ERI: Increasing the Fundamental Understanding of the Auxetic Behavior of Graphene Oxide Membranes

当材料在一个方向上拉伸时，在其他方向上的尺寸往往会减小。然而，一些高级材料，被称为塑性材料，表现出垂直于拉伸过程中施加的力的横截面膨胀。增塑剂材料目前用于防弹衣、包装材料、护膝和护肘以及海绵拖把等应用。氧化石墨烯膜具有生成性，这使其在生物医学、汽车、国防工业和清洁能源中具有广泛的分离和过滤应用前景。然而，对它们的潜在机制的理解仍然有限。在这个工程研究启动（ERI）项目中，将进行一系列实验，以更深入地了解氧化石墨烯膜的结构，从而导致其缺氧行为。该项目将为联合学院的本科生提供研究经验，特别是那些来自传统上代表性不足的背景的学生。这些研究经验将为学生的科学和技术事业，和/或纳米技术为基础的行业的研究生学习做好准备。此外，该研究将整合到联合大学的机械工程课程中，以改善工程教育。该项目的目标有两个方面：1)通过基于两种假设（“皱纹”和/或“auxetic框架”是导致这种行为的原因）的实验，对氧化石墨烯膜的auxetic行为有一个基本的了解；2)研究负泊松比定制如何影响膜的机械性能、稳定性、渗透性和潜在应用。具体而言，本实验研究将根据“皱纹”假说，探讨负泊松比与皱纹的大小、方向和变形之间的关系。本文还将研究负泊松比与氧/碳原子比之间的相关性。通过结合实验研究和动态分析，该项目不仅旨在确定氧化石墨烯膜的减氧行为的结构基础，而且还旨在设计定制这种行为的技术，以解决一系列工程挑战。该研究项目也有望为PI未来的短期和长期研究工作奠定基础。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。

When materials are stretched in one direction, it is typical that the dimensions in the other directions tend to decrease. However, some advanced materials, known as auxetic materials, exhibit a cross-sectional expansion that is perpendicular to the force applied during stretching. Auxetic materials are currently used in applications such as body armor, packing materials, knee and elbow pads, and sponge mops. Graphene oxide membranes are identified with auxetic behavior, which make them excellent candidate for a wide range of promising separation and filtration applications in the biomedical, automobile, and defense industries, and for clean energy. However, there is still a limited understanding of the underlying mechanism in their auxetic behavior. In this Engineering Research Initiation (ERI) project, a series of experiments will be carried out to gain a deeper understanding of the structure of graphene oxide membranes that causes its auxetic behavior. This project will provide research experiences for undergraduate students at Union College, especially those from traditionally underrepresented backgrounds. These research experiences will prepare students for scientific and technical careers, and/or graduate studies in nanotechnology-based industries. In addition, the research will be integrated into Union’s mechanical engineering curriculum to improve engineering education. The objectives of this project are two-fold: 1) to achieve a fundamental understanding of the auxetic behavior of graphene oxide membranes by conducting experiments based on two hypotheses - the “wrinkle” and/or the “auxetic framework” are responsible for the behavior, and 2) to investigate how negative Poisson ratio customization affects the mechanical properties, stability, permeability, and potential applications of the membranes. Specifically, this experimental research will explore the relationship between the negative Poisson ratio and the size, orientation, and deformation of wrinkles, as per the "wrinkle" hypothesis. It will also investigate the correlation between the negative Poisson ratio and the oxygen/carbon atomic ratio of the "auxetic framework" hypothesis. By combining experimental studies and dynamic analyses, this project aims to not only identify the structural basis of graphene oxide membrane's auxetic behavior but also devise techniques for customizing this behavior to address a range of engineering challenges. This research project is also expected to lay the groundwork for the PI’s future research endeavors in the short and long term.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.