Researchers in the journal Science have reported that they can now create a cloak that hides objects from static magnetic fields. There are a multitude of different applications, but some might subvert airport security.
The team was led by Alvaro Sanchez at the Autonomous University of Barcelona in Spain, working together with experimental scientists at the Slovak Academy of Sciences in Bratislava, and they’re describing a magnetic cloak that could be made inexpensively with readily available materials.
The interior of the cloak is lined with turns of tape made from a high-temperature superconductor, which can repel magnetic fields. Any magnetic fields enclosed within a superconductor would be undetectable from the outside. However, the superconductor itself can still perturb a magnetic field. To counter this, researchers coated the external side with a ferromagnet.
The two layers now cancel each other out. The antimagnet was tested by using liquid nitrogen to activate the superconductor. It was placed inside a uniform magnetic field, with a strength of 40 millitesla. A Hall probe was used to map the magnetic field and researchers discovered that the field lines did not enter the cloak itself. The exactness of this cloak which could be made perfect, using currently available materials.
This cloak is simpler than previous invisibility cloaks, since its permeability is isotropic instead of anisotropic, meaning that it has the same value in all directions. The resulting cloak is less than perfect, but it convincingly demonstrated the raw concept and that it can further be improved using existing materials.
The overall cost of this cloak was about €1,000 (US $1,000), which is a small amount when it comes to this kind of research. The technology could be used to hide metallic weapons from security portals. However, X-ray machines and sniffer dogs would probably not be defeated by this kind of cloak.