In recent years, scientists have conducted several studies dedicated to the development, simulation, and analysis of various types of metamaterials, along with a thorough analysis of their electromagnetic scattering phenomena. The fundamental goal of the studies is to analyze the occurrence of electromagnetic scattering within metamaterials and comprehend the propagation of guided electromagnetic waves.
Image Credit: luchschenF/Shutterstock.com
A Brief Introduction to Metamaterials
A recent article published in APL Materials defines metamaterials as artificial structures composed of subwavelength, atomic, or molecular-level components, possessing unique properties (such as electromagnetic scattering) absent in natural materials. While the microarchitecture largely dictates metamaterial properties and the process of electromagnetic scattering, the base material also significantly influences these properties.
The fabrication of metamaterials is usually done according to the targeted properties (required tensile properties, electromagnetic scattering properties, etc.). However, Additive Manufacturing (AM) is considered to be the most pivotal. AM is a preferred method due to its design flexibility, enabling the construction of intricate microstructures, which in turn are useful in developing materials with unusual properties.
What is Electromagnetic Scattering?
The interaction of electromagnetic waves with materials leads to changes in the pathway and properties termed as electromagnetic scattering. Electromagnetic scattering may occur due to reflection, refraction, or diffraction of waves.
The oscillating electromagnetic field of the incident wave causes charges to oscillate, which leads to secondary electromagnetic waves. Electromagnetic scattering is a complex process as these secondary waves also give rise to oscillations in other charges within the particle. Furthermore, when calculating the overall scattered field by combining these secondary waves, one must account for the evolving phase differences resulting from variations in both incidence and scattering directions.
Electromagnetic Scattering in Metamaterials
Researchers can customize the material's interaction with electromagnetic waves by arranging the components of metamaterials in a specific configuration. This typically involves subparts, like split-ring resonators or nano-antennas, designed to interact with incoming waves at specific frequencies.
Understanding and modeling electromagnetic scattering in metamaterials is done by Maxwell's equations, which govern the electromagnetic field behavior. To anticipate and enhance the electromagnetic scattering attributes of metamaterials, numerical techniques like finite element analysis (FEA) and finite-difference time-domain (FDTD) simulations are commonly employed.
The unconventional electromagnetic scattering characteristics of metamaterials make them a good choice for radar applications. The utilization of electromagnetic scattering in metamaterials is done by precise materials engineering approaches.
These methods involve altering the subwavelength structure of the metamaterial. Along with this, companies are also utilizing metamaterials with unique electromagnetic scattering attributes for the development of stealth frameworks in the aerospace sector.
Factors Affecting Electromagnetic Scattering in Metamaterials
The research published in Optik reveals that permittivity ε and permeability μ greatly affect the electromagnetic scattering in metamaterials. Both of these factors affecting electromagnetic scattering are dependent on the frequency of the electromagnetic wave, Drude frequency, and the collision frequency.
The researchers proved this by using a cylinder coated with a metamaterial bombarded with an electromagnetic wave of 6GHz frequency. With the increase in coating thickness, back electromagnetic scattering became smaller while the front electromagnetic scattering remained constant. The researchers used different collision frequencies from 0.05 GHz to .25 GHz with an increasing step of 0.05 GHz.
It was observed that various collision frequencies had minimal impact on the scattering properties of metamaterial, except within the range of bi-static angles spanning from 0 to 14 degrees and 347 to 359 degrees. Further experimentation revealed that except for the bi-static angle range between 175° and 205°, different Drude frequencies significantly affected the Radar Cross Section (RCS) of the target coated with metamaterial.
Electromagnetic Scattering Analysis in Metamaterials for Aerospace Applications
The airfoil presents a significant challenge in terms of radar electromagnetic scattering via reflection for aircraft, making the study of its stealth characteristics vital to minimize the overall radar cross-section of the aircraft. Typically, the airfoil serves as the primary lift-generating component of an aircraft. However, the introduction of metamaterials offers aircraft designers the potential to find a balance between stealth and aerodynamics.
Considering the substantial costs associated with conducting stealth tests to study electromagnetic scattering, the study published in the Journal of Physics: Conference Series recommends the utilization of numerical simulations to inform the design of metamaterial-based stealth solutions.
The research focused on investigating the bistatic radar cross-section (RCS) of an airfoil covered with metamaterial. To achieve this, the research team applied a 2-D auxiliary differential equation finite-difference time-domain (ADE-FDTD) method to simulate the electromagnetic scattering characteristics of the airfoil.
The numerical experiments revealed that the intricacies of the metamaterial's Drude frequency and collision frequency significantly affected the electromagnetic scattering. Nevertheless, by appropriately selecting metamaterial parameters, it is feasible to design airfoils with highly effective stealth capabilities.
Electromagnetic Scattering and Absorption by Water-based Metamaterials
The diverse applications and potential in mitigating unwanted electromagnetic scattering have made electromagnetic wave absorbers the center of attention. In the case of 3D patterned metamaterial absorbers (MMAs), their effectiveness remains closely tied to the attributes of their constituents, in addition to the geometric characteristics of their periodic unit cells.
A broadband, flexible metamaterial absorber (MMA) was skillfully developed through 3D printing using periodic cylindrical water resonators. The unit cell integrated a top layer constructed from flexible thermoplastic urethane (TPU). Remarkably, this design proposed by researchers in Results in Physics exhibited exceptional absorption capabilities, surpassing 90% efficiency across frequency ranges spanning 5.74–19.7 GHz and 25.2–40 GHz.
Notably, this absorber showcased consistent performance across a wide spectrum of incident angles and maintained its effectiveness regardless of polarization.
Metamaterials: An Overview
References and Further Reading
Bird, J. Electromagnetic Scattering Theory. [Online]
Available at: https://www.jhuapl.edu/Content/techdigest/pdf/V07-N01/07-01-Bird.pdf
Liu, J. et. al. (2020). Analysis and optimization of electromagnetic scattering characteristics of two-dimensional metal airfoil covered with metamaterial. Journal of Physics: Conference Series. 1633(1). 012019. IOP Publishing. Available at: https://www.doi.org/10.1088/1742-6596/1633/1/012019
Zhou, Q. et. al. (2022). Ultra broadband electromagnetic wave absorbing and scattering properties of flexible sandwich cylindrical water-based metamaterials. Results in Physics, 38, 105587. Available at: https://doi.org/10.1016/j.rinp.2022.105587
Ji, J. et. al. (2018). Research on scattering characteristics of metamaterials based on ADE-FDTD. Optik, 164, 402-406. Available at: https://doi.org/10.1016/j.ijleo.2018.03.046
Zadpoor, A. et. al. (2023). Design, material, function, and fabrication of metamaterials. APL Materials, 11(2). Available at: https://doi.org/10.1063/5.0144454
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.