EAPSI: Controlling and Utilizing Local Wave Resonance in Engineered Materials

该奖项支持有助于PI开发一种革命性材料的长期目标的研究，该材料结合了非传统材料特性和热膨胀两个概念，从而在材料的谐振区域产生受控驱动。研究人员将研究局部共振，以及它在许多尺度上的表现。当波被用来激发一个结构时，有一些特定的频率与结构相匹配，并引起极大的放大运动；这些是固有频率。这种类型的现象可以在地震中看到，当建筑物倒塌似乎是随机发生的，但与该结构的固有频率相匹配的地震波频率有关。这种现象被称为共振。这个项目将使用超声波在更小的范围内观察共振，超声波是一种频率高于人类可听到声音的纵波。这些快速波需要一个小得多的结构，以便落在可能发生共振的范围内。当共振发生时，产生的超声波浓度可以用来改变该区域的材料特性。地震波和声波具有相似的性质，受相似的方程支配，因为它们都是纵波的类型。因此，我们可以借助大规模的概念来帮助我们理解甚至非常小的物质结构。陆金雄博士和他在国立台湾大学的实验室团队所提供的资源和专业知识对这些概念的发展将是非常宝贵的，该团队拥有广泛的知识和过去关于波传播和行为基础的工作。在这个项目中，研究人员和陆博士的团队将进行实验并建立模型，以帮助预测和进一步了解工程材料中的局部共振。这些材料可以用来利用和控制波。将已建立的地震波理论和模拟应用到纳米材料中，将在广泛的工程尺度范围内提供对波浪行为更全面的理解。这种材料的研究影响以及随后对基本波理论的巩固，将把围绕超声加热传统上不受欢迎的副作用的思考转移到有目的的可控电阻和选择性驱动领域。通过在悬浮在软基质中的充满液体的腔室中使用超声波激发局部共振，假设液体可以被显著加热以产生体积热膨胀。这种膨胀无疑会对空腔造成向外的压力，从而对周围的软基质造成压力。这种驱动会产生一种阻力，这种阻力可以阻止由于外部压力而导致的材料结构变形。液体的驱动可以通过热膨胀系数来预测，这将允许产生可重复和可定制的结果压力。作为这项研究的下一步，研究人员的目标是开发一种具有相同共振的线性腔室的纳米复合材料。然而，在一个特定的腔室经历变形后，它会产生一个独特的、独立于未受干扰的腔室的局部共振，并且可以单独被激发。然后，这个腔室将进行隔离加压，导致集中驱动，限制在经历变形的外部压力的腔室。将声波共振理论与超声换热理论相结合，建立一种新型的驱动技术，形成新的波振动理论和数值模拟。实验方法和分析技术将是材料工程领域前所未有的，并将为已建立的结构健康监测和分析波传感器的新用途打开大门。该研究项目寻求跨规模、不同工程领域和独特个人背景的合作，为未来的合作和讨论创建网络。该奖项由美国国家科学基金会和台湾科技部共同资助，隶属于东亚和太平洋暑期研究所项目，支持一名美国研究生进行暑期研究。

This award supports research that contributes to the PI's long-term goal of developing a revolutionary material that combines the two concepts of nontraditional material properties and thermal expansion to produce controlled actuation in the resonant region of the material. The researcher will study local resonance, and how it behaves on many scales. As waves are used to excite a structure, there are particular frequencies which match the structure and cause extremely amplified motion; these are the natural frequencies. This type of phenomenon can be seen in earthquakes when building collapse happens seemingly at random, but is tied to the earthquake wave frequency matching the natural frequency of that structure. This phenomenon is known as resonance. This project will look at resonance on a much smaller scale using ultrasonic waves, which are longitudinal waves in the frequency above the audible sound for humans. These rapid waves require a much smaller structure in order to fall into a range where resonance is possible. When resonance occurs, the resulting concentration of the ultrasonic waves can be used to alter the material properties in that region. Earthquake waves and sound waves share similar properties and are governed by similar equations because they are both types of longitudinal waves. Therefore we can look to large-scale concepts to help us understand even very small material structures. The resources and expertise provided by Dr. Chin-Hsiung Loh and his laboratory group at National Taiwan University will be invaluable to the development of these concepts based on the group's extensive knowledge and past work concerning the fundamentals of wave propagation and behavior. In this project, the researcher and Dr. Loh's group will perform experiments and build models that can help predict and further understand local resonance within engineered materials. These materials can then be used to utilize and control waves. The implementation of established earthquake wave theories and simulations into nanomaterials will provide a more unabridged understanding of wave behavior over the broad range of engineering scale.The research impacts of this material and the subsequent consolidation of fundamental wave theories would shift the thinking surrounding the traditionally undesirable side effect of ultrasonic heating into the purposeful field of controlled resistance and selective actuation. By exciting local resonance using ultrasonic waves in a liquid-filled chamber suspended in a soft matrix, it is hypothesized that the liquid can be heated significantly to produce a volumetric thermal expansion. This expansion would undoubtedly cause an outward pressure on the cavity and therefore on the soft surrounding matrix. This actuation would produce a resistive force that could stop deformation of the material structure due to an external pressure. The actuation of the liquid can be predicted through the thermal expansion coefficient, which will allow for the production of a repeatable and tailorable resulting pressure. As a further step in this research, it is the goal of the researcher to develop a nanocomposite with sets of linear chambers having identical resonances. After a particular chamber undergoes deformation, however, it would have a local resonance that is unique and independent of the undisturbed chambers and could be excited individually. This chamber would then undergo isolated pressurization causing centralized actuation limited to the chamber experiencing the deforming external pressure. The research will create a new type of actuation technology along with coupling acoustic wave resonance theory with ultrasonic heat transfer to produce novel wave vibration theories and numerical modeling. The experimental methods and analysis techniques would be unprecedented in the materials engineering field and would open the door for new uses of well-established structural health monitoring and analysis wave sensors. This research project seeks to collaborate across scale, diverse engineering fields, and unique individual backgrounds to create networks for future collaboration and discussion.This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Ministry of Science and Technology of Taiwan.