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Item Metadata only Compact dual-band metamaterial absorber: Enhancing electromagnetic energy harvesting with polarization-insensitive and wide-angle capabilities(2024-08-01) Ullah N.; Islam M.S.; Hoque A.; Kirawanich P.; Alamri S.; Alsaif H.; Islam M.T.; Ullah N.; Mahidol UniversityA novel compact metamaterial (MM) energy harvester optimized for Wi-Fi frequencies (2.4 GHz and 5.8 GHz) is introduced in this study. The energy harvester exhibits polarization insensitivity and versatility across various incident angles. The energy harvesting (EH) efficiency is evaluated using numerical simulations and practical experiments. The design features ring and octagonal resonators constructed with Rogers RT 5880 Substrate, with each octagonal resonator incorporating a strategically placed gap for lumped elements. The structure's impedance is meticulously aligned with free space to efficiently absorb incident electromagnetic (EM) power with minimal reflection. The simulation outcomes indicate that normal incidence at 2.4 GHz and 5.8 GHz yields high-efficiency levels of 96 % and 98 %, respectively. To validate these results experimentally, we conducted tests in an anechoic chamber using a fabricated 3 × 3 array structure. The results showed a significant correlation between the simulation outcomes and experimental data. The proposed MM energy harvester is highly efficient and shows great promise as an alternative for various microwave applications, such as EH and wireless power transfer.Item Metadata only A highly sensitive modified triple split ring metamaterial-based sensor for blood sample detection based on dielectric property alteration(2024-07-01) Al Mahfazur Rahman A.; Islam M.T.; Kirawanich P.; Bais B.; Alsaif H.; Maash A.A.; Hoque A.; Moniruzzaman M.; Islam M.S.; Soliman M.S.; Al Mahfazur Rahman A.; Mahidol UniversityThis research paper demonstrates a metamaterial (MTM) based sensing technique to detect various blood samples by analyzing their dielectric properties. The performance of this MTM-based sensor is evaluated with the help of mimicked human blood samples that closely resemble the dielectric properties of actual human blood samples. Moreover, the ISM band frequency of 2.4 GHz is chosen as one of the reference resonance frequencies due to its various industrial and medical applications. The resonating patch is developed on the FR-4 substrate with a dimension of 10 × 20 mm2 that provides sharp reference resonances of 2.4 and 4.72 GHz for the spectra of the transmission coefficient with a good quality factor (Q-factor). The MTM sensor can detect the mimicked blood samples with a maximum frequency deviation of up to 650 MHz at 2.4 GHz and up to 850 MHz at 4.72 GHz, with maximum sensitivity of 0.917 and 0.707, respectively. The measured results using the prototype of the sensor support the simulation result with good agreement, indicating high sensing capability. Due to its high sensitivity, figure of merit (FoM), and frequency shifting with dielectric property changes in blood samples, the developed MTM-based sensor can be implemented effectively for quick sensing of infected blood samples and biomedical applications.Item Metadata only Design and experimental validation of a compact dual-band metamaterial perfect absorber for electromagnetic energy harvesting applications(2024-11-01) Ullah N.; Islam M.T.; Hoque A.; Kirawanich P.; Alsaif H.; Soliman M.S.; Islam M.S.; Ullah N.; Mahidol UniversityThis article introduces, characterizes, and experimentally validates an innovative design for a compact-sized metamaterial (MM) perfect absorber (PA) for electromagnetic (EM) energy harvesting (EH) applications. The absorber design, comprised of three octagonal ring resonators made of annealed copper, incorporates split gaps at 45-degree inclinations within the uppermost and middle resonators. A split strip line connects the inner octagonal ring resonators, while the split gaps of the outermost and inner rings are filled with a 50 Ω resistive load. This structure is made on a Rogers RT5880 substrate, and the back side of the proposed design is entirely coated with annealed copper. The proposed absorber achieves precise impedance matching with free space, facilitating efficient absorption and redirecting EM power toward the resistive loads. The absorber