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Positional misalignments of coils cause a sharp drop in the power transfer efficiency (PTE) of wireless power transfer (WPT) systems. To minimize this deterioration of the PTE, this study introduces a sphere-shaped (Rxs) to a three-coil magnetic resonance-coupled WPT system for implantable devices. To assess the significance of Rxs, its performance was compared to the well-known circular planar (Rxf), half-sphere-shaped (Rxhs), and solenoid (Rsl) coils. Moreover, a small and efficient voltage doubler as a rectifier was designed. This voltage doubler has a high conversion efficiency of 89% with an output voltage of >3 V at 15 dBm. To validate the concept, prototypes of the coils and voltage doubler were fabricated and measured in saline and minced pork. The PTEs of the Rxf, Rxhs, Rsl, and Rxs coils-based WPT systems were studied under different lateral and angular misalignments in both simulations and measurements. In perfect alignment conditions, the measured PTEs of Rxf, Rxhs, Rsl, and Rxs WPT systems were 7.68%, 10.18%, 25.01%, and 22.38%, respectively; however, when the (Rx) receiver coils rotated by 90°, the PTEs were 0%, < 0.2%, 0.15%, and 5.4%, respectively. Under lateral misalignments of $dx =25$ mm, the PTEs were 0.82%, 1.91%, 2.4%, and 4.87%, respectively. Furthermore, the PTE for the Rxs-based WPT system was measured in saline- and minced-pork-filled boxes and a saline-filled American Society for Testing and Materials (ASTM) model under different misalignment conditions to expand its applicability range to deep-body non-static implants. Both the simulated and remeasured results show that the proposed Rxs-based WPT system presented an improved and stabilized PTE under positional misalignments. [ABSTRACT FROM AUTHOR]

The interactions of medical implants in the human body with electromagnetic fields from newly introduced high-field technologies such as near-field wireless power transfer (WPT) are of great concern. In this study, the effects of implants on the specific absorption rate (SAR) in a head model were computationally evaluated in the immediate vicinity of a WPT system operating at 6.78 MHz with a transferred power of 50 W. The SAR in the head model located 30 mm above the WPT system was evaluated with a skull plate, bone plates (different shapes), miniplate, fixtures, and a deep brain stimulator. The results indicated that even small implants had notable effects on the SAR distribution and corresponding local peak and mass-averaged SAR values. Apart from the size and shape of the implant, the crucial factor influencing the SAR was the implant’s position with respect to the WPT system. Therefore, various position configurations were simulated for the WPT system to determine the worst case scenario for each specific implant. Although the local peak SAR value was increased by a factor of 600 in the worst-case scenario (for the skull plate), the SAR $_{\text{1}g}$ and SAR $_{\text{10}g}$ were only increased by factors of seven and four, respectively. Compliance with international safety limits was studied, followed by computing the maximum allowable transmit power (MATP). It was found that, without the implant, the MATP satisfying SAR $_{\text{1}g}$ was 43 W for the designed WPT system, and was reduced to 6.9 W in the presence of the skull plate. [ABSTRACT FROM AUTHOR]

An efficient noninvasive system for simultaneous transmission of wireless power and data is vital for continuous human health monitoring. In this article, we present a self-tuned spiral-shaped antenna with dual-band characteristics operating at 920 MHz and 2.4 GHz for efficient wireless power transfer (WPT) and data telemetry, respectively. To avoid vision blockage, the proposed smart contact lens (SCL) dipole antenna comprises two symmetrical spiral arms with inner and outer diameters of 10 and 14 mm, respectively. The SCL antenna was printed on a thin flexible polyimide substrate with a biocompatible polydimethylsiloxane (PDMS) coating. The influence of dispersed dielectric properties of PDMS on SCL antenna performance was investigated. Furthermore, the antenna was combined with a miniaturized rectifier and a micro-LED to demonstrate wireless LED illumination on a saline-filled model head. The power transfer efficiency (PTE) as a function of eye movement in the form of a path gain was also investigated. In addition, the PTE across the distance variations from 10 to 30 mm was computed, and a −17.85 dB was achieved at a separation of 12 mm. A specific absorption rate analysis was performed to determine human eye safety under radio frequency exposure from the external transmitter and the results complied with the International Commission on Non-Ionizing Radiation Protection guidelines. Furthermore, a theoretical link power budget analysis was experimentally validated using software-defined radio. Measurements of s-parameters were noted through the use of a saline solution to mimic a realistic human eye and were found to have a reasonable correlation with the simulated results. [ABSTRACT FROM AUTHOR]

