Reasearchers at Berkeley have created an ultrathin microscopic invisibility cloak that can "conform to the shape of an object and conceal it from detection with visible light" according to a release from the university. The cloak improves on bulky prior incarnations, bringing a science fiction staple into the realm of the possible.
The research, conducted by scientists at the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley, was published in the 18 September issue of Science in the article "An ultrathin invisibility skin cloak for visible light" by Xingjie Ni et al.
Our eyes detect objects as a result of the way in which light interacts with matter and is reflected. Light hitting an object wrapped with the gold nanoantenna skin cloak is reflected in the same way as that reflected off a flat mirror: the cloak essentially guides light around the object and renders it invisible. This is because the cloak is made from flexible, highly reflective, two-dimensional metamaterial – an artificial nanostructure made of thousands of nanoparticles and engineered with electromagnetic properties. The material reroutes reflected light waves when activated, rendering a 3D object (such as clump of cells) invisible to optical detection.
Researcher Zi Jing Wong explained that “a phase shift provided by each individual nanoantenna fully restores both the wavefront and the phase of the scattered light so that the object remains perfectly hidden”. “This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” noted Director of Berkeley Lab’s Materials Sciences Division Xiang Zhang.
In addition to a myriad of potential applications in areas such as stealth technology, optical computing, and encryption, Zhang thinks that one application of the cloak would be in cosmetics – to manipulate texture, colour and volume. There is also potential for use of the second skin in packaging. And although the cloak is just 80 nanometres thick, the principles underlying the technology mean that it has the potential to be scaled up to conceal macroscopic items.
Zhang said to Cosmetics Business that large scale manufacturing technology already exists; the technology just needs to be adapted to the cloak making. The large-scale cloak can be a fabric, or a spray (such as in sun block), and is already under development in Zhang's lab.
A more serious limitation is that the cloak currently works only when objects are static and light reflection remains the same. However, Zhang noted, "cosmetic use may always be 'static' - that is to say, if used to cover part of your face, and your face is moving, it would still be static use, because the cloak would move together with the skin." In other words, relative motion is what remains to be addressed.
