Mechanical Characterization of Nonlinear Soft Materials Using Surface Waves

该补助金将资助研究，使软材料的非线性特性的动态表征，应用于增材制造，组织工程，食品加工和生物医学诊断，从而促进科学进步，促进国家繁荣，健康和福利。软材料自然存在于生物组织中，并越来越多地用作工程系统中的承重元件，包括机器人设备和3d打印生物材料支架。其精确的机械特性可以实现肿瘤形成的体内诊断，确保柔性致动器的可靠性能，并支持移植的成功组织生长。现有的表征技术，如剪切波弹性成像和超声波，依赖于体波和监测线性材料的反应。因此，它们不能捕获与大变形和典型软材料的复杂构造相关的振幅和速率相关效应。在该项目中，将开发一种新的表征技术，该技术依赖于表面波，表面波比体波传播更长的距离，并与底层材料的非线性力学特性进行建设性的相互作用。该研究将演示基于表面波的方法如何在正常操作条件下实现软材料的可靠、快速、非接触和非破坏性表征。基于波的材料表征技术和仪器将在一个针对当地工业的研讨会上展示，并作为K-12学生和公众年度外展计划的互动展览的一部分。这项研究旨在揭示软材料上的表面波与本构非线性相互作用的机制，触发内部共振，并产生传播长距离并可由适当仪器检测的高阶谐波。将进行数值和实验研究，以关联表面波特性与速率相关的非线性特性，并确定这些相关性如何依赖于由于制造过程中残留或操作过程中引起的热，机械和化学效应而导致的软材料中的预载荷。该研究的直接成果将是实验验证的基于物理的本构非线性和色散，衰减和声弹性表面波之间的相关映射。此外，该项目还将通过电磁感应瞬态激励和先进的多点激光振动测量技术，推进当前机械波的测量和分析技术。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This grant will fund research that enables on-the-fly characterization of nonlinear properties of soft materials, with application to additive manufacturing, tissue engineering, food processing, and biomedical diagnostics, thereby promoting the progress of science and advancing the national prosperity, health, and welfare. Soft materials occur naturally in biological tissue and find increased use as load-bearing elements in engineered systems, including robotic devices and 3d-printed biomaterial scaffolds. Their accurate mechanical characterization could enable in-vivo diagnosis of tumor formation, ensure reliable performance of flexible actuators, and support successful tissue growth for transplantation. Existing techniques for characterization, such as shear-wave elastography and ultrasonics, rely on body waves and monitor linear material response. Consequently, they fall short of capturing amplitude- and rate-dependent effects associated with large deformations and the complex constitution of typical soft materials. In this project, a new characterization technique will be developed that relies on surface waves, which propagate longer distances than body waves and interact constructively with the nonlinear mechanical properties of the underlying material. The research will demonstrate how a surface-wave-based methodology can achieve reliable, quick, non-contact, and non-destructive characterization of soft materials under normal operating conditions. Wave-based material characterization techniques and instrumentation will be presented at a workshop targeting local industry and as part of interactive exhibits at annual outreach programs for K-12 students and the public.This research aims to uncover mechanisms whereby surface waves on soft materials interact with constitutive nonlinearities, trigger internal resonances, and generate higher-order harmonics that propagate long distances and are detectable by appropriate instrumentation. Numerical and experimental studies will be performed to correlate surface-wave characteristics to rate-dependent nonlinear properties and establish how those correlations depend on preloads in the soft materials due to thermal, mechanical, and chemical effects that are residual from fabrication or induced during operation. The direct outcome of the research will be experimentally validated physics-based correlation maps between constitutive nonlinearities and dispersion, attenuation, and acoustoelasticity of surface waves. In addition, the project will advance the current measurement and analysis techniques for mechanical waves via fracture-induced transient excitations and advanced multipoint laser vibrometry.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.