“Metamaterial” refers to a composite material with artificially designed structures that demonstrate extraordinary physical properties not found in natural materials.
Emerged in the 21st century, metamaterials represent a class of new materials that possess special properties absent in natural materials, with these properties primarily originating from artificially designed unique structures.
The design concept of metamaterials is innovative. This idea is based on breaking the constraints of certain apparent natural laws by designing various physical structures, thereby achieving extraordinary material functions.
The design concept of metamaterials suggests that, without violating basic physical laws, humans can artificially create “new substances” with extraordinary physical properties distinctly different from those in nature, leading the design and development of functional materials into a brand-new realm.
Typical examples of “metamaterials” include “left-handed materials”, photonic crystals, “supermagnetic materials”, and “metallic water”.
Six Categories of Advanced Materials
1. Self-Healing Material – Biomimetic Plastic
Scott White from the University of Illinois has developed a type of biomimetic plastic with self-healing capabilities. This polymer incorporates a “vascular system” made of liquid. When damaged, the liquid seeps out like blood and coagulates.
Unlike other materials that can only repair minute cracks, this biomimetic plastic can mend fractures up to 4 millimeters wide.
2. Thermoelectric Materials
A company named Alphabet Energy has developed a hotspot generator that can be directly inserted into the exhaust of a common generator, thereby converting waste heat into usable electricity.
This generator employs a relatively inexpensive and natural thermoelectric material known as Tetrahedrite, which is said to achieve an efficiency of 5-10%.
Scientists are currently researching a higher-efficiency thermoelectric material called Skutterudite, a cobalt-containing mineral.
Thermoelectric materials have already begun to be used on a small scale, such as on spacecraft.
However, Skutterudite, with its low cost and high efficiency, can be used to coat the exhaust pipes of cars, refrigerators, or any machinery.
Aside from crystalline silicon, perovskites can also serve as alternative materials for solar cell fabrication.
In 2009, solar cells produced with perovskites boasted a solar energy conversion rate of 3.8%. By 2014, this figure had increased to 19.3%, approaching the over 20% efficiency of traditional crystalline silicon cells.
Scientists believe that there is still potential for enhancement in the performance of this material.
Perovskites are a category of materials defined by a specific crystal structure, which can contain any number of elements, typically lead and tin for solar cell applications.
Compared to crystalline silicon, these raw materials are significantly less expensive and can be sprayed onto glass, eliminating the need for meticulous assembly in clean rooms.
Aerogels can be fabricated from any number of substances, encompassing silica dioxide, metal oxides, and graphene.
Due to air constituting the vast majority of their volume, aerogels serve as exceptional insulators. Their structure also endows them with extraordinary toughness.
Scientists at NASA are currently experimenting with a flexible aerogel made from polymers, to be used as insulating material for spacecraft during atmospheric re-entry.
5. Stanene—A Material with 100% Conductivity
Stanene, similar to graphene, is a material constructed from a single layer of atoms. However, by using tin atoms rather than carbon, it possesses a characteristic that graphene cannot achieve: 100% conductivity.
Stanene was first theoretically proposed in 2013 by Professor Shou-Cheng Zhang of Stanford University. Predicting the electronic properties of materials like Stanene is one of the specialties of Professor Zhang’s lab.
According to their model, Stanene is a topological insulator, meaning its edges are conductive while its interior is insulative. As such, Stanene can conduct electricity with zero resistance at room temperature.
6. Light-Manipulating Metamaterials
The nanostructure of light-manipulating metamaterials can scatter light in specific ways, potentially rendering objects invisible.
Depending on the fabrication method and materials used, metamaterials can also scatter microwaves, radio waves, and the less familiar T-rays.
In fact, any type of electromagnetic spectrum can be controlled by these metamaterials.