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About this Article
Written by: Emily Sylvester
Written on: June 27th, 2011
Tags: electrical engineering, ergonomics, material science, physics
Thumbnail by: Oleg Alexandrov/Wikimedia Commons
About the Author
Emily Sylvester was a junior in Aerospace Engineering at the time of writing this article. She was also a member of Society of Women Engineers (SWE) and played for the USC Women’s Ultimate team. In fall 2011, she started working as a Freshman Academy Coach for students entering the Viterbi School of Engineering. As a Harry Potter fan, she was very intrigued and excited by the idea of invisibility cloaks.
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Volume XIII Issue II > The Prospects of Invisibility Cloaks: Bending the Laws of Light

Challenges

As with any breakthrough, the path to accomplishing such an engineering feat is not an easy one. Success will require the manufacturing of materials with precise structures on the scale of nanometers. The metamaterials constructed at UC Berkeley were the first that could manipulate visible light, which was more difficult than manipulating microwaves (radar waves) or radio waves that previous researchers had done since the wavelength of visible light is much smaller. An electromagnetic spectrum can be seen in Fig. 4, listing different types of light from long wavelengths (on the left) to shorter wavelengths (on the right). Although the same principles apply at all wavelengths, current metamaterials are dispersive, meaning that they bend different wavelengths differently; as a result, a cloak that refracts red light may be unable to refract green light. True invisibility will require a single device that can simultaneously bend electromagnetic waves at all the visible wavelengths.
Inductiveload/NASA
Fi​gure 4: The electromagnetic spectrum.
In order to make something invisible to the naked eye, all wavelengths of visible light must be refracted around the object simultaneously. The visible spectrum ranges from 400-790 THz [1], as can be seen again in Fig. 4. As of now, metamaterials only work for a specific wavelength of light, and designing the materials to defer the entire spectrum of frequencies will require new insights.

Future Applications

Though invisibility to the naked eye is an exciting prospect, the ability to cloak objects from other forms of electromagnetic waves, as well as sound waves, has equally important benefits. Military defense is an area in which this engineering accomplishment may prove most useful. Radar is widely used to detect ships, tanks, and other military vehicles. Thus, a clear advantage is presented to anyone able to cloak these objects from their enemies’ radars. In addition, in the case of a disaster in which people are exposed to radiation, metamaterials could act as deflectors to ensure safety.
The cloaking of sound and elastic waves could prove easier than cloaking light and have even more dramatic impacts. The seismic waves caused by earthquakes typically have wavelengths on the order of kilometers, so a cloak could be built from relatively large components and could channel the destruction around buildings, or even entire cities. Completely soundproof rooms could be possible by deflecting sound waves around the walls of the room [7].
The possibilities of this new technology continue to excite the engineering community. Until Vesalago's research, scientists had erred through their overly restricted interpretation of Snell’s Law. Vesalago’s revolutionary realization that physics does not deny the possibility of negative indices of refraction has allowed scientists to break through old boundaries and explore new perspectives. Young and enthusiastic minds at universities all over the country are finally working to make invisibility possible. So hold your breath, Potter fans, because we are slowly engineering our imagination into reality.

References

    • [1] Kyle Sherer. "Invisibility metamaterials research breakthrough." Gizmag: New and Emerging Technology News. Internet: http://www.gizmag.co​m/3d-metamaterials-i​nvisibility/9804/17,​ Aug. 2008 [27 June 2011].
    • [2] David R. Smith and John B. Pendry. "Reversing Light: Negative Refraction." Physics Today. Internet: http://esperia.iesl.​forth.gr/~ppm/DALHM/​publications/papers/​PhysicsTodayv57p37.p​df, Dec. 2003 [23 June 2011].
    • [3] "David R. Smith Group: Publications." Faculty Listing: Duke Electrical and Computer Engineering. Duke University Internet: http://www.articlesb​ase.com/networking-a​rticles/acoustic-met​amaterials-3441645.h​tml#axzz1QUw3zwwo, [27 June 2011].
    • [4] JR Minkel. "Invisibility Cloak Sees Light of Day: Scientific American." Scientific American. Nature America, Inc., Internet: http://www.scientifi​camerican.com/articl​e.cfm?id=invisibilit​y-cloak-sees-l, Oct. 19, 2006 [6 July 2011].
    • [5] Kevin Wang. "Metamaterials research." DukEngineer Magazine. Duke Pratt School of Engineering, Internet: http://www.dukengine​er.pratt.duke.edu/no​de/143, [27 June 2011].
    • [6] "3D Negative Index Metamaterials." Inano: Integrated Nanodevices and Nanosystems Research. UC Davis Department of Electrical and Computer Engineering, Internet: http://www.ece.ucdav​is.edu/inano/project​s/nim.html, 1 July 2009 [27 June 2011].
    • [7] "Acoustic Metamaterials." Free online articles directory: ArticlesBase.com. Internet: http://www.articlesb​ase.com/networking-a​rticles/acoustic-met​amaterials-3441645.h​tml#axzz1QUw3zwwo, 10 Oct. 2010 [27 June 2011].