DMREF: Collaborative Research:Elastomers Filled with Electro- and Magneto-Active Fluid Inclusions: A New Paradigm for Soft Active Materials

在过去的二十年中，越来越多的研究工作致力于软有机固体的数学、力学和物理学，其最终目标是利用这些材料的潜力来实现广泛的新技术。在这些努力中，数学建模和聚合物加工的最新进展刚刚揭示了充满电和磁敏感流体（与传统固体相反）包裹体的弹性体作为一种潜在的革命性高级软有机固体，可能使大量下一代传感器和执行器能够表现出极端和前所未有的电和磁机械性能。在此背景下，该设计材料以革新和工程我们的未来（DMREF）奖支持一项关于数学和计算自下而上的分析和设计的研究合作，以及实验合成和表征充满三种类型流体包裹体的弹性体的耦合电和磁机械性能，即带电气体填充孔隙，液态金属包裹体，以及铁磁流体内含物——目的是加快对这类有前途的材料的基本理解和技术部署的步伐。该项目将培养三名从事学术界或工业界工作的研究生，并将研究成果整合到伊利诺伊大学厄巴纳-香槟分校和宾夕法尼亚州立大学的本科和研究生课程中。研究人员还将开展活动，通过创建课程模块和实验室演示，提高高中生在STEM项目中接受高等教育和职业的兴趣，特别是在数学和材料科学领域。该项目的总体目标有三个方面：1)推导并数值实现均匀化方程，该方程描述了填充可压缩和不可压缩流体包裹体的弹性体宏观电力学和磁力学响应，直接考虑弹性体/流体包裹体界面上的机械、电和磁界面力；2)利用推导出的均质化方程来指导流体包裹体的设计，从而得到多孔驻极体和弹性体，这些弹性体中充满了具有优异宏观电学和磁力学性能的液态金属和铁磁流体包裹体；3)制备并表征了具有代表性的几种带充气孔隙的驻极体、含液态金属包裹体的弹性体和含铁磁流体包裹体的弹性体的微观和宏观性质。理论部分涉及新的数学结果及其相关的数值实现，这些结果直接解释了控制方程（即动量平衡和麦克斯韦方程）均质化过程中空间电荷和界面力的快速空间变化（在流体包裹体的微观尺度上）。另一方面，实验部分需要合成这些新型多功能材料系统，并开发利用原位x射线断层扫描和热刺激退极化电流测量的新实验，以提取弹性体/流体包裹体界面的界面力、空间电荷含量和行为。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over the last two decades, increasing research efforts have been devoted to the mathematics, mechanics, and physics of soft organic solids with the ultimate objective of capitalizing on the potential that these materials hold to enable a broad spectrum of new technologies. Among these efforts, recent advances in mathematical modeling and polymer processing have just revealed elastomers filled with electro- and magneto-sensitive fluid (as opposed to the conventional solid) inclusions as a potentially revolutionary class of advanced soft organic solids that may enable a plethora of next generation sensors and actuators capable of exhibiting extreme and unprecedented electro- and magneto-mechanical properties. In this context, this Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports a research collaboration on the mathematical and computational bottom-up analysis and design and the experimental synthesis and characterization of the coupled electro- and magneto-mechanical properties of elastomers filled with three broad types of fluid inclusions - namely, electrically charged gas-filled pores, liquid-metal inclusions, and ferrofluid inclusions - with the objective of accelerating the pace of fundamental understanding and technological deployment of this promising class of materials. This project will train three graduate students for careers in academia or industry and will integrate research results in the undergraduate and graduate curricula at the University of Illinois Urbana-Champaign and the Pennsylvania State University. The investigators will also carry out activities to promote interest in high school students to pursue higher education and careers in STEM programs, and especially in the fields of mathematics and materials science, through the creation of lesson modules and laboratory demonstrations. The overarching objective of this project is three-fold: 1) derive and numerically implement the homogenized equations describing the macroscopic electro- and magneto-mechanical response of elastomers filled with compressible and incompressible fluid inclusions directly accounting for the mechanical, electric, and magnetic interfacial forces at the elastomer/fluid-inclusion interfaces; 2) deploy the derived homogenized equations to guide the design of fluid inclusions that lead to porous electrets and elastomers filled with liquid-metal and ferrofluid inclusions with exceptional macroscopic electro- and magneto-mechanical properties; and 3) fabricate and characterize the microscopic and macroscopic properties of representative classes of electrets with electrically charged gas-filled pores, elastomers filled with liquid-metal inclusions, and elastomers filled with ferrofluid inclusions. The theoretical component involves new mathematical results and their associated numerical implementation that directly account for the rapid spatial variation (at the microscopic scale of the fluid inclusions) of space electrical charges and interfacial forces in the homogenization of the governing equations, namely, balance of momenta and Maxwell's equations. The experimental component, on the other hand, entails the synthesis of these new classes of multifunctional material systems and the development of new experiments that leverage in-situ X-ray tomography and thermally stimulated depolarization current measurements to extract the interfacial forces and space charge content and behavior at the elastomer/fluid-inclusion interfaces.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.