Ursula Do Carmo Resende

This work presents a comprehensive modeling and optimization framework for graphene-based geometric diodes intended for visible-spectrum nano-rectenna systems. Carrier transport is described using a semiclassical Monte Carlo Method, which captures stochastic free-flight motion, boundary interactions, and relaxation-time scattering under a uniform-field electrostatic approximation. From the simulated I–V characteristics, a set of Figures of Merit (FoM)—including asymmetry, zero-bias resistance, and responsivity— is defined to quantify rectification performance and enable systematic comparison between device geometries. Single-objective optimization procedures based on Differential Evolution (DE) are applied to independently minimize the zero-bias resistance and maximize the responsivity, revealing the intrinsic trade-off between conduction efficiency and nonlinear rectification. To address this multi-criteria behavior, a multi-objective formulation is implemented using the NSGA-II algorithm, yielding a Pareto-optimal set of device configurations. The selected design achieves a balanced compromise between FoMs, exhibiting improved symmetry breaking, moderate conduction efficiency, and enhanced nonlinear response. The proposed methodology integrates stochastic transport modeling with metaheuristic optimization, providing a unified and physically consistent approach for the design of high-frequency geometric diodes.

This letter presents the design and experimental evaluation of a magnetic-resonant wireless power transfer (WPT) system for brain implants. A circuit-based model is proposed to predict the behavior of multicoil structures and to accurately estimate self- and mutual inductances under lateral and angular misalignment. A method is introduced to identify the spatial regions of approximately uniform mutual inductance, improving robustness relative to conventional repeater-assisted configurations. The influence of biological media is evaluated using an equivalent homogeneous head model representing the averaged dielectric properties of the underlying tissues. The proposed system was evaluated through the proposed modeling, full-wave CST simulations, and experimental measurements in air and in the equivalent biological medium. Results show close agreement among all approaches and confirm that tissue heterogeneity has negligible impact on coupling, resonance, and delivered power. The system operates stably across different implant positions, delivering the required power for neural devices implants.

This study presents a high-performance, ultra-thin metamaterial absorber consisting of nickel resonator disks arranged in a 4 × 4 matrix on a polytetrafluoroethylene (PTFE) substrate. The novelty of the design lies in the integration of nickel—a cost-effective alternative to noble metals—and PTFE, whose excellent thermal stability enhances the overall performance of the metamaterial. Additionally, the simplified unit cell structure enables scalability and offers a practical alternative to conventional absorbers. The proposed metamaterial absorber achieves broadband absorption across the ultraviolet, visible, and infrared spectra. A systematic parametric analysis was conducted to optimize the structural parameters, maximizing absorption efficiency while maintaining minimal thickness. Numerical simulations performed in CST Studio Suite^® validated the optimized design, demonstrating an average absorption of 99.00% and a peak absorption of 99.36% within the 375–850 nm range. Given the elevated absorption rates achieved, the analysis range was extended to 300–3000 nm, and a genetic algorithm was employed to refine the geometric parameters. This optimization resulted in a stable absorption profile with an average efficiency of 98.98%, and a peak of 99.96%. This structurally simple design offers an advantage by combining cost-effective material selection with high broadband absorption performance.

This study investigates four rectenna system configurations using microstrip patch antennas with different geometries fabricated on various substrates, including glass, paper, fiberglass (FR4), and polyester fabric. A voltage doubler rectifier circuit was designed for each antenna type to enhance performance. Metamaterial cells were incorporated into the glass, FR4, and paper‐based systems to improve electromagnetic wave capture. Simulations and optimizations were conducted using computer simulation technology (CST) and advanced design system (ADS) for operation at 2.45 GHz. Both the simulated and measured results that were obtained validate the potential of the proposed systems as efficient energy‐harvesting solutions.

The search will be carried out in the following databases: MEDLINE (PubMed), Cochrane Library, Embase-Elsevier, Scopus-Elsevier, Web of Science, LILACS-BVS, IEEE. To define the search strategies, we will have support from the library of the Faculty of Medicine of the Univesidade Federal de Minas Gerais (one of the institutions that are part of this project). Furthermore, we will use the software StaRt‱ to manage all the bibliographical references and to centralize all information necessary to build a database for this systematic review. References retrieved from search strategies will be exported to the software StaRt‱, and duplicates will be removed. After this procedure, two independent reviewers will select potential titles and abstracts, assessed for the inclusion criteria outlined above. Potentially relevant studies will have their full-text versions then independently assessed by two reviewers to determine if they meet the inclusion criteria. Discrepancies will be resolved by a third investigator. Excluded articles will be documented along with the reasons for exclusion. A total of nine reviewers is involved in this process. The final selection of included studies will be carried out for qualitative and quantitative analysis. Subsequently, data will be extracted, and the characteristics of the included studies will be detailed.