Invisibility cloak might not be out of reach

Scientists in Spain have found a way to make you invisible … but only if those looking at you have unusual eyes that view the world via very low-frequency electromagnetic light waves.

Researchers from the physics department of the Universitat Autònoma de Barcelona say they can achieve this certain kind of invisibility through a device called a dc metamaterial, which makes the inside of an object’s magnetic field zero but doesn’t alter the exterior field. The device, which up to date has only been studied in theory, thus acts as an invisibility cloak, making the object completely undetectable to very low-frequency electromagnetic waves.

The Spanish discovery is based on the work of Britons  Ben Wood and John Pendry (who’s considered the father of metamaterials), and marks a step forward in the quest to create devices which could make objects invisible at visible light frequencies.

“The theoretical work provides the details for constructing a real dc metamaterial and represents another step towards invisibility,” says Àlvar Sánchez, director of the research. “Now comes a very important stage: building a prototype in the laboratory and applying this device to improving magnetic field detection technology.”

Making objects invisible has always piqued the human imagination, and the dream has inspired numerous works of literature, from H.G. Wells’ “The Invisible Man” to Harry Potter and his invisibility cloak.

In theory, any object could be made invisible if it were covered with something which could make light surround it, instead of absorbing or reflecting it. Thus, it would be impossible to see the object because the light would pass around it; if one were to look directly at the object, one would only see what is behind it. The object itself would become imperceptible.

Until recently, scientists believed this type of “invisibility cloak” would be impossible to create, given that the trajectory of light in a specific environment is determined by electric and magnetic properties, with values that scientists thought could not be modified. However, more recent scientific discoveries have revealed that these values can be modified with the help of artificial materials containing unusual physical properties … that is, metamaterials.

Such materials have unique electric and magnetic properties which, at least in theory, could affect light in such a way that they could make light pass around an object and thus make it invisible.

Invisibility in visible light, the rainbow-colour spectrum we can see with our own eyes, has not yet been achieved with experiments. Nonetheless, scientists are working with other types of light such as microwaves — with experimental results in 2006 which signalled the first step towards invisibility — low-frequency electromagnetic fields (such as radio or television waves), or even with constant magnetic fields such as magnets or the Earth’s magnetic field.

The metamaterial designed by the Spanish research group consists in an irregular network of superconductors, which give materials specific magnetic properties that can create “invisible” areas in the magnetic field and in very low-frequency electromagnetic fields.

The discovery can be applied to medical purposes, such as magnetoencephalographic or magnetocardiographic techniques (used to measure the magnetic fields created by the brain or the heart), which in order to function properly need to shield out all other existing magnetic fields. They also can be used in other areas in which magnetic field detection is important such as in sensors, or to prevent the magnetic detection of ships or submarines.