[Reading Science] Invisible Cloaks and Divine Shields... Turning Imagination into Reality, the 'Meta Era' Arrives

Humanity Creates Metamaterials Not Found in Nature, Attempts to Cross the 'Divine Realm'
Some Technologies Like Ultrathin Lenses Reach Practical Use Stage
Cost, Technical Limits, and Flexible Operation Performance Are Key Challenges

Movie still cut from 'Wonder Woman'

[Asia Economy Reporter Kim Bong-su] Here is a quiz. What is the criterion used to divide human history? The answer is material. The Paleolithic, Neolithic, Bronze Age, and Iron Age are distinguished by the 'materials' primarily used during those periods. This signifies how greatly materials have influenced human life. Since entering the Iron Age, humanity has achieved remarkable advancements in productivity and scientific technology, leading up to modern society. Now, we are leaping into an era where materials that do not exist in nature are created and used by humans themselves. These are called metamaterials. Fictional materials with superpowers, such as Harry Potter's 'invisibility cloak' that hides appearances and Wonder Woman's shield 'Aegis' that blocks anything, are becoming realities through human innovation.

◇What Are Metamaterials?

“Meta” comes from the Greek word meaning ‘nonexistent,’ ‘virtual,’ or ‘transcendent.’ Metamaterials are materials that do not exist in nature but are artificially created with new properties. This goes beyond humans mixing or separating existing materials to create alloys or polymers; it involves creating entirely new materials. Academically, metamaterials refer to artificially arranged and designed substances that exhibit properties not observed in natural materials. Specifically, they are aggregates of structures composed of artificial atoms smaller than the wavelength of light or energy.

As a result, metamaterials interact locally with light, altering various characteristics such as the phase, intensity, and propagation direction of light. The most frequently mentioned and famous application of metamaterials is the ‘invisibility cloak,’ which changes the refractive index of light to hide the appearance of people or objects. The basic principle of the invisibility cloak is similar to a mirage phenomenon, understood as the bending of light due to differences in refractive indices. By freely controlling the refractive index of a medium, light can be bent in desired ways, and if light is prevented from reaching a specific object, invisibility can be achieved. Metamaterials precisely designed at the scale of hundreds of nanometers allow light to bypass a person wearing the invisibility cloak and reach the observer, creating the illusion that the person has disappeared from space and time.

Scientists believe that metamaterials can control not only light (optical waves) but also electromagnetic waves, seismic waves, sound waves, and water waves. Some even claim that metamaterials can slow down or speed up the speed of light, potentially leading to time machine technology. There are two main methods for fabricating metamaterials: the top-down process, which involves etching the base material to nanoscale using high-energy beams such as electron beams or ion beams, and the bottom-up process, which assembles nanomaterials like Lego blocks.

◇Imaging and Display Applications Are Within Reach

The concept of metamaterials began to take shape in 1969 when Russian physicist Veselago published research on virtual materials that cause light to refract negatively. In 1999, Professor Pendry of Imperial College London proposed an artificial atomic structure capable of achieving negative permeability in a narrow band, and in 2000, Professor Smith of Duke University in the United States created the first metamaterial with a negative refractive index, attracting worldwide attention.

Metamaterials have a wide range of applications. They can be used in aerospace industries, ultra-precise sensors for monitoring social infrastructure, LiDAR for autonomous vehicles, earthquake-resistant buildings that block seismic waves, stealth functions for airplanes, tanks, and warships, ultra-thin lenses, and improvements in acoustic sensors, among other fields.

In particular, ultra-thin lens technology was selected by the World Economic Forum (WEF) in 2019 as one of the top 10 next-generation technologies that will change the world. This is why imaging and display fields are considered the most likely areas for the first commercialization of metamaterials. In fact, Samsung Electronics is reportedly considering using ‘metalenses’ coated with metamaterials developed by Professor Noh Joon-seok’s team at Pohang University of Science and Technology to solve the ‘camera bump’ issue in smartphones. The goal is to reduce a 1 cm lens to about 1 μm, creating an ultra-high-performance ultra-thin lens that will bring another innovation to smartphones. Moreover, ultra-thin lens technology is actively applied in virtual reality (VR), augmented reality (AR), and wearable computing, drawing attention as a means to realize a ‘metaverse’ in reality that surpasses current ultra-high-performance computers with just a thin pair of glasses like ‘Google Glass.’

◇Challenges in Nanotechnology and Cost Must Be Overcome

Additionally, stealth functions that allow electromagnetic waves to pass through without reflection are already being researched at a significant level by the U.S. Department of Defense and are expected to be implemented in next-generation fighter jets and warships. As autonomous vehicle development accelerates, research on metamaterial materials combining sensor and lens functions to move LiDAR from the top of vehicles to headlights is underway. Professor Noh said, “Ultra-thin lenses (applied by coating nanomaterials) can be used in imaging technologies such as cameras, ultra-high-resolution microscopes, image recognition through contour detection, and LiDAR technology that scans light in desired directions to determine object depth. In the display field, it is expected that reflective displays based on structural colors that produce colors solely through nanostructures without dyes, as well as three-dimensional augmented and virtual reality display technologies using hologram generation devices, will become possible.”

Although research on metamaterials is currently very active, most work remains at the ‘laboratory’ level. The materials used to make metamaterials are very expensive and difficult to process, and above all, nanomanufacturing technology capable of mass production is still lacking. Furthermore, active driving technology that can freely and instantly change the properties of metamaterials is still at the testing stage. Metamaterials produced in laboratories worldwide are experimental samples about the size of a fingernail, costing between 50 million to 100 million KRW, and lack flexibility and active driving capabilities. Professor Noh predicted, “It usually takes about 50 years for science to become technology. Since the concept of metamaterials was established and research began about 20 years ago, commercialization is expected within the next 30 years.”