Search Results (290)

The convergence of artificial intelligence, biotechnology, and the Internet of Bio-Nano Things (IoBNT) is enabling the creation of a new generation of intelligent in-body medical devices for continuous diagnosis and monitoring. In this context, a compact, wideband, circularly polarized conformal microstrip antenna is proposed for capsule endoscopy applications. The antenna is integrated along the inner wall of a 10 mm-diameter capsule and achieves an impedance bandwidth of 2.06–5.39 GHz (89.39%), maintaining stable matching under varying biological tissue conditions. A 3 dB axial ratio bandwidth (ARBW) of 2.31–3.14 GHz (30.45%) ensures reliable circular polarization and robust wireless communication in lossy and dynamic in-body environments. To extend beyond conventional electromagnetic analysis, a physics-informed neural network (PINN) framework is introduced to model the thermal response of biological tissues based on the governing bioheat equation. This AI-driven approach enables fast and generalizable prediction of temperature rise under varying operational conditions without repeated numerical simulations. At 2.45 GHz, the antenna exhibits a maximum gain of $-31.1$ dBi with a radiation efficiency of approximately $-34$ dB, consistent with in-body propagation constraints. Simulation and experimental results in realistic tissue phantoms, including muscle, small intestine, large intestine, and stomach, confirm stable wideband and polarization performance. Specific absorption rate (SAR) analysis demonstrates compliance with IEEE C95.1-2019 safety limits, while link budget evaluation validates reliable telemetry over a 1–3 m communication range. The integration of advanced antenna design with physics-informed machine learning provides a scalable framework for intelligent, safe, and adaptive IoBNT-enabled capsule endoscopy systems. Full article

The brain and testes are connected via the hypothalamic–pituitary–gonadal (HPG) axis. Both are vulnerable to radiofrequency electromagnetic radiation (RF-EMR). However, no comprehensive study had evaluated the effects of RF-EMR on key hormones along this axis. Hereby, this study evaluated the effect of RF-EMR on the hormonal changes along the axis, including the neuropeptide kisspeptin. A total of 18 (N = 18) adult Sprague–Dawley rats were divided into three groups (n = 6): Control, 4 h, and 24 h. The Control group was sham-exposed to an inactive router. The exposed groups were subjected to 2.45 GHz RF-EMR for 4 and 24 h daily, for 60 days at a 20 cm distance. The power density was 0.141 W/m² with a whole-body specific absorption rate (SAR) of 0.41 W/kg. No significant changes were observed in hypothalamic Kiss1 gene expression or serum kisspeptin levels. GnRH levels increased significantly in both exposed groups, while FSH and LH remained unchanged. Testicular testosterone was significantly reduced in the 24 h group, while serum testosterone was elevated in the 24 h group compared to the 4 h group. In conclusion, prolonged 2.45 GHz RF-EMR exposure caused selective changes in components of the HPG axis, particularly involving GnRH and testosterone, suggesting potential endocrine effects on male reproductive regulation. Full article

This review comprehensively examines magnetic nanomaterials, ferrofluids, and their integration into ferrogel systems, systematically exploring their structural characteristics, dynamic behaviors, preparation techniques, and applications across medical and engineering fields. Structural characterization reveals that particle size and dispersibility directly influence functional efficiency in fluid and gel matrices, such as SAR (specific absorption rate) values in hyperthermia applications. For ferrofluids and magnetic gels, macroscopic behaviors and microscopic mechanisms are governed by key parameters like the magnetic Bond number. Preparation encompasses green synthesis, chemical reagent synthesis, and the cross-linking of these nanoparticles into hydrogel networks. Applications span diverse areas: in medicine, these include targeted hyperthermia, pH-responsive magnetic gel drug delivery, and MRI (magnetic resonance imaging); in engineering, applications range from efficient extraction and triboelectric power generation to magnetically regulated heat transfer and soft gel robotics. The paper also discusses current challenges, including material stability and unclear micro–macro correlations in complex fluid–gel systems, outlining future research directions for multifunctional magnetic materials. Full article

