materials have an effective dynamic modulus with negative values near the resonance frequency. As a result, these ultrasonic metamaterials can convey acoustic waves with a group velocity antiparallel to phase velocity, as observed experimentally. On the basis of homogenized-media theory, we calculated the dispersion and transmission, which agrees well with experiments near 30 kHz. As the negative dynamic modulus leads to a richness of surface states with very large wavevectors, this new class of acoustic metamaterials may offer interesting applications, such as acoustic negative refraction and superlensing below the diffraction limit.     

吸声超材料研究进展

介绍了基于局域共振机理的吸声超材料的基本原理和其负等效质量密度、负等效体积模量和两者"双负"的特点,详细介绍了基于局域共振机理的声子晶体型、薄膜型、声子玻璃型和频率编码型等吸声超材料的结构形式、基本原理和性能特点。还介绍了基于其它吸声机理的超材料的结构特点、吸声原理和最新研究进展。最后,对吸声超材料的未来发展方向进行了展望。     

A review of additive manufacturing of metamaterials and developing trends

The concept of metamaterials originates from the proposal of left-hand materials with negative refractive index, followed by which, varieties of metamaterials with kinds of fantastic properties that cannot be found in natural materials, such as zero/negative Poisson’s ratio, electromagnetic/acoustic/thermal cloaking effect, etc., were come up with. According to their application fields, the metamaterials are roughly classified into four categories, electromagnetic metamaterials, acoustic metamaterials, thermal metamaterials, and mechanical metamaterials. By designing structures and arranging the distribution of materials with different physical parameters, the function of metamaterials can be realized in theory. Additive manufacturing (AM) technology provides a more direct and efficient way to achieve a sample of metamaterial and experiment verification due to the great advantages in fabricating complex structures. In this review, we introduce the typical metamaterials in different application situations and their design methods. In particular, we are focused on the fabrication of metamaterials and the application status of AM technology in them. Furthermore, we discuss the limits of present metamaterials in the aspect of design method and the disadvantages of existing AM technology, as well as the development tendency of metamaterials.     

水下声学超材料研究

声学超材料在空气中应用的研究已经很多,通过对其声学负参数的研究可以实现负折射、 声隐身、 波束控制以及超分辨成像等功能.声学超材料在空气中的良好应用也让更多的研究者们聚焦水下声学超材料(简称水声超材料)声聚焦、声透射等的研究,其在水下的研究涉及到流固耦合以及模式转换的影响,会更加复杂.水下研究的主要难题有尺度大、低频性...     

What is negative refraction?

We review various published definitions associated with the phenomenon of negative phase velocity propagation of electromagnetic waves in meta-media, as observed through negative refraction. For the principal definition, based on the Poynting vector and the wave vector having negative scalar product, we summarise the various material constraints that have been derived. The distinction between criteria based on the Poynting vector and the group velocity are considered, both in respect of causality, and in the context of moving media. Instances where a fully covariant definition is necessary are also identified, and compared with other results from the extant literature. Satisfaction of the NPV propagation criterion is also considered for surface plasmons.     

Three-dimensional photonic metamaterials at optical frequencies

Metamaterials are artificially structured media with unit cells much smaller than the wavelength of light. They have proved to possess novel electromagnetic properties, such as negative magnetic permeability and negative refractive index. This enables applications such as negative refraction, superlensing and invisibility cloaking. Although the physical properties can already be demonstrated in two-dimensional (2D) metamaterials, the practical applications require 3D bulk-like structures. This prerequisite has been achieved in the gigahertz range for microwave applications owing to the ease of fabrication by simply stacking printed circuit boards. In the optical domain, such an elegant method has been the missing building block towards the realization of 3D metamaterials. Here, we present a general method to manufacture 3D optical (infrared) metamaterials using a layer-by-layer technique. Specifically, we introduce a fabrication process involving planarization, lateral alignment and stacking. We demonstrate stacked metamaterials, investigate the interaction between adjacent stacked layers and analyse the optical properties of stacked metamaterials with respect to an increasing number of layers.     

From jammed solids to mechanical metamaterials : A brief review

Here we review recent studies of mechanical metamaterials originating from or closely related to marginally jammed solids. Unlike previous approaches mainly focusing on the design of building blocks to form periodic metamaterials, the design and realization of such metamaterials exploit two special aspects of jammed solids, disorder and isostaticity. Due to the disorder, every single bond of jammed solids is unique. Such a bond uniqueness facilitates the flexible adjustment of the global and local elastic responses of unstressed spring networks derived from jammed solids, leading to auxetic materials with negative Poisson’s ratio and bionic metamaterials to realize allostery and flow controls. The disorder also causes plastic instabilities of jammed solids under load. The jammed networks are thus inherently metamaterials exhibiting multi-functions such as auxeticity, negative compressibility, and energy absorption. Taking advantage of isostaticity, topological mechanical metamaterials analogous to electronic materials such as topological insulators have also been realized, while jammed networks inherently occupy such topological features. The presence of disorder greatly challenges our understanding of jammed solids, but it also provides us with more freedoms and opportunities to design mechanical metamaterials.