Specific Absorption Rate Values Research Articles

Enhancement of off-body communications with a low-SAR, high-gain multiband patch antenna designed with a quad-band artificial magnetic conductor

Abstract The increasing demand for wireless communication has emphasized the need for multiband antennas. This study presents a novel design for a multiband antenna with reduced specific absorption rate (SAR), high gain, and improved front-to-back ratio (FBR) achieved through the integration with a 4 × 4 artificial magnetic conductor (AMC) surface. The proposed antenna covers a wide range of wireless frequency bands, including Industrial, Scientific, and Medical, Wireless Local Area Network, Worldwide Interoperability for Microwave Access, Wi-Fi 6E, and 7, with resonating frequencies at 2.4, 3.2, 5.5, 7.5, and 10 GHz. The AMC unit cell creates four zero-degree reflection phases with double negative properties at 2.5, 3.8, 5.5, and 7.5 GHz. The compact design measures 0.23λ0 × 0.296λ0 × 0.0128λ0 and placed 0.104λ0 above an AMC surface of size 0.512λ0 × 0.512λ0 × 0.1296λ0. This structure enhances the gain by up to 8.55dBi at 6.01 GHz. The proposed antenna has −10 dB impedance bandwidth for these corresponding frequencies viz 2.34–2.43 GHz (3.77%), 2.81–3.83 GHz (30.72%), 4.82–6.21 GHz (25.20%), 7–7.65 GHz (8.87%), and 8.06–10.31 GHz (24.5%). An overall average percentage reduction value of SAR taken at these frequencies has been found to be 96.11% with AMC structure. The antenna sample was successfully fabricated, and the experimental results have been found to match well with the simulation results. This integrated design offers a promising solution for wearable off-body communication devices.

Local SAR management strategies to use two-channel RF shimming for fetal MRI at 3 T.

This study evaluates the imaging performance of two-channel RF-shimming for fetal MRI at 3 T using four different local specific absorption rate (SAR) management strategies. Due to the ambiguity of safe local SAR levels for fetal MRI, local SAR limits for RF shimming were determined based on either each individual's own SAR levels in standard imaging mode (CP mode) or the maximum SAR level observed across seven pregnant body models in CP mode. Local SAR was constrained either indirectly by further constraining the whole-body SAR (wbSAR) or directly by using subject-specific local SAR models. Each strategy was evaluated by the improvement of the transmit field efficiency (average |B1 + |) and nonuniformity (|B1 + | variation) inside the fetus compared with CP mode for the same wbSAR. Constraining wbSAR when using RF shimming decreases B1 + efficiency inside the fetus compared with CP mode (by 12%-30% on average), making it inefficient for SAR management. Using subject-specific models with SAR limits based on each individual's own CP mode SAR value, B1 + efficiency and nonuniformity are improved on average by 6% and 13% across seven pregnant models. In contrast, using SAR limits based on maximum CP mode SAR values across seven models, B1 + efficiency and nonuniformity are improved by 13% and 25%, compared with the best achievable improvement without SAR constraints: 15% and 26%. Two-channel RF-shimming can safely and significantly improve the transmit field inside the fetus when subject-specific models are used with local SAR limits based on maximum CP mode SAR levels in the pregnant population.

Terahertz Microstrip Patch Antenna for Breast Tumour Detection

Breast cancer is one of the most common cancers among Malaysian women. It is critical to discover strategies to detect the tumour early on. Terahertz (THz) frequency provides excellent qualities for detecting tumours such as low photon energy and non-ionising radiation as compared to prior methods such as mammography, ultrasound, and magnetic resonance imaging (MRI) that use optical to X-ray frequencies. The purpose of this work is to analyse and locate a breast tumour as well as to compute the maximum specific absorption rate (SAR) value. It was designed a THz rectangular microstrip patch antenna with an inset feed. To improve the antenna's performance, graphene was used for the patch and polyimide for the substrate. This antenna covered a bandwidth of 31.6 GHz and worked in the frequency range of 0.283-0.599 THz. To identify the location of a tumour, compute the SAR value, and localise the tumour, SAR simulation was used. The maximum SAR shifted to the tumor's position due to greater absorption rate around its tissue due to higher dielectric constant features. It was calculated that 1e-05g of average mass is required to be less than total tissue mass, which is 2.0063e-05g. SAR study revealed a maximum SAR value of 2.49391e+06 W/kg, which was not more than the overall absorption rate for human body safety. The SAR calculation result revealed that the tumour is within the range of the tumor's initial location.

