Specific Absorption Rate Values Research Articles

Polynomial chaos expansion of SAR and temperature increase variability in 3 T MRI due to stochastic input data.

Numerical simulations are largely adopted to estimate dosimetric quantities, e.g., specific absorption rate (SAR) and temperature increase, in tissues to assess the patient exposure to the radiofrequency field generated during magnetic resonance imaging (MRI). Simulations rely on reference anatomical human models and tabulated data of electromagnetic and thermal properties of biological tissues. However, concerns may arise about the applicability of the computed results to any phenotype, introducing a significant degree of freedom in the simulation input data. In addition, simulation input data can be affected by uncertainty in relative positioning of the anatomical model with respect to the radiofrequency coil. The objective of this work is the to estimate the variability of SAR and temperature increase at 3 T head MRI due to different sources of variability in input data, with the final aim to associate a global uncertainty to the dosimetric outcomes. A stochastic approach based on arbitrary Polynomial Chaos Expansion is used to evaluate the effects of several input variabilities (anatomy, tissue properties, body position) on dosimetric outputs, referring to head imaging with a 3 T MRI scanner. It is found that head anatomy is the prevailing source of variability for the considered dosimetric quantities, rather than the variability due to tissue properties and head positioning. From knowledge of the variability of the dosimetric quantities, an uncertainty can be attributed to the results obtained using a generic anatomical head model when SAR and temperature increase values are compared with safety exposure limits. This work associates a global uncertainty to SAR and temperature increase predictions, to be considered when comparing the numerically evaluated dosimetric quantities with reference exposure limits. The adopted methodology can be extended to other exposure scenarios for MRI safety purposes.

Graphene oxide decorated with MnxCo1-xFe2O4 nanoparticles for highly efficiency magnetic hyperthermia

Based on the fact that tumor cells are more thermolabile and less oxygen resistant than normal cells, a novel minimally invasive tumor treatment modality, magnetic hyperthermia (MHT) is proposed. However, magnetic materials, which are necessities in MHT, are toxic to human tissue if they are excessively employed. Thus, magnetic materials with higher specific absorption rate (SAR) and intrinsic loss power (ILP) values becomes imperative to minimize their clinical application while mitigating damage to normal human tissues under identical treatment temperature conditions. In this study, the incorporation of soft magnetic MnFe2O4 into hard magnetic CoFe2O4 was introduced, leveraging the exchange coupling between these materials to enhance the magnetic saturation (Ms). Subsequently, we combined these magnetic nanomaterials with graphene oxide (GO) to establish an efficient heat conduction pathway, further augmenting the specific absorption rate (SAR) value of the resulting magnetic composites. Our findings reveal that the Mn0.5Co0.5Fe2O4-1%GO composite developed in this investigation boasts superior SAR values and intrinsic loss power (ILP) of 49.7 W/g and 5.90 nHm2/kg, respectively, when compared to other magnetic materials. The nanomaterials synthesized in this study have the potential to significantly enhance the effectiveness of tumor magnetothermal therapy.

Evaluation and SAR Analysis of Low Frequency and Broadband Electric Field Exposure Measurement Values in the Home Environment

In this study, the effective value of low-frequency (50 Hz) and high-frequency (700–2500 MHz) broadband electric field exposures was measured for 24 h in four different selected environments in a house. All the statistical values of 1000 data points recorded with two measuring devices for 24 h in each environment are calculated, the most appropriate curves are fitted to the data, and the curves are plotted by expressing their changes with respect to time. All statistical and parametric values of the density and cumulative probability functions of the curves are calculated and plotted. In broadband measurements, the broadband is divided into fifteen sub-bands, but the data are available in only six of these sub-bands. The six-layer human head model is created by using the middle frequencies of the six sub-bands used, and taking the permittivity (εr) and conductivity (σ) of each layer into consideration. The specific absorption rate (SAR) value in the brain is calculated by using the total transmission coefficient of six layers. The SAR value surrounding the head is obtained. These SAR values are interpreted by considering the Federal Communications Commission (FCC) and the Community European (CE) occupational and general public SAR limits.

