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Mechanistic Models of the Mechanical Response of Self-healing Hydrogels

自修复水凝胶机械响应的机理模型

基本信息

批准号：
1537087
负责人：
Chung-Yuen Hui
金额：
$ 42万
依托单位：
Cornell University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-08-15 至 2019-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537087&HistoricalAwards=false
关键词：
Mechanistic Models Mechanical Response Self

项目摘要

A hydrogel is a network of molecular chains into which water is absorbed and trapped, forming a material that is typically 90 percent or more water. Hydrogels have a wide range of current and potential applications such as scaffolds for laboratory grown tissue, drug delivery systems, biosensors, and consumer products. Hydrogels typically break at low levels of stretching, limiting their use in load bearing applications. Newly developed hydrogels consisting of stiff and soft interpenetrating networks can stretch like rubber. However, once they start to tear the damage is irreversible. By replacing the stiff network's covalent bonds with bonds that can reform, the material can become self-healing. This project seeks to understand the physics and mechanics of such gels and to develop mathematical models that will explain the self-healing behavior. Such models will establish connections between molecular scale features and mechanical response and enable researchers to build simulation models of engineered hydrogel systems. The model will be embedded in the context of an analysis code widely used in mechanics. We envision that such models would aid in the engineering of potential load-bearing applications of self-healing gels such as artificial cartilage and actuators for soft machines. The project will also provide opportunities for us to reach out to prospective students through hands-on discovery of the unexpected properties of self-healing hydrogels. In recent years polymer chemists have made tremendous strides in the synthesis of biocompatible, tough, low friction, self-healing hydrogels. Currently, models are lacking that link fatigue resistance, fracture, and time dependent, self-healing behavior to the underlying, rate dependent bond breaking and reformation processes. This research bridges this gap by: (a) designing and executing experiments to measure these mechanical behaviors using a model material system, (b) defining quantitative models relating these behaviors to bond breaking and reformation kinetics. Experiments will include tension testing, measurements crack growth rate tests and crack healing under monotonic and cyclic loading. The research will provide understanding of how the observed macroscale properties (strength, time dependence, fracture, fatigue and self-healing) are related to underlying deformation and separation mechanisms at the molecular level. The constitutive and failure models will also provide a quantitative link between these observable mechanical properties and relevant microscale parameters such as the different types of physical bonds, their strengths, and breaking/healing kinetics. The project will advance the field of mechanics by building a framework for constitutive and fracture models that are linked directly to the microstructure and that can be used in structural finite element simulations.

水凝胶是一种分子链网络，水被吸收和捕获，形成一种通常含有90%或更多水的材料。水凝胶具有广泛的当前和潜在应用，例如用于实验室生长组织的支架、药物递送系统、生物传感器和消费品。水凝胶通常在低水平的拉伸下断裂，限制了它们在承载应用中的使用。新开发的水凝胶由硬和软的互穿网络组成，可以像橡胶一样伸展。然而，一旦它们开始撕裂，损害就不可逆转。通过用可以改革的键取代刚性网络的共价键，材料可以自我修复。该项目旨在了解这种凝胶的物理和力学，并开发数学模型来解释自我修复行为。这些模型将建立分子尺度特征和机械响应之间的联系，并使研究人员能够建立工程水凝胶系统的模拟模型。该模型将被嵌入在力学中广泛使用的分析代码的上下文中。我们设想，这样的模型将有助于工程的潜在承载应用的自愈凝胶，如人工软骨和软机器的驱动器。该项目还将为我们提供机会，通过亲自动手发现自愈水凝胶的意想不到的特性来接触未来的学生。近年来，聚合物化学家在生物相容性、坚韧、低摩擦、自修复水凝胶的合成方面取得了巨大进展。目前，缺乏将抗疲劳性、断裂和时间依赖性、自愈合行为与潜在的速率依赖性键断裂和重组过程联系起来的模型。本研究通过以下方式弥合这一差距：（a）设计和执行实验，使用模型材料系统测量这些力学行为，（B）定义将这些行为与键断裂和重组动力学相关的定量模型。实验将包括拉伸测试，测量裂纹扩展速率测试和单调和循环载荷下的裂纹愈合。该研究将提供对所观察到的宏观性质（强度，时间依赖性，断裂，疲劳和自我修复）如何与分子水平上的潜在变形和分离机制相关的理解。本构和失效模型还将提供这些可观察到的机械性能和相关微观参数之间的定量联系，例如不同类型的物理键、它们的强度和断裂/愈合动力学。该项目将通过建立直接与微观结构相关并可用于结构有限元模拟的本构和断裂模型框架来推进力学领域。