demonstrates absorption peaks of 99.98 % at 2.4 GHz and 99.99 % at 4.9 GHz. In addition, the efficiency of absorption is assessed for different incident (θ) and polarization angles (ϕ) in both the Transverse Electric (TE) and Transverse Magnetic (TM) modes. Simulated harvesting efficiencies of 95.33 % at 2.4 GHz and 95.99 % at 4.9 GHz are recorded. An experimental validation is performed using a 3 × 3 array that measures 30 × 30 mm. The tests are carried out in an anechoic chamber. The measured harvesting efficiencies strongly correlate with the simulated results, indicating the reliability of the proposed design. This absorber's efficiency and compact size make it an excellent option for EH systems in wireless sensor networks (WSNs).Item Metadata only FT-FEDTL: A fine-tuned feature-extracted deep transfer learning model for multi-class microwave-based brain tumor classification(2024-12-01) Hossain A.; Islam R.; Islam M.T.; Kirawanich P.; Soliman M.S.; Hossain A.; Mahidol UniversityThe microwave brain imaging (MBI) system is an emerging technology used to detect brain tumors in their early stages. Multi-class microwave-based brain tumor (MBT) identification and classification are crucial due to the tumor's patterns and shape. Manual identification and categorization of the tumors from the images by physicians is a challenging task and consumes more time. Recently, to overcome these issues, the deep transfer learning (DTL) technique has been used to classify brain tumors efficiently. This paper proposes a Fine-tuned Feature Extracted Deep Transfer Learning Model called FT-FEDTL for multi-class MBT classification purposes. The main objective of this work is to suggest a better pathway for brain tumor diagnosis by designing an efficient DTL model that automatically identifies and categorizes the MBT images. The InceptionV3 architecture is utilized as a base for feature extraction in the proposed FT-FEDTL model. Thereafter, a fine-tuning method is applied to the additional five layers with hyperparameters. The fine-tuned layers are attached to the base model to enhance classification performance. The MBT data are collected from two sources and balanced by augmentation techniques to create a total of 4200 balanced datasets. Later, 80 % images are used for training, 20 % images are utilized for validation, and 80 samples of each class are used for testing the FT-FEDTL model for classifying tumors into six classes. We evaluated and compared the FT-FEDTL model with the three traditional non-CNN and seven pretrained models by applying an imbalanced and balanced dataset. The proposed model showed superior classification performance compared to other models for the balanced dataset. It attained an overall accuracy, recall, precision, specificity, and Fscore of 99.65 %, 99.16 %, 99.48 %, 99.10 %, and 99.23 %, respectively. The experimental outcomes ensure that the proposed model can be employed in biomedical applications to assist radiologists for multi-class MBT image classification purposes. The Anaconda distribution platform with Python 3.7 on the Windows 11 OS is used to implement the models.Item Metadata only Highly sensitive circle enclosed D-pad resonator-based narrowband Metamaterial Absorber for biosensing applications(2025-01-01) Ahmed S.; Alam T.; Kirawanich P.; Singh M.J.; Islam M.T.; Ahmed S.; Mahidol UniversityThis paper presents the development of an ultra-thin metamaterial-based absorber, meticulously engineered to exhibit nearperfect narrow-band absorption characteristics, specifically for sensing within the C band. The absorber consists of a copper ground, copper resonator, and Rogers RO4350B substrate, which incorporates a sophisticated metallic structure configured as a D-pad absorber. The overall size of the unit cell structure is 10x10 mm2. Through rigorous simulations and empirical measurements, the absorber achieves a highly concentrated absorption peak at 6.6 GHz, attaining a peak absorbance efficiency of 99.99%, with a full width at half maximum (FWHM) bandwidth of 260 MHz. The quality factor of the proposed sensor is analytically determined to be 253.85, with the sensitivity quantified at 1.47 GHz/RIU, and the figure of merit is calculated to be 38.8. Furthermore, this D-pad metamaterial absorber can be adapted for detecting various proteins, leveraging its high sensitivity