Synthesis of Cu0.5Zn0.5-xNixFe2O4 nanoparticles as heating agents for possible cancer treatment

Magnetic mixed ferrites with high heating efficacy have attracted lots of attention as a complementary method for cancer treatment via magnetic hyperthermia therapy. In the present study, magnetic Cu0.5Zn0.5-xNixFe2O4 nanoparticles were synthesized via a sol–gel combustion method. The effects of nickel substitution (x = 0.1, 0.2, 0.3, 0.4 and 0.5) on the magnetic and structural properties of the produced nanoparticles were investigated. The produced magnetic nanopowders were studied via X-ray diffraction (XRD), scanning electron microscopy (SEM), simultaneous thermal analysis (STA), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and vibrating-sample magnetometry (VSM) techniques. The results showed that the saturation magnetization and coercivity of ZnCuFe2O4 nanoparticles were strongly affected by nickel substitution in the structure so that saturation magnetization decreased from 55.4 emu/g to 36.0 emu/g, whereas coercivity increased from 87.9 Oe to 156.4 Oe. In addition, saturation magnetization for the Cu0.5Zn0.4Ni0.1Fe2O4 sample increases from 55 to 58.1 emu/g with a rise in calcination temperature from 400 to 700 °C, respectively. The heating efficiency of the samples was investigated under different magnetic fields for magnetic hyperthermia therapy. The Cu0.5Zn0.4Ni0.1Fe2O4 sample exhibits a temperature increase from 37 °C to 49.5 °C during 10 min in the exposure of a magnetic field of 400 Oe and frequency of 200 kHz. The specific absorption rate value calculated for the Cu0.5Zn0.5-xNixFe2O4 nanoparticles was 53.1 W/g. With the increase in the viscosity of the environment, the heating efficiency of nanoparticles is reduced. Despite this decrease, the magnetic characteristics of nanoparticles remained strong enough to envision their usage as heating agents in magnetic hyperthermia.

Fe3O4/CoFe2O4 core-shell nanoparticles with enhanced magnetic properties for hyperthermia application

Fe3O4/CoFe2O4 core/shell nanoparticles with varying shell thickness were fabricated by seed-mediated growth via thermal decomposition method. Ligand exchange process using poly(maleic anhydride-alt-1-octadecene) (PMAO) was performed to prepare the aqueous magnetic fluids from the as-synthesised nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Quantum Design PPMS VersaLab were utilised to characterise morphological and magnetic properties of the sample. XRD results showed that all the particles were single phase with spinel structure and the average crystallite size in the range of 11–17 nm. All particles were spherical in TEM images with similar size compared to results calculated from XRD. Magnetic measurements were performed at different temperatures (50 − 300 K) at 30 kOe. The result showed that the saturation magnetisation (M s) and coercivity (H C) were significantly increased with the formation of hard magnetic shell with varying thickness. The dynamic light scattering (DLS) analysis presented a narrow distribution and zeta potential of −16 to −35 mV, indicating a good stability of the ferrofluids. The cytotoxicity of the FOC3/PMAO ferrofluid, which has the highest SAR value of 372.02 W g−1, was tested on Hep-G2 cell line at different concentrations from 10 to 100 μg ml−1. Less than 30% of the cell was inhibited, indicating that the FOC3/PMAO particles have low toxicity at these tested concentrations. Thus, these as-synthesised core/shell nanoparticles with uniform particle size, high saturation magnetisation, good stability and five-time increased specific absorption rate (SAR) compared to the Fe3O4 core nanoparticles are very promising in hyperthermia and magnetic resonance imaging (MRI) applications.

Magnetic induction heating-assisted synthesis of biodiesel using an alumina/iron oxide nanocatalyst