The redox mechanisms of RAW 264.7 macrophages exposed to 2.45 GHz RF-EMF at subthermal specific absorption rates and to lipopolysaccharide (LPS) and/or the SARS-CoV-2 spike protein (CSP) were investigated. To this end, cellular responses (lysosomal and mitochondrial activity, nitric oxide (NO) production, and cell survival/death) were measured after 6, 24, and 48 h. Selective loss of viability in cells exposed to RF and LPS was observed at 6 h, consistent with early defects in membrane permeability. Lysosomal activity was significantly enhanced in cells treated with RF + LPS. Mitochondrial activity decreased in cells exposed to RF + LPS at 6 h and increased in cells treated with RF + CPS/LPS. Cell viability decreased greatly in cells treated with LPS and CSP + LPS after 24, particularly after 48 h. Nitrite levels peaked in non-irradiated cells treated with RF + LPS and in CSP + LPS at 24 h and decreased in irradiated cells after 48 h. Irradiation affected selection of the death mode: apoptosis decreased or remained unchanged in cells subjected to any of the treatments, while necrosis increased in cells treated with CPS, LPS, or both for 48 h. The combination of RF-EMF and infectious agents reprogrammed the interaction between mitochondria/lysosomes/nitric oxide (NO)/cell death in macrophages in a time- and stimulus-dependent manner. Full article

This work presents the design and characterization of a thermoregulated, bandwidth-enhanced TEM cell system optimized for bioelectromagnetic experiments on biological cells, with a focus on bioluminescence resonance energy transfer investigations at 700 MHz and 3.5 GHz. Bandwidth improvement, achieved through geometric modifications and optimized connector transitions, resulted in reduced return and insertion losses and improved field uniformity, particularly in the 2.5–6 GHz range. Numerical simulations showed homogeneous electric field and normalized specific absorption rate (SAR) distributions (~1 W/kg) at 700 MHz. At 3.5 GHz, the improved TEM cell provided the most uniform exposure of the biological sample with SAR values of 15 W/kg and 10.5 W/kg, for the bulk and surface (bottom layer), respectively. Experimental SAR measurements using a ~1 mm³ fluoro-optic probe agreed well with simulations. To counteract RF-induced heating, the system incorporated active thermoregulation at 37 °C. At 3.5 GHz and 20 W input power, a 1.5 °C rise over 120 s was effectively mitigated using water-circulation cooling. This work provides a controlled and reliable setup for future studies on the interaction of 5G-band electromagnetic fields with biological systems. Full article

The expansion of fifth-generation (5G) wireless networks has increased environmental exposure to mid-band and millimeter-wave radiofrequency electromagnetic fields (RF-EMF), but their molecular effects on male reproductive tissues remain insufficiently understood. This study evaluated whether repeated exposure to 3.5 GHz and 24 GHz RF-EMF alters testicular stress-associated molecular responses by integrating electromagnetic dosimetry with an in vivo rat model. Whole-body specific absorption rate (SAR) and 10 g peak SAR were estimated using a rat voxel model and scaled to the 20 cm antenna-to-cage geometry used during exposure. Thirty-six adult male Sprague Dawley rats were allocated to sham, 3.5 GHz, or 24 GHz groups and exposed for 1 h/day or 7 h/day over 60 days. Testes were examined histologically and assessed for HSP27, HSP70, and HSP90 protein expression. SAR values were low overall, although absorption was higher at 3.5 GHz than at 24 GHz. Histological evaluation showed preserved seminiferous tubule architecture without consistent structural injury. In contrast, molecular analysis demonstrated frequency- and duration-dependent modulation of heat shock proteins, including early HSP70 downregulation at both frequencies, followed by HSP90 upregulation at 3.5 GHz and HSP27 upregulation at 24 GHz. These findings indicate that low-level 5G-relevant RF-EMF exposure can modify molecular stress responses in testicular tissue even in the absence of overt histological damage. Full article

Polyolefin bonding technologies with metal foils are extensively employed in various sectors, particularly in automotive, electronics, and aerospace industries. This research examined the innovative electromagnetic joining of polyolefins to aluminum by evaluating the behavior of hot-melt adhesives derived from polyolefins containing metallic particles. The study aimed at establishing the specific absorption rate (SAR, expressed in W/kg) via electromagnetic simulation using CST Studio Suite software. It was observed that, regardless of particle size, Al was the most efficient particle, while the distribution of particles has a negligible impact on Total SAR values. The most significant beneficial effect of the inserts on the absorption capacity of the hot-melt material is primarily observed with a particle size of 1 μm. When connecting polyolefins to aluminum, the power loss density and SAR values exceed those for bonding polyolefins to polyolefins by at least 10 times, owing to aluminum’s conductive properties, which influence the absorption of additional energy in the hot melt mass, likely due to the Salisbury screen effect generated by the bonding arrangement. For hot melts made from polyethylene, a higher frequency of 5.8 GHz is suggested, which is a newly approved frequency used in advanced industrial applications. This positively impacts the effectiveness and viability of the bonding process of polyolefins to aluminum, resulting in reduced exposure times and/or decreased microwave exposure power. It was observed that the hot melts derived from HDPE and PP yielded greater SAR values. Conversely, the SAR values increase when aluminum is attached to HDPE. As a result, the strongest bond of polyolefins to Al occurs when connecting HDPE to Al using HDPE-based hot melts. The proposed simulation methodology may offer considerable improvement in evaluating the efficacy of bonding technology for dissimilar materials subjected to electromagnetic energy Full article

