Multiscale Mechanics of Composite Hydrogels Exposed to Shock Waves

这笔赠款将支持研究水凝胶对冲击波的响应，这一点还没有得到很好的理解。水凝胶(如Jell-O，造型凝胶)是一种由可溶于水的聚合物组成的材料，它可以膨胀形成相互连接的三维网络。由于水凝胶在机械性能上的相似性，它们也被用作软生物组织的替代材料。冲击波通过水凝胶可以作为研究爆炸引起的创伤性脑损伤的模型，例如，美国军人遭受的损伤。然而，首先需要表征受冲击的水凝胶的力学响应。该项目将检验这样一个假设，即来自冲击波的能量破坏水凝胶网络，导致水凝胶机械性能的变化。了解受冲击的水凝胶的行为将有助于材料科学家开发用于BLAST研究的组织替代材料，以及用于可穿戴传感器和软机器人应用的更具弹性的水凝胶配方。此外，这项研究项目将通过与现有组织的参与来补充，如爱荷华州立大学的卓越学术计划和女性科学与工程计划。通过向学生介绍流变学和生物材料等主题的外展活动，将建立支持招收和留住工程领域代表性不足学生的计划。研究的具体目标是从根本上了解冲击波暴露对用作组织模拟剂的复合水凝胶的体积和微观结构特性的影响。水凝胶中冲击波的分子动力学模拟表明，局部水浓度降低，导致整体力学性能发生变化。然而，水凝胶暴露在冲击波中的实验观察需要验证。因此，本项目的研究目标包括：(1)利用光学视频显微镜探测准静态条件下的水凝胶微结构，以测量粘弹性行为；(2)测量水凝胶在冲击波暴露前后的力学响应，以将微观结构变化与改进的整体力学行为联系起来；(3)在微观结构水平上量化水凝胶因冲击波暴露而产生的构象变化。主要的重点将是利用实验(I)更好地了解水凝胶在冲击波作用下经历的宏观结构和微观结构的变化，以及(Ii)将结构变化与粘弹性行为相关联。该项目将促进力学和材料科学以及计算科学方面的知识。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 support research to examine the response of hydrogels to shock waves, which is not well understood. A hydrogel (e.g. Jell-O, styling gel) is a material that consists of a water soluble polymer that can swell to form an interconnected three-dimensional network. Hydrogels have also been used as surrogate material for soft biological tissue due to their similarity in mechanical properties. The passage of a shock wave through hydrogels may serve as a model for investigating blast-induced traumatic brain injury as, for example, sustained by United States’ military service members. However, characterizing the mechanical response of shocked hydrogels is first needed. The project will test the hypothesis that the energy from shock waves disrupt the hydrogel network, leading to changes in hydrogel mechanical properties. An understanding of the behavior of shocked hydrogels would aid material scientists in developing tissue surrogate materials for blast studies, along with more resilient hydrogel formulations for wearable sensor and soft robot applications. Additionally, this research project will be complemented by engaging with existing organizations such as Iowa State University’s Academic Program for Excellence and the Program for Women in Science and Engineering. Initiatives that support the recruitment and retention of underrepresented students in the field of engineering will be established through outreach activities that introduce students to topics such as rheology and biomaterials.The specific goal of the research is to fundamentally understand the effect of shock wave exposure on the bulk and microstructural properties of composite hydrogels that act as tissue simulants. Molecular dynamic simulations of shock waves in hydrogels have shown a decrease in local concentration of water, leading to changes in bulk mechanical properties. However, experimental observations of hydrogel exposure to shock waves are needed for validation. Thus, the research objectives of this project include: (1) probing hydrogel microstructure at quasistatic conditions using optical video microscopy to measure viscoelastic behavior; (2) measurement of hydrogel mechanical response before and after shock wave exposure to connect microstructural changes to modified bulk mechanical behavior; and (3) quantification of the conformational changes of hydrogel due to shock wave exposure at the microstructural level. The overarching focus will be on the use of experiments to (i) obtain a better understanding of the macrostructural and microstructural changes that hydrogels undergo when exposed to a shock wave and (ii) correlating the structural changes with viscoelasticity behavior. This project will advance knowledge in mechanics and material science, along with computational science.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.