While generating biodiesel from vegetable oils presents various advantages over fossil fuels, ongoing actions aim to improve the efficiency of this production process. Emphasis is placed on optimizing experimental conditions, including the catalyst selection, reaction media and the energy source for heating and mixing, thereby revealing existing research gaps in biodiesel production. In this sense, we have designed a magnetic nanocatalyst based on iron oxide nanoparticles (IONPs) of 18 nm in diameter incorporated within an alumina matrix of around 500 nm infused with potassium hydroxide that provides the catalyst's mesoporosity and basicity. Magnetization analyses confirmed the superparamagnetic behaviour of the nanocatalyst at room temperature and a saturation magnetisation high enough to ease magnetic recovery for reuse. Additionally, magnetic nanoparticles can serve as nanoheaters when subjected to an alternating magnetic field. The heating efficiency of the isolated IONPs was assessed under various frequency and field conditions, yielding specific absorption rate values of up to 80 W/g. Such heating capacity has allowed the synthesis of fatty acid methyl ester (FAMEs), which constitute the biodiesel at 65 °C under optimal field conditions (100 kHz and 48 kA/m) and ideal reaction parameters: 5 % catalyst, methanol/oil ratio 12:1 and 6 h of reaction, with a conversion of up to 98.6 % determined through NMR characterization of the FAMEs and a 95.6 % yield. FAMEs presence was confirmed by optimizing a swift and efficient FTIR method and their purity by TLC. Overall, the designed nanocatalyst presented for FAME synthesis, which incorporates magnetic separability and effective heating capabilities, holds great promise for cost reduction and process efficiency.

Design and Modelling of an Induction Heating Coil to Investigate the Thermal Response of Magnetic Nanoparticles for Hyperthermia Applications

Magnetic Field Hyperthermia is a technique where tumours are treated through an increase in local temperature upon exposure to alternating magnetic fields (AMFs) that are mediated by magnetic nano-particles (MNPs). In an AMF, these particles heat-up and kill the cells. The relationship between an AMF and the heating-rate is complex, leading to confusion when comparing data for different MNP and AMF conditions. This work allows for the thermal-response to be monitored at multiple AMF amplitudes while keeping other parameters constant. An induction-heating coil was designed based on a Zero-Voltage-Zero-Current (ZVZC) resonant circuit. The coil operates at 93 kHz with a variable DC drive-voltage (12–30 V). NEC4 software was used to model the magnetic field distribution, and MNPs were synthesised by the coprecipitation method. The magnetic field was found to be uniform at the centre of the coil and ranged from 1 kAm−1 to 12 kAm−1, depending on the DC drive-voltage. The MNPs were found to have a specific absorption rate (SAR) of 1.37 Wg−1[Fe] and 6.13 Wg−1[Fe] at 93 kHz and 2.1 kAm−1 and 12.6 kAm−1, respectively. The measured SAR value was found to be directly proportional to the product of the frequency and field-strength (SARα f Ho). This leads to the recommendation that, when comparing data from various groups, the SAR value should be normalized following this relationship and not using the more common relationship based on the square of the field intensity (SARα f Ho2).

Investigating antitumor therapeutic efficacy using magnetic hyperthermia of Fe3O4 nanoparticles

Four sets of Fe3O4 nanoparticles were synthesized using a one-pot hydrothermal method using ethylene glycol (EG) and water reaction mixture. The EG coated Fe3O4 nanoparticles were characterized using XRD (X-ray diffraction) and DLS (dynamic light scattering). The nanoparticles hydrodynamic sizes are in the range 60-100 nm and showed good dispersibility in water and cellular medium without any aggregation. The specific absorption rate (SAR) under an alternating magnetic field (AMF) was measured to evaluate the magneto hyperthermic effect of the nanoparticles under field amplitudes of 51.85, 43.87, 35.89, and 27.92 kA/m and field frequencies in the range 384.5-167.30 kHz. The nanoparticles synthesized using 30% EG showed the highest SAR value of 372.95 W/g, whereas the particles synthesized using 70% EG showed a SAR value of 217.12 W/g. SAR values show a linear dependency on the AC frequency whereas the field amplitude displayed a nonlinear effect on the SAR. Breast cancer cells (MDA) treated with the nanoparticles for 30 minutes under an AMF of frequency of 384.5 kHz and strength of 24.67 kA/m showed a 50% decrease in cell viability. The cellular viability further decreased to 25% after 24 h treatment under the AMF which is remarkable for the therapeutic application of the nanoparticles. The apoptotic cell death showed a dependency on the AMF frequency and strength combinations.