and specificity. Through the absorber’s surface functionalization with specific binding agents, it is capable of identifying and quantifying different proteins, making it a versatile tool for applications in medical diagnostics, environmental monitoring, and food safety. This multifunctional capability highlights the absorber’s potential as a highly effective sensor in diverse scientific and industrial domains.Item Metadata only A novel oblique-incident stable dual-band octagonal symmetric metamaterial absorber for sensing applications(2026-05-05) Chowdhury M.Z.B.; Islam M.T.; Alawad M.A.; Kirawanich P.; Bais B.; Ouda M.; Alkhrijah Y.; Alenezi A.M.; Chowdhury M.Z.B.; Mahidol UniversityPowdered food products such as milk powder, horlicks, lactogen, and coffee powder exhibit varying dielectric properties that can be leveraged for material characterization and quality monitoring. Conventional methods for analyzing such materials often involve complex, time-consuming procedures. This paper presents a novel dual-band octagonal symmetric metamaterial absorber designed to detect dielectric variations in powdered foods through high-sensitivity electromagnetic sensing. The absorber operates at resonant frequencies of 9.86 GHz and 12.50 GHz with a unit cell dimension of approximately 0.591 λ0 × 0.591 λ0 at the lower frequency, corresponding to an effective medium ratio of 1.69. The X-band is dedicated to powdered food sensing, while the Ku-band supports general microwave absorption applications. The structure achieves an absorption rate of up to 99.99% at both bands and maintains stable performance under oblique incidence angles up to 60°, demonstrating strong angular resilience. Numerical simulations validate the absorber's electromagnetic response and confirm close alignment with theoretical predictions. The proposed design offers a compact, sensitive, and angularly stable solution involving dielectric property detection and electromagnetic wave absorption, making it suitable for wireless and sensing technologies.Item Metadata only A metamaterial-based biosensing approach for detecting dilution level change of blood(2026-01-15) Mahfazur Rahman A.A.; Islam M.T.; Kirawanich P.; Moniruzzaman M.; Shamsan Z.A.; Alenezi A.M.; Soliman M.S.; Mahfazur Rahman A.A.; Mahidol UniversityThis research illustrates a biosensing approach utilizing metamaterial (MTM) to detect variations in dilution levels in blood samples. The MTM resonator utilizes Rogers RT5880 substrate features a distinctive design that attains a reference resonance of 11.47 GHz for the transmission coefficient, S21 along with two additional resonances of 13.46 GHz and 14.33 GHz, respectively. The simulation of the biosensor model is accomplished within 10 GHz–15 GHz in the CST microwave studio platform. The MTM resonator effectiveness is assessed using electric and magnetic fields, as well as surface current movements. The overall biosensing performance is evaluated using mimicked blood samples of different dilution levels that intently align the dielectric properties of the actual sample. The results correspond with the simulation model's outputs, demonstrating its enhanced sensing capability. Furthermore, an unknown sample prediction model is constructed utilizing MATLAB/Simulink, based on the responses of the known samples, to determine the permittivity and dilution level of the samples. This MTM-based biosensor, distinguished by its strong Q-factor, frequency shifts, sensitivity, selectivity, and figure of merit (FoM), is relevant for detecting changes in dilution levels in blood samples to identify diseases and anomalies in the samples, as well as for other biomedical applications.Item Metadata only Advanced Microwave Sensing: Cylinder-Shaped Resonator-Integrated Transmission Line Based Sensor for Mustard oil Quality Estimation(2025-01-01) Uddin M.K.; Alam T.; Islam M.T.; Kirawanich P.; Baharuddin M.H.; Uddin M.K.; Mahidol UniversityThe quality assessment of edible oils, particularly mustard oil, is a critical aspect of food safety and consumer health. This article presents a design and investigation of a Cylindrical Resonator-Integrated Transmission Line (CRITL) sensor for rapid and precise quality assessment of mustard oil. The proposed CRITL offers a notable advantage over the traditional sensors, responding to the small variations in