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Posted: Jan 30, 2015
Nanotechnology and nanomaterials for camouflage and stealth applications (page 5 of 5)
Futuristic Stealth Materials
Meta-materials for Invisible Cloak
Invisibility is no more a matter of science fiction. To make an object invisible, perfectly invisible device should exhibit the same scattering properties as that of vacuum. In other words, the device together with the object to be camouflaged should reflect no light and cast no shadow. Neither the illusionary see through effect in the computer mediated camouflage nor the reduced radar cross section in stealth technology can offer ultimate apparatus of invisibility.
Fig. 5: (a) Schematic representation of metamaterial showing bending of light and (b) effect of bending seen in the phenomenon of refraction of light12
Fortunately, the emerging artificially structured metamaterials have enabled exceptional flexibility in manipulating electromagnetic waves and producing new functionalities and have brought the ancient dream one step closer to reality thatis to make an object invisible11. A metamaterial is man made composite having properties that cannot be found in nature. These metamaterials have ability to bend light in deferent manner as compared with the conventional materials that enable them not to be recognized by normal eye (Fig. 5).
The following example, better known as quantum stealth, demonstrates the application of metamaterials to achieve the invisibility. The quantum stealth is achieved by using metamaterial, which renders the target completely invisible by bending light waves around the target. This metamaterial removes not only visual, infrared (night vision) and thermal signatures but also the target shadow. Hyperstealth Biotechnology in Canada has successfully demonstrated this concept13.
Further efforts are being made to develop a range of new metamaterials to extend this concept and make target invisible in other regions of electromagnetic spectrum including microwaves.
Plasmonic Nanostructures for Camouflaging in Infrared
In the past decade, many new applications have emerged for plasmonic nanostructures, which include nanoscale imaging devices, light concentrators, invisible cloak, etc14. Plasmonic nanostructures have been reported to show very interesting interaction with optical radiations, particularly in the infrared region of the electromagnetic spectrum15. Herein it has been shown that this class of materials can very effectively control the reflection/ emission of infrared radiation and present great scope for tuning the emissivity of the materials. This feature of plasmonic nanostructures has potential for their applications for infrared stealth.
1) J. V. Ramana Rao: 'Introduction to Camouflage and Deception'; Defence Research & Development Organisation, Ministry of Defence (1999), ASIN: B0006FEG5Y
6) V.K. Singh, A.K. Shukla, M.K. Patra, et al., Carbon, 50 (2012) 2202-2208
7) V. Gupta, M.K. Patra, A. Shukla, et al., J. Nanoparticle Res. , 14 (2012) 1-10
8) J.H. Shin, H.K. Jang, W.H. Choi, et al., 'Design and fabrication of RAS with graphene added Kevlar fibre reinforced composites', 18th International Conference on Composites, 21-26 Aug 2011, ICC Jeju, South Korea.
10) K.D. Cincott and T. Kracker, 'Assemblies and systems for simultaneous multispectral adaptive camouflage, concealment and deception', Patent No: US 20100288116A1, (Filed on May 6, 2009), Assignee: Military Wraps Research and Development, Inc., U.S.
11) W. Cai and V. Shalaev, 'Optical Metamaterials: Fundamental and Applications', Springer (2010), ISBN 978-1-4419-1151-3
14) G. V. Naik, J. L. Schroeder, X. Ni, et al., Optical Materials Express, 2 (2012) 478
15) F. Marquier, K. Joulain, M.P. Mulet, et al., Optics Communications, 237 (2004) 379
By S. R. Vadera and Narendra Kumar, Defence Laboratory, Jodhpur. For more information, interested readers may please contact Dr. S. R. Vadera at [email protected] and obtain a copy of the full-text article in pdf format.