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

直到最近，惯性空化气泡的快速，不稳定的增长和崩溃一直是最有名的环境中，如泵，涂层和身体组织的破坏剂。目前医学的进展旨在利用惯性空化来使用超声无创地切割组织，但这一目标受到可用数据的限制。目前的挑战是组织和各种软材料系统是复杂的，具有沿沿着不同内部方向的界面和刚度梯度。该奖项支持表征，建模和预测非均匀软材料的机械响应受到快速气泡崩溃和振荡。例如，这些知识可以用于加速基于超声的手术过程中的评估，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学生跨学科的流体和固体力学，材料科学。该团队将通过开发两本用多种语言编写的儿童读物和关于软材料力学的推广活动，鼓励广大早期学习者进行科学学习。同时探索材料的超高速率和有限变形机制的单一测试一直是难以捉摸的。先前的工作已经建立了惯性空化流变作为一个有前途的候选人，但该技术限制性地假设球对称。这个项目的目的是利用周围的非球面被视为一个问题，在原来的技术，作为一个关键指标，评估当地的材料梯度的数量。一个多视角，超高速率显微镜平台，用于表征分级，紫外光可调水凝胶使用气泡运动学，和全场变形确定通过嵌入式基于散斑平面的数字图像相关性包括实验设置。同时，数值方法利用（a）全场运动学场与模拟和（B）气泡形状扰动信息与运动和守恒的控制方程的修改后的一维扰动模型将建立一套基线问题。同时，在逆校准问题中的关键可测量的量将被用来建立一个快速的降阶模型，用于描述材料的行为和梯度。这种方法将提供用于生产线性分级水凝胶的方法，超高速率有限粘弹性水凝胶行为的数据库，利用球面扰动和模拟的升级的逆校准程序，以及用于快速流变学的降阶方法，或与─该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准。

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.