the quality of mustard oil. The proposed CRITL design achieves exceptional resonance at 2.047 GHz with an S21 of –78.5 dB. The sensing characteristics of the proposed CRITL are investigated for different mustard oil samples, which achieve an outstanding sensitivity of 40.41, a high Q-factor of 950, and an elevated Figure of Merit (FoM) of 52,002.9. Comprehensive full-wave simulations and experimental validation confirm its ability to detect subtle dielectric variations, where the CRITL sensor demonstrated significant linear variations in transmitted signals ranging from 2.17 GHz to 1 GHz across all oil samples. Results demonstrate that the sensor represents a non-invasive, fast, and highly sensitive means of quality detection for mustard oil, exceeding precision and detection ability compared to conventional methods. The key novelty of this work lies in its advancement of sensing technology through the development of a non-invasive, highly sensitive, and real-time monitoring approach, highlighting its strong potential for industrial food safety applications.Item Metadata only Design and analysis of a dual-band circular split-ring resonator-based metamaterial absorber for sensing applications(2025-01-01) Alawad M.A.; Rabbani M.G.; Islam M.T.; Kirawanich P.; Alkhrijah Y.; Ouda M.; Misran N.; Soliman M.S.; Alawad M.A.; Mahidol UniversityThis study introduces a dual-band circular split-ring resonator (CSRR)-based metamaterial absorber (MTMA) designed for high-sensitivity sensing of both solid and liquid materials. The proposed structure, fabricated on a Rogers RT 5880 substrate with copper layers, achieves near-perfect absorption rates of 99.99% at 10.48 GHz (X-band) and 99.97% at 14.57 GHz (Ku-band), optimized through CST Microwave Studio simulations. The MTMA’s triple-stage design refinement enhances resonance characteristics, enabling precise detection of dielectric variations in substrates and liquids via measurable frequency shifts. Experimental validation confirms robust performance, with sensitivity of up to 2.51 GHz/εᵣ and quality factors reaching 189, thus outperforming existing single-band metamaterial sensors. The absorber’s compact size and consistent response under varying permittivity’s make it suitable for applications in biomedical diagnostics, fuel adulteration detection, and industrial quality control. By bridging gaps between simulation and real-world implementation, this work advances metamaterial-based sensing technology, offering a scalable and efficient solution for electromagnetic wave manipulation in next-generation sensor systems.Item Metadata only 500HN polyimide film sandwich metamaterial absorber with enhanced sensing capabilities and assisted machine learning absorption forecasting(2025-05-01) Hossen M.S.; Islam M.T.; Kirawanich P.; Hoque A.; Alenezi A.M.; Baharuddin M.H.; Alsaif H.; Soliman M.S.; Hossen M.S.; Mahidol UniversityThe proposed research is about unleashing the absorption properties and parametric forecasting of 500HN polyimide film sandwich deposited metamaterial absorber (MMA) in THz regime. The proposed micro-structure unit cell is ultra-thin (7.9μm) and compact (60μm) at its lowest operational frequency, with multiple absorption peaks at 4.66, 5.06, 5.82, 6.59, and 6.75 THz. The proposed MMA exhibits multiple absorption peaks with absorption coefficients of 88.51%, 99.84%, 99.72%, 95.89%, and 84.95%. To analyze the proper characteristics of polyimide absorption values was observed in different MMA configuration (i.e. unit cell dimension, available substrate height, outer patch radiator). The modified meandered line configuration at the top with gold material (Au) gives this sandwich structure a good stability in terms of sensing which have been verified in TE, TM, and TEM mode (E-field, H-field, and surface current distribution). The sensing capabilities were evaluated using six liquid samples, achieving a maximum sensitivity of 1.4 THz/RIU and a figure of merit (FoM) of 185 RIU−1, outperforming existing designs. Machine learning assisted forecasting analysis in TC-40, TC-50, TC-60 for the different MMA configurations indicates the absorption values can be predicted with a good accuracy. The regression algorithm models was assessed using R2, adjusted R2, and MSE which reveal the models goodness of fit, forecasting accuracy, and generalization for MMA.