Specific Absorption Rate Values Research Articles

A Wideband Bear-Shaped Compact Size Implantable Antenna for In-Body Communications

Biomedical implantable antennas play a vital role in medical telemetry applications. These types of biomedical implantable devices are very helpful in improving and monitoring patients’ living situations on a daily basis. In the present paper, a miniaturized footprint, thin-profile bear-shaped in-body antenna operational at 915 MHz in the industrial, scientific, and medical (ISM) band is proposed. The design is a straightforward bear-shaped truncated patch excited by a 50-Ω coaxial probe. The radiator is made up of two circular slots and one rectangular slot at the feet of the patch, and the ground plane is sotted to achieve a broadsided directional radiation pattern, imprinted on a Duroid RT5880 roger substrate with a typical 0.254-mm thickness ( ϵr = 2.2, tan δ = 0.0009). The stated antenna has a complete size of 7 mm × 7 mm × 0.254 mm and, in terms of guided wavelength, of 0.027λg × 0.027λg × 0.0011λg. When operating inside skin tissues, the antenna covers a measured bandwidth from 0.86 GHz to 1.08 GHz (220 MHz). The simulations and experimental outcomes of the stated design are in proper contract. The obtained results show that the calculated specific absorption rate (SAR) values inside skin of over 1 g of mass tissue is 8.22 W/kg. The stated SAR values are lower than the limitations of the federal communications commission (FCC). Thus, the proposed miniaturized antenna is an ultimate applicant for in-body communications.

Modelling and Evaluating Electromagnetic Field Exposure in the Multiple-Source Scenario of Using IoT HF RFID Readers.

The aim of this study was to evaluate Specific Absorption Rate (SAR) and induced electric field (Ein) values in the model of a body of a person present near multiple HF RFID readers of a passive proximity integrated circuit card (PICC) working in an IoT application in a public transport vehicle, in order to test the hypothesis that even the simultaneous use of modelled readers does not cause electromagnetic field (EMF) exposure exceeding relevant limits provided for the evaluation of exposure of the general public. SAR and Ein values were evaluated under various exposure scenarios, designed to mimic EMF exposure under realistic conditions of HF RFID readers used on a public bus and covering various reader locations and the presence of a person using a PICC and a bystander. The results obtained from numerical modelling showed that the absorption of EMF emitted continuously by HF RFID readers (located 10 cm away from a body) in the human body may have a significant influence on humans when the PICC reading ranges are longer than 15–23 cm (depending on the class of PICC) for a single reader and when multiple sources of exposure are used in a public transport vehicle—even at reading ranges 15% shorter (13–20 cm).

Optimization of Zn–Mn ferrite nanoparticles for low frequency hyperthermia: Exploiting the potential of superquadratic field dependence of magnetothermal response

Magnetothermal applications of nanoparticles in biomedicine are currently limited by low thermal responses to oscillating magnetic fields on one side and by detrimental physiological effects of electromagnetic radiation on the other side. In this paper, using Zn–Mn ferrite nanoparticles, we demonstrate that an appropriate choice of size and chemical composition of magnetic nanoparticles results in the superquadratic (upto 5th power) dependence of the Specific Absorption Rate (SAR) on a magnetic field (SAR proportional to H5). This gives an opportunity to obtain SAR values above 10 W/g in an oscillating magnetic field, while maintaining the field-frequency product at a level close to the physiological Brezovich's limit ∼ 109A/(m s).

