Nonlinear Acoustic Meta-Materials for Wave Propagation Management and Control

该研究探索了周期性超材料中的非线性声子行为，旨在开发具有新功能，增强性能和自适应可调谐性的低功率波基器件。具有周期性微结构的声子超材料表现出非凡的波特性，例如带隙、响应方向性、左手性和负声折射，所有这些都可以用于在宽范围的频率和长度尺度上操作的声学设备的设计。随着设备的集成化，非线性行为成为常态，而不是例外，这在一定程度上可以通过用于描述小尺度相互作用的复杂势来证明。本研究探讨了非线性对色散特性、带隙和方向性的影响，并特别探讨了非线性作为实现丰富周期性介质设计空间的新功能的手段。硬化和软化效应、响应的正常模式与剪切模式、振幅相关的色散以及超谐波和次谐波的存在实际上可以积极地影响给定介质的波导特性，并且可以被利用来实现波特性的可调谐性。分析和计算技术将制定调查的非线性声子系统的非线性的性质，并预测其波动力学效应。开发的工具将使可调带通滤波器的设计与可控带宽和声学超材料能够引导和聚焦声能向特定方向。将这些概念应用于执行各种基于声学的信号处理功能的滤波器、波导、逻辑端口和超声换能器阵列是非常有吸引力的，特别是在电子器件遭受严重功率限制的频率处。预计该项目将大大推进非线性超材料波动力学一般领域的知识和理解，这对于开发通信系统（移动的电话、全球定位系统等）中使用的高频可调谐设备将是重要的。噪声隔离、能量导向材料、用于医疗设备的可调超声、可调声学麦克风和接收器以及声学波束形成器。

The research explores nonlinear phononic behavior in periodic meta-materials, with the intent of enabling the development of low-power wave-based devices with novel functionality, enhanced performance, and adaptive tunability. Phononic meta-materials with periodic microstructures exhibit extraordinary wave properties such as band-gaps, response directionality, left-handedness, and negative acoustic refraction, all of which can be employed for the design of acoustic devices operating over a broad range of frequencies and length scales. As devices miniaturize, nonlinear behavior becomes the norm and not the exception, as witnessed in part by the complex potentials used to describe small-scale interactions. This research investigates the effects of nonlinearities on dispersion characteristics, band-gaps, and directionality and specifically explores nonlinearities as means to achieve novel functionalities that enrich the design space of periodic media. Stiffening and softening effects, normal versus shear modes of response, amplitude-dependent dispersion, and the presence of super- and sub-harmonics may in fact positively affect the wave guiding characteristics of a given medium and may be exploited to achieve tunability of the wave properties. Analytical and computational techniques will be formulated to investigate the nature of nonlinearities in nonlinear phononic systems, and to predict their wave mechanics effects.The developed tools will enable the design of tunable pass-band filters with controllable bandwidth and of acoustic meta-materials capable of directing and focusing the acoustic energy towards specific directions. The application of these concepts to filters, waveguides, logic ports, and ultrasonic transducer arrays which perform a variety of acoustics-based signal processing functions is very attractive particularly at frequencies where electronics suffer from severe power limitations. The project is expected to significantly advance knowledge and understanding in the general area of nonlinear meta-material wave mechanics, which will be important for the development of high-frequency, tunable devices for use in communication systems (mobile phones, GPS units, etc.), noise isolation, energy-directing materials, tunable ultrasound for medical devices, tunable acoustic microphones and receivers, and acoustic beamformers.