Size Dependent Mechanical Properties for Elastic Polymer Gels

技术概述：该项目由材料研究部的聚合物计划和土木工程、机械和制造创新司的材料力学计划支持，将发展超软材料的机械性能的基础知识。主要目标将是通过实验研究尺寸尺度对在超软材料中实现大应变、弹性机械响应的影响。具有这些属性的超软材料对于从防护设备到组织工程的许多应用都是重要的。最近，许多模仿天然凝胶的新型聚合物，如resilin，已经被证明取得了一些成功，但这些聚合物往往是复杂的，可能难以实际实现。通过了解超软材料在小尺寸范围内的机械性能，可以找到另一种策略。这一策略的动机是金属和陶瓷的一个众所周知的属性，即尺寸可以影响在机械载荷下对缺陷的敏感性。因此，以小尺寸制造的金属和陶瓷可以显示出非凡的机械性能。对于超软材料，这些效应还没有经过实验测量。在所提出的研究中，标度关系提供了指导性假设，预测对于膨胀的聚合物网络的大应变可逆变形存在优化的尺寸尺度。这些假设将在两种不同的凝胶材料上使用标准和新的表征方法进行实验验证。这项研究的结果将导致对合成凝胶和活组织的新的表征方法和理解，以及创造能够实现高应变、高强度和高弹性的超软材料的新材料策略。非技术概述：超软材料在从防护装备到组织工程的许多技术中都具有吸引力。目前，这些材料要么是脆性的，不能伸展很远，要么就是能够通过消耗能量伸展很远，类似于愚蠢的油泥的工作方式。最近的努力集中在创造模仿生物蛋白质的结构和性质的新聚合物，如resilin。然而，这些新材料很复杂，可能很难实际实施。克服这些挑战的一种可能的策略是利用预测的小尺寸机械性能增强。众所周知，相对于分子尺寸，金属和陶瓷在小尺寸尺度上表现出更好的力学性能；然而，类似的实验研究还没有在超软材料上进行。这项拟议的研究将对小尺寸超软材料的机械性能进行实验研究，以实现高应变、高强度和高弹性。预计吸取的经验教训将影响新保护装置的开发；影响包括活组织在内的软材料的特性；并引发与脑等软生物组织的创伤性损害有关的新问题。此外，还将开发一个关于生物灵感材料设计的创新工作坊计划，以激励来自不同背景的高中生追求未来的科学和工程职业生涯。该项目将让马萨诸塞州西部的学生和公众认识到材料和力学研究的重要性，创造力在科学和工程发现中的作用，以及在没有基本原则的情况下使用生物灵感所产生的困难。

TECHNICAL SUMMARY:This project, supported by the Polymers Program of the Division of Materials Research and the Mechanics of Materials Program of the Division of Civil, Mechanical, and Manufacturing Innovation, will develop fundamental knowledge of mechanical properties for ultra-soft materials. The primary goal will be to experimentally investigate the effect of size scale on achieving large strain, resilient mechanical responses in ultra-soft materials. Ultra-soft materials with these attributes are important for numerous applications, from protective devices to tissue engineering. Recently, many novel polymers which mimic naturally-occurring gels, such as resilin, have been demonstrated with some success, but these polymers are often complex and potentially difficult to implement practically. An alternative strategy may be found by understanding the mechanical properties of ultra-soft materials at small size scales. This strategy is motivated by a well-known property for metals and ceramics that size can influence the sensitivity to defects under mechanical loading. Thus, metals and ceramics fabricated on small size scales can display extraordinary mechanical properties. For ultra-soft materials, these effects have not been experimentally measured. In the proposed research, scaling relationships provide guiding hypotheses that predict the existence of optimized size scales for large strain reversible deformations for swollen polymer networks. These hypotheses will be experimentally confirmed using standard and novel characterization methods on two different gel materials. The results of this research will lead to new characterization methods and understanding for both synthetic gels and living tissues, as well as new materials strategies for creating ultra-soft materials that can achieve high strains, high strength, and high resiliency.NON-TECHNICAL SUMMARY:Ultra-soft materials are attractive for many technologies, from protective gear to tissue engineering. Currently, these materials are either brittle, not allowing them to stretch very far, or they are able to stretch far by dissipating energy, similar to the way Silly Putty works. Recent efforts have focused on creating new polymers that mimic the structure and properties of biological proteins, such as resilin. However, these new materials are complex and may be difficult to implement practically. One possible strategy for overcoming these challenges is to take advantage of predicted mechanical property enhancements at small size scales. It is well known that metals and ceramics display improved mechanical performance on small size scales relative to their molecular size scale; however, similar experimental investigations have not been conducted on ultra-soft materials. The proposed research will experimentally investigate the mechanical properties of ultra-soft materials at small sizes to achieve high strains, high strength, and high resiliency. The lessons learned are anticipated to impact the development of new protective devices; to influence the characterization for soft materials including living tissues; and to provoke new questions related to traumatic damage in soft biological tissues, such as the brain. In addition, an innovative workshop program on Bioinspired Materials Design will be developed to inspire high school students from diverse backgrounds to pursue future careers in science and engineering. This program will allow students and the general public in Western Massachusetts to realize the importance of materials and mechanics research, the role of creativity in scientific and engineering discovery, and the difficulties that arise when bioinspiration is used without foundational principles.