Dosimetry of Microelectrodes Array Chips for Electrophysiological Studies Under Simultaneous Radio Frequency Exposures

Studying the response of neuronal networks to radio frequency (RF) signals requires the use of a specific device capable of accessing and simultaneously recording neuronal activity during electromagnetic fields (EMF) exposure. In this study, a microelectrode array (MEA) that records the spontaneous activity of neurons is coupled to an open transverse electromagnetic (TEM) cell that propagates EMF. We characterize this system both numerically and experimentally at 1.8 GHz. Two MEA versions were compared, for the first time, to determine the impact of their design dissimilarities on the response to EMF. Macroscopic and microscopic measurements using, respectively, a fiber-optic probe and a temperature-dependent fluorescent dye (Rhodamine-B) were carried out. Results indicate that one MEA shows more stability toward the changes of the surrounding environment compared to the other MEA. Using a fiber-optic thermometer, the measured specific absorption rate (SAR) probe value in the center of the more stable MEA was 5.5 ± 2.3 W/kg. Using a Rhod-B microdosimetry technique, the measured SAR value at the level of the MEA electrodes was 7.0 ± 1.04 W/kg. SAR values are normalized per 1 W incident power. Due to the additional metallic planes and a smaller chip aperture, this new recording chip is steadier in terms of SAR and temperature stability allowing high exposure homogeneity as required during biological experiments. A typical neuronal activity recording under EMF exposure is reported.

Study on Some Effects of Radiofrequency on Human Brain

The study is based on determining the impact of radiofrequency on humans by taking into account the SAR (Specific Absorption Rate) value and the temperature elevation through the brain. SAR represents a parameter given by each phone manufacturer regarding the amount of radiation emitted and absorbed by the brain. Was used the FlexPDE software to solve the Pennes’ bioheat equation and to determine the temperature elevation in the brain due to radiofrequency. In the graphical output, it was observed a sudden temperature rise above the normal brain one, of 370C, but stabilization after a short period. This study targets to make people aware of both the advantages and disadvantages of GSM usage.

Towards optimal thermal distribution in magnetic hyperthermia

A linear combination of spherically symmetric heat sources is shown to provide optimal stationary thermal distribution in magnetic hyperthermia. Furthermore, such spatial location of heat sources produces suitable temperature distribution in biological medium even for assemblies of magnetic nanoparticles with a moderate value of specific absorption rate (SAR), of the order of 100–150 W/g. We also demonstrate the advantage of using assemblies of spherical magnetic nanocapsules consisting of metallic iron nanoparticles covered with non magnetic shells of sufficient thickness in magnetic hyperthermia. Based on numerical simulation we optimize the size and geometric structure of biocompatible spherical capsules in order to minimize the influence of strong magneto-dipole interaction between closely spaced nanoparticles. It is shown that assembly of capsules can provide sufficiently high SAR values of the order of 250–400 W/g at moderate amplitudes H0 = 50–100 Oe and frequencies f = 100–200 kHz of alternating magnetic field, being appropriate for application in clinics.

Wireless Electromagnetic Radiation Assessment Based on the Specific Absorption Rate (SAR): A Review Case Study

Employing electromagnetic fields (EMFs) in new wireless communication and sensing technologies has substantially increased the level of human exposure to EMF waves. This paper presents a useful insight into the interaction of electromagnetic fields with biological media that is defined by the heat generation due to induced currents and dielectric loss. The specific absorption rate (SAR) defines the heating amount in a biological medium that is irradiated by an electromagnetic field value. The paper reviews the radio frequency hazards due to the SAR based on various safety standards and organisations, including a detailed investigation of previously published work in terms of modelling and measurements. It also summarises the most common techniques utilised between 1978 and 2021, in terms of the operational frequency spectrum, bandwidth, and SAR values.

Design and analysis of circular microstrip patch probe array for precise specific absorption rate measurement at quad-band

AbstractThis paper distinguishes the design and analysis of 3 × 2 circular microstrip patch probe array for specific absorption rate (SAR) measurement at quad-band. This novel approach consists of FR4 substrate radial dimension of 88 mm and it has six circular array elements with a radius of 17 mm; out of these six elements, three array elements are having rectangular slots with dimensions of 1.8 × 1.5 × 1.5 mm3. The array elements are coupled with six probes which have a dimension of 100 mm with a 2.5 mm tip radius; these six probes are embedded into a tissue-equivalent liquid-filled human head mannequin. In this mannequin, instantaneous SAR at any six positions has been investigated. The proposed design resonates at 1.8, 2.1, 2.4, and 2.5 GHz with a return loss of −11.53, −15.90, −15.73, and −25.49 dB. The circular microstrip probe array is fed by a 50 Ohm coaxial feed. In addition, the 3D human head model analysis is also presented. The precisely estimated SAR values are 0.135, 0.108, 0.167, and 0.244 W/kg at 1 g of tissue. For the traceable measurements, each source of uncertainty budget has been estimated.

