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Nano-magnets in metamaterials pave the way to invisibility cloaks


January 6, 2010

A Dutch team of scientists has made a huge step toward manufacturing a Harry Potter-style invisibility cloak.

A Dutch team of scientists has made a huge step toward manufacturing a Harry Potter-style invisibility cloak.

A Harry Potter-style invisibility cloak is one more step closer to reality thanks to the work of a research team at the FOM Institute for Atomic and Molecular Physics (AMOLF) in the Netherlands, which has successfully harnessed the magnetic field of light to develop meta-materials that can deflect light in every possible direction.

Metamaterials are a broad class of materials which have been specifically engineered to exhibit peculiar properties, particularly with regard to how light behaves when traveling in them: metamaterials with negative refractive indexes could even reflect light so to make entire objects invisible, and scientists have been making progress towards an invisibility cloak that, a few years back, belonged more to the pages of a fantasy novel than to those of a scientific paper. There's certainly still a long road ahead, but continous advancements have consistently made this dream less and less laughable in the recent past.

As with all electromagnetic waves, light has two oscillating components, an electrical and a magnetic one, meaning that — theoretically — both electricity and magnetism can be used to control how it propagates within an object. However, atoms in standard materials interact only weakly with magnetic fields oscillating over 500THz. Because visible light ranges approximately from 400THz to 800THz, this means we simply can't hope to exploit magnetism here to help us in our quest for invisibility.

But, the AMOLF team found out, the picture changes dramatically when metamaterials are involved. Set to find out more about the behavior of magnetic fields at this threshold frequencies, they engineered very small U-shaped metamaterials called "nano-rings" and studied how they interacted with light.

The electromagnetic field of light, they found, drives electrical charges back and forth the nano-rings, generating an alternating current that transforms each of them into a small electromagnet whose polarity alternates 500 billion times every second. Unlike classical materials, metamaterials show a strong interaction with the magnetic component of light as well as the electrical one.

This particular piece of research is notable not only because it shows that metamaterials look once more like the right way to go, but also because it provides scientists with a mechanism — the nano-rings — to actually manipulate light in them. It also appears that the nano-magnets can influence and can transfer power to each other, which is sure to be a handy variable in follow-up research.

Now, in fact, the team will need to figure out how to perfect this technique to direct light appropriately around an object containing these nano-rings. If this is achieved, the world could soon see — or, rather, not see — its first invisibility cloak.

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion. All articles by Dario Borghino

Weird that the 1st thing they consider with this is a stealth suit... surely being able to generate an alternating current purley from light has application in solar energy generation?


They must then also be looking at the development of glasses or binoculars or screens that wil see/decloak/display cloaked items... I hope... What if aliens have that technology perfected already and are hanging around everywhere but we just can\'t see them? Maybe they do but once so often they fly through an unusually strong magnetic field and become declaoked and hence we get UFO sightings... This certainly loosens up the mind to conspiracy theories and stories... :)

Theo Viljoen
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