A group of electrical engineer working in Slovakia and Spain have prototyped a device that could become a cheap way to hide objects from magnetic fields. This is an interesting innovation because many security scanners and other devices use magnetic fields to detect hidden objects, whether a concealed weapon or a piece of metal lodged inside your body. But now, it seems that people might be able to use this device to create "cloaks" around objects they want to conceal from magnetic scanners.
A release from Science about the study explains:
Fedor Gömöry and colleagues in Slovakia and Spain have now designed and demonstrated a cloak for a direct current magnetic field. These "dc" magnetic fields are static (as opposed to oscillating ac fields) and are generated by a permanent magnet or a coil carrying a direct current. They're used in MRI imaging devices, in hospitals, and in many security systems, such as those in airports. The researchers' device consists of a cylinder with two concentric layers. The inner layer is a superconducting material that repels magnetic fields, and the outer layer is a ferromagnetic material that attracts them. When placed in a magnetic field, the device doesn't perturb the field lines, creating neither a shadow nor a reflection. An object inside the cylinder thus won't be detected. Because the device is made from commercially available materials, and because it operates under relatively strong magnetic fields and relatively warm liquid nitrogen temperatures, it could be readily be put to practical use, the authors say.
In their paper, published today in Science, the researchers write:
Invisibility to electromagnetic fields has become an exciting theoretical possibility. However, the experimental realization of electromagnetic cloaks has only been achieved starting from simplified approaches (for instance, based on ray approximation, canceling only some terms of the scattering fields, or hiding a bulge in a plane instead of an object in free space). Here, we demonstrate, directly from Maxwell equations, that a specially designed cylindrical superconductor ferromagnetic bilayer can exactly cloak uniform static magnetic fields, and we experimentally confirmed this effect in an actual setup.
While this is exciting — and scary — the researchers are still very much in the experimental stages with their work. Don't expect armed crazy people to be getting through airport security with these devices any time soon.
Read the full paper via Science