Uploaded byCharu Lakshmi
Metamaterials
This document provides an overview of metamaterials. It begins by defining metamaterials as materials engineered to have properties that do not occur naturally, such as a negative index of refraction. The document then discusses the history of metamaterials, including early theoretical work in the 1960s and recent developments in fabrication. Examples of potential applications mentioned include invisibility cloaking, subwavelength imaging, and smaller antennas. The document also provides brief descriptions of common metamaterial structures and fabrication techniques using nanostructures like split-ring resonators.
Metamaterials
- 1. BY CHARU LAKSHMI TR ROLL NO. : 4 SEM 1 M.Sc MATERIALS science date :04/09/2013 METAMATERIALS
- 2. OUTLINE INTRODUCTION : Thoughts oninvisibility METAMATERIALS : At a glance HISTORY HOW IT IS MADE ? CURRENT STATUS : Benefits REFERENCES
- 3. METAMATERIALS Originates from aGreek word META means “beyond ” . Metamaterials are woven out of materials smaller than the wavelengths of that of light. If you think of a Metamaterial as a piece of cloth, the "threads" that make it up are somewhere between 400 to 700 nanometers in size.
- 4. BE IT … JERRYOR HARRY SAME EXPRESSION !!
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- 6. VISIBI LITY OFAN OBJECT
- 7. WHAT HAPPENS IFTHIS IS THE CASE ?? IT’S INVISIBILITY Cloaking technique
- 8. hypothetical invisibility !! Conceptualapproach to change the way light travels !! Its not practical as light can be bent by only those objects which have large mass or high energy. Only those objects can wrap light. This is according to Einstein and his general relativity
- 9. How to bendlight like that !!! Refraction at surface obeys Snell’s law : n =sinθ1 / sinθ2 where ‘n’ is the refractive index of the material. In a Mirage , a refractive index varies continuously on the road surface. This is what happens in cloaking technique !!!
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- 11. NEGATIVE INDEX OFREFRACTION - negative refraction can be achieved when both µr and εr are negative. - negative µr and εr occur in nature, but not simultaneously. -silver, gold, and aluminum display negative εr at shorter rrn 1))(())(( 2/2/2/1 jjjjj rr eeeee
- 12. Negative refractive indexwill lead to negative refraction , negative Doppler effect, planar focusing etc . Snell’s law is still satisfied when one of the materials has a negative refractive index, but the direction of the light ray is ‘mirror-imaged’ about the normal to the surface.
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- 15. Metamaterials : ata glance Metamaterials are built of artificial or ‘meta’ atoms, which are resonant structures such as split-ring resonators, paired metal nanorods or nanostrips. The ‘meta’ atoms can be engineered and arranged such that their permittivity, permeability and refractive index are positive , negative or even zero for a selected frequency. These are artificially designed subwavelength Composites possessing extraordinary optical properties that do not exist in nature. They can alter the propogation of electromagnetic waves resulting in negative refraction, subwavelength imaging and cloaking
- 16. The size ofthese features has to be much smaller than the wavelength of light Model Image of a nano- fabricated material
- 17. They can bedesigned to have a refractive index that varies throughout, even taking on a negative value in some cases. By carefully selecting and arranging the components, a metamaterial antenna could be made much smaller than a conventional antenna — but offer similar performance. Other exciting applications of metamaterials include making of super lens and nanocircuits. They also find application in stimulating the cosmological theories such as the “Big Bang Theory”
- 18. history The possibilityof negative refractive index was first raised by the Russian physicist, Victor Veselago, in the 1960s . He realised that if two quantities, the electric permittivity and the magnetic permeability, of the material, were both negative, Maxwell's equations of electromagnetism would give a negative refractive index.
- 19. Sir John Pendryshowed practical method of making Metamaterials in 1999 . The recent boom in negative index materials was inspired by him. He made critical contributions to the field , including prediction of NIM-based superlens with resolution beyond the
- 20. This is anew tool devised by Sir John Pendry in 2006 It is called Transformation Optics It tells us how we must shape the refractive index , so light goes the way we want it to go in cloaking technique. It makes uses of coordinate transforms and
- 21. METHODS USED TOMAKE METAMATERIALS The scientists of California university laid down copper resonators with negative permeability, and copper wire strips with negative permittivity, on opposite sides of the same piece of printed circuit board. The result had negative refractive index. In 2006,a metamaterial made at Durham, North Carolina and Imperial College made an object invisible to microwave radiation Fiberglass rings patterned with copper elements 1 mm
- 22. METASCREEN is constructivestrips of copper tape 66 µm thick (thickness of human hair) attached to 100 µm thick polycarbonate film (a material commonly used in DVD's and CD’s) in a fishnet design . In the test case the cylinder was 18cm long . it only works best in the microwave regime , so the size of the object to be cloaked has to be in “microns” . March 2013
- 23. BENEFITS : RADARPROOF STEALTH EQUIPMENTS A team of scientists in the USA from Purdue University, Indiana and Norfolk State University, Virginia have invented a new Metamaterial which makes objects invisible to radar. This material is composed of an array of extremely thin silver wires (35nm in diameter) embedded in 0.4 inch squares of aluminium oxide.
- 24. references EXOTIC METAMATERIALS :A REVIEW -BY MADHURYA P. TENDULKAR . NANO VISION ,VOL.1 ISSUE 3, OCT 2011 NANOTECH INSIGHTS VOLUME 1, ISSUE 3, OCT 2012 PHYSICS FOR ENTERTAINMENT BOOK 2 -BY YA.PERELMAN MIR PUBLISHERS , MOSCOW MATERIALS TODAY -MARCH 2009 ,VOL 12, ISSUE 3 YOUTUBE VIDEO LECTURES OF J.B.PENDRY
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