Mechanical Characterization of Nonlinear Soft Materials Using Surface Waves

这笔赠款将用于研究软材料的非线性特性，并将其应用于添加剂制造、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，并在工程系统中越来越多地用作承重元件，包括机器人设备和3D打印的生物材料支架。其精确的机械特性可以在体内诊断肿瘤的形成，确保柔性致动器的可靠性能，并支持移植成功的组织生长。现有的表征技术，如剪切波弹性成像和超声波，依赖于体波并监测线性材料响应。因此，它们不能捕捉与大变形和典型软材料的复杂结构相关的幅度和速率相关的效应。在这个项目中，将开发一种新的表征技术，它依赖于表面波，它传播的距离比体波更远，并与底层材料的非线性力学性质建设性地相互作用。这项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对软材料的可靠、快速、非接触和无损表征。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学生和公众年度推广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，并产生传播远距离的高次谐波，并可通过适当的仪器进行检测。将进行数值和实验研究，以将表面波特性与速率相关的非线性特性关联起来，并确定这些关联如何依赖于软材料中的预载荷，这些预载荷是由于制造过程中残留的或在操作过程中诱导的热、机械和化学效应造成的。这项研究的直接结果将是基于实验验证的基于物理的表面波的频散、衰减和声弹性之间的相关性图。此外，该项目将通过骨折诱导的瞬时激励和先进的多点激光测振技术来推进当前的机械波测量和分析技术。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。

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.