Numerical Evaluation of Human Body Near Field Exposure to a Vehicular Antenna for Military Applications.

BackgroundThe use of electromagnetic (EM) technologies for military applications is gaining increasing interest to satisfy different operational needs, such as improving battlefield communications or jamming counterpart's signals. This is achieved by the use of high-power EM waves in several frequency bands (e.g., HF, VHF, and UHF). When considering military vehicles, several antennas are present in close proximity to the crew personnel, which are thus potentially exposed to high EM fields.MethodsA typical exposure scenario was reproduced numerically to evaluate the EM exposure of the human body in the presence of an HF vehicular antenna (2–30 MHz). The antenna was modeled as a monopole connected to a 3D polygonal structure representing the vehicle. Both the EM field levels in the absence and in the presence of the human body and also the specific absorption rate (SAR) values were calculated. The presence of the operator, partially standing outside the vehicle, was simulated with the virtual human body model Duke (Virtual Population, V.3). Several exposure scenarios were considered. The presence of a protective helmet was modeled as well.ResultsIn the area usually occupied by the personnel, E-field intensity radiated by the antenna can reach values above the limits settled by international safety guidelines. Nevertheless, local SAR values induced inside the human body reached a maximum value of 14 mW/kg, leading to whole-body averaged and 10-g averaged SAR values well below the corresponding limits.ConclusionA complex and realistic near-field exposure scenario of the crew of a military vehicle was simulated. The obtained E-field values radiated in the free space by a HF vehicular antenna may reach values above the safety guidelines reference levels. Such values are not necessarily meaningful for the exposed subject. Indeed, SAR and E-field values induced inside the body remain well below safety limits.

Specific absorption rate reduction for sub-6 frequency range using polarization dependent metamaterial with high effective medium ratio

This research study introduces a multi-layered square-shaped metamaterial (MSM) structure for the electromagnetic (EM) absorption reduction in wireless mobile devices. Usually, wireless devices, for example, a cellular phone emits radiofrequency (RF) energy to the surroundings when used it. Moreover, fast-growing wireless communication technologies that support cellular data networks have also motivated this study. Hence, the focus of the research was to reduce the Specific Absorption Rate (SAR) for the Sub-6 frequency range by designing a multi-layered and compact, 10 × 10mm2 sized metamaterial structure that can be attached inside a mobile phone by avowing any overlapping with existing parts. Overall, six distinct square-shaped metamaterials were constructed on 0.25 mm thick Rogers RO3006 substrate material to reach the target of this investigation. Furthermore, numerical simulations of the proposed metamaterial electromagnetic properties and SAR reduction values were performed by adopting Computer Simulation Technology (CST) Microwave Studio 2019 software. From these simulations, the proposed MSM structure exhibited multi-band resonance frequencies accurately at 1.200, 1.458, 1.560, 1.896 GHz (at L-band), 2.268, 2.683 2.940, 3.580 GHz (at S-band) and 5.872 GHz (at C-band). Simultaneously, the proposed MSM structure was simulated in High-Frequency Structure Simulator (HFSS) to authenticate the numerical simulation data. The comparison of simulation data shows that only the primary and last resonance frequencies were reduced by 0.02 and 0.012 GHz, whereas the rest of the frequencies were increased by 0.042, 0.030, 0.040, 0.032, 0.107, 0.080, and 0.020 GHz in sequential order. In addition, the introduced MSM structure manifests left-handed behaviour at all the resonance frequencies. Nevertheless, the highest recorded SAR values were 98.136% and 98.283% at 1.560 GHz for 1 g and 10 g of tissue volumes. In conclusion, the proposed MSM met the objectives of this research study and can be employed in EM absorption reduction applications.

