Emerging Materials and Designs for Low‐ and Multi‐Band Electromagnetic Wave Absorbers: The Search for Dielectric and Magnetic Synergy?

Abstract

Vigorous development of 5G communication technologies can boost mobile networks yet bring in electromagnetic interferences and safety concerns in utilizing electronic devices. Particularly, 5G network can not only involve a low‐frequency band of n78 (3.3–3.8 GHz) but also cover multi‐frequency bands of n77 (3.3–4.2 GHz) and n79 (4.4–5.0 GHz), displaying multiple electromagnetic radiations. Countless efforts have been devoted to investigating electromagnetic wave (EMW) absorbers with low‐ and multi‐band absorption properties. However, in terms of emerging materials and designs, few reports propose the mechanisms related to those properties. This perspective briefly reviews the impressive achievements of low‐ and multi‐frequency EMW absorbers and analyzes the design strategies that may enable low‐ and multi‐frequency absorption. Furthermore, the cutting‐edge mechanisms of corresponding electromagnetic responses, such as Snoek limit, quarter wavelength, and dielectric‐magnetic synergy effects are elaborated. Thus, this perspective can shed light on the new trends and ongoing challenges for EMW absorbers and further promote their practical application.

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“…The higher the attenuation constant degree, the fewer electromagnetic waves transmitted and reflected back to the transmitting source. The impedance matching and attenuation constant characteristics can be expressed by the following equations where Z and Z 0 are absorber and free space impedance values, respectively, α is the attenuation constant value, ε r is the actual value of the relative complex dielectric constant, μ r is the actual value of permeability, Z in is the normalized input impedance, f is the microwave frequency, c is the light velocity in a vacuum, and d is the thickness of the absorber. − …”

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“…The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202205376. DOI: 10.1002/adma.202205376 microwave-absorption materials (MAMs), such as carbon-based materials (graphene, MXene, carbon nanotubes), [6,7] metalbased materials (transition metal oxides/ sulfides, alloy), [8] and conductive polymer [9] provided super absorption efficiency but very limited controllability and poor processability. Recently, some flexible MAMs have been developed for more complicated target applications, such as metastructures and polymer-reinforced composites.…”