Metamaterials: Revolutionary Impact in the Military Industry

Metamaterials are a technology that breaks through the limitations of certain apparent natural laws by orderly designing the structure of key physical dimensions of materials to obtain extraordinary materials with properties beyond the ordinary physical properties of nature. Metamaterials are a cutting-edge technology field with important military application value and broad application prospects, and will have a revolutionary impact on the development of future weapons and equipment and combat.

Metamaterials: subverting traditional theories

Although the concept of metamaterials emerged around 2000, its origins can be traced back even further. In 1967, Soviet scientist Victor Veselago proposed that if a material has both a negative dielectric constant and a negative magnetic permeability, the relationship between the electric field vector, the magnetic field vector and the wave vector will no longer follow the classical electromagnetic equation. According to the basic “right-hand rule” of science, it shows the opposite “negative refractive index relationship”.

This substance will subvert the optical world, making light waves appear to flow backwards, and exhibit unnatural behavior in many aspects, such as negative refraction of light, “retrograde light waves,” and the anomalous Doppler effect. Once this idea was proposed at the time, it was considered a “fantasy” by the scientific community. As the limitations of traditional material design ideas are increasingly exposed, it is becoming more and more difficult to significantly improve the comprehensive performance of materials. The high performance of materials is increasingly dependent on scarce resources. It is necessary to develop new material designs that exceed the performance limits of conventional materials. ideas have become an important task in the research and development of new materials.

Metamaterials: Magical functions will change future warfare

Metamaterials have always been favored by people due to their unique physical properties and have great application prospects in the military field. In recent years, the application results of metamaterials in the fields of stealth, electronic countermeasures, radar, etc. have continued to emerge, showing great application potential and development space.

Stealth is the most frequently used metamaterial application in recent years, and it is also the most concentrated direction of metamaterial technology research so far. For example, the US F-35 fighter and DDG1000 large destroyer both use metamaterial stealth technology. In the future, metamaterials have great application potential in electromagnetic stealth, optical stealth and acoustic stealth, and will be widely used in various aircraft, missiles, satellites, ships and ground vehicles, bringing about a revolutionary change in military stealth technology. The difference between metamaterials and traditional stealth technology is that metamaterials enable incident electromagnetic waves, visible light or sound waves to bypass the hidden object, technically achieving true stealth.

In terms of electromagnetic stealth

In 2006, Duke University in the United States and Imperial College in the United Kingdom jointly proposed an electromagnetic stealth design scheme for the microwave frequency band. This design scheme consists of 10 concentric cylinders and adopts a rectangular open ring resonator unit structure. The experimental results confirm that it is feasible to use negative refractive index materials for stealth objects. In 2012, Northeastern University in the United States used a combination of scandium-doped M-type barium ferrite sheets and copper wires to design and test a negative refractive index material that can be adjusted in the 33-44 GHz electromagnetic band. Raytheon Company in the United States has developed a “transmittance controllable artificial composite skin material”. This material uses a metal microstructure frequency selective surface embedded with a variable capacitor. By controlling the bias voltage loaded on the variable capacitor, the electromagnetic parameters of the frequency selective surface can be changed, thereby realizing artificial control of the material’s wave transmission characteristics. It can be applied to various advanced radar systems and the intelligent stealth skin of the next generation of stealth fighters.

In terms of optical stealth

In 2012, the Canadian company Super Stealth Bio invented a magical material called “quantum stealth”. It can refract and bend the surrounding light, making the objects or people covered by it completely invisible. It can not only “fool” the human eye, but also successfully hide under the detection of military night vision goggles and infrared detectors. This material can not only help special forces complete raids during the day, but also is expected to be used in the next generation of stealth fighters, ships and tanks. In 2014, a research team at the University of Florida in the United States developed a metamaterial that can achieve visible light stealth. The key to achieving this technological breakthrough is to use nano-transfer printing technology to create a multi-layer three-dimensional metamaterial. Nano-transfer printing technology can change the surrounding refractive index of this metamaterial, allowing light to bypass it and achieve stealth.

