CAREER: Mechanics of Active Polymers and Morphing Structures: Determine the Role of Molecular Interactions and Stiffness Heterogeneity in Reversible Shape Morphing

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。这项教师早期职业发展（Career）资助将支持创新活性聚合物和变形结构力学的基础研究。软变形聚合物可以在暴露于外部刺激时改变其形状和功能，这对于许多应用非常重要，包括软机器人、人造肌肉和组织修复。尽管在这个令人兴奋和不断发展的领域取得了进步，但由于缺乏对液晶弹性体等新型活性聚合物的基本力学理解，创新变形材料和结构的合理设计、制造和应用受到了极大的限制。本研究项目将以液晶弹性体为模型材料系统，建立新型活性材料在分子、材料和结构层面上缺失的复杂关联。这项工作的教育目标是吸引不同层次的学生和公众研究变形材料和结构的前沿。将启动“超越想象的变形”项目，向小学生提供简单而有趣的变形花、蜘蛛、章鱼的演示，并用于帮助高中生制定课程，以促进他们对STEM相关研究的追求。通过暑期实习生和麦克奈尔学者项目，为本科生，特别是女性和低收入家庭学生提供研究经验。本课题的研究目标是以液晶弹性体为例，揭示分子相互作用、非均相材料性质和结构形状变形行为之间的复杂关系，为变形材料和结构的合理设计建立一个完整的实验和计算框架。为实现这一目标，该项目的具体任务包括：(1)建立分子相互作用（交联密度、链向和链长）与材料性能（双向形状变化时的刚度和驱动应变）之间的相关性；(2)建立综合实验和计算框架，研究分子-材料相互作用下液晶弹性体结构的形状变形；(3)研究复杂空间介观排列和刚度异质性下的形状变形和重编程。这项工作的研究成果将有助于理解和优化新型活性聚合物和变形结构的设计，这些结构具有定制的链取向、刚度非均质性和复杂负载条件和外部刺激下的形状变形特性。此外，该项目将对其他学科产生广泛的影响，包括化学、物理、材料科学和生物医学工程。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This Faculty Early Career Development (CAREER) grant will support research on fundamental studies of the mechanics of innovative active polymers and morphing structures. Soft morphing polymers that can change their shapes and therefore functionalities upon exposure to external stimuli are important for many applications, including soft robotics, artificial muscles, and tissue repair. Despite advancement in this exciting and ever-growing field, the rational design, manufacturing, and applications of innovative morphing materials and structures have been significantly limited by the lack of fundamental mechanics understanding of novel active polymers like liquid crystal elastomers. This research project will establish the missing complicated correlations across the molecular, material, and structural levels of novel active materials by using liquid crystal elastomers as a model material system. The educational objective of this work is to engage students at different levels and the general public to research frontiers in morphing materials and structures. An overarching program “Morphing Beyond Imagination” will be started, where simple and entertaining demonstrations of morphing flowers, spiders, and octopuses will be provided to elementary students and will be used to help develop curricula for high school students to promote their pursuit of STEM related studies. Research experiences to undergraduate students especially female and low-income students through a summer intern and a McNair scholar program will be provided. The research objective of this project is to uncover the complicated relationships among molecular interactions, heterogeneous material properties, and the shape morphing behavior of structures, and establish an integrated experimental and computational framework for the rational design of morphing materials and structures by using liquid crystal elastomers as an example. To achieve this objective, the specific tasks of this project include: (1) establish the correlations between molecular interactions (crosslinking density, chain alignment, and chain length) and material properties (stiffness and actuation strain in two-way shape changes), (2) build an integrated experimental and computational framework to study the shape morphing of liquid crystal elastomer structures under molecular-material interactions, and (3) investigate shape morphing and reprogramming under complicated spatial mesogen alignment and stiffness heterogeneities. The research outcomes of this work will help understand and optimize the design of novel active polymers and morphing structures with tailored chain alignment, stiffness heterogeneity, and shape morphing properties under complicated loading conditions and external stimuli. In addition, the project will generate broad impacts on a variety of other disciplines, including chemistry, physics, materials science, and biomedical engineering.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.