Wearable antenna sensor based on bandwidth-enhanced metasurface for elderly fall assistance detection

With the aggravation of aging, sudden falls have become one of the important causes of death. This article presents a metasurface-based wearable antenna sensor for fall assistance detection of the elderly. The dimension of the wearable metasurface antenna sensor (WMAS) is (50 × 50) mm2, and it works in the C-band-based wireless body area network. Both the metasurface and the slot antenna are printed on the flexible felt substrate, achieving wearability and comfort. The theoretical principle of realizing circular polarization is explained by analyzing the metasurface unit and the metasurface unit array using characteristic mode theory. By loading the metasurface onto the slot antenna, the operating bandwidth is increased by 189 %, and polarization conversion is achieved. As the applied pressure increases, the coupling degree of the metasurface and the slot antenna increases, and the bandwidth and the number of resonance points of the WMAS will increase accordingly. Based on this characteristic, by setting benchmarks for the bandwidth and the number of resonance points, it can be determined whether the elderly have fallen or not. The measured sensitivity of WMAS operating bandwidth and axial ratio bandwidth is 165 MHz/mm and 320 MHz/mm, respectively. By constructing a human tissue model to measure the radiation degree of WMAS to the human body, the results show that the specific absorption rate values are in line with international standards. Experimental results show that the proposed WMAS with broadband, circular polarization, and high sensibility is a promising candidate for assisted fall detection in the elderly.

Specific Absorption Rate and Temperature Distributions in the Human Head with Implanted Deep Brain Stimulation Subjected to Mobile Phone Electromagnetic Radiation

Deep Brain Stimulation (DBS), also known as the brain pacemaker, has gradually evolved from a scientific experiment into an effective clinical treatment for movement disorders as a method of improving movement disorders. At present, there are few studies on the effects of 5G mobile phone antenna radiation on the heads of adult patients implanted with DBS. In this study, COMSOL Multiphysics was used to establish a mobile phone model with a 5G/4G patch antenna, a real human head, and the DBS models. Then, we calculated the specific absorption rate (SAR) of various layers of the head tissues with the mobile phone at different distances from the human head, as well as the temperature change rule of the head and the DBS irradiated by the antenna for 30 min. The simulation results showed that when the frequency is 3500 MHz, the electromagnetic radiation of the phone to the patient’s head is generally greater than that of the 2400 MHz. When at 3500 MHz, the distance between the phone and the head is inversely proportional to the SAR value; thus, when the distance between the phone and the head is 1 cm, the maximum SAR value—which is 1.132 W/kg—appeared in the skin layer of the head with implanted DBS. But it is worth noting that the largest temperature rise appeared in the brain layer at 2400 MHz and at a distance of 1 cm, which is 0.2148 °C. Although the SAR values and temperature rise obtained from all simulations are below the limits of 2 W/kg and +1 °C specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), we still recommend that patients with implanted DBS maintain a distance when using the phones.

Direct Temperature Measurements of Cardiac Stent during MRI Examinations

Nowadays, Magnetic Resonance Imaging (MRI) is considered the gold standard for imaging the brain, spinal cord, musculoskeletal system, head and neck, and complex congenital heart malformations; consequentially, the number of MRI scans in patients with implantable electronic devices has simultaneously increased. During the entire length of the MRI exam, patients are exposed to electromagnetic fields with different characteristics (static, low frequency, radiofrequency fields), which are related to different risks. The scarce available literature about MRI-induced heating on cardiac stents suggests that excessive temperature rise occurs only in unfavorable cases. Ideally, RF safety assessment could be performed during the anamnestic process, but this simulation process’s results are too slow to be performed before patient MRI examination. In this context, we developed a dedicated measurement set-up by focusing our target on the measurement of the heating of a cardiac stent during an MRI examination. Results for the temperature rise trend along the entire stent length during a clinical MRI protocol are shown together with the local Specific Absorption Rate (SAR) values and cumulative equivalent minutes at 43 °C (CEM43°C), in order to ensure the safety of patients with MR-conditional devices, also with a view to not inappropriately preclude their access to MRI scans. The obtained results show that the maximum temperature rise (4.12 °C) is within the limit of 5 °C stated in the stent manual for 15 min of continued scanning with the specific conditions. The maximum temperature rise was in correspondence with the stent tips and calculated SAR confirms the fact that two hotspots are present near the tips of the stent. Finally, the calculated CEM43°C remained well below the proposed threshold for muscle tissue.

