In 2006, researchers in the ECE department at Pratt School of Engineering, in collaboration with Imperial College of London, created a brilliant 'cloak' that deflects passing microwaves and behaves as if it were invisible. This was achieved using metamaterials, which in simple terms, can bend light the unexpected way. They can be modified to produce a negative refractive index. The metamaterials were specifically designed and arranged in circles to interact with electromagnetic waves in a way that natural elements cannot. This is the first breakthrough that highlights the uses of metamaterial technology over electromagnetic properties to create the effect of invisibility.
The following is a video of the working model of the first ever invisibility cloak at Duke, which hides a spherical metal cylinder from microwaves:
Even after this achievement, the researchers were not convinced. There were theories which said that the same theory of invisibility would work for 2-D acoustic cloaks, but not for 3-D, as electromagnetic and sound waves fail to be equivalent in 3 dimensions.
As Steven Cummer, Jeffrey N. Vinik Associate Professor of Electrical and Computer Engineering at Duke's Pratt School of Engineering, said 2 years later , "It was hard for me to imagine that something you could do with electromagnetic waves would be completely undoable for sound waves". So, in 2008, the same team devised a mechanism for another invisibility cloak, this time a 3 D acoustic cloak. Working on the same mathematical model they used 2 years earlier, the team proved that an object can be prevented from reflecting sound waves too.Building upon all this work, scientists at University of California - Berkeley have conducted studies on metamaterials that can bend light the wrong way in 3 dimensions.
Even though we are far from a War of the Worlds or a Time Machine, in the case of an Invisible Man, there is not much longer we need to wait.