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This article presents a novel real-time meta-material (MM) sensor based on a non-invasive method that operates in microwave frequency ranges at 8.524 GHz to measure blood glucose levels with quality factor 184 is designed and fabricated. A cross enclosed between two square shapes produces a strong interaction between glucose samples and electromagnetic waves. In this study, 5 were tested noninvasively using the proposed glucose resonant sensor with a range of glucose-level changes from 50 to 130 mg/dL. For this range of glucose-level changes, the frequency detection resolution is 5.06 MHz/(mg/dL), respectively. Despite simulations, fabrication procedures (F.P.) have been carried out for more precise result verification. For the purpose of qualitative analysis, the proposed MM sensor is considered a viable candidate for determining glucose levels.

State-of-the art research on conventional microwave substrates reveals limitations of restricted flexibility, poor adaptability to irregular surfaces, and reduced effectiveness in complex sensing environments, leading to the development of a flexible microwave substrate using Co–Ca ferrite for feasible applications in detecting industrial chemicals. In this paper, CoxCa (0.90-x) Ni0.10Fe2O4 (x = 0.25, 0.50, and 0.75) based flexible substrate is developed through the sol-gel method, and a rectangular enclosed cross-dumbbells (RECD) metamaterial structure is designed for industrial chemical contamination sensing. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to morphological analysis of the nanoparticles of the substrate. XRD patterns shows the presence of crystalline phases, which facilitate the determination of strain within these materials. FESEM images demonstrate a structural composition characterized by nanosized grains and capillary-nanopores, where these nanosized grains are found uniformly distributed across the film's surface and results structural homogeneity. The synthesized nanoparticles are employed as a solid substrate utilizing PVA (polyvinyl alcohol) to ensure a uniform structure. The dielectric constant of the developed substrate is measured using the DAK 3.5 dielectric measurement kit, and it shows dielectric permittivity values ranging from 1.77 to 3.32 with loss tangents ranging from 0.031170 to 0.1929 for x = 25 % to x = 75 %. Metamaterial characteristics of the fabricated RECD structure on Co–Ca ferrite is analysed and μ-negative characteristics is achieved from 4.7 GHz to 6 GHz. Additionally, the reflection coefficient of the RECD metamaterial is also investigated for different bending condition up to an angle of 30ο. The simulated and measured S21 results strongly match each other. The sensing performance is evaluated for three concentrations of methanol and ethanol, demonstrating excellent contamination sensing capabilities with sequential frequency shifting. This study undoubtedly revealed that Co–Ca ferrite-based flexible metamaterial have great potential for high performance industrial chemical contamination sensing applications.

This paper introduces a metamaterial energy harvester that is compact, highly efficient, and capable of operating at wide angles. The proposed design has an outer ring resonator housing inverted T-shaped resonators, and it can operate at two distinct frequencies, 3.2 GHz and 5.4 GHz. The structure's impedance is carefully designed to align with that of free space, ensuring efficient capture of incident electromagnetic power with minimal reflection. This enables the resistor load to receive power in the most efficient manner. Based on the simulation findings, the proposed harvester exhibits a notably higher conversion efficiency of around 97 %. To ensure the accuracy and reliability of the simulation outcomes, we fabricated a 3x3 cell array of the proposed design and conducted experimental tests within an anechoic chamber. The simulation and experimental results exhibit a strong correlation. Existing metamaterial-based energy harvesting designs frequently confront size, absorption band, and polarization sensitivity limitations. Our compact design is distinguished by its ability to accomplish near-unity absorption and greater power conversion efficiencies at the desired frequency bands. This makes it an ideal option for energy harvesting systems for wireless sensor networks prioritizing efficiency and size.

This paper provides a metamaterial for microwave absorbers relying on asymmetric square split rings with a partial E shape in the centre-based resonator. The wideband frequency range shows its sensing capabilities in identifying various oil samples. The optimized MTM unit cell has electrical dimensions of 0.122λο × 0.122λο, where is λο the predicted wavelength at 3.64 GHz resonance frequency, for a total size of 10 × 10 mm2. The FR-4 dielectric substrate, 1.6 mm in thickness, produces the unit cell. The MTM has a maximum absorption peak of 91.46 % at 3.64 GHz, 99.72 % at 5.99 GHz, 96.89 % at 7.47 GHz, and 98.45 % at 10.01 GHz. This MMA has four absorption peaks, making it suitable for use in the triple band (S, C, and X). The centre split gaps and partial E shapes increase unit cell absorption, and the defective CSRR back layer structure improves the transmission coefficient. High absorption is influenced by the central split gaps and an appropriate electric field and magnetic field optimized in the centre ring when the structure is in an Orthogonal orientation. The research used a frequency domain solver operating between 2 and 12 GHz. The scattering characteristics (coefficient of transmission) of the relevant unit cell's equivalent circuit were confirmed using ADS software and the CST result. At frequencies between 3 and 5 GHz, the proposed asymmetric unit cell functions as a double negative (DNG) metamaterial absorber due to its negative permeability and permittivity. Since oil samples have different dielectric constants, the resonance frequency and Q factor are likewise different. Here, we receive a spectrum of frequencies that can be adjusted for use in sensing. The data showed that the suggested sensor is sensitive enough to pick up a variety of oils. The proposed sensor is useful for various applications, from liquid detection to microfluidic sensing and beyond, due to its cheap cost, high sensitivity, high-quality factor, and high electromagnetic radiation (EMR).