Optical, microstructural, and magnetic hyperthermia properties of green-synthesized Fe3O4/carbon dots nanocomposites utilizing Moringa oleifera extract and watermelon rinds

Cancer therapy with targeted-localized heating is one of the breakthroughs in the biomedical field. The incorporation of magnetic nanoparticles and fluorescent nanoparticles was one of the crucial issues for magnetic hyperthermia applications. This research investigates the magnetic hyperthermia properties of green-synthesized Fe3O4/CDs. Fe3O4 nanoparticles were synthesized using the coprecipitation method with Moringa oleifera leaf extract as a reducing agent and stabilizer. In contrast, CDs were synthesized using a hydrothermal method with watermelon rind waste as a carbon source. X-ray diffraction analysis confirmed the presence of cubic inverse spinel and a reduction in crystallite size with increasing CDs concentration. Transmission electron microscopy revealed particle size distributions of 9.7 nm for Fe3O4 and 7.5 nm for Fe3O4/CDs. Scanning electron microscopy showed that CDs were distributed on the surface of Fe3O4. The detection of characteristic FeO, CC, CO, and CO-C bonds indicated the presence of CDs on the surface of Fe3O4. Ultraviolet-visible spectroscopy spectra absorption peaks at 282 nm for CDs and 193 nm for Fe3O4. Photoluminescence spectra indicated shifts from 509 to 505 nm in excitation wavelength for both CDs and Fe3O4/CDs, situated within the green region of visible light. The vibrating sample magnetometer revealed that the nanocomposites displayed characteristics of soft ferromagnetic materials. Furthermore, the specific absorption rate (SAR) value of Fe3O4/CDs was found to be dependent on magnetization. The SAR value of Fe3O4/CDs decreased as the concentration of CDs increased, and the frequency and strength of the AMF increased. Therefore, these results can promote Fe3O4/CDs nanocomposites as a promising candidate for magnetic hyperthermia applications.

CA and/or EDTA functionalized magnetic iron oxide nanoparticles by oxidative precipitation from FeCl2 solution: structural and magnetic study

Four samples containing magnetic iron oxide nanoparticles (MIONs) of various sizes are prepared employing a simple low-temperature method of oxidative precipitation from FeCl2∙4H2O–NaOH–NaNO3 aqueous solution. For the preparation of two samples, the usual oxidation-precipitation synthesis protocol is modified by using ethylenediaminetetraacetic acid (EDTA) chelating agent as a stabilizer of the Fe2+ ions in a solution, which results in the partial capping of the prepared MIONs with EDTA molecules. Three out of four samples are subjected to citric acid (CA) functionalization in the post synthesis protocol. Structural and magnetic properties of the synthesized MIONs are assessed using various experimental techniques (XRD, TEM, Fourier transform infrared, dynamic light scattering, Mössbauer, and SQUID). The average size of spherical-like MIONs is tuned from 7 nm to 38 nm by changing the synthesis protocol. Their room temperature saturation magnetization, M s, is in the range of 43 to 91 emu g−1. Magnetic heating ability, expressed via specific absorption rate value, which ranges from 139 to 390 W/gFe, is discussed in relation to their structural and magnetic properties and the possible energy dissipation mechanisms involved. The best heating performance is exhibited by the sample decorated with EDTA and with a bimodal size distribution with average particle sizes of 14 and 37 nm and M s = 87 emu g−1. Though this sample contains particles prone to form aggregates, capping with EDTA provides good colloidal stability of this sample, thus preserving the magnetic heating ability. It is demonstrated that two samples, consisting of 7 nm-sized CA- or 14 nm-sized EDTA/CA-functionalized superparamagnetic MIONs, with a similar hydrodynamic radius, heat in a very similar way in the relatively fast oscillating alternating current magnetic field, f = 577 kHz.

