Specific Absorption Rate Values Research Articles

Influence of Na+ disorder on cytoplasmic conductivity and cellular electromagnetic (EM) energy absorption of human erythrocytes (PONE-D-21-36089).

Cytoplasmic conductivity of human erythrocytes may be significantly disturbed by the composition of the external suspending media. Effects of external NaCl on cytoplasmic conductivity of human erythrocyte (Human Red Blood Cells, HRBC) were investigated in a simple NaCl system. Using thermodynamic theory cytoplasmic conductivities could be calculated from internal [K+], [Na+], [Cl-] and [HCO3-]. Effect of cell volume and cell water changes were introduced and allowed for using the Debye-Hückel-Onsager relation and Walden's rule of viscosity. Cell volume and cell water change of HRBCs were measured in suspending isotonic solutions with conductivities from 0.50 S m-1 up to hypertonic solutions of conductivity of 2.02 S m-1 at selected temperatures of 25°C (standard benchmark temperature) and 37°C (physiological temperature). In isotonic solutions, cytoplasmic conductivity of human erythrocyte decreases with rise in the external media ionic concentration and vice versa for hypertonic solutions. The HRBC is capable of rapidly regulating its volume (and shape) over quite a wide range of osmolality. Specific Absorption Rate (SAR, 900 MHz) values (W kg-1) of electromagnetic radiation are below safe limits at non-physiological 25°C but above legal limits at 37°C [National Council on Radiation Protection and Measurements, NCRP]. However, at 37°C under both hypertonic [Na+] and isotonic but low [Na+], SAR increases further beyond legal limits.

A Compact Dual-Mode Pattern-Reconfigurable Wearable Antenna for the 2.4-GHz WBAN Application

In this communication, a novel reconfigurable antenna operating at both ON- and OFF-body mode is proposed. Initially, the study is dedicated to the construction of omnidirectional and unidirectional radiation using the fundamental TM00 and TM10 mode of the rectangular patch. Then, a rectangular slot is cut out of the patch to shift the resonance of the unidirectional mode to a lower frequency, which not only minimizes the antenna’s overall size but also enables the omnidirectional and unidirectional modes to have overlapping impedance bandwidths. In order to switch arbitrarily, four p-i-n diodes are mounted to control the operating mode. The measured results show that the overlapped bandwidth achieves 3.8% and could cover the 2.4-GHz ISM band. Besides, stable performance of the antenna is obtained when setting on different parts of the human body. The calculated specific absorption rate (SAR) values of both ON- and OFF-body mode meet the standards of the United States and Europe. These properties make the proposed antenna suitable for wearable systems.

A Novel Reverberation Chamber for In Vitro Bioelectromagnetic Experiments at 3.5 GHz

In this article, a mode-stirred reverberation chamber (RC) was designed and proposed for the first time as a cell culture incubator for in vitro electromagnetic waves exposure of adherent cells in tissue culture plates (TCPs). Typical cell incubators require specific conditions, such as temperature of 37 °C and humidity rate of 95%, which are challenging conditions for an RC. The chamber was characterized as an RC through an innovative experimental methodology based on the measurements of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> parameter of the emitting antenna. The proposed RC is adapted for in vitro bioelectromagnetic experiments for simultaneous exposure of up to 10 TCPs under highly homogeneous exposure conditions at 3.5 GHz, i.e., the mid-frequency band of the 5G telecommunication networks. Experimental results showed that the specific absorption rate (SAR) in the exposed samples extracted from temperature measurements was similar (an acceptable maximum variation lower than 30% was observed) in reason of the homogeneity and the uniformity of the field within the chamber. Specifically, measured SAR values were around 1.5 and 1 W/kg per 1 W incident, in 6-well or 96-well plates used for biological exposure, respectively. To validate our system, numerical simulations were performed. Overall, we showed that experimental and numerical SARs are in good agreement with differences <30% considering the standard deviation.

