Researches

Altinozen, E. A numerical study of graphene-based nested split-ring terahertz for sensing applications. Opt Quant Electron 58, 181 (2026). https://doi.org/10.1007/s11082-026-08761-z 

Abstract:

The dynamic manipulation of terahertz (THz) waves is important for sensing tasks where resonance features must be interpreted under varying measurement conditions. This work studies a graphene-assisted THz sensor based on a periodic array of gold nested split-ring resonators integrated with graphene patches, whose surface conductivity is adjusted through electrostatic biasing. Unit-cell behavior is evaluated through simulated scattering parameters (S11 and S21), and the resulting spectral responses are used to construct features for data-driven interpretation. The main contribution of this work is the integration of an additional classification stage into the numerical analysis of THz sensor data, providing an extended and more application-oriented sensing framework for sensor designers. To quantify the classification capability of sensing outputs, eleven learning approaches are benchmarked over ten independent runs and organized into four families: margin-based methods (SVM, polyhedral conic), instance-based learning (k-NN), probabilistic models (Gaussian NB, Bernoulli NB, LDA), and linear/neural discriminative models (Logistic Regression, Perceptron, Ridge, Deep Learning). In this evaluation, the margin-based group performs best overall, with SVM achieving the highest mean accuracy (96.42%) and low variability across runs (CV = 1.38%), followed by strong results from the linear/neural group (Perceptron at 94.17%, Deep Learning at 91.04%)incorporating a supervised classification step offers a practical way to interpret simulated THz response features in terms of application-relevant classes. Importantly, separability is not driven by any single resonant feature; rather, discrimination arises from the collective multi-frequency structure of the response. The reported performance and method rankings are therefore conditional on the present dataset, feature construction, and evaluation setup, and may differ for other sensor configurations, sensing conditions, or target analytes. 

Altinozen, E. Graphene-Based Terahertz Metasurface with Molybdenum Disulfide for Refractive Index Sensing Applications. Sens Imaging 27, 62 (2026). https://doi.org/10.1007/s11220-026-00758-y 

Abstract:

This theoretical and numerical work presents a graphene-enabled metamaterial refractive-index sensor concept for terahertz (THz) biosensing, aimed at exploring routes toward early-stage screening of biological agents. The proposed metasurface employs a dual elliptical-ring resonator designed to maintain stable operation under different polarization states while enabling bidirectional resonance tuning. The sensing mechanism is studied using numerical full-wave electromagnetic simulations and supported by theoretical interpretation of the resonance physics through field distributions and surface-current responses. When an analyte layer is introduced, a pronounced resonant absorption feature is obtained in simulation, and the resonance position is shown to be governed primarily by the analyte dielectric response. This behavior enables spectral discrimination among representative dielectric models of biosensing targets, including bacterial samples and malignant-cell analogs. Reconfigurability is investigated through two complementary strategies: (i) tuning the graphene chemical potential to strengthen near-field confinement and enhance simulated refractive-index sensitivity, and (ii) introducing a molybdenum disulfide (MoS2) layer to shift the operating band and expand the accessible tuning range. Simulated field maps and current distributions corroborate the resonance behavior and indicate robust sensing characteristics under the studied conditions. Overall, the results numerically suggest that the proposed architecture could serve as a promising platform for THz biosensing and spectroscopy, motivating future experimental validation 

Assessing the Impact of Twisting and Bending Deformations on Flexible Interconnect Performance ALTINÖZEN EKREMInstitute of Electrical and Electronics Engineers (IEEE), http://dx.doi.org/10.1109/jflex.2022.32324702 

Abstract:

Flexible interconnects are essential components for signal transmission for foldable and wearable electronics. As such, they are exposed to a variety of mechanical deformations that can degrade their electromagnetic performance. This article analyzes the impact of bending and twisting deformations on the transmission properties of a variety of commercially available polymer and elastomer-based interconnects and compares with the performance of flat interconnects fabricated on rigid substrates. The analysis of the impact of deformations also takes into account the degradation in the conductivity of the printed lines due to reported mechanical deformations.

Assessment of the Robustness of Flexible Antennas to Complex Deformations ALTINÖZEN EKREM, Vukovic Ana, Sewell Phillip Institute of Electrical and Electronics Engineers (IEEE),http://dx.doi.org/10.1109/tap.2023.32626713 

Abstract:

Wearable antennas can suffer from a variety of mechanical deformations that are induced by the body dynamic. The article analyses how these complex deformations impact the performance of a flexible antenna operating in the 5–6 GHz band. The Green Coordinates (GC) spatial manipulation technique is used to generate a range of complex 2-D deformations, namely spherical, saddle, and twisting deformation. Generating full geometries is a key enabler in this study. The results offer valuable insight into the stability of antenna performance under in situ deformations. 

Systematic Generation of Arbitrary Antenna Geometries ALTINÖZEN EKREM, Harrison Ian, Vukovic Ana, Sewell Phillip Institute of Electrical and Electronics Engineers (IEEE),http://dx.doi.org/10.1109/tap.2022.3165539

Abstract:

Applications for conformal, wearable antennas are growing for consumer electronics. Hence, it is important to assess to what degree antenna performance can be tolerant to in situ deformations that can take the form of bending, crumpling, and twisting and combinations of these effects. However, generating geometries of arbitrary antenna deformations such as bending, crumpling, and twisting, which can be processed by standard electromagnetic (EM) software, is a major challenge that significantly complicates full assessment of in situ antenna performance. Constructive solid geometry methods of generating geometries is difficult to robustly apply to nonconformal antennas and more flexible techniques required to progress the antenna studies further. To address this challenge, this article investigates the utility of the green coordinate (GC) method for spatial manipulation of 3-D objects. First, calibration of a straightforward application of the GC method against a reference case of a patch antenna bent over a cylindrical surface, which can also be generated exactly, is undertaken. This article shows that systemic scaling distortions are introduced by the GC method and introduces a compensation method that can overcome these distortions. Subsequently, the compensated method is used to obtain new predictions of the EM performance of patch antennas with deformations.