This study introduces a Metamaterial 'M.M.' sensor designed and evaluated to detect pure and adulterated fuels and oils. The reflection coefficient was measured using advanced design systems and computer simulations, followed by computational and experimental analyses of the performance evolution of the proposed sensor. The proposed sensor was evaluated using samples of varying compositions of Coconut Oil 'C.O.', petrol and kerosene. The results demonstrated a noticeable change in the Resonance Frequency 'R.F.' of the samples upon modification of their concentration. The reflection coefficient values for petrol and a 20 % combination of kerosene were determined to be −44.81 dB at a frequency of 10.29 GHz and −41.07 dB at a frequency of 10.15 GHz. Similarly, for coconut oil and refined coconut oil, the reflection coefficient values were found to be −47.34 dB at a frequency of 11.239 GHz and −41.981 dB at a frequency of 11.15 GHz. The sensor exhibits a high-quality factor of 451.58, a good sensitivity value of 5.65 and a figure of merit of 2551.427, indicating its excellent performance and efficiency. The results demonstrate the versatility of the proposed sensor, making it suitable for a range of applications such as microfluidics and industrial settings.

A unique shaped metamaterial sensor is proposed for detecting a wide range of pure and adulterated fuels and oils. The functionality of the designed structure has been examined both theoretically and practically ways, and the results show that it performs incredibly well. A new sample holder is built for more convenient functioning, and it is attached directly behind the constructed structure. In the field of research on liquids sensing, the purpose of this work was to present an alternative methodology. The CST microwave studio software is used to test a variety of different designs to determine which ones would result in the resonator having the best possible dimensions. The resonance frequency shifted 270, 410, and 180 MHz; between pure petrol and a mixture of 20 % kerosene and 80 % petrol, 100 % diesel and a mixture of 20 % ethanol and 80 % diesel, and clean olive oil and a mixture of 20 % corn oil and 80 % olive oil, respectively. The sensor has a quality factor of 430, high sensitivity of 1.99, and a figure of merit of 855.70, which indicates that it performs well and efficiently. In addition, the sensor that has been presented can accurately differentiate between various liquids by making use of the frequency shifting feature. The findings obtained demonstrate that this concept is readily applicable for a wide variety of electrochemical sensing applications even if the permittivity of the sample is altered; this is indicated by the findings. Because the sensor that is recommended possesses high sensitivity, a high-quality factor, and outstanding performance, it is suitable for use in the fuel industry, oil industry, and microfluidics industry.

The paper presents the preparation and measurement of six-layered human head phantoms for the sensor-based microwave brain imaging system (SMBIS) for the diagnosis of tumors in the head. The head phantom has been constructed based upon three-dimensional arrangements filled-up with numerous biochemical combinations that imitate the six brain tissues: DURA, CSF, White Matter, Gray Matter, Fat, and Skin regarding permittivity within the wideband frequency band (1 GHz to 4 GHz). For imaging purposes, the malignant and benign tumor(s) are also fabricated and placed in different locations in the 3D skull model to validate the performance of the phantom. After being formulated, the dielectric properties are measured by utilizing a dielectric kit linked with a vector network analyzer. The measured dielectric properties are compared to real human head tissue’s dielectric properties. After that, the human phantom model, including tumors, is validated using a SMBIS. The investigational dielectric characteristics of the brain tissues showed good agreement with the dielectric properties of the real brain tissues of the head. The experimental imaging outcomes demonstrated the legitimacy of the proposed six-layered tissue mimicking phantoms that can be used as an alternate to the actual human brain tissue for the diagnosis of brain tumors in SMBIS.