Magnetic hyperthermia of AFe2O4 (A = Fe, Mn, Co) nanoparticles prepared by Co-precipitation method

With 10 million deaths in 2020 cancer remains one of the most challenging diseases in contemporary medicine. Chemotherapy, surgery, and radiation therapy are commonly used to treat tumors. These treatments harm healthy tissues and succeed rarely in advance stages of cancer. Recent studies indicate that magnetic hyperthermia, which involves targeted delivery of magnetic nanoparticles to tumor cells followed by localized remote heating of cancer tissues could revolutionize clinical practice in the treatment of cancer, either as standalone intervention or adjunct to radiotherapy and chemotherapy. Water dispersible magnetic nanoparticles (MNPs) of ferrites (AFe2O4; A = Fe, Mn, Co) are the promising candidates for magnetic hyperthermia due to their high chemical stability, biocompatibility, moderate magnetization and high specific absorption rates (SAR). In this article, we have evaluated magnetic hyperthermia efficiency of water based magnetic fluids of AFe2O4. AFe2O4 NPs were synthesized by chemical co-precipitation method. Nanoparticles were coated with a bilayer of oleic acid and dispersed in water. Structural and magnetic properties of MNPs were investigated by X-Ray diffraction (XRD) and vibrating sample magnetometer (VSM). XRD study revealed that AFe2O4 NPs exhibits cubic inverse spinel structure. Fe3O4 (Ms = 48 emu/g, Mr = 2.60 emu/g, Hc = 49 Oe), MnFe2O4 (Ms = 40 emu/g, Mr = 2.60 emu/g, Hc = 35 Oe) and CoFe2O4 (44 emu/g, Mr = 10.10 emu/g, Hc =440 Oe) NPs exhibits soft ferromagnetic behaviour. Magnetic hyperthermia measurements were performed as a function of magnetic field strength (2–10 mT), field frequency (162–935.6 kHz) for 10 minutes. MNPs exhibits highest SAR values for 10 mT field strength at 935.6 kHz. Amongst the tested MNPs, Fe3O4 possess the highest SAR value (27.35 W/g), followed by MnFe2O4 (1.91 W/g) and CoFe2O4 (0.94 W/g). Considering this, it is concluded that amongst the inverse spinel ferrites AFe2O4, Fe3O4 NPs and most suitable for magnetic hyperthermia applications.

Microstructures, Magnetic Properties and Specific Absorption Rate of Polymer-Modified Bismuth Ferrite Nanoparticles

Bismuth ferrite nanoparticles were successfully synthesized by the co-precipitation method and modified by polyethylene glycol (PEG) 4000. X-ray diffraction patterns showed a sillenite structure of bismuth ferrite (Bi25FeO40) with a crystallite size of 35.0 nm and the new phase appeared after surface modification. The new phase was Bi2Fe4O9. Crystallite size increased after surface modification of nanoparticles with PEG. The highest increase of crystallite size after surface modification with PEG was 40.1 nm. Transmission electron microscopy images showed that samples before and after surface modification were polycrystalline and still agglomerated. Spectra of Fourier transform infrared showed the presence of C-O stretching at 1080 cm-1 and C-H bending vibration at 1342 cm-1 in the bismuth ferrite/PEG sample, which did not appear in bismuth ferrite sample. The magnetic measurement indicated the weak ferromagnetic properties of the samples. Saturation magnetization did not appear after a maximum external magnetic field (15 kOe) was applied. The maximum magnetization of nanoparticles was 0.5 emu/g and tended to decrease to 0.2 emu/g after surface modification with PEG. Optical properties analysis showed a shift in the maximum absorption peak of bismuth ferrite nanoparticles towards a lower wavelength (blue shift) after surface modification of the nanoparticles. The specific absorption rate (SAR) value of nanoparticles increased by increasing an alternating magnetic field (AMF) strength. The SAR values of bismuth ferrite nanoparticles were 48.8, 61.4, and 84.4 mW/g and decreased to 32.0, 45.2, and 83.3 mW/g after surface modification at the AMF strength of 150, 200, and 250 Oe, respectively.

Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Nanoparticles Prepared by Coprecipitations Method for Hyperthermia Therapy

Magnetic nanoparticles (Fe3O4) have considerable attention in various biomedical applications such as biosensors, drug delivery systems in the body, magnetic resonance imaging (MRI), and hyperthermia therapy. Hyperthermia therapy uses heat controlled by applied AC (Alternating Current) magnetic to kill cancer cells. This research aims to determine the effect of changes in temperature caused by the AC magnetic field on the varied magnetic nanoparticle solution. The Synthesize of Fe3O4 used the coprecipitation method to produce Fe3O4 nanoparticles. Mass of Fe3O4 nanoparticles varied of 95 mg and 125 mg. Nanoparticles physical properties were characterized using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and vibrating sample magnetometer (VSM). XRD profiles indicated that magnetic (Fe3O4) nanoparticles were successfully synthesized with a crystal size of 7.76 nm. SEM characterization of Fe3O4 nanoparticles was carried out at a magnification of 150.000 times and the average diameter of Fe3O4 powder nanoparticles was 20 nm. The temperature change measurement was performed using an AC magnetic field of 2.8 mT and frequency of 343 Hz, and time recorded changes temperature in 660 seconds. The temperature changes for solution concentrations of 95 mg and 125 mg were 7.7°C and 9.8°C, respectively. the concentration of solutions affects the value of the Specific Absorption Rate (SAR). The SAR values of each concentration of Fe3O4 solution were 0,0069 W/g and 0.0096 W/g. It proves that Fe3O3 prepared by coprecipitation method has potential for hyperthermia therapy application.

Application of Machine learning to predict RF heating of cardiac leads during magnetic resonance imaging at 1.5 T and 3 T: A simulation study

Predicting magnetic resonance imaging (MRI)-induced heating of elongated conductive implants, such as leads in cardiovascular implantable electronic devices, is essential to assessing patient safety. Phantom experiments have traditionally been used to estimate radio-frequency (RF) heating of implants, but they are time-consuming. Recently, machine learning has shown promise for fast prediction of RF heating of orthopaedic implants when the implant position within the MRI RF coil was predetermined. We explored whether deep learning could be applied to predict RF heating of conductive leads with variable positions and orientations during MRI at 1.5 T and 3 T. Models of 600 cardiac leads with clinically relevant trajectories were generated, and electromagnetic simulations were performed to calculate the maximum of the 1 g-averaged specific absorption rate (SAR) of RF energy at the tips of lead models during MRI at 1.5 T and 3 T. Neural networks were trained to predict the maximum SAR at the lead tip from the knowledge of the coordinates of points along the lead trajectory. Despite the large range of SAR values (∼230 W/kg to ∼ 3200 W/kg and ∼ 10 W/kg to ∼ 3300 W/kg), the root- mean-square error of the predicted vs ground truth SAR remained at 223 W/kg and 206 W/kg, with the R2 scores of 0.89 and 0.85 on the testing set for 1.5 T and 3 T models, respectively. The results suggest that machine learning is a promising approach for fast assessment of RF heating of lead-like implants when only the knowledge of the lead geometry and MRI RF coil features are in hand.

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe3O4 Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field.

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe3O4 phases, high saturation magnetizations (Ms = ~40 emu·g-1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm2/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τR = 5.41 × 10-7 s), which was compared to the Brownian relation time value (τB = 11 × 10-7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe3O4 MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications.

Non-pyrogenic highly pure magnetosomes for efficient hyperthermia treatment of prostate cancer.

We report the fabrication of highly pure magnetosomes that are synthesized by magnetotactic bacteria (MTB) using pharmaceutically compatible growth media, i.e., without compounds of animal origin (yeast extracts), carcinogenic, mutagenic, or toxic for reproduction (CMR) products, and other heavy metals than iron. To enable magnetosome medical applications, these growth media are reduced and amended compared with media commonly used to grow these bacteria. Furthermore, magnetosomes are made non-pyrogenic by being extracted from these micro-organisms and heated above 400°C to remove and denature bacterial organic material and produce inorganic magnetosome minerals. To be stabilized, these minerals are further coated with citric acid to yield M-CA, leading to fully reconstructed chains of magnetosomes. The heating properties and anti-tumor activity of highly pure M-CA are then studied by bringing M-CA into contact with PC3-Luc tumor cells and by exposing such assembly to an alternating magnetic field (AMF) of 42 mT and 195kHz during 30min. While in the absence of AMF, M-CA are observed to be non-cytotoxic, they result in a 35% decrease in cell viability following AMF application. The treatment efficacy can be associated with a specific absorption rate (SAR) value of M-CA, which is relatively high in cellular environment, i.e., SARcell = 253 ± 11W/gFe, while being lower than the M-CA SAR value measured in water, i.e., SARwater = 1025 ± 194W/gFe, highlighting that a reduction in the Brownian contribution to the SAR value in cellular environment does not prevent efficient tumor cell destruction with these nanoparticles. KEY POINTS : • Highly pure magnetosomes were produced in pharmaceutically compatible growth media • Non-pyrogenic and stable magnetosomes were prepared for human injection • Magnetosomes efficientlydestroyed prostate tumor cells in magnetic hyperthermia.

