Collaborative Research: Integrated Experiments and Modeling for Spatial, Finite, and Fast Rheometry of Graded Hydrogels using Inertial Cavitation

直到最近，惯性空化--气泡快速、不稳定的生长和破裂--一直被认为是泵、涂层和身体组织等环境中的一种破坏性因素。目前医学的发展目标是利用惯性空化来利用超声波非侵入性地切割组织，但这一目标受到现有数据的限制。目前的一个挑战是，组织和各种软材料系统是复杂的，沿不同的内部方向具有界面和刚度梯度。该奖项支持表征、建模和预测非均匀软材料在气泡快速崩塌和振荡时的机械响应。例如，这一知识可以用来加快超声手术期间的评估，并为减轻快速力量造成的伤害提供关键的见解。因此，这项研究不仅将促进科学的进步，而且将促进国家的健康、繁荣和福利。该项目将进一步培养跨流体和固体力学以及材料科学学科工作的学生。该团队将通过开发两本用多种语言编写的儿童书籍和关于软材料机械的推广活动，鼓励广大早期学习者进行科学学习。同时探索超高速和有限变形材料制度的单一测试一直难以捉摸。以前的工作已经确定惯性空化流变学是一种很有前途的候选方法，但该技术严格假设为球对称。该项目旨在利用非球面周围的数量--在原始技术中被视为一个问题--作为评估局部材料梯度的关键指标。实验装置包括多角度、超高速显微镜平台，用于表征分级、紫外光可调水凝胶的气泡运动学，以及通过嵌入散斑平面的数字图像相关确定的全场变形。同时，数值方法利用(A)全场运动场的模拟和(B)气泡形状摄动信息以及运动和守恒控制方程的修正的一维摄动模型将建立一系列基线问题。总之，反校准问题中的临界可测量将被用来建立一个快速降阶模型，用于描述材料的行为和其中的梯度。这种方法将提供一种生产线性梯度水凝胶的方法，超高速有限粘弹性水凝胶行为的数据库，利用球面扰动和模拟升级的逆校准程序，以及在没有、有或有耦合性质梯度的情况下进行快速流变学的降阶方法。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。

Until recently, inertial cavitation—the rapid, unstable growth and collapse of bubbles—has been best known as a damaging agent in environments such as pumps, coatings, and bodily tissues. Current advances in medicine aim to harness inertial cavitation to cut tissues noninvasively using ultrasound, but this goal is limited by available data. A present challenge is that tissues and various soft material systems are complex, with interfaces and stiffness gradients along different internal directions. This award supports characterizing, modeling, and predicting the mechanical response of non-uniform soft materials subject to rapid bubble collapse and oscillation. This knowledge could be used, for example, to speed up assessment during ultrasound-based surgery and provide critical insight into mitigating injury from rapid forces. Thus, the research will not only promote the progress of science but will also advance national health, prosperity, and welfare. This project will further train students working across disciplines of fluid and solid mechanics, and materials science. The team will encourage scientific learning in a broad early-learner audience via the development of two children's books written in multiple languages and outreach activities about soft material mechanics.A single test probing ultra-high-rate and finite deformation regimes of materials simultaneously has been elusive. Prior work has established inertial cavitation rheometry as a promising candidate, but the technique restrictively assumes spherical symmetry. This project aims to leverage quantities surrounding asphericity—regarded as a problem in the original technique—as a critical metric for assessing local material gradients. A multi-perspective, ultra-high-rate microscopy platform for characterizing graded, ultraviolet-light-tunable hydrogels using bubble kinematics, and full-field deformations determined via embedded speckle plane-based digital image correlation comprise the experimental setup. Concurrently, numerical methods leveraging (a) full-field kinematic fields with simulation and (b) bubble shape perturbation information with a modified 1D-perturbation model of the governing equations of motion and conservation will establish a suite of baseline problems. Together, critical measurable quantities in the inverse calibration problem will be used to establish a fast reduced-order model for describing both material behavior and gradients therein. This approach will provide a methodology for producing linearly graded hydrogels, a database of ultra-high-rate, finite viscoelastic hydrogel behavior, upgraded inverse-calibration procedures leveraging spherical perturbations and simulations, and a reduced-order approach for fast rheology without, with, or with-coupled property gradients.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.