Jul 27 2009
One of the first things that come to mind when thinking about Harry Potter and his cloak is ... invisibility. Researchers in Spain have developed a device that makes objects invisible under a certain kind of light. Called 'dc metamaterial', the device brings the inside of the magnetic field down to zero but does not change the exterior field. The results of the study are published in the journal Applied Physics Letters.
The researchers from the Universitat Autònoma de Barcelona (UAB) in Spain said the device, which has only been studied in theoretical works until now, acts like an invisibility cloak which makes the object undetectable thanks to the light (i.e. very low frequency electromagnetic waves).
The initial idea of Ben Wood and John Pendry, who is considered by many as being 'the father of metamaterials', was what prompted this research to get off the ground. Because of this work, devices that could make objects invisible at visible light frequencies might be just around the corner.
'A realistic dc metamaterial made of a lattice of present-technology, high-temperature, superconducting thin plates may be constructed for cloaking an object from a static magnetic field,' the authors wrote.
For his part, UAB's Professor Àlvar Sánchez who led the study, said: 'The theoretical work provides the details for constructing a real dc metamaterial and represents another step towards invisibility.'
Professor Sánchez, who is a member of the Steering Committee of the European Science Foundation's programme Arrays of Quantum Dots and Josephson Junctions (AQDJJ), added: 'Now comes a very important stage: building a prototype in the laboratory and applying this device to improving magnetic field detection technology.'
For the longest time, people have wanted to make objects invisible. From a technical standpoint, becoming invisible is as easy as covering an object with something that could make the light surround rather than absorb or reflect it. Experts have said that it would not be possible to see the object because the light would pass around it; also, if a person looked directly at the object, they would only see what is behind it. The end result is an imperceptible object.
Despite a number of misgivings on the creation of this 'invisibility cloak' - due in particular to the fact that medium electric and magnetic properties determine the trajectory of light in a specific environment, and that researchers believed the values could not be altered, thus making invisibility impossible - latest studies have shown the use of artificial materials can indeed alter the values.
These materials contain metamaterials, which have unusual physical properties. They are able to affect light, effectively making it pass around an object, which then becomes invisible. By using certain materials and arranging them in specific patterns and shapes, researchers can combine their properties. The behaviour of metamaterials depends on the properties of materials that make it up and the way the materials are put together.
According to the researchers, the metamaterial designed by the UAB team consists of an irregular network of superconductors that give materials specific magnetic properties that can generate 'invisible' areas in the magnetic field and in very low-frequency electromagnetic fields.
Ultimately, the results of this study can be applied in the medical field. The researchers said magnetoencephalographic or magnetocardiographic techniques could benefit from this discovery, since they need to have all other existing magnetic fields shielded out in order to work properly.
The research was funded under the Spanish project NANOSELECT, which seeks to generate knowledge, products and devices that enable the development of emerging technologies. These technologies would have the capacity to generate new developments and industrial products in electrical energy, electronics, and information services.
Source: Cordis