Structural, magnetic, and biocompatibility evaluations of chromium substituted barium hexaferrite (Co2–Y) for hyperthermia application

In the present work, chromium-substituted cobalt-based Y-type barium hexaferrite ceramics having a general formula of Ba2Co2Fe12-xCrxO22 (0.0 ≤ x ≤ 0.5) have been studied to evaluate its potential candidacy as an optional replacement for various soft ferrite materials in the field of magnetic hyperthermia. The as-obtained ferrite powders are characterized for structural, magnetic, and morphological properties after being calcined at 1200 °C for 2 h. The structural parameters confirm single-phase nanocrystalline Y-type barium hexaferrite formation within all the samples. The room temperature magnetic parameter, i.e., saturation magnetization (Ms), is found to decrease (from 39.07 to 33.50 emu/g), and the coercive field (Hc) is increased (86.87–281.84 Oe) consistently. Later, oleic acid-coated ferrite samples' heating capability is governed within the applied AC magnetic field (25 mT at a frequency of 114.1 kHz) in terms of specific absorption rate (SAR) using time-dependent temperature performance. The superiority of the sample having the greatest SAR value (84.39 w/g for Ba2Co2Fe11.7Cr0.3O22) is interrelated with the particles' geometry, size distribution, magnetic parameters, and surface chemistry obtained from the XPS analysis. This sample is further analyzed for its biocompatibility performance against the MG-63 cell line; the results indicate that it may be a potential candidate for magnetic hyperthermia due to its significant SAR & ILP value along with better biocompatibility.

SAR reduction using dual band EBG method based on MIMO wearable antenna for WBAN applications

A wearable ultra-wideband MIMO antenna using conductor and polyester fiber fabrics is proposed in this paper. The antenna’s total dimension is 115 × 70 mm2. As a result, the antenna can be installed on curved or bent surfaces due to its flexibility. This proposed antenna has a frequency range of 2 GHz – 30 GHz, a gain of 3.75 dBi on average, and a correlation coefficient of 0.5. That can be utilized for interior installation of the 5G frequency spectrum (2.6 GHz and 26 GHz), as well as WBAN application (2.4 GHz, 5.2 GHz, and 3.1 GHz – 10.6 GHz). Additionally, the researchers designed an electromagnetic band gap (EBG) and constructed a square loop plate with a square plate that reflects resonance characteristics in the 2.4 GHz and 5.2 GHz bands by placing unit cells in 3 × 5 cells to decrease the antenna’s specific absorption rate (SAR). The proposed antenna with EBG could minimize the SAR values to 0.088 W/kg and 0.070 W/kg, which obtains a gain of 6.59 dBi and 11.6 dBi, at 2.4 GHz and 5.2 GHz, respectively. Also, the results are lower than the conventional SAR value of 2.0 W/kg at 10 g.

DUAL-BAND HALF-CIRCULAR RING IMPLANTABLE ANTENNA WITH METAMATERIAL SRR FOR BIOMEDICAL APPLICATIONS

This paper presents a half-circular ring antenna with a rectangular slot that operates in the industrial, scientific, and medical (ISM) band at 2.45 GHz. A metamaterial (MTM) split-ring resonator operating in the lower ISM band at 0.9 GHz is added to the proposed implantable antenna in order to obtain a dual-band frequency result of 0.9 and 2.45 GHz. Some methods of miniaturization are used in the design of the proposed antennas, such as the addition of a MTM resonator to the antenna, the use of the Roger 3010 with its high permittivity, the shorting pin to connect the patch and the ground plane, and slot shapes. To check the presence of the MTM, the permeability is extracted by the Nicolson method. A high-frequency structure stimulator is used to design and simulate the proposed antenna in free space, one-layer, and three-layer tissue models. The specific absorption rate values and the maximum input power for the antenna with and without the MTM resonator are also calculated.