A Virtual Environment for Evaluation of Wearable Antenna Performance Vukovic Ana, ALTINÖZEN EKREM, Sewell Phillip, Harrison Ian2021 International Conference on Electromagnetics in Advanced Applications (ICEAA) , http://dx.doi.org/10.1109/iceaa52647.2021.95396162 

Abstract:

Patch antennas that are woven or printed onto flexible clothing substrates are gaining increased interest in body-wearable electronics and for applications such as sport and medical monitoring. However, the flexibility of the substrate and the movements of the body means that the shape of wearable antennas is not fixed, rather it changes in a variety of ways including bending, twisting, crumpling and warping and in many cases results in a shape that is a combination of these effects. To date only one-dimensional (1D) bending deformations, i.e. deformations over a cylinder, have been investigated both theoretically and experimentally [1] . The main reason for this lies in the fact that generating the geometrical CAD models of such deformations is not straightforward under the Cartesian and Constructive Solid Geometry (CGS) framework that most electromagnetic (EM) software are based upon. Furthermore, CAD files produced for the purpose of manufacture often have unphysical gaps between surfaces which are detrimental to EM simulations. Therefore, we identify the generation of the geometries of such flexible antenna shapes as the main obstacle to full evaluation and characterization of wearable antenna performance.

Characterization of Flexible Interconnects ALTINÖZEN EKREM, Vukovic Ana, Sewell Phillip 2022 Microwave Mediterranean Symposium (MMS) http://dx.doi.org/10.1109/mms55062.2022.98256023

Abstract:

Flexible interconnects are essential for power and signal transmission in wearable electronics. This paper provides a computational study of the transmission properties of interconnects fabricated on a variety of popular substrates, namely PDS, PI, PET and PU. The contributions to the reflection and transmission losses attributable to each mechanism namely, connector loss, modal loss and conductive loss, are systematically analyzed and quantified. Throughout, the study assumes realistic dielectric and conductive losses.

Green Coordinates for Generation of Conformal Antenna Geometries ALTINÖZEN EKREM2020 14th European Conference on Antennas and Propagation (EuCAP) , http://dx.doi.org/10.23919/eucap48036.2020.9135814

Abstract:

Conformal antennas and antenna arrays have emerged as a powerful platform for a wide number of applications from mobile and stationary communication to aerospace. In many cases producing numerical models of conformal antennas is not trivial especially in cases of complex feed circuits. In this paper, we investigate the Green Coordinate method for space manipulation of three-dimensional objects and apply it to generating geometries of conformal antennas. By considering a special case of antenna bent over a developable cylindrical surface, the paper explores the impact of the Green Coordinate method on the object deformations and its impact on the electromagnetic simulations, i.e., on the accuracy of antenna parameters, namely the reflection coefficient and the far-field radiation patterns.

Impact of Torsion on Flexible Interconnects ALTINÖZEN EKREM, Vukovic Ana, Sewell Phillip2022 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS) , http://dx.doi.org/10.1109/fleps53764.2022.97815175

Abstract:

This paper reports on a computational model that is used to assess the reflection loss and transmission of flexible interconnects fabricated on a PI substrate and exposed to torsion deformation. Realistic material parameters that include dielectric and metallic losses typical of interconnects fabricated on the PI substrate are used in the model.

Modelling of Conformal Antennas using Time-Domain TLM Method Dimitrijevic Tijana, ALTINÖZEN EKREM, Atanskovic Aleksandar, Jokovic Jugoslav, Vukovic Ana, Sewell Phillip, Doncov Nebojsa 8TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING ET(R)AN , https://www.etran.rs/2021/zbornik/Papers/074_MTI_1.2.pdf

Recent Advances in the Unstructured Transmission Line Modelling (TLM) Method Vukovic Ana, Sewell Phillip, Dimitrijevic Tijana, ALTINÖZEN EKREM, Yan Kaiqi IEEE MTT-S INTERNATIONAL CONFERENCE ON NUMERICAL ELECTROMAGNETIC AND MULTIPHYSICS MODELING AND OPTIMIZATION (NEMO 2022) 

Simulation Platform for Flexible Electronics Vukovic Ana, ALTINÖZEN EKREM, Dimitrijevic Tijana, Sewell Phillip 2021 15th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS) , http://dx.doi.org/10.1109/telsiks52058.2021.96063248 

Transmission Line Modelling of an Eccentrically Loaded probe Coupled Cylindrical Cavity Jokovic Jugoslav, Dimitrijevic Tijana, Atanskovic Aleksandar, Doncov Nebojsa, ALTINÖZEN EKREM, Vukovic Ana, Sewell Phillip 2022 XIV International Symposium on Industrial Electronics and Applications (INDEL) ,http://dx.doi.org/10.1109/indel55690.2022.9965465

Abstract:

In this paper, numerical Transmission Line-Matrix (TLM) method is applied to model an eccentrically loaded cylindrical cavity in order to analyze an impact of the eccentricity on the resonant frequency values. Two different types of meshes are considered, the structured, rectangular mesh and the unstructured, tetrahedral mesh and their possibilities and advantages are emphasized.