Background

Hydrogels are one of the most ubiquitous polymeric materials. Among them gelatin, agarose and polyacrylamide-based formulations have been effectively utilized in a variety of biomedical and defense-related applications including ultrasound-based therapies and soft tissue injury investigations stemming from ballistic and blast exposures. Interestingly, while in most cases accurate prediction of the mechanical response of these surrogate gels requires knowledge of the underlying finite deformation, high-strain rate material properties, it is these properties that have remained scarce in the literature.

Objective

Building on our prior works using Inertial Microcavitation Rheometry (IMR), here we present a comprehensive list of the high-strain rate (> 10\(^3\) 1/s) mechanical properties of these three popular classes of hydrogel materials characterized via laser-based IMR, further showing that the choice in finite-deformation, rate-dependent constitutive model can be informed directly by the type of crosslinking mechanism and resultant network structure of the hydrogel, thus providing a chemophysical basis of the the choice of phenomenological constitutive model.

Methods

We analyze existing experimental gelatin IMR datasets and compare the results with prior data on polyacrylamide.

Results

We show that a Neo-Hookean Kelvin-Voigt (NHKV) model can suitably simulate the high-rate material response of dynamic, physically crosslinked hydrogels like gelatin, while the introduction of a strain-stiffening parameter through the use of the quadratic Kelvin-Voigt (qKV) model was necessary to appropriately model chemically crosslinked hydrogels such as polyacrylamide due to the nature of the static,covalent bonds that comprise their structure.

Conclusions

In this brief we show that knowledge of the type of underlying polymer structure, including its bond mobility, can directly inform the appropriate finite deformation, time-dependent viscoelastic material model for commonly employed tissue surrogate hydrogels undergoing high strain rate loading within the ballistic and blast regimes.

中文翻译：

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物理和化学交联水凝胶的弹道和爆炸相关的高速率材料特性

背景

水凝胶是最普遍的聚合物材料之一。其中，基于明胶、琼脂糖和聚丙烯酰胺的配方已有效地应用于各种生物医学和国防相关应用，包括基于超声的治疗和弹道和爆炸暴露引起的软组织损伤研究。有趣的是，虽然在大多数情况下，准确预测这些替代凝胶的机械响应需要了解潜在的有限变形、高应变率材料特性，但这些特性在文献中仍然很少。

客观的

基于我们之前使用惯性微空化流变仪 (IMR) 的工作，我们在此列出了这三类流行的水凝胶材料的高应变率 (> 10 \(^3\) 1/s) 机械性能的综合列表，其特征在于基于激光的 IMR，进一步表明有限变形、速率依赖本构模型的选择可以直接通过水凝胶的交联机制和所得网络结构的类型来确定，从而为现象学本构模型的选择提供了化学物理基础模型。

方法

我们分析了现有的实验明胶 IMR 数据集，并将结果与​​聚丙烯酰胺的先前数据进行比较。

结果

我们证明 Neo-Hookean Kelvin-Voigt (NHKV) 模型可以适当地模拟动态物理交联水凝胶（如明胶）的高速材料响应，同时通过使用二次 Kelvin-Voigt 引入应变硬化参数由于构成化学交联水凝胶（例如聚丙烯酰胺）结构的静态共价键的性质，（qKV）模型对于适当模拟化学交联水凝胶是必要的。

结论

在这篇简报中，我们表明，对基础聚合物结构类型（包括其键迁移率）的了解，可以直接为在弹道和爆炸中经受高应变率载荷的常用组织替代水凝胶提供适当的有限变形、时间依赖性粘弹性材料模型政权。