Simulating the specific absorption rates in different human tissues at 4G frequencies for mobile phones

Employing electromagnetic waves in mobile communication networks has increased the level of human exposure to electromagnetic fields that may result in concerns about health hazards associated involves the soaking up of cellular phone electromagnetic energy. The human body is penetrated by the electromagnetic fields that emit from a cell phone. The specific absorption rate (SAR) that is generated in the human head and body layers usually expresses the thermal effect on human tissue. The main objective of this paper is to investigate the thermal effects of the electromagnetic field induced inside the human head and body through the construction of a simplified model for both. The RF-source and human body models are built by using the ANSYS high-frequency structural simulator (HFSS). A planar inverted-F antenna (PIFA) will use to assign SAR values to different body tissues for the fourth generation (4G) of mobile phone communication at an operational frequency of 2.6 GHz and power radiated of 125 mW. The model is simulated and analyzed to evaluate the SAR induced at different human tissues depending on the source-to-antenna distance and its generated values must not exceed the safe limits for harmful thermal effects.

A Conformal Tri-Band Antenna for Flexible Devices and Body-Centric Wireless Communications.

A conformal tri-band antenna tailored for flexible devices and body-centric wireless communications operating at the key frequency bands is proposed. The antenna is printed on a thin Rogers RT 5880 substrate, merely 0.254 mm thick, with an overall geometrical dimension of 15 × 20 × 0.254 mm3. This inventive design features a truncated corner monopole accompanied by branched stubs fed by a coplanar waveguide. The stubs, varying in length, serve as quarter-wavelength monopoles, facilitating multi-band functionality at 2.45, 3.5, and 5.8 GHz. Given the antenna's intended applications in flexible devices and body-centric networks, the conformability of the proposed design is investigated. Furthermore, an in-depth analysis of the Specific Absorption Rate (SAR) is conducted using a four-layered human tissue model. Notably, the SAR values for the proposed geometry at 2.45, 3.5, and 5.8 GHz stand at 1.48, 1.26, and 1.1 W/kg for 1 g of tissue, and 1.52, 1.41, and 0.62 W/kg for 10 g of tissue, respectively. Remarkably, these values comfortably adhere to both FCC and European Union standards, as they remain substantially beneath the threshold values of 1.6 W/kg and 2 W/kg for 1 g and 10 g tissues, respectively. The radiation characteristics and performance of the antenna in flat and different bending configurations validate the suitability of the antenna for flexible devices and body-centric wireless communications.

Preparation of Fe3O4@pectin nanocomposite hydrogel with high heating efficiency for hyperthermia applications

In this paper, magnetic nanoparticles (Fe3O4) were prepared by the co-precipitation method. The synthesized magnetic nanoparticles were added to the biocompatible polymer, pectin, for synthesizing Fe3O4@pectin (F@P) nanocomposite hydrogels. The structural, morphological, and magnetic characterizations were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and vibrating sample magnetometer (VSM) techniques. The XRD pattern confirmed the existence of the cubic phase of Fe3O4 nanoparticles. The FTIR spectra revealed the incorporation of pectin on the surface of Fe3O4 nanoparticles. The VSM measurement shows the proper magnetization curve of F@P nanocomposites, and good saturation magnetization value (∼33 emu/g). The results of hyperthermia temperature reveal an excellent heating efficiency of F@P nanocomposite hydrogel. The heating efficiency was quantified by a specific absorption rate (SAR) value and was obtained as 214 W/g for F@P nanocomposite hydrogels. This good hyperthermia result with biocompatible polymer (pectin) and hydrogel structure can be used for developing cancer treatment studies.

SAR assessment of miniaturized wideband MIMO antenna structure for millimeter wave 5G smartphones

This work introduces a wideband two-element Multiple-Input Multiple-Output (MIMO) antenna array that covers the desired frequencies of 28/38 GHz for millimeter-wave (mmW) 5G smartphones. The antenna array demonstrates significant isolation and gain increase based on dual-mode planar dipole antennas. The proposed structure was designed using CST Microwave Studio 2019. The design is implemented on a Rogers RT 4003 substrate measuring 14.76 × 8.38 mm2 with a dielectric constant of 3.55. It features two planar dipole antennas positioned at the corners in a perpendicular arrangement to each other. To achieve the desired wideband performance, each element consists of a dipole antenna and a partial ground plane. The spacing between elements, including the parasitic element (PE), is set to 0.5λ₀ to increase isolation between the MIMO antenna elements while keeping complexity and cost to a minimum. Simulation results demonstrate an improvement in mutual coupling between array members, with measured values ranging from −55 dB to −75 dB. The envelope correlation coefficient (ECC) is also improved. Furthermore, enhancements are observed in the total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG). The measured gains of the proposed designs range from 6 dBi across the entire band to 10 dBi at 40 GHz, with a radiation efficiency close to 95%. The antenna performs well in the presence of the handset and human head model during simulation. The study identifies a safe and acceptable specific absorption rate (SAR) value, which provides a low SAR10g of about 0.963 W/Kg at 28 GHz and 0.583 W/Kg at 38 GHz. while maintaining superior efficiency and radiation patterns. When the antennas are constructed and tested, the experimental results surpass the modeling results. The simulation and test findings demonstrate a satisfactory fit within the target band, suggesting that the proposed structure could be applied to millimeter-wave 5G smartphones.