Impact of next-generation 5G cellular communications on honey bees

The article discusses the impact of ultra-high-frequency (microwave) radiation of a new generation of 5G networks on honey bees. It has been shown that alternating electromagnetic fields can have a harmful effect on bees. Exposure standards are considered, an analysis of the 5G electromagnetic radiation (EMR) effect on bees and methods of protection against exposure is carried out. The Specific Absorption Rate (SAR) value was calculated and it was concluded that the specific absorbed power is significantly less than the value causing the thermal effect on a honey bee. EMP protection can be provided by time, distance and shielding. An effective means of protection against the electromagnetic radiation effects is shielding of radiation sources using shields. When shielding high-frequency electromagnetic fields, the induced currents are concentrated near the screen surface; wherein at the penetration distance δ into the screen material the magnitude of components E and H decreases by 2.73 times. The results of calculating the efficiency of shielding bee hives from 5G EMR and energy flux density (EFD) inside bee hives showed the applicability of shields made of aluminum and steel to protect bees from 5G radiation.

Numerical Modeling of Smartphones with WCDMA, LTE, and WLAN Bands for Epidemiological Studies

This paper presents the representative numerical modeling of smartphones with wideband code division multiple access (WCDMA), long-term evaluation (LTE), and wireless local area network (WLAN) bands for epidemiological studies. For this purpose, based on specific absorption rate (SAR) test reports for commercial smartphones released in South Korea from 2013 to 2019, we determined the smartphone size, frequency band categorization, antenna locations, and target 1-g peak-spatial SAR (psSAR) values for a specific anthropomorphic mannequin (SAM) phantom. Numerical results showed that the designed numerical smartphone models yielded good matching and radiation performance, and more importantly, their 1-g psSAR values were within ±16% of the target 1-g psSAR values.

Design and analysis of varactor‐loaded bi‐state switchable active artificial magnetic conductor reflector for wearable antenna integration

A low profile, bi-state switchable, and flexible active AMC (AAMC) reflector metasurface is presented for wearable antenna integration to improve radiation performance with low specific absorption rate (SAR). The unit cell structure contains concentric rectangular rings with 2-varactor diodes. The unit cell is designed on a flexible PDMS substrate with dimensions 20 × 20 × 1 mm3. Controlled DC bias is applied to both varactor diodes. In state-1, that is, on state, the AMC surface resonates at 3.5, 5.8, and 8.1 GHz frequency, and in state-2, that is, off state, it resonates at 3.5, 5.8, and 7.5 GHz frequencies with zero degrees reflection phase. The proposed AAMC reflector performance is analyzed by integrating a 3 × 3 AAMC surface with the quad-band wearable textile antenna designed to resonate at 3.5, 5.8, 7.5, and 8.1 GHz frequencies. By controlling operating voltages of the integrated AAMC, the antenna radiation performance is improved in bi-state by adapting to reflection pattern switching. In On-state, the peak gain (dBi), FBR (dB) of integrated antenna improved to 7.36, 9.05, 8.9, 7.53 and 9.25, 11.9, 19.7, 16.70; In Off-state, the values are improved to 7.8, 8.98, 8.33, 7.92 and 12.24, 11.37, 14.6, 16.85, respectively. The proposed AAMC with antenna integration is fabricated, and its measured results are well satisfying. The low SAR values are obtained under a 2 mm gap (<0.924 W/kg) and direct contact (<1.5 W/kg) as well. The enhanced radiation performance characteristics with the bi-state switchable feature make it preferable for wearable antenna integration to meet current WBAN demands.