A novel Compact Complementary Split Ring Resonator (CSRR) metamaterial unit cell with perfect absorption, beneficial for ambient power harvesting, is proposed to operate in the S- and C-band. The size of the structure is 15 × 15 × 1.575 mm3 with dimensions of 0.18λ0 × 0.18λ0 × 0.019λ0 at the lowest absorption frequency. The proposed compact-sized CSRR structure exhibits notable characteristics such as high absorption coefficients and polarization-insensitive behaviours across a wide range of angles. The results demonstrate a notably high absorption efficiency of 97%, 99%, and 98% at 3.7275 GHz, 4.7075 GHz, and 5.9325 GHz. A 3 × 3 array is designed and verified by experimental results. The proposed design exhibits superior performance compared to previously published designs, which suffer from significant limitations such as a large metamaterial structure, reduced absorption frequency bands, and a lower fraction of absorption bands. The proposed design exhibits potential for utilization in developing wireless sensor network applications that require compact and highly efficient harvesting systems.

In this article, a meander line with parasitic resonator based on ENG metamaterial is introduced, with nonlinear regression of sensitivity for sensing applications. The unit cell is manufactured on a dielectric substrate of FR-4 with a thickness of 1.5 mm. The electrical dimension of the optimized cell is 0.098λ×0.094λ, where λ is the calculated wavelength at 7.2 GHz resonance frequency. A sensor has been designed by the unit cell to measure the thickness of the polypropylene. The offered metamaterial architecture exhibits resonance frequency 7.2 GHz at C-band with the amplitude of −21.72 dB. The NRW approach based MATLAB software shows properties with an ENG behavior and permeability close to zero. For the analysis procedure, a frequency domain solver with the frequency range of 2–12 GHz was used. ADS software verified the scattering parameters (coefficient of transmission) of the equivalent circuit for the corresponding unit cell with the CST result. The result indicates that this design has SNG features at C-band. The EMR (effective medium ratio) of this suggested unit cell is 10.60 at 7.2 GHz resonance frequency. The bandwidth of the optimized cell is 6.75–7.36 GHz, and the negative permittivity region is 7.2–7.8 GHz 1 × 2, 2 × 2, 4 × 4, and 16 × 16 array of unit cell results have been examined. All the array results show the same with the unit cell. Substrate material has also been changed to see the effect of resonance frequency in the parametric study. Finally, the proposed meander line structure performance was further simulated numerically and experimentally investigated for sandwich combination thickness sensing. It shows a narrow bandwidth sensing range between 6.25 and 6.47 GHz with significant sensitivity (S) and accuracy. The design complies with superior effective medium parameters and affords miniaturization factor for the size. Due to its low profile and high EMR, the planned ENG metamaterial can be a suitable C-band aspirant for sensing applications.

In this paper, we present a computational analysis method for the study of silicon dioxide (SiO2) graphene-based and amorphous silicon (a-Si)-graphene based nano meta-atoms in the terahertz (THz) regime. The proposed meta-atoms were modeled using a SiO2 substrate, optimized using a-Si substrate, and “sandwiched” between graphene layers. The octagonal-shaped torus was geometrically designed as a 3D structure to achieve optimal electromagnetic wave absorption from separate atoms. The upper and lower tori had identical diagonal arms to capture the maximum number of photons with minimal absorption losses. Graphene was chosen as the upper and ground layer material to optimize the electrical and optical properties of our proposed nano metamaterial. Finally, the following four fractional bandwidths with absorption percentages were optimized from the simulation: 4 bands (225.7–254.74 THz, 99.8%; 356.64–401.1 THz, 97.28%; 525.4 THz, 99.19%; 656.34 THz, 94.94%). The multi-band fractional absorption characteristic in the THz regime highlighted our proposed nano meta-atom as a potential candidate for absorption in the infrared and visible spectrum.

This paper reports, a metasurface absorber which is U-joint loaded Double Split O shaped with a square split patch at the center and Double Negative (DNG) property. The proposed absorber shows significant absorption for potential applications like radar signal absorption and satellite communication, remote sensing, RF shielding. The vertical U joint and split O mutually creates substantial resonance and expedite by the center square patch, to cover two consecutive X and Ku band absorption peaks at 11.56 GHz with 82.31%, 12.27 GHz with 98.91% and 14.19 GHz with 97.79%. Besides, balanced geometrical shape with insensitivity polarization for TE and TM mode wave propagation enhances the robustness and tunability of the structure. The absorption mechanism analyzed and discussed with the Finite Integration Technique (FIT). Characterization of S-parameter executed with an established method for dielectric property extraction and finally compared the proposed absorber with existing literature. Keywords: Metamaterial, Absorber, DNG, Wideband, Ku band