Functional analysis in the body environment for a circularly polarized hybrid reconfigurable textile antenna

This paper presents the functional analysis of a hybrid reconfigurable circularly polarized (CP) textile antenna in different on-body environments. The Tai-Chi sign inspires the current textile antenna design, where the primary radiator and ground elements are sickle-shaped structures. Hybrid reconfigurability was achieved by successfully operating two RF PIN-Diodes in the basal ground plane’s elliptical and rectangular structures. Thus, four switching states are attained by operating the textenna at 3.5, 4.5 and 5.4 GHz in the S1. 4.39 and 5.8 GHz in S2, 5 and 5.9 GHz in S3 and 2.4, 4.3, 5.8, and 9.4 GHz in S4 state. The reconfigurable textenna was devised to function on the human body. Its functional behavior in proximity to the human body was rigorously validated through testing involving bending at various vertical and horizontal angles. Additionally, a Specific Absorption Rate (SAR) analysis was conducted using a three-layered human phantom. The results revealed that the maximum SAR value is below 1.6 W Kg−1 for 1 gram of tissue and 2 W kg−1 for 10 grams of tissue. These findings establish the safe operational parameters for the proposed model. The developed antenna functionalities were also tested in other circumstances like body sweating environment and interaction with body fluids (Blood, Plasma, SBF and DMEM). In these body fluid conditions, a peak gain of 4.88 dBi at S1, 6.97 dBi at S2, 7.99 dBi at S3, and 4.13 dBi at S4, was observed while interacting with Plasma, and the measured efficiency in the above configuration is between 77%–79%. The textenna durability analysis was measured using an electrochemical workstation while interacting with different body fluids. All these results confessed the applicability of the developed antennas for on-body wireless communication applications in different on-body conditions.

Heating efficiency of Gd- and Co-doped γ-Fe2O3 nanoparticles measured by AC magnetometer for magnetic-mediated hyperthermia

Most research groups, including us, utilize calorimetric methods to determine the heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF). Herein, we report the heating efficiencies of γ-Fe2O3 and doped γ-Fe2O3 NPs using AC magnetometry, which allows us to directly calculate the AC hysteresis loop area from which the heating abilities can be deduced. First, all NPs were prepared and thoroughly characterized both structurally (XRD, Rietveld, and TEM) and magnetically (DC and AC magnetization measurements). Structural analysis indicated the phase purity (γ-Fe2O3) and crystallite sizes (∼10 nm) of the as-prepared γ-Fe2O3 NPs. Both DC and AC measurements indicated the superparamagnetic behavior for γ-Fe2O3 and Gd-doped γ-Fe2O3(Gd-5%) NPs, while Co-doped γ-Fe2O3(Co-5%) NPs exhibited ferrimagnetic nature. The heating abilities and specific absorption rate (SAR) values were then analyzed at frequency, f = 132 kHz and several AC field amplitudes (µ0HAC) ranging from 0 to 88 mT. From AC magnetometry calculations, the SAR values were found to be 20 W/g and 17 W/g for γ-Fe2O3 and γ-Fe2O3(Gd-5%) NPs, respectively, while that of γ-Fe2O3(Co-5%) NPs reached SAR of 120 W/g, almost 6 times higher. This high heating efficiency of γ-Fe2O3(Co-5%) sample is attributed to their higher effective anisotropy and saturation magnetization where the heat release is mainly dominated by Neel relaxation. Finally, a viability assay against metastatic breast cancer cells was conducted, indicating the biocompatibility and low toxicity of the as-synthesized γ-Fe2O3 and doped γ-Fe2O3 NPs. These results strongly suggest the promising utilization of γ-Fe2O3 NPs, particularly Co-doped, as a potential candidate for magnetic-mediated hyperthermia.