On the Performance of a Miniaturized Reactive Loaded Monopole Antenna for Ex Vivo Catheter Applications

In this paper, we propose a miniaturized series L-C loaded monopole antenna for catheter application in microwave ablation systems. Initially, a quarter wavelength long monopole antenna (Design1), having length 30 mm (≈ 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> represents the free-space wavelength at 2.4 GHz operating frequency) using series LC loading concept is designed. The initial design is further extended to a miniaturized version (Design2) having length 5 mm (≈ 0.04λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), showing nearly 83% size reduction compared to its former.Both the antennas are designed and simulated by immersing inside high permittivity egg white phantom (ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>r</i></sub> = 63.84). Antenna Design 1 and 2 exhibit good impedance matching ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < –12 dB) at and around the operating frequency with uniform monopolar radiation pattern having co-to-cross isolation of nearly 30-35 dB. Further, the in-phantom Specific Absorption Rate (SAR) values for both antennas are evaluated using simulation and verified with the measured SAR values such as 22 W/kg and 19.6 W/kg for Design1 and 2 respectively, using an in-house experimental setup. Moreover, the microwave ablation property of the proposed antennas is studied using simulated transient thermal gradient which translates to ablation zone formation. Here, Design 2 shows the advantage of having a low invasive diameter of 1.5 mm and near unity aspect ratio (AR) for the ablation zone as compared to Design1.

A 37 GHz Millimeter-Wave Antenna Array for 5G Communication Terminals

This work presents, design and specific absorption rate (SAR) analysis of a 37 GHz antenna, for 5th Generation (5G) applications. The proposed antenna comprises of 4-elements of rectangular patch and an even distribution. The radiating element is composed of copper material supported by Rogers RT5880 substrate of thickness, 0.254 mm, dielectric constant (εr), 2.2, and loss tangent, 0.0009. The 4-elements array antenna is compact in size with a dimension of 8 mm × 20 mm in length and width. The radiating patch is excited with a 50 ohms connector i.e., K-type. The antenna resonates in the frequency band of 37 GHz, that covers the 5G applications. The antenna behavior is studied both in free space and in the proximity of the human body. Three models of the human body, i.e., belly, hand, and head (contain skin, fat, muscles, and bone) are considered for on-body simulations. At resonant frequency, the antenna gives a boresight gain of 11.6 dB. The antenna radiates efficiently with a radiated efficiency of more than 90%. Also, it is observed that the antenna detunes to the lowest in the proximity of the human body, but still a good impedance matching is achieved considering the −10 dB criteria. Moreover, SAR is also being presented. The safe limit of 2 W/kg for any 10 g of biological tissue, specified by the European International Electro Technical Commission (IEC) has been considered. The calculated values of SAR for human body models, i.e., belly, hand and head are 1.82, 1.81 and 1.09 W/kg, respectively. The SAR values are less than the international recommendations for the three models. Furthermore, the simulated and measured results of the antenna are in close agreement, which makes it, a potential candidate for the fifth-generation smart phones and other handheld devices.

Numerical Modeling and Computer Simulation of a Meander Line Antenna for Alzheimer's Disease Treatment, a Feasibility Study.

Alzheimer's disease (AD) is a brain disorder that eventually causes memory loss and the ability to perform simple cognitive functions; research efforts within pharmaceuticals and other medical treatments have minimal impact on the disease. Our preliminary biological studies showed that Repeated Electromagnetic Field Stimulation (REFMS) applying an EM frequency of 64 MHz and a specific absorption rate (SAR) of 0.4 - 0.9 W/kg decrease the level of amyloid-β peptides (Aβ), which is the most likely etiology of AD. This study emphasizes uniform E/H field and SAR distribution with adequate penetration depth penetration through multiple human head layers driven with low input power for safety treatments. In this work, we performed numerical modeling and computer simulations of a portable Meander Line antenna (MLA) to achieve the required EMF parameters to treat AD. The MLA device features a low cost, small size, wide bandwidth, and the ability to integrate into a portable system. This study utilized a High-Frequency Simulation System (HFSS) in the design of the MLA with the desired characteristics suited for AD treatment in humans. The team designed a 24-turn antenna with a 60 cm length and 25 cm width and achieved the required resonant frequency of 64 MHz. Here we used two numerical human head phantoms to test the antenna, the MIDA and spherical head phantom with six and seven tissue layers, respectively. The antenna was fed from a 50-Watt input source to obtain the SAR of 0.6 W/kg requirement in the center of the simulated brain tissue layer. We found that the E/H field and SAR distribution produced was not homogeneous; there were areas of high SAR values close to the antenna transmitter, also areas of low SAR value far away from the antenna. This paper details the antenna parameters, the scattering parameters response, the efficiency response, and the E and H field distribution; we presented the computer simulation results and discussed future work for a practical model.

