US-Ireland R&D Partnership: Mechanics of the Formation and Function of 2D Material Pleats

实现纳米材料巨大潜力的一个核心挑战是，它们很难控制、操纵和大规模生产成有用的结构和设备。这在一定程度上是因为它们的体积很小，它们容易粘在一起，而且它们对热振动很敏感。因此，重要的是要了解这些效应背后的纳米级力量，包括粘附力和摩擦力。发展这种知识的关键在于理解和利用这些力量的有益方面。一种这样的情况是自组装现象，即纳米材料将自己组织成有序结构。该奖项支持了一项研究，该研究旨在了解在这种行为的一个特别引人注目的案例中，力是如何协同作用的：原子薄的二维材料自发形成的长而折叠的褶皱，可以用简单的放大镜看到。实验和模拟将被用来理解是什么控制和驱动这个过程，由一个跨学科的合作者团队进行，他们将结合他们独特和理想的专业知识来解决这个问题。其目标是揭示支配这些褶皱形成的机械原理。这项工作具有广泛的科学和技术影响，因为它专注于这些材料的基本力学，但着眼于控制它们的组装和建造，使其成为有用的结构和装置。该奖项还将通过培训本科生、研究生和博士后研究人员来支持教育推广。这将包括在合作者的实验室之间进行有指导的国际人员交流；让K-12学生和公众参与外联活动；以及为研究人员开发关于这些材料的纳米级力学的在线短期课程。二维材料褶皱是最近发现的长而折叠的结构。它们的形成是通过用纳米压头刺穿衬底支撑的二维材料(如石墨烯)来触发的。紧随其后的是二维材料的折叠丝带的生长，最大可达10‘S微米。然而，人们对这些非凡结构的基本机制知之甚少。虽然已经发展了一个连续统水平的模型，给出了对褶皱形成的一些定性的见解，但对于支配这一现象的机制还没有原子水平的理解。该项目通过对褶皱形成机制及其形成后的机械性能进行原子级知情调查来解决这一差距。要做到这一点，需要集成材料合成、纳米机械表征以及原子化和粗粒度模拟的努力。一个由来自美国、爱尔兰共和国和北爱尔兰、英国的合作伙伴组成的跨学科团队将利用他们独特的专业组合来解决这个问题。主要目标是揭示控制褶皱成核、生长和与环境相互作用的基本力学原理。这项工作的长期、广泛的影响将是建立从广泛且不断增长的二维和薄材料阵列制造有用设备的设计原则。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A central challenge in fulfilling the tremendous potential of nanoscale materials is that they are hard to control, manipulate, and mass-produce into useful structures and devices. This is in part due to the small size, their tendency to stick to one another, and their susceptibility to thermal vibrations. Thus, it is important to understand the nanoscale forces behind these effects, including adhesion and friction. The key to developing this knowledge lies in understanding and taking advantage of the beneficial aspects of these forces. One such case is the phenomenon of self-assembly, where nanoscale materials organize themselves into ordered structures. This award supports research which aims to understand how forces conspire in a particularly striking case of such behavior: the spontaneous formation of long, folded pleats of atomically thin, two-dimensional materials that can be seen with a simple magnifying glass. Experiments and simulations will be used to understand what controls and drives this process, conducted by an interdisciplinary team of collaborators who will combine their unique and ideal expertise to tackle the problem. The goal is to uncover the mechanical principles governing the formation of these pleats. The work has broad scientific and technological impact, as it focuses on the fundamental mechanics of these materials but with a view toward controlling their assembly and construction into useful structures and devices. The award will also support educational outreach by training undergraduate, graduate, and postdoctoral researchers. This will include mentored international personnel exchanges between the collaborators’ laboratories; engaging K-12 students and the public in outreach events; and developing an online short course for researchers about the nanoscale mechanics of these materials. Two-dimensional material pleats are long, folded structures that have been recently discovered. Their formation is triggered by puncturing a substrate-supported two-dimensional materials like graphene with a nanoindenter tip. This is followed by subsequent growth of a folded ribbon of the two-dimensional material, up to 10’s of micrometers. However, little is known about the fundamental mechanics of these remarkable structures. While a continuum-level model has been developed that gives some qualitative insight into pleat formation, there is no atomistic-level understanding of the mechanisms that govern the phenomenon. This project addresses this gap by performing an atomistically-informed investigation of the mechanics of pleat formation and their mechanical properties once formed. Doing this requires an effort that integrates material synthesis, nanomechanical characterization, and atomistic and coarse-grained simulations. An interdisciplinary team of collaborators from the US, the Republic of Ireland, and Northern Ireland, UK will use their unique combination of expertise to tackle this problem. The primary goal is to uncover the fundamental mechanical principles governing pleat nucleation, growth, and interaction with the environment. A long-term, broad impact of this work will be to establish design principles for fabricating useful devices from the wide and growing array of two-dimensional and thin materials.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.