Hiding behind a life-sized negative of yourself won’t actually turn you invisible. But researchers at the University of Texas at Austin have figured out how to use that same idea to make real-world objects vanish when shot with microwave energy.
Most attempts at cloaking real-world objects have relied on metamaterials that route incoming light around the hidden object wholesale in order to make it appear invisible. The University of Texas team instead employed plasmonic materials that affected just the electric and magnetic fields the incoming light used. These materials present a “photo negative” of the hidden object that cancels the disruption the object causes to these fields.
As the image below shows, incoming microwave light gets all pinched and distorted as it refracts off the object. But, when that object is coated in a plasmonic-material “shell,” the shell and object itself cancel out each other’s disruption, effectively making the object invisible from all angles.
As Professor Andrea Alu of the UT research team explained to BBC news,
What we do is different; we realise a shell that scatters [light] by itself, but the interesting point is that if you combine the shell with the object inside, the two counter out and the object becomes completely invisible.
These plasmonic materials can be designed to affect specific electric and magnetic fields, but only in the microwave range of the energy spectrum. They likely won’t prove viable in the visible spectrum. It also has the drawback of being object-specific since the shell and object have to reflect one another. Professor Alu envisions this new technology to be incorporated into scanning microscopes to improve their resolution at short wavelengths.