Metamaterial

In this universe, lots of materials exist with only certain properties, therefore limiting their potential for scientific application. The creation of new material, which does not exist in nature, is important as to explore the new possibility of advancing science towards the benefit of mankind. Such a material, called a metamaterial, usually is engineered in order to have specific properties by manipulating its structure of composition.

The research in metamaterials begin when scientists were intrigued about exploring the possibility of having a negative refractive index. In positive refractive index, the light that enters a medium from one direction with an angle of incidence will be refracted towards the opposite side with a refracted angle that can be less or more than the angle of incidence depending on the medium. However in negative refractive index, the light is refracted towards the same side from the imaginary line, the property in which makes invisibility to become reality.

Diagram showing the difference between positive refraction
index(right) with negative refraction index(left).

Metamaterial allows the impossible application such as invisibility cloak to be possible. Some applications that are rendered possible because of metamaterial can be seen below:

1. Terahertz metamaterial - Terahertz frequency is a frequency that is higher than microwave but lower than infrared and visible light. Terahertz wave is used widely in medical imaging to detect tumor, radio astronomy spectroscopy and at some point, for security detection of chemicals, biological agents and weapons.
2. Cloaking device - Many proof of working invisibility cloak have been shown although most of them are creating invisibility not in visible wavelength. You can read about the latest achievement in invisibility cloak here.
3. Acoustic metamaterial - This artificially created metamaterial is important in work involving sound wave. The fabricated metamaterial is important in order to direct, order or manipulate sound waves. With acoustic metamaterial, sonic waves can now enter the negative refraction domain. 

These are just some of the vast possibility of new applications that can be made by employing the properties govern by metamaterial.

Metamaterial could be used to create high def ultrasound image.

Sort of invisible cloak created by David R Smith from Duke University