Background/Objectives: MRI-guided neurovascular interventions could benefit from lower-field systems due to reduced magnetic and radiofrequency hazards. However, safety and practical visibility of commonly used neurointerventional devices at 0.55 T remain insufficiently characterized. We evaluated magnetic field interactions, RF-induced heating, and qualitative device visibility in 11 commercially available and commonly used neurovascular devices on a 0.55 T MRI system. Methods: Eleven devices, including stent retrievers, guidewires, catheters, and one embolization implant, were tested at 0.55 T. Magnetostatic interactions were quantified using the American Society for Testing and Materials (ASTM)-guided deflection methods for translational force (ASTM-F2052) and a two-string suspension apparatus for torque (adapted from Stoianovici et al.). RF-induced heating was measured in an in vitro perfused cerebral vessel phantom using a 15 min high-specific absorption rate spin echo sequence under static and flow conditions. Qualitative device visibility was assessed using a turbo spin echo (TSE) and balanced steady-state free precession (bSSFP) imaging on each device individually. Results: Eight of eleven devices passed the translational force test, while three devices (D, E, and G), containing significant ferromagnetic components, failed with deflection angles > 45°. Eight devices passed torque testing, remaining below the critical threshold in all rotation positions; three devices (D, G, and J) failed by exceeding the 54° criterion, including one guidewire and two devices with braided/coiled metallic structures. Under static conditions, RF-induced heating ranged from negligible to 10.4 °C (maximum in device D) and generally decreased under flow; in the flow configuration, temperature rise remained below 2 °C for 6/11 devices. Qualitative imaging performance differed by sequence, with bSSFP enabling improved delineation of device structure (best for devices A, C, and H), whereas devices D, E, F, and J produced extensive signal voids that precluded reliable visualization in both sequences. Overall, three devices satisfied all safety criteria while remaining clearly visible under MRI. Conclusions: Devices that pass safety thresholds at 0.55 T can serve as candidates for further sequence optimization and preclinical workflow development, enabling the design of low-SAR, device-compatible imaging protocols tailored for neurointerventional workflows. These results provide key safety data supporting the feasibility of MR-guided neurovascular procedures at 0.55 T. Full article

A dual-band flexible wearable MIMO antenna with two operating modes, namely low-frequency narrowband and high-frequency broadband, is proposed and investigated in this paper. The antenna is based on a polyimide (PI) flexible printed circuit (FPC) substrate and has a compact size (90 mm × 40 mm × 0.1 mm), enabling easy integration into helmet-mounted devices. The antenna elements are fed by a coplanar waveguide (CPW) and integrated with a ground decoupling structure, achieving an isolation of at least 23.4 dB between the two ports across the entire operating frequency band. In addition, the impedance-matching characteristics of the antenna under bending conditions and the Specific Absorption Rate (SAR) of this MIMO antenna in a 1 g human-tissue model at 3.7 GHz and 4.6 GHz were evaluated. The results indicate that the antenna’s key electromagnetic performance remains relatively stable under bending conditions, and the SAR values comply with international limit requirements, verifying its feasibility for application in head-worn terminals. With an impedance bandwidth of −10 dB, this antenna achieves dual-band coverage at 3.42–3.84 GHz (relative bandwidth of 11.6%) and 4.37–7.80 GHz (relative bandwidth of 56.4%), effectively meeting the requirements of 5G/6G communication frequency bands. Full article

