“Metamaterial” refers to a composite material with artificially engineered structures that demonstrate extraordinary physical properties not found in natural materials.
Emerging in the 21st century, metamaterials represent a class of new materials that have special properties absent in natural materials, with these properties originating mainly from unique artificially designed structures.
The design concept of metamaterials is innovative. This idea is based on breaking the restrictions of certain apparent natural laws by designing various physical structures, thus achieving extraordinary material functions.
The concept of metamaterial design suggests that, without violating basic physical laws, humans can artificially create “new substances” with extraordinary physical properties distinctly different from those in nature, taking the design and development of functional materials into an entirely 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 flows like blood and clots.
Unlike other materials that can only repair tiny cracks, this biomimetic plastic can repair fractures up to 4 millimeters wide.
2. Thermoelectric Materials
A company called Alphabet Energy has developed a hotspot generator that can be inserted directly into the exhaust of a regular generator, thus converting waste heat into usable electricity.
This generator employs a natural and relatively inexpensive thermoelectric material known as Tetrahedrite, which achieves an efficiency of 5 to 10%.
Scientists are currently researching a higher-efficiency thermoelectric material called Skutterudite, a mineral that contains cobalt.
Thermoelectric materials have already begun to be used on a small scale, such as in spacecraft.
However, Skutterudite, with its low cost and high efficiency, can be used to coat car exhausts, refrigerators or any machinery.
3. Perovskite
In addition to crystalline silicon, perovskites can also serve as alternative materials for manufacturing solar cells.
In 2009, solar cells produced with perovskites had a solar energy conversion rate of 3.8%. In 2014, this number increased to 19.3%, approaching the more than 20% efficiency of traditional crystalline silicon cells.
Scientists believe there is still potential for improvements in the performance of this material.
Perovskites are a category of materials defined by a specific crystalline 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 cheaper and can be sprayed onto glass, eliminating the need for meticulous assembly in clean rooms.
4. Aerogels
Aerogels can be manufactured from numerous substances, including silica dioxide, metal oxides and graphene.
Because air makes up the vast majority of their volume, aerogels serve as exceptional insulators. Their structure also gives them extraordinary resistance.
NASA scientists are currently experimenting with a flexible airgel made from polymers, to be used as an insulating material for spacecraft during atmospheric reentry.
5. Stanene – a material with 100% conductivity
Stanene, similar to graphene, is a material constructed from a single layer of atoms. However, because it uses tin atoms instead of carbon, it has a characteristic that graphene cannot achieve: 100% conductivity.
Stanene was first theoretically proposed in 2013 by Stanford University professor Shou-Cheng Zhang. Predicting the electronic properties of materials like Stanene is one of the specialties of Professor Zhang's laboratory.
According to their model, Stanene is a topological insulator, meaning its edges are conductive while its interior is insulating. As such, Stanene can conduct electricity with zero resistance at room temperature.
6. Light-handling metamaterials
The nanostructure of light-manipulating metamaterials can scatter light in specific ways, potentially making objects invisible.
Depending on the manufacturing 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.
