The Invisibility Cloak

A new material that is flexible and bends visible light makes such a cloak a real possibility

An invisibility cloak, a material you don to turn invisible is hard­ly unique to Harry Potter. As a device in fiction, it has a long history, but as far as scientific practicality goes it is only now that it has traversed the huge gap between the impossible and possible. Scientists in Scotland have finally been able to design a flex­ible material—Meta-flex—that can control the flow of visible light fall­ing on it.

Metamaterials that make invisibili­ty possible have a negative refraction index, meaning they can bend elec­tromagnetic waves, including light, around an object. This then tricks the eye into thinking the object is invis­ible by bending light that it would normally block, around it, allow­ing the eye to see beyond the object. Work on this field had already yield­ed two important breakthroughs. The first was materials that could di­rect light of large wavelengths, such as infrared, but not visible light with much smaller wavelengths.  The sec­ond was certain meta-materials em­bedded on hard surfaces that could act on visible light but could not be detached from their substrate.

Now, in work published in New Journal of Physics, researchers from Scotland have described how they tackled these challenges. The mate­rial is flexible and bends light that falls in the middle of the visible range. Briefing the media, Andrea Di Falco, head of the research team, said, “What I’ve done here is fabri­cate a single layer—I lift it off so that at the end I am left with a self-stand­ing membrane—and show that it has the properties required to create a 3D flexible metamaterial.”

This material has applica­tions that go beyond invisibility. “Metamaterials give us the ultimate handle on manipulating the behav­iour of light. The impact of our new material Meta-flex is ubiquitous. It could be possible to use Meta-flex for creating smart fabrics, and, in the pa­per, we show how easy it is to place Meta-flex on disposable contact lens­es, showing how flexible superlenses could be used for visual prostheses.”

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Hartosh Singh Bal