Micro- to Nanoscale Granular Contact Dynamics and Nonlinear Granular-Elastic Metamaterials

粒状晶体是由弹性粒子紧密排列而成的，能有效地调节声波的传播。然而，到目前为止，颗粒晶体通常是在宏观长度尺度上构造的，并且设计用于影响声波的频率。这项拨款为研究微到纳米级颗粒晶体的非线性接触动力学提供资金。将颗粒晶体扩展到微尺度和纳米尺度有可能使基于颗粒的设备在兆赫兹和千兆赫兹频率下工作。尺寸尺度也很重要，因为在宏观尺度上可以忽略不计的影响，如附着力，在微观尺度上变得很重要。颗粒晶体将通过自组装制造。光声技术将被用于研究基于基本接触动力学的微粒子和纳米粒子，以及研究更复杂的微尺度颗粒系统中的非线性波传播。实验结果将结合非线性动力系统、固体力学和声学超材料等领域的技术进行建模。将探讨局部共振颗粒-弹性超材料构型的非线性。该项目具有潜在的重大社会影响，因为微纳米级颗粒晶体和局部共振颗粒弹性超材料可能在信号处理、无损评估和粘附特性、生物医学超声成像和治疗等领域具有潜在的应用前景。预计该项目将建立对微尺度颗粒介质中非线性波传播的基本认识。研究工作将与重要的教育组成部分相结合，并将在课堂和实验室中为多样化的学生群体提供独特的跨学科教育机会。拟议的研究将纳入由PI领导的新开发的课程，并将开发有关实验的简化版本，以便通过外展活动提高对科学和工程的兴趣。

Granular crystals are close-packed arrays of elastic particles, and are effective at tailoring acoustic wave propagation. However, so far granular crystals are typically constructed at macroscopic length scales and designed to affect sonic frequency acoustic waves. This grant provides funding for the study of the nonlinear contact-based dynamics of micro to nanoscale granular crystals. Extending granular crystals to the microscale and nanoscale has the potential to enable granular-based devices that operate at megahertz and gigahertz frequencies. The size scale is also important, as effects which are negligible at the macroscale, such as adhesion, become significant at microscales. Granular crystal will be manufactured by self-assembly. Photoacoustic techniques will be utilized to study the fundamental contact-based dynamics of micro- and nanoparticles, as well as to study nonlinear wave propagation in more complex microscale granular systems. The experimental findings will be modeled using a combination of techniques drawn from the areas of nonlinear dynamical systems, solid mechanics, and acoustic metamaterials. Nonlinearities in locally-resonant granular-elastic metamaterial configurations will be explored.This project has the potential for significant societal impact, as micro- to nanoscale granular crystals and locally-resonant granular-elastic metamaterials may have potential future applications to areas such as signal processing, non-destructive evaluation and adhesion characterization, and biomedical ultrasound imaging and therapy. It is also anticipated that this project will establish the fundamental understanding of nonlinear wave propagation in microscale granular media. The research efforts will be combined with a significant educational component, and will provide a diverse student group with a unique interdisciplinary educational opportunity in the classroom and the laboratory. The proposed research will be incorporated into a newly developed course led by the PI, and simplified versions of relevant experiments will be developed to generate increased interest in science and engineering through outreach activities.