Effect of Gd substitution on structure, optical and magnetic properties, and heating efficiency of Fe3O4 nanoparticles for magnetic hyperthermia applications

This work presents the synthesis of Fe3-xGdxO4 nanoparticles and the investigation of the impact of Gd content (x) on structural characteristics of nanoparticles, including lattice parameters, crystallite size, and X-ray density. The high-resolution images of Transmission Electron Microscopy reveal that the synthesized Fe3-xGdxO4 nanoparticles have a narrow distribution in size statistics between 9 and 12.5 nm. Interestingly, analyzing different prepared samples reveals that both the saturation magnetization and magnetic anisotropy decrease simultaneously with the increase of band gap while remaining independent of the specific absorption rate (SAR) value. The SAR is greater than that of pure Fe3O4 nanoparticles. In a specific case of Fe2.75Gd0.25O4 sample where the optimal value of x is 0.25, the highest SAR value obtained is 237.4 W/g. Besides, the experimental results demonstrate an optimal doping content with the highest SAR value of Fe2.75Gd0.25O4 nanoparticles along with the theoretical explanation by analyzing the Linear Theory Response framework based on the relationship between magnetic anisotropy and diameter with SAR value. The theoretical and experimental evidence fully demonstrate that doping is an effective approach for optimizing as-synthesized NPs to enable efficient hyperthermia applications.

Annular Ring UWB Wearable Textile Antenna for Telemetry and Healthcare Applications

A wearable microstrip UWB antenna employing jeans textile material as a substrate is proposed and analyzed. Two variants of conducting material comprising copper tape and copper wire of thickness of 0.1mm are utilized as patch and ground. The overall antenna volume is 50 × 50 × 1 mm3 with an impedance bandwidth of 24.13 GHz (0.87 to 25 GHz) and a peak gain of 10.93 dB at 14.80 GHz. The design comprising an annular ring structure with connecting feed at the optimized location has been analyzed and optimized using FEM based ANSYS High-Frequency Structural Simulator. The low values of Specific Absorption Rate (SAR) 1.23W/kg, 1.26W/kg, and 0.64W/kg averaged over 1-g of tissue for arm, leg, and head respectively at 2.45 GHz validate the antenna design for wearable telemetry applications. The proposed design is also analyzed under different bent radii for wearable applications. Measured results for both prototypes agree well with the simulated results.

Electric field and SAR distribution in the vicinity of dental implants exposed to the cell phone electromagnetic radiation

PurposeThe purpose of this paper is to determine the electric field and specific absorption rate (SAR) distribution within biological tissues in the vicinity of dental implants, exposed to the mobile phone radiation.Design/methodology/approachThis research was performed for the frequency of 2.6 GHz, which corresponds to 4G mobile network. The adequate 3D realistic numerical models of the mobile phone user’s head, dental implants and actual smartphone model are created using packages based on the finite integral technique numerical method.FindingsThe obtained results yield to a conclusion that the presence of dental implants affects the increase in electric field intensity and SAR values within biological tissues in its vicinity.Research limitations/implicationsThe presented procedure is limited to the 4G mobile network frequency of 2.6 MHz. The study should be extended to other mobile network frequencies to be more general.Practical implicationsThe criteria for selection of the materials used for dental implants production should be extended with the recommended material characteristics related to their influence on the electric field and SAR distribution, to keep their values in the limits prescribed by standards.Social implicationsThe obtained results provide the foundation for future research in mobile devices’ electromagnetic fields’ influence on human health.Originality/valueThe accurate determination of the electric field and SAR values within different biological tissues and organs in the vicinity of dental implants exposed to mobile phone electromagnetic radiation, demands highly realistic model of observed biological structures. For purposes of the current study, the procedure for modeling of highly nonhomogeneous structure with finite number of homogenous domains having known electromagnetic parameters is described in the paper. As a result, the 3D complex users’ head model formed of 16 homogeneous domains of different electromagnetic parameters is created.