In terms of acoustic stealth

In 2011, Professor Kamer’s team at Duke University in the United States developed a two-dimensional acoustic cloak that can prevent a 10-centimeter wooden block from being detected by sound waves. In March 2014, Duke University created the world’s first three-dimensional acoustic cloak, which is an acoustic stealth device made of acoustic stealth metamaterials. It can make the incident sound waves propagate along the surface of the cloak without reflection or transmission, thus achieving invisibility to the detection sound waves. The three-dimensional acoustic cloak is composed of some plastic plates with repeatedly arranged small holes, which can show perfect stealth effect under 3 kHz sound waves, verifying the feasibility of using acoustic cloaks in active sonar confrontation. In addition, the US Navy independently developed a submarine acoustic stealth technology called “metal water”, manufacturing an aluminum material with a hexagonal unit cell structure and incorporating it into the silent material covering the outside of the submarine hull to guide the sound waves and achieve the purpose of stealth. The development of acoustic stealth metamaterial technology will have a revolutionary impact on the stealth of submarines and other underwater equipment, and may change the “game” rules of future underwater battlefields.

In terms of tactile invisibility

In addition to traditional invisibility, metamaterials have also made new breakthroughs in tactile invisibility. In 2014, researchers at the Karlsruhe Institute of Technology in Germany used mechanical metamaterials to make a tactile invisible cloak. This is a new stealth technology that can deceive the sensors of the human body and detection equipment. This tactile invisible cloak is made of metamaterial polymers and has a specially designed crystal structure with sub-micron precision. The crystal is composed of needle-like cones that touch each other at the tip, and the size of the contact point must be accurately calculated to meet the required mechanical properties. The invisible cloak made of this metamaterial can shield the sense of touch of instruments or the human body. For example, if a protruding object on the table is covered with an invisible cloak, although the protrusion is visible, it cannot be felt when the object is touched by hand, just like touching a flat table. Although this technology is still in the pure basic physics research stage, it will open up a new path for defense applications in recent years.

Antennas and radomes are another application area for metamaterials. Many foreign experiments have shown that applying metamaterials to antennas of missiles, radars, and spacecraft can greatly reduce antenna energy consumption, increase antenna gain, expand the bandwidth of antenna operation, and effectively enhance the focus and directionality of antennas.

In terms of antennas, Raytheon has developed a metamaterial dual-band miniaturized GPS antenna. Through precise artificial microstructure design, it can improve the isolation between antenna units and reduce electromagnetic coupling between antenna components, thereby greatly expanding the bandwidth of the antenna. It can be used in aircraft platforms and personal portable tactical navigation terminals that have strict requirements on antenna size.

In terms of radar antenna covers, with the support of the US Navy, a US company successfully developed a metamaterial intelligent structure for radar covers and applied it to the US military’s new generation of E2 “Hawkeye” early warning aircraft, greatly improving its radar detection capability. By adopting the special design of metamaterials, the project provides a solution to the problem of image distortion of traditional radar covers. At the same time, this metamaterial electromagnetic structure is light in weight, convenient for later modification and maintenance, and greatly improves the overall performance of the E2 “Hawkeye” early warning aircraft.

In terms of missile radomes, the American company Raytheon has developed a missile radome based on metamaterials, which can prevent the electromagnetic waves passing through the missile radome from being effectively refracted, effectively improving the missile’s strike accuracy.

Metamaterials used to make optical lenses can be used to make lenses that are not limited by the diffraction limit, highly directional lenses, and high-resolution flat optical lenses. Among them, lenses that are not limited by the diffraction limit are mainly used in the fields of trace pollutant detection, medical diagnostic imaging, single molecule detection, etc.; highly directional lenses are mainly used in lens antennas, miniaturized phased array antennas, super-resolution imaging systems, etc.; high-resolution flat optical lenses are mainly used in the fields of optical guide components of integrated circuits. In 2012, the University of Michigan completed the research on a new type of metamaterial lens, which can be used to observe objects less than 100 nm in size and has good working performance in the spectrum range from infrared light to visible light and ultraviolet light.

The significance of metamaterials is not only reflected in several major types of artificial materials, but most importantly, it provides a new way of thinking – people can obtain “new materials” with extraordinary physical properties that are completely different from those in nature without violating the basic laws of physics. “One generation of materials, one generation of equipment”, the birth and development of innovative materials will inevitably give birth to new weapons and equipment and combat styles. Can the “super material” that has been supported by the world shortly after its birth become the next new material legend? It can’t help but make people imagine and look forward to it.