创新背景

折射是材料中的常见特性，例如，一杯水中的吸管似乎总是向侧面移动，或者眼镜中的镜片聚焦光线的方式。

但是负折射不仅仅涉及将光向一侧移动几度。相反，光以与进入材料的角度完全相反的角度发送。这在自然界中没有被观察到，但从20世纪60年代开始，理论上发生在所谓的人工周期性材料中——即构建具有特定结构图案的材料。直到现在，制造工艺才赶上理论，使负折射成为现实。

创新过程

新创建的纳米结构材料表现出以前理论上可行的特性：它可以向后折射光线，而不管光线照射到材料的角度如何。

这种性质被称为负折射，这意味着折射率（光可以通过给定材料传播的速度）在所有角度的电磁波谱的一部分上都是负的。负折射对纳米光子学的未来至关重要，纳米光子学试图理解和操纵光在尽可能小的尺度上与材料或固体结构相互作用时的行为。
这种新材料通过在纳米和微尺度上的组织组合以及通过时间和劳动密集型过程添加薄金属锗膜涂层来实现其不寻常的特性。

Greer是创造这种纳米结构材料的先驱，这些材料的结构是以纳米级规模设计和组织的，因此表现出不寻常的，通常令人惊讶的特性例如，非常轻巧的陶瓷在压缩后会像海绵一样弹回原来的形状。

在电子显微镜下，新材料的结构类似于空心立方体的晶格。每个立方体都非常小，以至于构成立方体结构的横梁的宽度比人类头发的宽度小100倍。晶格是使用聚合物材料构建的，这种材料在3D打印中相对容易使用，然后涂有金属锗。

结构和涂层的结合赋予了晶格这种不寻常的特性。研究小组通过艰苦的计算机建模过程（以及天竺葵是一种高折射率材料的知识）将立方体晶格结构和材料进行正确的组合。

为了用金属均匀地涂覆聚合物，研究小组需要开发一种全新的方法。最后，研究人员使用了一种溅射技术，其中锗盘被高能离子轰击，这些离子将锗原子从圆盘中射出并喷到聚合物晶格的表面上。

创新关键点

这种新材料通过在纳米和微尺度上的组织组合以及通过时间和劳动密集型过程添加薄金属锗膜涂层来实现其不寻常的特性。

创新价值

该技术在电信、医学成像、雷达伪装和计算方面具有潜在的应用。

该项研究朝着演示实现3D光子电路所需的光学特性迈出了重要一步。由于光的移动速度比电子快得多，因此从理论上讲，3D光子电路将比传统电路快得多。

New nanostructured materials can negatively refract light

The newly created nanostructured material exhibits a property that was previously theoretically possible: it refracts light backwards, regardless of the Angle at which it hits the material.

This property is known as negative refraction, which means that the index of refraction (the speed at which light can travel through a given material) is negative for a portion of the electromagnetic spectrum at all angles.

Negative refraction is crucial to the future of nanophotonics, which seeks to understand and manipulate how light behaves when interacting with materials or solid structures at the smallest possible scale.

This new material achieves its unusual properties through a combination of tissues at the nanoand microscales and by adding a thin metallic germanium film coating through a time and labor intensive process. Greer is a pioneer in creating such nanostructured materials, whose structures are designed and organized at the nanoscale and thus exhibit unusual and often surprising properties, such as very lightweight ceramics that spring back to their original shape like a sponge upon compression.

Under the electron microscope, the structure of the new material resembles a lattice of hollow cubes. Each cube is so small that the width of the beam that makes up the cube structure is 100 times smaller than the width of a human hair. The lattice was constructed using a polymer material, which is relatively easy to use in 3D printing, and then coated with the metal germanium.

The combination of structure and coating gives the lattice this unusual property The team used a painstaking computer modeling process (and the knowledge that geranium is a high-index material) to get the cube lattice structure and material right.

To coat the polymer uniformly with metal, the team needed to develop an entirely new method. Finally, the researchers used a sputtering technique in which the germanium disk was bombarded with high-energy ions that ejected the germanium atoms from the disk and sprayed them onto the surface of the polymer lattice.