EFRI NewLAW: Topological acoustic metamaterials for programmable and high-efficiency one-way transport

在这项研究中，物理学家，波动力学家和材料科学家将共同设计，制造和表征具有非互易波传播属性的新型超材料。 声波领域是人类之间最古老的交流方式，在现代材料技术和工程的背景下正在经历复兴，其应用范围从医学成像和回声定位到声学隐身。 控制波在流体和固体介质中传播的一个基本原理，称为“互易性”，是波在介质中任意两个任意选择的点之间向前和向后的传输率必须相等。 打破这一原则的能力，即实现单向机械或声学“二极管”，将使具有新功能的新型机械系统的设计成为可能，包括自适应传感器和隔振装置。它还将为新兴的材料逻辑领域提供变革性的贡献，这是一种设计范式，其中简单的结构和材料模块被用作工程构建模块，以创建任意复杂的机械设备。 研究背后的核心概念思想源于“拓扑保护”的概念，该概念用于获得对无序和噪声具有鲁棒性的波传播特性。通过这项研究开发的知识将推动技术的发展，包括但不限于：a）机械计算，其中声学逻辑端口可以被视为能够执行一系列数学运算的构建模块，以及B）具有新的热传输特性的设备，利用热声子和机械振动之间的类比在机械设备的空间和时间尺度上。这项研究还将通过一个有公共教程的讲习班向更广泛的社区传播，通过加强不同学术机构的现有项目，扩大STEM领域代表性不足的群体的参与，并将在YouTube视频中与公众分享发现。该项目将对声子带拓扑结构如何控制系统的声学特性进行基本理解，时空调制，导致这种类型的时间反演对称性破缺现象的正式解释框架。通过该项目开发的强大工具包将允许在声波控制策略中使用拓扑状态的当前边界之外进行各种各样的设计。这项研究将跨越凝聚态物理学、波动力学和材料科学的前沿。 实现拓扑保护非互易波传播的两个主要概念是：（1）利用拓扑能带理论的原理对时空调制材料中的声子能带结构进行编程，以及（2）利用麦克斯韦晶格在其类金属相和类拓扑绝缘体相中的对比波传播特性。 研究团队将推进对拓扑保护在非互易波传播中所起的密切作用的理论理解，使用最先进的制造技术，使用各种材料平台实现不同尺度的声学二极管原型，并部署激光使能波重建能力，以表征制造的超材料样本中的非互易波传播现象。通过开发和应用跨尺度的拓扑和材料逻辑设计原理，该项目将把一组简单的机械组件转变为下一代声学逻辑端口的通用平台，具有可编程声学传输和时间反转对称性破坏能力。

In this research, physicists, wave mechanicians and materials scientists will come together to design, fabricate and characterize novel metamaterials with nonreciprocal wave propagation attributes. The field of sound waves, which represent the oldest way of communication between human beings, is experiencing a revival in the context of modern material technology and engineering, with a myriad of applications ranging from medical imaging and echolocation to acoustic cloaking. A fundamental principle governing wave propagation in both fluid and solid media, called "reciprocity", is that the transmission rate of waves must be equal forward and backward between any two arbitrarily selected points in a medium. The ability to break this principle, that is, the realization of one-directional mechanical or acoustic "diodes" will enable the design of new classes of mechanical systems with novel functionalities, including adaptive sensors and vibration isolation devices. It will also provide a transformative contribution to the emerging field of material logic, a design paradigm where simple structural and material modules are used as the engineering building blocks to create mechanical devices of arbitrary complexity. The core conceptual ideas behind the research originate from the notion of "topological protection", which is exploited to obtain wave propagation properties that are robust against disorder and noise. The knowledge developed through this research will advance technologies, including but not limited to: a) mechanical computing, where acoustic logic ports can be seen as building blocks capable of carrying out an array of mathematical operations, and b) devices with novel thermal transport properties, exploiting the analogy between thermal phonons and mechanical vibrations at the spatial and temporal scales of mechanical devices. The research will also be disseminated to the broader community through a workshop with public tutorials, broaden the participation of underrepresented groups in STEM fields through enhancing existing programs at the different academic institutions and will result in YouTube videos to share the discoveries with the general public.This project will develop a fundamental understanding of how the phonon band topology governs the acoustic properties of systems experiencing spatial-temporal modulation, leading to a formal interpretation framework for this type of time-reversal symmetry breaking phenomena. The powerful toolkits to be developed through the project will allow for a rich variety of designs beyond the current boundaries of the use of topological states in acoustic wave control strategies. The research will span frontiers of condensed matter physics, wave mechanics, and materials science. The two main conceptual ideas to be used for the realization of topologically protected nonreciprocal wave propagation are: (1) program the phonon band structure in spatial-temporal modulated materials using principles of topological band theory, and (2) exploit the contrasting wave propagation properties of Maxwell lattices in their metal-like and topological insulator-like phases. The research team will advance the theoretical understanding of the intimate role played by topological protection in nonreciprocal wave propagation, use state-of-the-art fabrication techniques to realize prototypes of acoustic diodes at different scales using a variety of material platforms, and deploy laser-enabled wave reconstruction capabilities to characterize the nonreciprocal wave propagation phenomena in the fabricated metamaterial specimen. By developing and applying principles of topology and material logic design across the scales, the project will transform a set of simple mechanical components into a versatile platform for the next generation acoustic logic ports with programmable acoustic transport and time reversal symmetry breaking capabilities.