Researchers at China’s Zhejiang University yesterday became the first to create an invisibility cloak for an object with a technique known as topological optimisation. Excitingly, this technique allows for a cloak to be built from scratch in a mere 15 minutes. Sure, Mr Potter would have been caught if had he needed to warm up his cloak for 15 minutes, but it’s a step in the right direction.
Until now, invisibility cloaks created in labs have relied on ‘metamaterials’- synthetic materials made up of a repeating structure designed to interact with light in such a way that it directs it around the object it is shielding. These metamaterials are expensive and time consuming to create, which makes them impractical for anything more than a lab bench experiment.
The method favoured by Lu Lan and his fellow researchers (available here) is not afflicted with these issues though. Their strategy utilises topological optimisation, a technique where a material – in this case Teflon – is modelled on a computer until the best shape for directing incoming light is found. This shape is then sent to an engraving machine and can be ready to use before you can say ‘expelliarmus’.
The ‘Teflon eyelid’ cloak produced offers a good but imperfect level of cloaking comparable with that of more conventional metamaterial cloaks. Lu’s demonstration model hides a disc of metal the size of a poker chip from microwaves, but there’s no reason why the same approach cannot be used to hide objects from visible light wavelengths. “Such a cloaking setup won’t be a big problem to replicate in the THz or even optical spectrum,” he says.
The whole process is cheap and easily scaled up to mass production, a big advantage over older techniques. Next up for Lu and his colleagues is further development of the cloak to enable it to work at a range of angles and frequencies. Will we have invisibility cloaks in the home soon? Watch this space- there might be something hiding it.