Synthesizing 3D Metamaterials for RF, Microwave and THz Applications

该项目的目的是设计和制造3D电磁超材料，用于从可见光到无线电频率的应用。所提出的结构将是快速高效的增材制造（AM）技术的结果，利用适当的材料，结合表面功能化方法，如电镀或溅射沉积。这项研究是较大的“SYMETA”项目的一部分，属于EPSRC“微电子设备技术”研究领域。在超材料的设计和制造过程中，一个至关重要的因素是应用所针对的工作波长。更具体地说，三维元原子的尺寸需要在工作波长的亚波长范围内。出于这个原因，对一套跨越所有感兴趣的长度尺度的制造技术有很高的需求。一般的概念是在电介质模具上建立三维超材料。在毫米-厘米的尺度上，我们可以采取很多方法，其中之一就是印刷和绘画方法。这是一个两步的过程，其中电介质形式被打印，然后填充导电涂料。在我们的案例中，ABS被用作电介质，导电涂料由铜颗粒和粘合剂组成。或者，介质和导电部件可以通过使用多材料打印机同时打印，例如体素8模型。采用聚乳酸和双亲银纳米颗粒油墨。最后，可以选择在低温烧结陶瓷中打印固体银导体。整个系统是在玻璃基板上制造的。最后一种方法仍在开发中，但有可能达到微米级的分辨率。3D打印方法很难达到这个尺度的分辨率，所以这是至关重要的，因为它将分辨率限制推向更高。3D超材料制造的最新发展已经成功地用导电材料（例如铜）覆盖超材料的表面，以增加其导电性。对超材料的研究应该解决利用不同技术制造基于超材料的设备的潜力。结论制备的三维超材料将被用作制造工作频率从MHz到THz的完全可操作的超材料器件的基石。在做任何其他事情之前，应该对现有的材料进行深思熟虑的研究，以便培养对手头问题的深刻理解。广泛使用的CST微波工作室可以提供宝贵的见解，不同的几何形状和它们之间的安排。该项目最大的挑战是在厘米到微米的尺寸范围内创建功能原型。在项目结束时，我们希望建立一个完整的制造过程，在这个过程中，基于3D超材料的设备可以在所有感兴趣的长度尺度上高效、快速地生产出来。

INTRODUCTIONThe aim of this project is to design and fabricate 3D electromagnetic metamaterials, to be used as building blocks for applications ranging from visible to radio frequencies. The proposed structures will be the result of rapid and efficient Additive Manufacturing (AM) technologies utilizing appropriate materials, combined with surface functionalization methods, such as Electroplating or Sputter Deposition. This research is part of the larger "SYMETA" project and falls within the EPSRC "Microelectronic device technology" research area.FABRICATIONA crucial factor in the design and fabrication process of metamaterials is the operating wavelength the application is aimed at. More specifically, the size of the 3D meta-atoms needs to be in the subwavelength scale of the operating wavelength. For that reason, there is a high demand for a set of fabrication techniques across all length scales of interest. The general concept is to have the 3D metamaterials built on a dielectric mold. In the mm-cm scale, one can take quite a few approaches, one of which is the print-and-paint methods. This is a two-step process, where the dielectric form is printed and then filled with conductive paint. In our case, ABS is used as dielectric and the conductive paint consists of copper particles and a binder. Alternatively, the dielectric and conductive parts can be printed simultaneously by using a multi-material printer, such as the voxel 8 model. PLA and ambiphilic silver nanoparticle inks are used. Finally, there is the option of printing solid silver conductors inside a low temperature sintering ceramic. The whole ensemble is fabricated on a glass substrate. The last method is still under development but can potentially reach a resolution in the micrometre scale. 3D printing methods are having a hard time reaching resolution in this scale, so this is crucial because it pushes the resolution limit even higher. Recent developments in 3D metamaterial manufacturing have successfully covered the surface of the metamaterial with a conductive material, e.g. Copper, in order to increase their electrical conductivity. Research on metamaterial should adress the potential of utilizing different technologies for manufacturing metamaterial-based devices. CONCLUSIONSThe fabricated 3D metamaterials will be used as building blocks for manufacturing fully operational metamaterial devices operating from MHz to THz. Before anything else, a thoughtful study of the available materials, should take place, in order to cultivate a deep understanding of the matter at hand. The widely used CST Microwave Studio can provide invaluable insight about different geometries and arrangements between them. The greatest challenge of the project is the creation of functional prototypes from a size range between cm-micrometre. By the end of the project, we hope to have established a thorough fabrication process, in which 3D metamaterial-based devices can be efficiently and rapidly produced across all length scales of interest.