Mechanical Characterization of Nonlinear Soft Materials Using Surface Waves

该基金将资助能够实时表征软材料非线性特性的研究，并应用于增材制造、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。软质材料自然存在于生物组织中，在工程系统中作为承重元件的使用越来越多，包括机器人设备和3d打印生物材料支架。它们精确的力学特性可以实现肿瘤形成的体内诊断，确保柔性执行器的可靠性能，并支持移植组织的成功生长。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响应。因此，它们无法捕获与典型软材料的大变形和复杂结构相关的振幅和速率依赖效应。在本项目中，将开发一种新的表征技术，该技术依赖于表面波，表面波比体波传播距离更远，并与底层材料的非线性力学特性建设性地相互作用。该研究将展示基于表面波的方法如何在正常操作条件下实现可靠、快速、非接触和非破坏性的软材料表征。基于波的材料表征技术和仪器将在针对当地工业的研讨会上展示，并作为K-12学生和公众年度推广计划的互动展览的一部分。本研究旨在揭示软材料表面波与本构非线性相互作用的机制，触发内部共振，并产生长距离传播的高阶谐波，并通过适当的仪器检测到。将进行数值和实验研究，将表面波特性与速率相关的非线性特性联系起来，并确定这些相关性如何取决于软材料中的预载荷，这些预载荷是由制造过程中残留的热、机械和化学效应引起的，或者是在操作过程中引起的。该研究的直接结果将通过实验验证本构非线性与表面波的色散、衰减和声弹性之间的物理相关图。此外，该项目将通过裂缝诱导瞬态激励和先进的多点激光振动测量技术来推进当前的机械波测量和分析技术。该奖项反映了美国国家科学基金会的法定使命，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.