Circularly polarized implantable MIMO antenna for skin, brain and heart implantation with wide axial ratio bandwidth

SummaryA unique MIMO antenna with circular polarization characteristics that works similarly for skin, brain and heart phantoms has been proposed in this paper. The twin rectangular X‐shaped slot that serves as the basic structure of the proposed antenna is entirely planar and low‐profile but has a defective ground plane. For three different phantoms, the proposed antenna resonates at 2.4–2.45 GHz ISM band. With a dimension of , the antenna exhibits compactness. Rogers RT/duroid 6010 substrate material has been used to fabricate the antenna in order to validate the designed antenna structure. Utilizing the high dielectric material for both substrate and superstrate, both skin‐mimicking gel and minced hog meat were employed in the experiment setup at 2.45 GHz ISM band. At ISM band, −28.3 dBi has been observed has realized peak gain. The obtained fractional bandwidth (FBW) and Axial Ratio Bandwidth (ARBW) values are 30.67% and 45%, respectively. Also, the maximum specific absorption rate (SAR) values are found to be in the acceptable limit regulated by IEEE.

A novel textile-based UWB patch antenna for breast cancer imaging.

Breast cancer is the second leading cause of death for women worldwide, and detecting cancer at an early stage increases the survival rate by 97%. In this study, a novel textile-based ultrawideband (UWB) microstrip patch antenna was designed and modeled to work in the 2-11.6 GHz frequency range and a simulation was used to test its performance in early breast cancer detection. The antenna was designed with an overall size of 31*31 mm using a denim substrate and 100% metal polyamide-based fabric with copper, silver, and nickel to provide comfort for the wearer. The designed antenna was tested in four numerical breast models. The models ranged from simple tumor-free to complex models with small tumors. The size, structure, and position of the tumor were modified to test the suggested ability of the antenna to detect cancers with different shapes, sizes, and positions. The specific absorption rate (SAR), return loss (S11), and voltage standing wave ratio (VSWR) were calculated for each model to measure the antenna performance. The simulation results showed that SAR values were between 1.6 and 2 W/g (10g SAR) and were within the allowed range for medical applications. Additionally, the VSWR remained in an acceptable range from 1.15 to 2. Depending on the size and location of the tumor, the antenna return losses of the four models ranged from 36 to 18.5 dB. The effect of bending was tested to determine the flexibility. The antenna proved to be highly effective and capable of detecting small tumors with diameters of up to 2mm.

A Dual-Band Low SAR Microstrip Patch Antenna with Jean Substrate for WBAN Applications

This paper presents a low-profile dual-band microstrip patch antenna operated at the 2.45/5.8 GHz ISM bands, targeting wireless body area network (WBAN) applications. The proposed antenna is fabricated on a jean substrate measuring 74×82 mm2. The four corners of the conventional rectangular patch are cut to activate an additional operating frequency and to enhance the radiation pattern. The circular slot is added to the radiating patch to fine-tune the desired frequencies. The measured impedance bandwidth of the proposed antenna at 2.45 GHz and 5.8 GHz bands is 3.68% (2.40 GHz–2.49 GHz) and 3.81% (5.67 GHz–5.89 GHz), respectively. The measured maximum gains are 3.08 dBi at 2.45 GHz and 2.15 dBi at 5.8 GHz. Moreover, the antenna’s performance when placed on flat and rounded body surfaces is also investigated. The proposed antenna achieves stable radiation pattern and low specific absorption rate (SAR) value with low complexity in design. The results indicate that the proposed antenna can be a promising candidate for WBAN applications.

A magnetic cross-linked alginate-biobased nanocomposite with anticancer and hyperthermia activities

This research study focuses on a new magnetic nanobiocomposite designed and synthesized by the formation of cross-linked alginate (Alg) hydrogel using CaCl2 cross-linker agent, its modification with flaxseed mucilage hydrogel and silk fibroin (SF) biopolymer extracted, and as well, the in-situ synthesis of Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) in the presence of this biopolymeric substrate. FT-IR, EDX, FE-SEM, XRD, VSM, and TG technical analyses clarified the physical and chemical features of magnetic cross-linked Alg/flaxseed mucilage hydrogel/SF nanobiocomposite. Following the structural characterization of this magnetic natural-based composition, the in-vitro cytotoxicity and hemolysis assay studies with different concentrations resulted in prominent biological outcomes. The survival rates of normal HEK293T cells (95.74%, 94.18%) and breast cancer BT549 cells (79.23%, 77.76%) after 48 and 72 h verified the biocompatibility and anticancer properties of this new nanobiocomposite. Also, less than 5% of the hemolytic effect disclosed its hemocompatibility. Furthermore, a high specific absorption rate value (72.42 W/g) is generated by 1 mg/mL of this magnetic nanobiocomposite. Overall, it can be deduced that magnetic responsive cross-linked Alg/flaxseed mucilage hydrogel/SF nanobiocomposite could functionally perform in magnetic hyperthermia treatment.