Nano‐magnetic Copper Complexes as Double‐Edged Sword against MCF‐7 Breast Cancer Cells

AbstractA multi‐step synthesis and characterization of nano‐magnetic copper complexes [Nano‐magnetite‐Lys@Cu(PPh3)I] and [Nano‐magnetite‐Arg@Cu(PPh3)I] with size of ∼ 12 nm and∼15 nm is reported. Complexes displayed significant anti‐cancer activity against MCF‐7 breast cancer cells with IC50 of 104.38 μg/mL and 95.81 μg/mL respectively as compared to the standard drug cis‐platin (IC50=88.91 μg/mL). The hyperthermia studies of both the complexes revealed remarkable specific absorption rate (SAR) values of 36.83‐85.81 W/g and 97.67‐125.58 W/g with therapeutic temperature of 48 °C and 43 °C respectively. The studies revealed that both the complexes can act as a double edged sword in anti‐breast cancer therapy through combined effect of hyperthermia and chemotherapy.

X-Shaped Slotted Patch Biomedical Implantable Antenna for Wireless Communication Networks

Biomedical implantable antennas have a major role in biomedical telemetry applications. Therefore, a compact-size low-profile implantable antenna working in industrial, scientific, and medical (ISM) band at 915 MHz is presented. The presented antenna is a simple slotted patch fed with a coaxial probe of 50 Ω impedance. The patch consists of four slotted resonators printed on a flexible Roger Duroid RT5880 substrate ( ε r = 2.2 , tan δ = 0.0009 ) with the standard thickness of 0.254 mm. The complete volume of the designed antenna is 7 mm × 7 mm × 0.254 mm ( 0.08 λ g × 0.08 λ g × 0.003 λ g ). The antenna covers the bandwidth from 800 MHz to 1 GHz (200 MHz) inside skin tissue. A good agreement between the simulation and measurements of the antenna has been obtained. Finally, the specific absorption rate (SAR) values have also been analyzed through simulations as 8.17 W/kg inside skin over 1 g of mass tissue. The proposed SAR values are less than the limit of the Federal Communications Commission (FCC). This antenna is miniaturized and an ideal applicant for applications in biomedical implants.

Tailoring Interfacial Exchange Anisotropy in Hard-Soft Core-Shell Ferrite Nanoparticles for Magnetic Hyperthermia Applications.

Magnetically hard–soft core-shell ferrite nanoparticles are synthesized using an organometallic decomposition method through seed-mediated growth. Two sets of core-shell nanoparticles (S1 and S2) with different shell (Fe3O4) thicknesses and similar core (CoFe2O4) sizes are obtained by varying the initial quantities of seed nanoparticles of size 6.0 ± 1.0 nm. The nanoparticles synthesized have average sizes of 9.5 ± 1.1 (S1) and 12.2 ± 1.7 (S2) nm with corresponding shell thicknesses of 3.5 and 6.1 nm. Magnetic properties are investigated under field-cooled and zero-field-cooled conditions at several temperatures and field cooling values. Magnetic heating efficiency for magnetic hyperthermia applications is investigated by measuring the specific absorption rate (SAR) in alternating magnetic fields at several field strengths and frequencies. The exchange bias is found to have a nonmonotonic and oscillatory relationship with temperature at all fields. SAR values of both core-shell samples are found to be considerably larger than that of the single-phase bare core particles. The effective anisotropy and SAR values are found to be larger in S2 than those in S1. However, the saturation magnetization displays the opposite behavior. These results are attributed to the occurrence of spin-glass regions at the core-shell interface of different amounts in the two samples. The novel outcome is that the interfacial exchange anisotropy of core-shell nanoparticles can be tailored to produce large effective magnetic anisotropy and thus large SAR values.

Comparison of the influence of superparamagnetic nanoparticles concentration and coverage on the alternating magnetic field thermal effect

Magnetic nanoparticles (MNP)s of Fe3O4 were synthesized in the co-precipitation reaction of iron chlorides dissolved in water and ammonia water. To produce polyethylene glycol (PEG) coatings of the NMPs, we added PEG to the ammonia water during the fabrication process. Magnetic fluids, ferrofluids, for research were prepared as oleic acid suspension of bare and PEG-coated nanoparticles at four concentrations. The results of the conducted calorimetric experiments confirmed that the efficiency of heating ferrofluids strongly depends on the concentration of nanoparticles in fluids. The results also indicate that the ferrofluids containing PEG-coated NPs heat up more than ferrofluids with bare nanoparticles. They are characterized by a higher specific absorption rate (SAR) value calculated from the initial slope of temperature versus time curve during heating.