On comparison of sensing capabilities of three-dimensional printed wearable sensors

As reported in the literature, several studies have been performed on the fabrication of wearable sensors using silver-ink screen printing or copper tape on a fabric. But hitherto little has been reported on the four-dimensional capabilities of such sensors fabricated using screen printing/copper tape. In this work, an interfacial layer of thermoplastic polyurethane was three-dimensional printed on the cotton (80%)-lycra (20%) woven fabric. The conductive layers of the sensor were made by screen printing using silver ink or copper tape pasted on fabric to develop two types of wearable sensors. To ascertain the four-dimensional capabilities, a 25 N tensile load as a stimulus was applied to the fabric-based sensor leading to warpage over the silver-ink screen printed surface and delamination of thermoplastic polyurethane from the fabric. The sensor developed as a microstrip patch antenna was designed for a resonance frequency ( Rf) of 2.45 GHz. The specific absorption rate was calculated using a high-frequency structure simulator to be 1.383 W/kg for screen-printed microstrip patch antenna. The specific absorption rate value for copper-tape-based sensors was higher than permissible at 30.52 W/kg, so the patch design was altered (to get it within the range). Finally, the prepared functional sensor with screen-printed silver ink shows an Rf of 2.44 GHz in the industrial, scientific, and medical band, whereas the copper-tape-based sensor has an Rf of 3.04 GHz.

A multiband slot antenna with groundless EBG structure for wearable WLAN/WiMAX applications

ABSTRACT A multiband microstrip antenna integrated with an electromagnetic bandgap (EBG) structure operating at WLAN and WiMAX frequencies is proposed for wearable applications. The antenna consists of a circular patch surrounded by the ground plane, separated by a ring slot. The size of the integrated antenna has been significantly reduced to 0.28 λ ×0.28 λ and thickness of 0.024 λ . A single-layered planar groundless EBG structure has been designed to suppress the wideband of frequencies from 2.2 to 5.4 GHz. An equivalent circuit model is presented to explain the zero-degree reflection phase of the EBG. Integration of the antenna with the EBG structure and a simple resonator bestows operating bands at 2.45 and 5.2, 5.5 and 5.8 GHz with significantly low back radiation. The gain and directivity of the antenna have been increased to 5.41 dB and 6.2 dB, respectively. The Specific Absorption Rate (SAR) of the antenna has been reduced to 0.0859W/kg, which is significantly lower than the admissible SAR value recommended by the Federal Communications Commission (FCC). The antenna is fabricated on an FR4 substrate, and its measured radiation characteristics are well matched to the simulated one.

A threefold increase in SAR performance for magnetic hyperthermia by compositional tuning in zinc-substituted iron oxide superparamagnetic nanoparticles with superior biocompatibility

In this work, we report a ultrahigh specific absorption rate (SAR) performance in Zn-substituted magnetite superparamagnetic (SPM) nanoparticles (NPs) for potential application in magnetic hyperthermia (MHT)-based cancer treatment. Although MHT shows promise in cancer therapy, challenges such as low heating performance, agglomeration of magnetic nanoparticles (MNPs) in blood veins, cytotoxicity, and hemocompatibility have hindered clinical uses. To overcome these challenges, we adopted a reverse-micelles based coprecipitation synthesis approach to prevent MNPs agglomeration and optimized the substitution of Zn ions in magnetite to enhance heating performance. Calorimetric measurements showed SAR values of 118 W/g and 181 W/g for magnetite NPs using the initial slope method (ISM) and Box Lucas method (BLM), respectively. Through our compositional optimizations, we achieved a significant increase in SAR value by consciously substituting Zn2+ ions in the magnetite lattice. Specifically, we obtained SAR values of 325 W/g and 579 W/g (>300% increase) for Zn0.3Fe2.7O4 MNPs using ISM and BLM, respectively. This enhancement can be attributed to improved saturation magnetization (174–257 kA/m) and magneto-crystalline anisotropy (12–24 kJ/m3). The increase in saturation magnetization in the magnetite MNPs can be explained by the higher magnetic moment resulting from increased Zn concentration up to ZnxFe3-xO4(x = 0.3), strengthening the JAB interaction. However, further increases in Zn concentration lead to a decrease in saturation magnetization due to non-collinearity, as described by the Yafet-Kittle model. Our optimized MNPs exhibit improved heating performance, enabling the use of lower MNPs concentrations for cancer treatment, reducing potential toxicity effects. Biocompatibility investigations demonstrated a low hemolysis rate (<5%) in a hemolysis assay with red blood cells and high cytocompatibility (>92% cell viability) in MTT assays for all compositions, confirming their potential suitability for clinical applications. This study offers a promising approach to enhance SAR performance, addressing MHT-based cancer treatment challenges, and improving clinical suitability.