Evaluation of neonatal outcomes according to the specific absorption rate values of phones used during pregnancy.

The aim was to compare neonatal outcomes according to cell phone specific absorption rate (SAR) levels and daily time spent on cell phones by pregnant women. Women who gave birth at Konya City Hospital between September 2020 and February 2021 were included in this retrospective study. Gestational ages, birth weight, birth length, head circumference, sex, 5-minute APGAR scores, neonate postpartum resuscitation requirement, delivery type, the model of phone used by the pregnant women, and the average time spent on the phone during a day were recorded. To determine the relation between the SAR values of the phones used and delivering a small for gestational age (SGA) baby, receiver operating characteristic curve analysis was performed. In total 1495 pregnant women were included. The rate of delivering a SGA fetus was significantly higher in women who used phones with higher SAR values (p=0.001). The cut-off value for the SAR level was 1.23 W/kg with 69.3% sensitivity and 73.0% specificity (area under the curve: 0.685; 95% confidence interval: 0.643-0.726). No correlation was found between time spent on the phone and SGA birth rate. Although both phone SAR values and time spent on the phone were higher in the symmetrical SGA group compared to the asymmetrical SGA group, the difference was not significant (p>0.05). Although the women who had preterm delivery had higher phone SAR values and had spent more time on the phone compared to those who had term deliveries, the difference was again not significant (p>0.05). As the SAR values of cell phones used during pregnancy increased, there was a trend towards delivering a SGA baby.

Evaluation of Antiproliferative Properties of CoMnZn-Fe2O4 Ferrite Nanoparticles in Colorectal Cancer Cells.

The PEG-coated ferrite nanoparticles Co0.2Mn0.6Zn0.2Fe2O4 (X1), Co0.4Mn0.4Zn0.2Fe2O4 (X2), and Co0.6Mn0.2Zn0.2Fe2O4 (X3) were synthesized by the coprecipitation method. The nanoparticles were characterized by XRD, Raman, VSM, XPS, and TEM. The magnetic hyperthermia efficiency (MH) was determined for PEG-coated nanoparticles using an alternating magnetic field (AMF). X2 nanoparticles displayed the highest saturation magnetization and specific absorption rate (SAR) value of 245.2 W/g for 2 mg/mL in a water medium. Based on these properties, X2 nanoparticles were further evaluated for antiproliferative activity against HCT116 cells at an AMF of 495.25 kHz frequency and 350 G strength, using MTT, colony formation, wound healing assays, and flow cytometry analysis for determining the cell viability, clonogenic property, cell migration ability, and cell death of HCT116 cells upon AMF treatment in HCT116 cells, respectively. We observed a significant inhibition of cell viability (2% for untreated control vs. 50% for AMF), colony-forming ability (530 cells/colony for untreated control vs. 220 cells/colony for AMF), abrogation of cell migration (100% wound closure for untreated control vs. 5% wound closure for AMF), and induction of apoptosis-mediated cell death (7.5% for untreated control vs. 24.7% for AMF) of HCT116 cells with respect to untreated control cells after AMF treatment. Collectively, these results demonstrated that the PEG-coated (CoMnZn-Fe2O4) mixed ferrite nanoparticles upon treatment with AMF induced a significant antiproliferative effect on HCT116 cells compared with the untreated cells, indicating the promising antiproliferative potential of the Co0.4Mn0.4Zn0.2Fe2O4 nanoparticles for targeting colorectal cancer cells. Additionally, these results provide appealing evidence that ferrite-based nanoparticles using MH could act as potential anticancer agents and need further evaluation in preclinical models in future studies against colorectal and other cancers.

