Chinese physicists have come up with a complete new way to produce invisibility cloaks. Produce what? Yes, produce invisibility cloaks. The scientists use an approach that is entirely different to the theoretical light-bending mathematics physicists have used until now.
The team of Chinese scientists from the Zhejiang University in Hangzhou wondered if they could make an invisibility cloak from other materials that the metamaterials which are created by assembling a repeating pattern of structures that interact with the light they are designed to cloak. This ‘metamaerials’ approach works by steering electromagnetic fields around an object in a way that hides it. The necessary material must be able to repeat this kind of light distortion in real life. The downside of this approach is that making metamaterials is an expensive and time-consuming process.
So therefore the Chinese physicists designed a new approach wherein they use a computer model of the cloak in the form of a conventional material with fixed light bending properties. This model simulates how this conventional material distorts light as it passes by. The computer then changes the shape and topology of the material to reduce this distortion. By repeating this process many times, it is possible to find a topology that minimises the distortion of light so that it remains more or less unchanged as it passes by. The result is an invisibility cloak; not a perfect one but one that can hold its own against many of those made of metamaterials.
Using this ‘topology optimisation’ method the Chinese scientists managed to create such an invisibility cloak. They carved it out of Teflon and it took them only 15 minutes using a computer-controlled engraving machine. As a result the fabrication process of a sample is substantially simplified, bringing invisibility suddenly into the realms of mass production.