[Display omitted] • GO-based membranes have attracted substantial attention in separation processes. • The dye rejection performance of the GO membranes is critically evaluated. • The membrane stability performance and mechanisms of dye rejection are described in detail. • Technological hurdles are underscored while proposing avenues for future research. In the realm of water treatment, the utilization of two-dimensional (2D) graphene and its derivative, graphene oxide (GO), has emerged as a pioneering avenue for the development of nanoporous membranes. These membranes hold immense promise due to the remarkable attributes inherent to GO, notably its expansive specific surface area and the profusion of oxygen-containing surface functional groups. This comprehensive review elucidates the recent advances in the fabrication and utilization of GO-based membranes, specifically tailored for the efficacious removal of dyes from aqueous environments. A detailed analysis of the key physicochemical characteristics, which distinctly influence the synthesis and performance of GO-based membranes, is performed. Furthermore, a profound explication of the intricate mechanisms underpinning the rejection of dyes by these membranes is presented, accompanied by a thorough investigation into the stability performance of the deployed GO-based membranes. A quick comparison of GO membranes with other 2D materials and the application potential of these membranes in treating real textile effluents is also provided. In the end, salient research gaps are pinpointed, leading to clear suggestions for overcoming the mentioned hurdles. This article aimed to help the research community understand GO-based membranes deeply, and also provide valuable ideas about their growing effectiveness in cleaning dyes from various wastewater sources. [ABSTRACT FROM AUTHOR]

Advancement in the technology of leadless cardiac pacemakers (LCPs) has led to ultracompact designs of implantable antennas. In this study, a small-sized antenna for integration with an LCP, which can be operated in the industrial, scientific, and medical (ISM) band of 2.4 GHz, is developed. The proposed antenna was constructed in a spiral shape to provide superior miniaturization, less sensitivity to body tissue variation, and low specific absorption rate (SAR) values, and avoid fabrication complexities due to its small size. The antenna with a footprint of $3 \times 4\,\,\times0.5$ mm3 was constructed on a high dielectric material, namely, Rogers RT/duroid 6010. To the best of the authors’ knowledge, this is the smallest footprint with enhanced performance when compared to previous reports related to implantable antennas. In addition, the antenna was integrated with a 3-D printed LCP having dummy electronics and experimentally validated in saline solution and minced pork. The antenna sustained good impedance matching at the ISM band with a measured bandwidth of 21.88% and 15.46% with the device and without the device, respectively. Due to the smooth electric field (surface currents) over the patch, the antenna system had 270.28 and 31.04 W/kg peak SAR for 1 and 10 g of tissues, respectively, with a maximum peak gain of −25.95 dBi. We also discussed the effects of a coaxial cable and the antenna orientation on its performance. From the measured received signal strength, a stable biotelemetric link can be established between the implant and external controlling device up to a distance of 2 m. [ABSTRACT FROM AUTHOR]

Numerical dosimetry with regards to a resonance-based wireless power transfer (RBWPT) system for charging electric vehicles (EVs) has been conducted. The RBWPT system operating at 13.56 MHz frequency with a transferred power of 5.3 kW is placed below the center of the vehicle body. Specific absorption rate (SAR) in anatomically-based human models Duke and Ella with and without a medical implant is evaluated using four exposure scenarios (i.e., Duke and Ella models sitting in the EV without an implant, the Ella model: With an InterStim neurostimulator implant, having a prosthetic hip implant, or having a cardiac pacemaker implant). The results indicate that change in radio frequency (RF) energy absorption occurs when conductive implants are placed in the near field of an RF source. Enhancement of the SAR close to the implants is predicted. The peak averaged SAR over 10 g of tissues exceeds the standard limiting value posed by international guidelines except for the leadless pacemaker, which is in compliance with the prescribed limits. However, the temperature increase never exceeds the localized temperature rise limit of 2 °C. Compliance with the recommended limits of SAR in the worst-case exposure scenario is likely to limit the transferred power. [ABSTRACT FROM AUTHOR]

This communication presents a metamaterial (MTM)-loaded compact dual-band circularly polarized antenna system suitable for multiple bio-telemetric applications. The proposed antenna system operates in the industrial, scientific, and medical (ISM) bands with center frequencies: 915 MHz (902–928 MHz) and 2450 MHz (2400–2480 MHz). The integration of an MTM structure with epsilon-very-large property on the superstrate layer of the antenna produces significant gain enhancement and strong circular polarization (CP) behavior at both the operating frequencies. The key features of the proposed antenna system are its compact size (7 mm $\times 6$ mm $\times $ 0.254 mm), dual-band CP characteristics, significantly high gain values (−17.1 and −9.81 dBi in the lower and upper bands, respectively), and slot-less ground plane that reduces the complexity and backscatter radiation. The performance of the MTM-loaded antenna system is validated experimentally. The antenna is fabricated and integrated with dummy electronics and batteries and is enclosed in a 3-D printed device. The hermetically sealed device is tested in minced pork muscle to validate the simulation results. The measured impedance bandwidths of 35.8% and 17.8% are obtained in the lower and upper ISM bands, respectively. The specific absorption rate of the antenna system is evaluated at both frequencies in different tissues. Additionally, to determine the wireless communication range, the link margin is estimated at data rates of 100 kbps and 1 Mbps. [ABSTRACT FROM AUTHOR]