Analysis and implementation of shorting pins in microstrip patch antenna for SAR reduction

Specific absorption rate (SAR), is the safety measure to quantify human exposure to electromagnetic radiation from mobile phones and other wireless devices, which must be kept within the permissible levels to avoid various health concerns. This paper provides an experimental study on the effectiveness of SAR reduction, using shorting pins, and its corresponding effects on antenna performance. A compact, single-element, microstrip patch antenna design, using shorting pins, with reduced SAR value, is also presented. The surface current distribution on the patch can be modified by the strategic positioning of shorting pins to produce a mushroom shaped radiation pattern having nearly omnidirectional nature in the +Z direction with a near-field null in the vicinity of the user’s direction. This completely minimizes the back lobes in the E-plane, with minor back lobes in the H-Plane creating a deep null, which reduces the SAR value without compromising the signal coverage. The antenna is fabricated and cross-verified by experimental evaluation in an anechoic chamber for return loss, gain, and radiation pattern.

A dual‐band dual‐polarized omnidirectional patch antenna for on‐body application

AbstractAiming at the 3.5 GHz world interoperability for microwave access band and 5.8 GHz industrial scientific medical band, a dual‐band antenna operating in omnidirectional mode is proposed. The antenna uses a single‐layer dielectric substrate made of FR‐4, which is cheap and easy to process. It uses circular patches and metal branches to generate orthogonal electric fields to achieve circular polarization. At the same time, the upper patch is symmetrically slotted in a T shape, so that the patch produces two resonance frequencies. The measured impedance bandwidth of the antenna in circular polarization on‐body mode and linear polarization on‐body mode is 110 MHz (3.41–3.52 GHz) and 460 MHz (5.42–5.88 GHz), respectively. In addition, the antenna shows good performance under bending conditions and close to human tissue. At the same time, the low specific absorption rate value proves that the antenna is safe to wear on the human body.

Implanted Rhombus Ring Partial Inset-Fed Circularly Polarized Microstrip Monopole Antenna for WBAN Applications

In the present article, a design approach to accomplish circular polarization-based rhombus ring microstrip-fed monopole antenna working at 5.8 GHz for wireless body area network (WBAN) applications is proposed. The input impedance calculation using an electromagnetic theory of transmission line in a travelling wave coupled to the parallel-plate inductor model is conducted. Radiated electric field pattern calculation of the conventional square ring microstrip patch antenna (MSPA) using Biot and Savart’s law is reported. The circular polarization of the proposed antenna is accomplished by loading the radiating path with a capacitive element sectioned in the neighbourhood of the feed line. The proposed planar monopole antenna of volume 0.38λ0×0.38λ0×0.029λ0 (λ0 is evaluated at the resonant frequency of 5.8 GHz) achieves a -10 dB impedance bandwidth of 86.20% in the band (3-8 GHz) with a stable real gain of 8.29 dBic in circular polarization at the resonant frequency of 5.8 GHz and axial ration bandwidth of about 32.75% in the (5-6.9 GHz) band. Specific absorption rate (SAR) evaluation of the studied antenna is computed numerically on a part of the human phantom model to justify its use in WBAN applications. It is noted that the maximum amount of radiation absorbed by a part of the human phantom model is limited to a maximum SAR value of 1.45 W/kg and 0.754 W/kg on 1 g and 10 g of tissue mass, respectively. The prospective design has been fabricated and tested, and the experimental results are in good agreement with the simulation outcomes.

Design and Analysis of a Quad-Band Antenna for IoT and Wearable RFID Applications

The role of antennas in wireless communication is critical for enabling efficient signal transmission and reception across various frequency bands, including those associated with IoT (Internet of Things), X-band, S-band, and RFID (radio-frequency identification) systems. This paper presents a small quadruple-band antenna with 25 × 40 × 1.5 mm3 dimensions designed for diverse wireless applications. It is adept at operating in the S-band (2.2 GHz), wireless local area network (WLAN) (5.7 GHz), microwave RFID frequency band (5.8 GHz), and X-band (7.7 GHz and 8.3 GHz). While the majority of existing research focuses on antennas covering two or three bands, our work stands out by achieving quad-band operation in the proposed antenna design. This antenna is constructed on a semiflexible Rogers RT5880 substrate, making it well-suited for wearable applications. Computer Simulation Technology (CST) Microwave studio (2019) simulation package software is chosen for design and analysis. The antenna design features a comb-shaped radiating structure, where each “tooth” is responsible for resonating at a distinct frequency with an appropriate bandwidth. The antenna retains stability in both free space and on-body wearability scenarios. It achieves a low specific absorption rate (SAR), meeting wearable criteria with SAR values below 1.6 W/Kg for all resonating frequencies. The proposed antenna demonstrates suitable radiation efficiency, reaching a maximum of 82.6% and a peak gain of 6.3 dBi. It exhibits a bidirectional pattern in the elevation plane and omnidirectional behavior in the azimuth plane. The antenna finds applications across multiple frequencies and shows close agreement between simulated and measured results, validating its effectiveness.

