The science of invisibility is rapidly moving from a focus on research to a focus on development. In other words, this discipline is changing from one of science to one of engineering
So we’re beginning to glimpse how engineers are turning the few hugely complex and expensive cloaks made so far into much simpler and cheaper devices.
Today, Oliver Paul at the University of Kaiserslautern in Germany and a few friends reveal an eminently practical way of making invisibility cloaks of any size and shape.
Their idea is simple. Creating a cloak that exactly follows the shape of the object it is intended to hide is hard because curve cloaks are hard to make.
Instead, Paul and co approximate the shape using flat facets. These ‘invisibility tiles’ fit together in the same way as the triangular facets in a computer animation. And since each flat tile is relatively simple and easy to make, it becomes much cheaper and easier to build complex cloaks.
So far this is just an idea. Their paper outlines the approach and simulates how well a dodecahedral cloak can hide a sphere. The faceted cloak isn’t as good as a smooth one but it’s not bad either.
One interesting question is how big the tiles should be. Obviously, smaller tiles can more accurately model a given shape, which should improve the performance of a cloak.
Balanced against this is the properties of the joins between the tiles, which are unlikely to be as invisible as the tiles. And since smaller tiles mean more joins, an important question is how this changes the invisibility.
Another interesting question is whether the joins can be made flexible. It’s not hard to see how, with the help of flexible links, the tiles could be placed on a material that bends and flexes and so can be thrown over objects of almost any shape. A true invisibility cloak.
Of course, this is just a first step in the engineering of these kinds of devices. But cloaks based on tiles should be much easier to make than existing designs.
One of the authors of this work is David Smith at Duke University, the man who built he first invisibility cloak almost ten years ago. An interesting feature of his work is that his theoretical announcements have often been rapidly followed by experimental confirmations.
So if the past is anything to go by, Smith and his team will already be making invisibility facets and tiling them into all kinds of shapes. Which means we’ll see practical invisibility tiles sooner rather than later
Ref: arxiv.org/abs/1110.5604: Flat-Face Approximations Of Invisibility Cloaks With Planar Metamaterial Layers