Transcript METAMATERIALS

ECIV 303
11/30/2010
METAMATERIALS
Caleb Hughes
Hassan Ismail
Brett McCutchan
Scope
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What are Metamaterials
How They Work
Types
Applications
Recent Advances
What are Metamaterials?
Engineered (at the atomic level) materials that
have unique properties not found in nature due
to the arrangement and design of their
constituents
NOTE: THE PROPERTIES ARE THAT
OF THE ENTIRE ARRANGEMENT AND
NOT THE CONSTITUENTS
THEMSELVES
“Meta” = above, superior,
beyond
Some History
• Theoretical design by Victor Veselago in 1968
– Predicted metamaterials act in exact opposite manner
than natural materials (like negative refractive index)
• Dr. John Pendry showed practical method of making
metamaterials in 1999
Sir John
Pendry
V. G. Veselago
http://cobweb.ecn.purdue.edu/~ece695s/Lectures/Lecture_15.pdf
How Does it Work?
Normally, waves propagate and
interact with different media
according to Snell’s Law
Metamaterials “Grab” waves
and smoothly redirects them
due to negative index of
refraction
Material units must be small
relative to the wavelength
being manipulated
http://www.newscientist.com/blog/technology/labels/physics.html
Types of Metamaterials
• Electromagnetic
– Transverse waves
• Acoustic
– Longitudinal waves
• Seismic
– Transverse and Longitudinal waves
Electromagnetic Metamaterials
Negative Refractive Index
http://www.imagico.de/pov/metamaterials.html
Refractive
index
Electric
permittivity
Magnetic
permeability
Electromagnetic Metamaterials
• Antennas
– Negative index of refraction means more wave bending
which means smaller antenna (few mm)
―Can double
frequency
range
―Increase
radiated power
http://www.metacloak.net/FractalMetamaterialMonopoleAntennaWhatWeDid.pdf
Electromagnetic Metamaterials
• Invisibility
– Visible light waves must be
manipulated
Cloak OFF
http://cobweb.ecn.purdue.edu/~ece695s/Lectures/Lecture_16.pdf
Cloak ON
Acoustic Metamaterials
• Acoustic waves are different than
electromagnetic waves
– Longitudinal waves rather than
Transverse waves
• Common physical concepts of waves
– Wave vector
– Wave impedence
– Power flow
• Negative Refractive index
– Negative Mass Density
– Negative Bulk Modulus
Mass Density
Bulk Modulus
Refractive index
Acoustic Metamaterials
• Soundproof Room
• Invisible Submarines (Sonar Blocking)
• Seismic Metamaterials
- Negate the destructive effect of seismic waves on
surface structures
- Requires the decoupling of longitudinal pressure
waves and transverse shear waves, redirecting
them around a cylindrical metamaterial cloak
Creation of Metamaterials
• Contact Photolithography used for larger
nanomaterials
• Electron Beam Lithography used for smaller,
more detailed structures
http://www.memsnet.org/mems/processes/lithography.html
http://en.wikipedia.org/wiki/File:Left-handed_metamaterial_array_configuration.jpg
Limitations
• Small wavelengths
require very small units
• Must be able to handle
range of wavelengths
for some applications
– Frequency Selective Surfaces
(FSS aka Tunable)
http://www.joeruff.com/ar
truff/physics/Light/emspec
.gif
Further Reading
Purdue university—Nanophotonics &
Metamaterials ECE 695s
http://cobweb.enc.purdue.edu/~ece695s
D.R. Smith at Duke University—
http://people.ee.duke.edu/~drsmi
th/pubs_smith.htm
Questions?