METAFLEX - Metamaterials on Flexible optically transparent substrate

超材料（mm）是一种人造材料，具有不寻常的电磁特性，通常在自然界中找不到。它们是实现隐形斗篷和完美镜片等非凡特性的关键。目前，它们体积庞大，只能在实验室使用。如果它们是灵活的，它们可以变得更加通用和实用。在这里，我提出了一个柔性mm的新概念，它将把当前的隐形设备从盔甲变成真正的斗篷。折射率的概念是mm物理的基础，可以用一个例子来说明。光穿过两种介质之间的界面时所采取的方向取决于它相对于表面的初始方向和介质的折射率。这就是为什么铅笔浸入水中会出现扭结的原因。在自然界中，所有透明材料都像水一样具有正折射率。因此，铅笔的图像总是向同一个方向弯曲。相反地，MM是用负折射率制造的，因此在MM中铅笔的扭结将出现在相反的方向。这种看似纯粹出于好奇的效应，驱使着mm们的非凡行为。目前制造的光学mm的技术要求强加了一个平面刚性几何。例如，这阻碍了由柔软织物制成的光学斗篷的现实实现。我的目标是克服这些限制。这个项目的目的是制造柔性的mm，极薄的膜（METAFLEX）。Metaflex将在更灵活的框架中保留mm典型材料设计的所有功能及其控制光线的能力。我已经完成了这个项目的第一个里程碑，在厚度只有几纳米的聚合物柔性膜上打印mm。Metaflex的物理学是一个丰富而未开发的研究领域。这个雄心勃勃的项目是围绕他们最引人注目的属性构建的：-Metaflex可以包裹在物体周围并堆叠，这是现实隐形应用程序的重要一步。-Metaflex堆叠可以很容易地微调后制造，例如通过变形，因此光可以控制额外的自由度。Metaflex的灵活性允许设计和制造伪装系统，因为材料响应可以感知和适应周围环境。这为智能织物和智能纺织品提供了一个显著的例子，目前这是学术界和工业界一个蓬勃发展的研究领域。-Metaflex提供了一个新的框架来研究光和机械力之间的相互作用，如光捕获或光力学的新领域。潜在的应用包括非常小的光学麦克风。-Metaflex很轻。它们可以利用光束引发的吸引力和排斥力，使其像纳米飞毯一样悬浮起来。这将是生物医学纳米应用领域的一个突破，比如药物传递和单分子操作。我对Metaflex的兴趣源于光子结构和纳米制造方面的各种理论和实验项目，以及在这些项目中获得的知识，包括mm的物理和应用。这个项目包含了许多令人兴奋的科学挑战，它提供了在日常生活中开发mm的非凡特性的可能性，这在几年前是不可想象的。

Metamaterials (MMs) are man made materials with unusual electromagnetic properties that are not typically found in Nature. They are the key to achieving such extraordinary properties as invisibility cloaks and perfect lenses. At present, they are bulky and confined to laboratories. If they were flexible, they could become much more versatile and practical. Here, I propose a novel concept for flexible MMs that will turn current cloaking devices from suits of armour into true cloaks.The concept of index of refraction underpins the physics of MMs, which can be illustrated with an example. The direction that light takes when it crosses the interface between two media depends on its initial direction with respect to the surface and on the refractive indices of the media. This is the reason why a pencil appears to kink when immersed in water. In nature, all transparent materials have a positive refractive index, like water. As a result, the image of the pencil always kinks in the same direction. Conversely, MM are manufactured with a negative refractive index, thus in a MM the kink of the pencil would appear in the opposite direction. This effect, which may seem to be a mere curiosity, drives the extraordinary behavior of MMs.The technological requirements of currently fabricated optical MMs impose a flat rigid geometry. This impedes the realistic implementations of an optical cloak made of soft fabric, for example. I aim to overcome such limits.The aim of this project is to fabricate MMs in flexible, extremely thin membranes (METAFLEX).Metaflex will retain all the power of material design typical of MMs and their ability to control light, in a more flexible framework. I have already achieved the first milestone of the project and printed MMs on polymer flexible membranes with thickness down to few nanometers.The physics of Metaflex is a rich and unexplored field of research. This ambitious project is structured around their most striking properties:-Metaflex can be wrapped around objects and stacked, a vital step to realistic cloaking applications.-Metaflex stacks can be easily fine tuned after fabrication, e.g. via deformation, hence light can be controlled with additional degrees of freedom. The flexibility of Metaflex permits the design and fabrication of a camouflaging system, as the material response can sense and adapt to the surrounding environment. This offers a remarkable example of smart fabrics and intelligent textiles, currently a thriving area of research in academia and industry.-Metaflex provide a new framework to study the interaction between optical and mechanical forces, as in Optical Trapping or the new field of Optomechanics. Potential applications include very small optical microphones.-Metaflex are very light. They could take advantage of the attractive and repulsive forces triggered by optical beams in order to levitate and behave as nano-flying carpets. This would be a breakthrough in biomedical nano-applications such as drug-delivery and single molecules manipulation.My interest in Metaflex arises from diverse theoretical and experimental projects in photonic structures and nanofabrication and from the knowledge gained throughout these projects, including the physics and applications of MMs. This project contains many exciting scientific challenges, which offer the possibility of developing the extraordinary properties of MMs for every-day life applications that were unimaginable only a few years ago.