Textile UWB 5G Antenna for Human Blood Clot Measurement

The antenna plays an essential role in the medical industry. The short-range 5th Generation (5G) communication can be used for seamless transmission, reception, patient monitoring, sensing and measuring various processes at high speeds. A passive Ultra Wide Band (UWB) antenna, used as a sensor in the measurement of Prothrombin Time (PT) i.e., blood clot is being proposed. The investigated micro-strip patch UWB antenna operating in the frequency range of 3.1 to 10.6 GHz consists of a circular patch with a diamond-shaped slot made of jeans substrate material with good sensing properties is accomplished by adjusting the copper thickness of the patch. Due to the turbidity in blood plasma, PT measurement is the repetitive approach to get accurate value. In order to solve this issue, an antenna is designed, fabricated and analysed to obtain the accurate PT measurements from blood plasma. The blood clotting is observed by electromagnetic emitted voltage converted into the frequency range of 5 to 10 GHz and voltage range of 0.66 to 0.87 mV. The circular UWB antenna is constructed employing jean’s substrate with a partial ground plane to improve the S-parameter, gain, bandwidth and performance characteristics. The proposed antenna with Specific Absorption Rate (SAR) value within the acceptable range can be used as a wearable device in the human body, leveraging 5G technology. This antenna is well suited for various other applications like wireless sensors, wearable devices and short-range communication applications.

Remote Monitoring of Skin Temperature Through a Wristband Employing a Printed VO Sensor

The need for highly sensitive, environmentally stable, mechanically flexible, and low-cost temperature sensors for on-body measurements has been increasing with the wide adoption of personal healthcare-Internet-of-Things (H-IoT) devices. Printed electronics (PE) is a good platform for such sensors because it enables the realization of flexible devices through simple and rapid methods at a relatively low cost. However, previously reported printed temperature sensors suffer from poor sensitivity and/or environmental instability. In this article, we report a custom tungsten (W)-doped vanadium dioxide (VO2) ink-based screen-printed temperature sensor having the highest temperature coefficient of resistance (TCR) of 2.78% C-1 with a resolution of 0.1 °C between 30 °C and 40 °C. To protect it from environmental effects, a fluoropolymer-basedpassivation layer is added for accurate temperature readings even in 90% relative humidity. The sensor is printed on a flexible substrate and shows minimal deterioration in performance over 1000 bending cycles. For wearability and remote monitoring, the sensor is integrated with a custom Bluetooth low energy (BLE) wireless readout in the form of wristband. The BLE readout comprises an ultrathin and flexible patch antenna optimized for both BLE bandwidth (BW) and human wearability. It demonstrates a minimal specific absorption rate (SAR) value of only 0.068 W/kg, making it safe to wear. Despite the antenna’s thin structure (0.004λ), it has a gain of 1.65 dBi, enabling an excellent communication range. The proposed wristband is tested on ten volunteers and under daily activities, which shows promising results with a maximum error of 0.16 °C with reference to those of a commercial thermometer.