This work presents the design of a compact, wideband circular microstrip patch antenna for microwave imaging-based brain tumor detection. The main contribution is the development of a compact antenna structure incorporating enhanced ground-plane slot modifications, which significantly improves impedance bandwidth while maintaining a small electrical size, making it highly suitable for medical imaging systems. In addition, the study integrates antenna design, safety evaluation, and microwave imaging analysis within a unified framework to assess tumor localization feasibility using a realistic head model in CST Microwave Studio. The proposed antenna is fabricated on an FR-4 substrate with dimensions of 37 × 54.5 × 1.6 mm³, corresponding to an electrical size of 0.176λ × 0.260λ × 0.0076λ at the lowest operating frequency of 1.43 GHz. Ground-plane slot enhancements are introduced to achieve wideband performance, resulting in an impedance bandwidth from 1.43 to 4 GHz and a fractional bandwidth of 94.7%. The antenna exhibits a maximum realized gain of 3.7 dB. To evaluate its suitability for medical applications, specific absorption rate (SAR) analysis is performed using a realistic human head model at multiple antenna positions and at 1.5, 2.1, 2.5, 3.3, and 3.9 GHz frequencies. The computed SAR values range from 0.109 to 1.56 W/kg averaged over 10 g of tissue, satisfying the IEEE C95.1 safety guideline limit of 2 W/kg. For tumor detection assessment, time-domain simulations are conducted in CST Microwave Studio using a monostatic radar configuration, where the antenna operates as both transmitter and receiver at twelve angular positions around the head with 30° increments. The collected scattered signals are processed using the Delay-and-Sum (DAS) beamforming algorithm to reconstruct dielectric contrast maps and localize the tumor. It should be noted that the tumor-imaging demonstrations presented in this work are based on numerical simulations, while experimental validation is limited to the characterization of the fabricated antenna. Nevertheless, the findings indicate that the proposed antenna is a promising candidate for noninvasive, low-cost microwave brain tumor imaging applications. Full article

Electromagnetic field-based stimulation has emerged as a promising noninvasive approach for enhancing bone fracture healing. Beyond conventional pulsed electromagnetic field (PEMF) therapies employing spatially uniform fields, dielectrophoretic-force-based (DEPF) stimulation exploits electromagnetic field non-uniformities to induce localized interactions to enhance fracture healing. However, the thermal behavior associated with DEPF-driven PEMF exposure in the presence of metallic orthopedic implants remains largely unexplored. In this study, the thermal response of tissue-like tibia phantoms with and without metallic implants is investigated using an integrated experimental and numerical framework. A custom-designed conical coil is employed to generate non-uniform DEPF excitation capable of affecting the fracture site. Surface temperature evolution is measured using infrared thermal imaging, while electromagnetic power absorption is quantified through specific absorption rate (SAR)-based thermal measurement coupled with a bio-heat formulation. Anatomically realistic tibia phantoms reconstructed from computed tomography data are fabricated via a 3D printer to represent clinically relevant fracture configurations. Experimental results show that the metallic implant exhibits a rapid temperature increase of approximately $0.4 °\mathrm{C}$ within the first few minutes of exposure, followed by thermal stabilization, corresponding to an effective absorbed power of ${\mathrm{SAR}}_{\mathrm{eff},\mathrm{implant}}\approx 2.2 \mathrm{W}/\mathrm{kg}$ inferred from the initial temperature slope. In contrast, the non-conductive resin phantom displays a temperature rise of only $0.05 °\mathrm{C}$ over the same interval, yielding ${\mathrm{SAR}}_{\mathrm{eff},\mathrm{resin}}\approx 0.8 \mathrm{W}/\mathrm{kg}$. These findings demonstrate that implant-related eddy-current losses dominate localized heating under DEPF excitation, while tissue-like media remain weakly affected. This work provides SAR-based experimental evaluation of DEPF stimulation in implanted tibia fracture models, offering new insight into implant-induced electromagnetic heating and its implications for the safety and optimization of DEPF-based bone-healing therapies. Full article

This paper presents the design, modeling, and numerical validation of a compact artificial magnetic conductor (AMC)–backed flexible UHF RFID tag antenna intended for on-body biomedical and wearable sensing applications. Human tissue proximity typically causes severe detuning, radiation efficiency degradation, and increased specific absorption rate (SAR) for conventional RFID tag antennas. To address these limitations, a miniaturized AMC metasurface based on a modified Jerusalem-cross geometry with meandered and interdigitated features is developed on a high-permittivity biocompatible substrate using CST Studio Software (2025). Full-wave simulations demonstrate that the proposed design, with an ultra-compact footprint of 0.0246 λ² (32.12 mm × 64.24 mm), functions as an effective shielding element, significantly enhancing the tag antenna gain and reading range by an order of magnitude compared to conventional on-body tags, while simultaneously reducing backward radiation and SAR. The antenna demonstrates robust platform tolerance and excellent isolation from the human body, ensuring high reliability. Fabricated on a thin, flexible, biocompatible, silicon-doped dielectric substrate, this device also functions as an epidermal antenna for on-skin health parameter sampling. This research paves the way for advanced, non-invasive wearable medical devices with superior performance. Full article

