Analyzing and Organizing Soft Matter with Acoustic Holography

非技术描述声波可以施加足够大的力，使物体悬浮并在三维方向上移动。声学悬浮物体也会影响声场，散射声波并改变其作用力的方向。散射波在物体之间的相互作用中起中介作用，使它们自己组织成动态的三维集合。这些波-物质复合系统构成了一种在很大程度上未被探索的物质状态，具有非凡的和潜在的有用性质。“声全息分析和组织软物质”项目致力于发展控制声力所需的基本原理和实用技术，阐明波-物质复合系统的物理，并提出一种基于散射声定量分析的材料表征新范式。这一实验计划的动机是首席研究员最近在波-物质相互作用理论方面的突破，该理论解释了如何设计和投射移动物质的声波。从这些研究中得出的原则既是一般性的，也是基本的。此外，它们在非接触式制造和3D显示等多个领域都有实际应用。这些应用的技术转让已经在进行中，通过声全息术进行声操纵的科学有助于在K-12部门进行有效的STEM推广。它还为本科生提供了丰富的可访问的研究项目，从而帮助建立了STEM研究中的多样性和包容性的管道。技术描述最近推出的声动学框架解释了声波的幅度和相位分布如何在辐射物体上产生力和力矩。一种类似的方法在光学微操纵领域被证明是非常有成效的，它提供了实现所需力景观的光学全息图的设计原则。将光学操作原理转化为实验实现得益于高度先进的光波前整形技术。目前还没有这样的声音技术。因此，要实现声动力学的好处，需要一种新的计算全息术方法。该计划通过引入光谱全息术作为计算全息术的新范例来弥合这一技术差距。光谱全息术是一种波前雕刻的方法，它依赖于在少数离散发射器上控制波的幅度和相位，但在很大的频率范围内。标准单色全息图创建静态的时间平均力场，而光谱全息图可以在广泛的时间和长度范围内具有动态内容。沉浸在这种多尺度景观中的单个物体和多体系统的随时间变化的行为是一个新兴的研究领域。研究这些系统的预期结果包括经典波-物质相互作用基础科学的进展，以及软物质和颗粒材料中自组织新原理的发现。惯性在声音介导的自组织中的关键作用构成了基本发现的一个特别有前途的前沿，例如波动驱动振荡器的显着动力学行为。该计划还为行业提供了令人振奋的技术转移机会，包括用于制造的非接触式材料运输、用于体积显示的快速3D扫描和大规模远程材料表征。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical DescriptionSound waves can exert forces that are large enough to levitate objects and move them in three dimensions. Acoustically levitated objects also influence the sound field, scattering sound waves and redirecting their forces. Scattered waves mediate interactions among the objects that cause them to organize themselves into dynamic three-dimensional assemblies. These wave-matter composite systems constitute a largely unexplored state of matter with extraordinary and potentially useful properties. The program on “Analyzing and Organizing Soft Matter with Acoustic Holography” is dedicated to developing the fundamental principles and practical techniques needed to control acoustic forces, elucidating the physics of wave-matter composite systems, and advancing a new paradigm for materials characterization based on quantitative analysis of scattered sound. This experimental program is motivated by the Principal Investigator’s recent breakthrough in the theory of wave-matter interactions that explains how to design and project sound waves that move matter. Principles emerging from these studies are both general and fundamental. They have practical applications, moreover, in areas as diverse as non-contact manufacturing and 3D displays. Technology transfer for these applications already is under way, The science of acoustic manipulation through acoustic holography lends itself to effective STEM outreach in the K-12 sector. It also provides a wealth of accessible research projects for undergraduates, thereby helping to build the pipeline for diversity and inclusion in STEM research.Technical DescriptionThe recently-introduced acoustokinetic framework explains how the amplitude and phase profiles of a sound wave give rise to forces and torques on insonated objects. An analogous approach has proved extraordinarily fruitful for the field of optical micromanipulation by providing design principles for optical holograms that implement desired force landscapes. Translating principles of optical manipulation into experimental realizations has benefitted from highly advanced technology for shaping the wavefronts of light. No such technology currently exists for sound. Realizing the benefits of acoustokinetics therefore requires a novel approach to computational holography. This program bridges this technological gap by introducing spectral holography as a new paradigm for computational holography. Spectral holography is an approach to wavefront sculpting that relies on controlling the wave’s amplitude and phase at a small number of discrete emitters but over a wide range of frequencies. Whereas standard monochromatic holograms create static time-averaged force fields, spectral holograms can have dynamic content over a wide range of time and length scales. The time-dependent behavior of individual objects and many-body systems immersed in such multi-scale landscapes represent an emerging area of research. Anticipated outcomes from studying these systems include advances in the fundamental science of classical wave-matter interactions and discovery of new principles of self-organization in soft-matter and granular materials. The critical role of inertia in sound-mediated self-organization constitutes a particularly promising frontier for fundamental discoveries such as the remarkable dynamical behavior of wave-driven oscillators. This program also provides exciting opportunities for technology transfer to industry, including contact-free materials transport for manufacturing, rapid 3D scanning for volumetric displays and large-scale remote materials characterization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.