Double-Layer Fatty Acid Nanoparticles as a Multiplatform for Diagnostics and Therapy.

Today, public health is one of the most important challenges in society. Cancer is the leading cause of death, so early diagnosis and localized treatments that minimize side effects are a priority. Magnetic nanoparticles have shown great potential as magnetic resonance imaging contrast agents, detection tags for in vitro biosensing, and mediators of heating in magnetic hyperthermia. One of the critical characteristics of nanoparticles to adjust to the biomedical needs of each application is their polymeric coating. Fatty acid coatings are known to contribute to colloidal stability and good surface crystalline quality. While monolayer coatings make the particles hydrophobic, a fatty acid double-layer renders them hydrophilic, and therefore suitable for use in body fluids. In addition, they provide the particles with functional chemical groups that allow their bioconjugation. This work analyzes three types of self-assembled bilayer fatty acid coatings of superparamagnetic iron oxide nanoparticles: oleic, lauric, and myristic acids. We characterize the particles magnetically and structurally and study their potential for resonance imaging, magnetic hyperthermia, and labeling for biosensing in lateral flow immunoassays. We found that the myristic acid sample reported a large relaxivity, superior to existing iron-based commercial agents. For magnetic hyperthermia, a significant specific absorption rate value was obtained for the oleic sample. Finally, the lauric acid sample showed promising results for nanolabeling.

A Soft Surface Based Low Profile Wearable Antenna for Biomedical Telemetry

A soft surface based low profile wearable antenna operating on 5.8 GHz Industrial, Scientific and Medical (ISM) band (5.725-5.875 GHz) is presented for high speed biomedical telemetry. The flexible substrate of Ethylene-Vinyl Acetate (EVA) foam makes the structure water proof, ultra-violet resistant and mechanically stable. First, the basic antenna structure (reference) with inset feeding is designed. Initially, the forward to back power ratio obtained is 14.1 for basic design. The back radiation is further reduced by introducing soft surface around the patch. Use of two different materials as soft surface has been studied and analyzed. The maximum gain of 5.2 dBi and Front to Back Ratio (FTBR) of 25.63 is achieved for the chosen resonant frequency. The absorption of electromagnetic field by the body is reduced by 9.35 % and gain is improved by 23.68/24.40 % with reference to our basic design of antenna without soft surface. The value of Specific Absorption Rate (SAR) is 1.26 W/kg for 10 gm of human body tissue which is within the specified limits. The software simulated and experimented results are presented.

Analysis of a Flexible Dual-Channel Octagonal Coil System for UHF MRI

Nowadays, MRI is focused on using ultra-high static magnetic fields (> 7 T) to increase the signal-to-noise ratio. The use of high fields, on the other hand, requires novel technical solutions as well as more stringent design criteria for specific absorption rate levels, reducing radiative effect and coil resistance. In this paper, two flexible RF coils for 7 T human magnetic resonance, and 298 MHz ultra-high frequency operations were analyzed and characterized. Imaging of lower human limbs is regarded as a case study. The lumped element theory and subsequent numerical simulations were used to fine-tune the single-coil element and the dual-coil array design, respectively. Here, we demonstrate how the shape, size, configuration, and presence of the sample influence the coil performance. The penetration depth of the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -field and the specific absorption rate values have been determined numerically using two numerical surface phantoms: saline and a multilayer human tissue. A preliminary study in the presence of a saline solution phantom has been carried out to develop and validate the dual-coil system. The frequency response of the dual-coil array was measured to assess its robustness when coupled to twelve human volunteers. We found that our design is robust to variations in the anatomical properties of the human thighs, and hence to coil bending. The presented approach can be useful for the implementation of flexible devices with high sensitivity levels and low specific absorption rate.