Electromagnetic Shields Based on MXene Nano-Metamaterials

所有现代电子产品都使用电磁屏蔽来减少电子干扰，因为电子干扰会完全破坏电子元件存储和传递的信息。这在军事应用、医疗电子产品和消费无线系统（包括可穿戴设备和5G手机）中尤为重要。目前的电磁屏蔽技术面临着挑战，以跟上对更轻、更小的需求。目前常用的传统金属盾牌体积庞大，缺乏机械灵活性。提出的工作重点是开发新的高效电磁屏蔽，大大减轻重量和尺寸。它们比纸张还薄，而且完全具有柔韧性。这项新技术是基于最近发现的一类名为MXenes的新材料。该提案将开发MXene电磁屏蔽，它可以覆盖在柔性电子设备上，甚至可以喷涂在上面。我们将学习如何优化这些新材料的屏蔽性能，并开发软件和模型，以帮助现代电子产品的创造者设计最有效的电磁屏蔽。虽然先前的研究表明，MXene层比典型的铜屏蔽层更薄，能够屏蔽射频和微波区域的电磁场，但对于如此出色的性能背后的原因还没有明确的解释。然而，了解这一点对于开发更薄、更轻、更灵活的屏蔽装置至关重要。初步测量表明，尽管MXene的电导率低于铜，但其有效介电常数异常高。这似乎导致材料特性阻抗足够低，足以解释MXene的良好屏蔽性能。众所周知，高介电常数可以在人工制造的导电结构中获得，称为超材料。我们推测MXene具有某些微观结构特征，尽管有些随机，但会导致类似于超材料的行为。为了更好地理解这种行为并设计更有效的屏蔽，建议的工作将分析和数值电磁建模和模拟与MXene屏蔽装置的制造及其实验测试相结合。建模和仿真工作将集中在MXenes的准周期微观结构上，以确定这些材料在何种情况下具有高有效介电常数和高有效电导率。最有可能产生最佳屏蔽的候选MXene结构将被制成片状和填充环氧基屏蔽，并使用波导和近场测量进行测试。建模和仿真结果将与实验测量结果进行比较，以验证模型。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。

All modern electronics uses electromagnetic shields to cut down on electrical interferences that can completely destroy information stored and passed by the electronic components. This is particularly important in military applications, medical electronics and consumer wireless systems including wearable devices and 5G cell phones. The present day electromagnetic shielding technology is challenged to keep up with the need for being lighter and smaller. Conventional metal shields commonly used today are bulky and lack mechanical flexibility. The proposed work focuses on developing new highly effective electromagnetic shields of dramatically reduced weight and size. They will be thinner than sheets of paper and completely flexible. This new technology is based on the recently discovered new class of materials called MXenes. The proposal will develop MXene electromagnetic shields that can be laid over flexible electronics and even spray painted over it. We will learn how to optimize shielding behavior of these novel materials and develop software and models to help creators of modern electronics to design the most effective electromagnetic shields.While previous work demonstrated that MXene layers thinner than typical copper shields are capable of shielding electromagnetic fields in the RF and microwave region just as well, there has been no clear explanation for the reasons behind such outstanding performance. Yet, understanding is critical to developing thinner, lighter and more flexible shielding devices. Preliminary measurements indicate that MXene, despite having conductivity lower than copper, has an anomalously high effective dielectric constant. This seems to result in the material characteristic impedance low enough to explain MXene’s great shielding performance. It is known that high dielectric constant can be obtained in artificially created conducting structures known as meta-materials. We conjecture that MXene has certain micro-structural features that, although somewhat random, result in meta-material-like behavior. To develop a much better understanding of this behavior and to design more effective shields, the proposed work will combine analytical and numerical electromagnetic modeling and simulations with fabrication of MXene shielding devices and their experimental testing. Modeling and simulation work will focus on quasi-periodic micro-structure of MXenes in order to determine the circumstances under which these materials would have high effective dielectric constant combined with high effective conductivity. Candidate MXene structures most likely to yield best shields will be fabricated into sheets and filler epoxy-based shields and tested using waveguides and near-field measurements. Modeling and simulation results will be compared with the experimental measurements for model validation.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.