Invisibility cloaks are not just the stuff of Harry Potter anymore. Researchers at Hong Kong University are not so far from making one. For this purpose, they will be using meta-flex.
Meta-flex is an independent, flexible stack of meta-atoms from a meta-material. Meta materials are the materials which gain their properties from structure rather than composition. We know that materials are composed of atoms and molecules and when light wave enters a material, the electric and magnetic waves cause electrons to move around. Exchange of energy with the atoms and molecules of the materials is mean by which materials control and manipulate light waves.
Usually, the spacing of atoms in naturally occurring materials is of the order of angstroms whereas visible light has a range of wavelength in hundreds of nanometers. Thus, when light strikes a material it reflects back making that material visible for us. If we adjust the composition of a material such that size and spacing of atoms are much smaller than the wavelength of light, light can no more resolve its structure and it becomes a meta-material. Such material then becomes a cloak which refracts the light that strikes it so that the light moves around, past the cloak reflecting nothing and leaving the cloak and its contents invisible.
Such an invisibility cloak has been made in 2D for micro-range. This was done by carefully designed split-ring resonators with a structure size much smaller than the wavelength. Only ten stacked layers were enough for making a 2D invisibility cloak. But for 3D, challenges are great. The first step would be to make meta-atoms small enough to interact with light and the second step would be to detach fabrication of meta-materials from a hard surface making a meta-flex.
Both groups of researchers have published their findings in their papers listed under 'Further Reading' below.
Andrea Di Falco, Martin Ploschner and Thomas F Krauss, 'Flexible metamaterials at visible wavelengths', New J. Phys. 12 (2010)
Yun Lai, Huanyang Chen, Zhao-Qing Zhang, and C. T. Chan, “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell.” Physical Review Letters (2009)