Science & Technology

Another Step for Humanity…Toward Invisibility Cloaks

Note: This article is hosted here for archival purposes only. It does not necessarily represent the values of the Iron Warrior or Waterloo Engineering Society in the present day.

There are many technologies expected to help advance society as a whole; one of these is metamaterials. These materials often contain properties that cannot be found in nature. Such properties tend to arise from the material’s unique structure that create effective macroscopic behaviour. An example of this is using nano-features on a metamaterial to cause light to bend in such a way that it appears as if the object weren’t there. In fact, different types of metamaterials, including electromagnetic, acoustic and seismic, have been created and are the focus of many research groups. By using these properties, metamaterials have promising applications in devices. Some examples include remote aerospace applications, sensor detection and more.

Though all these devices appear revolutionary, one problem with metamaterials is that it is very difficult to produce these materials on the bulk scale. These materials require features on the nanoscale which require time consuming methods such as electron beam lithography. These methods also tend to be fairly expensive meaning that if metamaterials were to be manufactured on a larger scale, it would require a great deal of time and money not ideal for standard bulk production processes.

However, a research group at the University of Illinois in Urbana-Champaign has developed a new printing method to produce metamaterials. This printing method is for one of the most interesting type of metamaterials, capable of bending near-infrared light in the ‘wrong’ direction. Such materials with a ‘negative’ index of refraction will be able to produce invisibility cloaks and sophisticated waveguides for telecommunications. The difference between this method and the standard production method is that the printing technique promises to create the materials on the bulk scale.

This stamp-based printing starts with the moulding of a hard plastic stamp covered with an elevated fishnet pattern. Using an evaporation chamber, the stamp is coated with a sacrificial layer, followed by alternating layers of materials that contribute to the metamaterial composition. These materials are often made from silver and magnesium fluoride. This layering system creates a mesh on the stamp which is then transferred onto a sheet of glass or flexible plastic by removing the sacrificial layer. Once this is performed, the metamaterial is ready.

Currently, the University of Illinois lab has been able to produce materials that are a few inches wide, but if more stamps are used this length can increase dramatically to possibly a few feet wide. Furthermore, another interesting aspect of this method is that the stamped materials appeared to show better optical properties than metamaterials created through the more expensive and lengthy methods. The only downfall to this new method is the amount of care that is required to produce the mould. However, once the mould is made, it can produce many stamps that are reusable.

This powerful printing technique has already brought a great deal of attention from experts around the world. It appears to have solved the greatest metamaterial problem: scalability. And now with that issue solved, the only thing we can hope for is the creation of a full-body invisibility cloak for us to enjoy.