Maurya Santosh K, Pandey Abhishek, Shukla Shobha, Saxena Sumit
Nanostructures Engineering and Modeling Laboratory, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India.
R Soc Open Sci. 2018 May 16;5(5):171042. doi: 10.1098/rsos.171042. eCollection 2018 May.
Metamaterials are engineered materials that offer the flexibility to manipulate the incident waves leading to exotic applications such as cloaking, extraordinary transmission, sub-wavelength imaging and negative refraction. These concepts have largely been explored in the context of electromagnetic waves. Acoustic metamaterials, similar to their optical counterparts, demonstrate anomalous effective elastic properties. Recent developments have shown that coiling up the propagation path of acoustic wave results in effective elastic response of the metamaterial beyond the natural response of its constituent materials. The effective response of metamaterials is generally evaluated using the 'S' parameter retrieval method based on amplitude of the waves. The phase of acoustic waves contains information of wave pressure and particle velocity. Here, we show using finite-element methods that phase reversal of transmitted waves may be used to predict extreme acoustic properties in space coiling metamaterials. This change is the difference in the phase of the transmitted wave with respect to the incident wave. This method is simpler when compared with the more rigorous 'S' parameter retrieval method. The inferences drawn using this method have been verified experimentally for labyrinthine metamaterials by showing negative refraction for the predicted band of frequencies.
超材料是经过设计的材料，能够灵活操控入射波，从而实现诸如隐形、超常传输、亚波长成像和负折射等奇特应用。这些概念在很大程度上是在电磁波的背景下进行探索的。声学超材料与其光学对应物类似，展现出异常的有效弹性特性。最近的研究进展表明，盘绕声波的传播路径会导致超材料产生超出其组成材料自然响应的有效弹性响应。超材料的有效响应通常使用基于波幅的“ S”参数检索方法进行评估。声波的相位包含波压力和粒子速度的信息。在此，我们使用有限元方法表明，透射波的相位反转可用于预测空间盘绕超材料中的极端声学特性。这种变化是透射波相对于入射波的相位差。与更为严格的“S”参数检索方法相比，该方法更简单。通过对迷宫式超材料在预测频率范围内显示出负折射，已通过实验验证了使用该方法得出的推论。