This paper proposed an ultra-miniaturized four-port dual-band multi-input multi-output (MIMO) antenna designed for wireless biomedical implantable devices, including wireless capsule endoscopy (WCE) and cardiac leadless pacemakers. The antenna supports operation in the wireless medical telemetry service (WMTS) band of 1.395–1.4 GHz and the industrial, scientific, and medical (ISM) band of 2.4–2.4835 GHz for wireless power transfer and data telemetry applications. Miniaturization is achieved through a partial meandered structural configuration, yielding an overall size of 8 × 6.4 × 0.5 mm³. The antenna is encapsulated within implantable biomedical devices containing batteries, sensors, and electronic components, and evaluated in both homogeneous and realistic heterogeneous body phantoms, including the large intestine and heart. The full-wave electromagnetic simulation results demonstrate good performance, including reflection coefficients of −31.19 dB and −30.07 dB, gains of −27.5 dBi and −17.5 dBi, −10 dB impedance bandwidths of 170 MHz and 370 MHz, mutual coupling below 20 dB, and fractional bandwidths of 12.2% and 15.1% at 1.4 GHz and 2.45 GHz, respectively. Specific absorption rate (SAR) analysis satisfies implantation safety limits. Link budget analysis confirms reliable communication over distances more than 20 m in both frequency bands with high-data rates up to 100 Mbps. MIMO channel parameters such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC) confirm the usefulness of the proposed MIMO antenna. Consequently, the proposed MIMO antenna emerges as a highly promising candidate with, ultra-miniaturization, isolation, multiband operation ability with omnidirectional-like radiation pattern characteristics for several biomedical implants in wireless health monitoring systems. Full article

This study presents a computational, simulation-based investigation of the dielectric response of human hand tissues, skin, fat, muscle, and bone to radiofrequency (RF) electromagnetic fields emitted by mobile devices. The widespread adoption of handheld devices and the deployment of fifth-generation (5G) networks, including millimetre-wave (mmWave) bands, have intensified concerns regarding localized human exposure to RF radiation, particularly in the hand, which serves as the primary interface during device operation. Using validated dielectric property datasets, numerical simulations were performed across the frequency range of 0.5–40 GHz, employing the Finite-Difference Time-Domain (FDTD) method to solve Maxwell’s equations, with analytical evaluations conducted in Maple-18. A heterogeneous multilayer hand phantom was developed, and simulations were conducted under controlled exposure conditions, including a transmitted power of 1 W, antenna gain of 2 dBi, and incident power density of 5 W/m², consistent with ICNIRP and NCC safety guidelines. Tissue responses were assessed over a temperature range of 10–40 °C to account for thermal variability. The results demonstrate strong frequency- and temperature-dependent behaviour of dielectric properties, intrinsic impedance, reflection coefficient, attenuation, and specific absorption rate (SAR). At lower frequencies (<1 GHz), RF energy penetrated more deeply with distributed absorption and relatively low SAR values, whereas higher frequencies (3–40 GHz) produced highly localized absorption in superficial tissues, particularly skin and muscle. Increasing temperature led to significant increases in permittivity, conductivity, and SAR, with up to a twofold enhancement observed between 10 °C and 40 °C. These findings confirm that 5G and mmWave exposures result in predominantly surface-confined energy deposition in hand tissues. The study provides a robust computational framework for evaluating hand device electromagnetic interactions and offers quantitative insights relevant to antenna design, exposure compliance assessment, and the development of evidence-based safety guidelines. Full article

This paper proposes a small size meander-line patch antenna which is designed to have biomedical telemetry applications using the Industrial, Scientific and Medical (ISM) band from 2.40 to 2.48 GHz supported by the equivalent circuit model (ECM). Antenna miniaturization is realized by the effective use of several slot structures placed in the rectangular microstrip patch structure, in order to realize electrical length extension and reduce the physical size. The antenna has overall dimensions of 12 × 22 × 0.787 mm³ and is made on a low-loss Arlon AD 450 (ε_r = 4.50 and tanδ = 0.0035) dielectric substrate, which has the desired stable electrical behavior and, importantly, can be used in implantable environments. Experimental validation is done by implanting the fabricated prototype into a laboratory-manufactured tissue-mimicking phantom, and it showed good agreement with simulated results. The designed antenna has a peak gain of 1.29 dBi in free space and −24.99 dBi at a frequency of 2.45 GHz and a fractional impedance bandwidth of about 250 MHz, which will guarantee reliable operation in the face of diversity and fluctuation in the surrounding environment (biological tissues). Furthermore, specific absorption rate (SAR) analysis is carried out in order to comply with international safety standards with peak SAR values kept within the permissible level of 2 W/kg for 10 g averaging tissue. The results show that the proposed antenna provides a good trade-off between the reduction in size, radiation performance and safety to the patient, making it a good candidate for short-range in-body wireless communication, implantable medical devices, and biomedical monitoring systems. Full article