Energy Harvesting Rectenna Using High-Gain Triple-Band Antenna for Powering Internet-of-Things (IoT) Devices in a Smart Office

A new rectenna that can be utilized for sending/receiving data and scavenging radio frequency (RF) waves for linking and powering the Internet-of-Things (IoT) devices is proposed. The rectenna has three operating frequency bands; the lower frequency band is used for energy harvesting, and the other two frequency bands are assigned for data communication. It comprises a stacked four-layer antenna integrated with a voltage doubler rectifier. The antenna consists of a driven element, a planar reflector, and a planar director composed of a periodic structure of a square patch with a hexagonal slot in its center. The measurement results show that the proposed antenna covers 1.86–2.65, 2.84–3.64, and 5.34–6 GHz with an impedance bandwidth of 35%, 24.7%, and 11.64%, respectively. The antenna exhibits a high measured gain of 8.1, 8.9, and 9 dBi at 2.3, 3.5, and 5.7 GHz, respectively. The Industrial, Scientific and Medical (ISM) 2.45-GHz frequency band is selected for energy harvesting. Moreover, specific absorption rate (SAR) calculations are done for the antenna using the Hugo model to ensure lower absorption operation. The proposed antenna provides acceptable values of SAR; the values are under the safety standard limits for RF exposure. Then, a rectifier circuit is designed, fabricated, and tested separately. Finally, the rectifier is integrated with the proposed enhanced-gain antenna to produce a rectenna system. The rectenna presents a power conversion efficiency (PCE) of 69.7% and a dc output voltage of 1.9 V at an input power of 2 dBm. The PCE of the proposed rectenna is over 50% at a range of input power from −6.5 to 4.7 dBm.

A Compact Penta-Band Low-SAR Antenna Loaded with Split-Ring Resonator for Mobile Applications

A compact rectangular patch with dual-ring SRR (split-ring resonator) is presented in this article. An antenna is designed on FR4 substrate with an overall footprint size of 26 mm × 30 mm × 1.6 mm. The antenna presented operates in five bands from 2.95 to 3.06 GHz, 3.79 to 3.87 GHz, 4.11 to 4.19 GHz, 5.39 to 5.51 GHz, and 5.97 to 6.11 GHz. Mobile and fixed voice communication, WiMAX (Worldwide Interoperability for Microwave Access), 5G (5th generation), WLAN (Wireless Local Area Network), and ISM (Industrial Scientific and Medical) are some applications that utilized the above resonating bands. The penta-band operation is due to the inclusion of dual-ring SRR. The optimum values of the critical parameter of the SRR are identified using parametric analysis, and the results are presented. The antenna is also analyzed for the SAR (specific absorption rate) values, and it was found to be less than 2 W/kg for 10 g volume of tissue. The designed antenna is fabricated and tested, and the presented results show that there is good agreement between the simulated and measured results. Penta-band operation with simple structure, stable radiation pattern, and low SAR makes this antenna more intelligent and suitable for the mobile application.

AMC-Based Low-Profile Dual-Band Slotted Patch Antenna for IoT Devices in the Healthcare System

An artificial magnetic conductor (AMC)-based patch antenna with a low profile is developed for wireless devices in IoT-based healthcare systems. The proposed antenna comprises two pairs of circular-shaped patches with circular-shaped slots and a dual-band 4 × 4 array of AMC reflectors with two zero-degree reflection responses to enhance the antenna's radiation performance. For the 2.45 GHz ISM and 5.4 GHz WLAN bands, the patch antenna has dimensions of 0.44λ0 × 0.52λ0 × 0.013λ0, with partial ground structures to improve radiation characteristics. Following that, a unique dual-band symmetrical AMC unit cell with dimensions of 22 × 22 × 1.6 mm3 is developed. There is a gap of 15 mm between the antenna and the AMC surface. The antenna is supported by a 4 × 4 AMC array that has a total dimension of 0.72λ0 × 0.72λ0 × 0.15λ0. The reflection coefficient values of less than − 10 dB in the 1.7–2.5 and 5.1–5.6 GHz bands, with a bandwidth percentage of 38 and 9.3%, respectively. The antenna's gains were 7.2 and 4 dBi inside the bands. Furthermore, the Specific Absorption Rate (SAR) value did not match the WHO's safety and health guidelines. The issue was solved by including an AMC surface in the proposed antenna. At 2.45 and 5.4 GHz, SAR values of 0.58 and 1.04 W/Kg were measured. Vector network analyser and anechoic chamber were used to test the performance of antenna and AMC surface prototypes. There is a substantial agreement among measured and simulated parameters of an antenna. Consequently, the developed antenna combination with the AMC structure is suited for wireless devices in ISM and WLAN bands, often used in IoT-based healthcare systems.