META MATERIALS

What is a meta material?

A periodic material that derives its properties from its structure rather than its components

PROPERTIES OF META MATERIALS:

They are assemblies of multiple individual elements fashioned from conventional microscopic materials such as metals or plastics, but the materials are usually arranged in periodic patterns.

Their precise shape, geometry, size, orientation and arrangement can affect the waves of light or sound in an unconventional manner, creating material properties which are unachievable with conventional materials.

The primary research in meta materials investigates materials with negative refractive index.

The research in meta materials is interdisciplinary and involves such fields as electrical engineering, electromagnetics, solid state physics, microwave and antennae engineering, optoelectronics, classic optics, material sciences, semiconductor engineering, Nano science and others

HISTORY OF META MATERIALS

Winston E. Kock developed materials that had similar characteristics to metamaterials in the late 1940s.

Materials, which exhibited reversed physical characteristics were first described theoretically by Victor Veselago in 1967.

A little over 30 years later, in the year 2000, Smith et al. reported the experimental demonstration of functioning electromagnetic metamaterials by horizontally stacking, periodically, split-ring resonators and thin wire structures.

Later, a method was provided in 2002 to realize negative index metamaterials using artificial lumped-element loaded transmission lines in micro strip technology.

At microwave frequencies, the first real invisibility cloak was realized in 2006. However, only a very small object was imperfectly hidden.

In 2007, one researcher stated that for metamaterial applications to be realized, several goals must be achieved.

• Negative refractive index is an important characteristic in metamaterial design and fabrication. As reverse-refraction media, these occur when both permittivity ε and permeability µ are negative.

• In negative index metamaterials (NIM), both permittivity and permeability are negative resulting in a negative index of refraction.

INVISIBILITY USING META MATERIALS

The things which our eyes are not able to see are considered as “Invisible.

Light is neither absorbed nor reflected by the objects, passing like water flowing around a rock

Meta-material is a type of composite material that has unusual electromagnetic properties.

. According to the researchers, light rays incident on the material would be bent around the object, only to emerge on the other side in exactly the same direction as they began.

Process Design

2-D photoresist pattern

Phase mask

Sol-gel infiltration

3-D pattern

Titania structure

Interference lithography

Coat

Exposure

Develop

plain Si wafer

coat with HMDS to promote adhesion

coat with SU-8 20xx photoresist using spin coater

soft bake @95° to evaporate solvent and cut into pieces

UV exposure for xx seconds

flip 90° and expose again

post bake at first 65° then 95° to promote crosslink formation

submerge in PM acetate to dissolve unexposed photoresist (20 min）

submerge in isopropanol to wash away all remnants—final structure

2004:

• Miniaturized antennas based on negative permittivity materials—Lucent Technologies

• Metamaterial scanning lens antenna systems and methods—The Boeing Company

2003:

• Metamaterials employing photonic crystal—MIT

• Methods of fabricating electromagnetic metamaterials—The Boeing Company

2002:

• Resonant antennas—Lucent Technologies

APPLICATIONS

There'd be plenty of applications in the civilian world as well, even for rudimentary cloaking devices.

For example, you could create receptacles to shield sensitive medical devices from disruption by MRI scanners, or build cloaks to route cellphone signals around obstacles.

Potential applications of meta materials are diverse:

remote aerospace applications,

sensor detection and infrastructure monitoring,

smart solar power management,

public safety, radomes, high-frequency battlefield communication .

lenses for high-gain antennas, improving ultrasonic sensors, and even shielding structures from earthquakes.

BARRIERS IN DEVELOPMENT OF META MATERIALS

Although we have thorough knowledge of theoretical concept of invisibility but we have not enough practical implementation of these concepts.

Meta-material still needs more consideration and a lot has remained undiscovered and needs thorough study.

Security concern is another serious issue.

The tiny structures embedded in the metamaterial would have to be smaller than the wavelength of the electromagnetic rays you wanted to bend.

That's a tall order for optical invisibility, because the structures would have to be on the scale of nanometers, or billionths of a meter.

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