Development of experimental device for inductive heating of magnetic nanoparticles

Inductive heating using magnetic nanoparticles is a critical process extensively investigated for cancer treatment. However, the high cost of commercially available equipment hinders its accessibility for many research groups. In response, this paper introduces a simple electronic circuit with low-cost components, making it easy to construct even for non-electronic experts. Operating within the 50–200 kHz range, the circuit employs a parallel inductor-capacitor configuration, providing a maximum induction magnetic field of 23.6 mT. Ltspice software simulations align well with oscilloscope measurements. Using commercial iron oxide nanoparticles (∼16 nm) in water suspensions (1–10 mg ml−1), the device exhibited a concentration-dependent reduction in specific absorption rate values, consistent with literature findings. Hyperthermia temperatures were achieved in a few minutes at 52.5 kHz and 23.6 mT in the highest concentration. At 81.9 kHz and 21.5 mT, a temperature of 93 °C was achieved after 22 min at 10 mg ml−1. Additionally, the device demonstrated stable and safe operation over a 100 min period, as validated by an ice-melting experiment. These results highlight the device’s efficacy for hyperthermia experiments in both biological and non-biological systems, particularly advantageous for larger nanoparticles in a blocked state. The proposed device holds significant potential for contributing to hyperthermia studies across diverse research groups. Future development will focus on frequency adjustment without reducing the alternating magnetic field amplitude and a thorough investigation of field homogeneity inside the coils.

Preparation of stable colloidal dispersion of surface modified Fe3O4 nanoparticles for magnetic heating applications

The effect of surface modification on enhancing the magnetic heating behavior of magnetic nano fluids were investigated, for this purpose Fe3O4 nanoparticles were synthesized using co-precipitation method and surface modification was done using citric acid, ascorbic acid, tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and polyethylene glycol (PEG). Experimental heating tests using AC magnetic field were done in the frequency of 100 kHz and different magnetic field (H) intensities. Theoretically the specific absorption rate (SAR) in magnetic nano fluids is independent of nanoparticles concentration but the experimental results showed different behavior. The theoretical SAR value @ H = 12kA.m–1 for Nano fluids containing bare Fe3O4 nanoparticles was 11.5 W/g but in experimental tests the obtained value was 9.72 W/g for nano fluid containing 20,000 ppm of dispersed nanoparticles. The experimental SAR calculation was repeated for sample containing 10,000 ppm of nanoparticles and the results showed increase in experimental SAR that is an evidence of nanoparticles agglomeration in higher concentrations. The surface modification has improved the dispersion ability of the nanoparticles. The Ratio of SAR, experimental, 20000ppm to SAR, experimental, 10000ppm was 0.85 for bare Fe3O4 nanoparticles dispersion but in case of surface modified nanoparticles this ratio has increased up to 0.98 that shows lower agglomeration of nanoparticles as a result of surface modification, although on the other hand the surface modification agents were magnetically passive and so it is expected that in constant concentration the SAR for bare Fe3O4 nanoparticles to be higher than this variable for surface modified nanoparticles. At lower concentrations the dispersions containing bare Fe3O4 nanoparticles showed higher SAR values but at higher concentrations the surface modified Fe3O4 nanoparticles showed better results although the active agent amount was lower at them. Finally, it should be noted that the nanoparticles that were surface modified using polymeric agents showed the highest decrease in experimental SAR amounts comparing theoretical results that was because of the large molecules of polymers comparing other implemented surface modification agents.