Metamaterials, recognized as advanced artificial materials endowed with distinctive properties, have found diverse applications in everyday life, military endeavors, and scientific research. Starting from monolayer metamaterials, multilayer ones are increasingly researched, especially in the field of electromagnetic wave absorption. In this article, we propose a multilayer metamaterial-absorber (MA) structure comprising two resonant layers crafted with copper and FR-4 dielectric. The presented multilayer MA structure exhibited an absorption greater than 90% in a frequency range from 4.84 to 5.02 GHz, with two maximum absorption peaks at 4.89 and 4.97 GHz. The bandwidth of the multilayer MA surpassed that of the individual single-layer MAs, with extension fractions reaching 360% and 257%, respectively. Through the simulation and calculation, the field distribution and equivalent circuit model elucidated that both individual magnetic resonances and their interplay contribute significantly to the absorption behavior of the multilayer MA. The absorption of the proposed multilayer MA structure was also investigated for the oblique incidence in the transverse electric (TE) and transverse magnetic (TM) modes. In the TE mode, the absorption intensity of two maximum peaks was maintained at over 93% up to an incident angle of 40 degrees and dropped to below 80% at an incident angle of 60 degrees. In the TM mode, the absorption was more stable and not significantly affected by the incident angle, ranging from 0 to 60 degrees. An absorption greater than 97% was observed when the incident angle increased from 0 to 60 degrees in the TM mode. Additionally, the approach in our work was further demonstrated by adding more resonant layers, making 3- and 4-layer structures. The results indicated that the absorption bandwidths of the 3- and 4-layer structures increased by 16% and 33%, respectively, compared to the bilayer structure. Furthermore, we analyzed the thermal distribution within the MA to understand the dissipation of absorbed electromagnetic energy. This research offers valuable insight into the augmented MA through a multilayer structure, presenting the implications for microwave applications like electromagnetic shielding, as well as in the design of MAs for terahertz devices and technologies, including emission and thermal imaging. These findings contribute to the advancement of knowledge in enhancing the absorption capabilities across various frequency ranges, expanding the potential applications of metamaterials.

Enhancing the efficiency is an essential target of the wireless power transfer (WPT) technology. Enabling the WPT systems requires careful control to prevent power from being transferred to unintended areas. This is essential in improving the efficiency and minimizing the flux leakage that might otherwise occur. Selective field localization can effectively reduce the flux leakage from the WPT systems. In this work, we propose a method using a digital honeycomb metamaterial structure that has a property operation as a function of switching between 0 and 1 states. These cavities were created by strongly confining the field by using a hybridization bandgap that arose from wave interaction with a two-dimensional array of local resonators on the metasurface. A WPT efficiency of 64% at 13.56 MHz was achieved by using the metamaterial and improved to 60% compared to the system without the metamaterial with an area ratio of Rx:Tx~1:28. Rx is the receiver coil, and Tx is the transmitter one.

In this research, we have designed a hybrid metamaterial absorber (HMA) based magnetic material from C to the Ku-band. The magnetic material was prepared by the ball milling method with differences in the mass ratio of the FeCo alloy to C. The HMA structure consists of four layers: FeCo–C, metallic structure (two punched-in rings with four L-shape in the edges), dielectric (FR-4), and continuous metallic layer. The widest absorption spectrum of structure based FeCo–C (75%C) in a frequency range of 6.9–16.8 GHz with absorption exceeding 90%. The absorption mechanism has also been carefully analyzed through the distribution of surface current and power loss density. These findings may advance the design of devices leveraging metamaterials, including applications in stealth radar technology, electromagnetic shielding for health and safety, and reduction of electromagnetic interference for high-performance electronic and communication systems.

This study addresses the challenges of high-power consumption and complexity in conventional infrared (IR) gas sensors by integrating metamaterials and gold coatings into IR radiation sources to reduce radiation loss. In addition, emitter design optimization and material selection were employed to minimize conduction loss. Our metasurface exhibited superior performance, achieving a narrower full width at half maximum at 4197 and 3950 nm, resulting in more confined emission spectral ranges. This focused emission reduced energy waste at unnecessary wavelengths, improving efficiency compared to traditional blackbody emitters. At 300 °C, the device consumed only 6.8 mW, while maintaining temperature uniformity and a fast response time. This enhancement is promising for the operation of such sensors in IoT networks with ultra-low power consumption and at suitably low costs for widespread demands in high-technology farming.

Wireless power transfer (WPT) in conductive environments faces significant challenges due to the induction of eddy currents within the medium when exposed to a varying magnetic field. These eddy currents lead to transmission losses in the WPT system by increasing the radiation resistance of the resonant coils. In this report, we present a WPT system operating at 13.56 MHz, which is composed of a one-dimensional metamaterial array. When this system operates in highly conductive media such as seawater, wet soil, or implanted devices, its performance rapidly deteriorates. By proposing patterned ground shielding (PGS), we have minimized the losses caused by eddy currents generated by high-frequency magnetic field variations. The transmission coefficient of the WPT system in a medium with electrical conductivity equivalent to seawater (3.5 S m⁻¹) at a transmission distance of 500 mm achieves a value of 0.29, which significantly increases to 0.62 with the implementation of PGS.