Abstract In this study, pristine multi-walled carbon nanotubes (MWCNTs) were functionalized by using Ar/O 2 plasma treatment technique, which enhanced adsorptive membrane filtration of zinc ions from water and wastewater. The XPS analysis showed that plasma treatment largely increased the surface oxygen groups content of MWCNTs from 2.78% to 6.79%. This change increased the surface negative charged, dispersion and adsorption properties of MWCNTs without causing any damages to the integrity of the nanotube pattern. Pressure-driven filtration of plasma-treated MWCNT (P-CNT) dispersion formed a stable layer inside the lumen of a hollow fiber membrane. The contact angle analysis demonstrated that after incorporation of P-CNT into the HF membrane increased membrane hydrophilicity. The P-CNT membrane effectively removed almost 100% of zinc from synthetic waters and approximately 80% of zinc from a wastewater effluent by surface complexation reaction. A follow-up regeneration study demonstrated that the adsorptive removal of zinc by the CNT membrane was reversible under selected conditions, thus making it possible to repeatedly use the membrane for long-term zinc filtration. This study suggests that HF membranes modified with P-CNTs possess superb adsorption properties for metal ions, allowing the operation of CNT membranes for water treatment. Graphical abstract Unlabelled Image Highlights • In this work, we fabricated Ar/O 2 plasma-treated CNT membranes. • The efficiencies of functionalized CNT membranes were evaluated for the removal of zinc from water and wastewater effluent. • We examined the behaviors and mechanisms of CNT membranes by using different characterization techniques. • The plasma-treated CNT membranes exhibited superior removal capacity to heavy metal ions in wastewater effluent. • The exhausted CNT membranes were efficiently regenerated by using acidic eluents. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is an emerging technology for the separation of organic solvents that are relevant to the petrochemical, pharmaceutical, food and fine chemical industries. The separation performance of OSN membranes has continued to push the boundary up through advanced membrane fabrication techniques and novel materials for fabricating the membranes. Despite the many advantages, OSN membranes still face such challenges as low solvent permeability and durability in harsh organic solvent conditions. To overcome these limitations, attempts have been made to incorporate nanomaterial fillers into OSN membranes to improve their overall performance. This review analyzes the potential and use of nanomaterials for OSN membranes, including covalent organic frameworks (COFs), metal-organic frameworks (MOFs), metal oxides (MOs) and carbon-based materials (CBMs). Recent advances in the state-of-the-art nano-based OSN membranes, in the form of thin-film nanocomposite (TFN) membranes and mixed matrix membranes (MMMs), are reviewed. Moreover, the separation mechanisms of OSN with nano-based membranes are discussed. The challenges faced by these OSN membranes are also elaborated, and recommendations for further research in this field are provided. [Display omitted] • Recent advances in organic solvents nanofiltration (OSN) processes are discussed. • Various nanomaterials (COFs, MOFs, MOs, and CBMs) for the modification of OSN membranes are reviewed. • The nanoengineering of thin-film nanocomposite (TFN) and mixed matrix membranes (MMMs) is discussed. • The separation performance and mechanisms of OSN membranes are elaborated. • Key challenges are highlighted and recommendations for future research are provided. [ABSTRACT FROM AUTHOR]

Thin-film composite (TFC) nanofiltration (NF) and reverse osmosis (RO) membranes have been widely used to remove pharmaceutically active compounds (PhACs) from water and wastewater. However, limited information is available to present the rejection of neutral PhACs under complex water matrices. In this study, we used acetaminophen (AAP) as a representative neutral pollutant to study the effects of feedwater matrices on the rejection of neutral PhACs by NF and RO membranes. The results showed that the permeation of solutes and water through NF and RO membranes followed the classical solution-diffusion model. The corresponding permeability coefficients of AAP for the RO membrane showed good consistency, with average values ranging between (6.19–7.56) × 10−6 μm s−1 in fresh and brackish feedwater. Meanwhile, the NF membrane exhibited stable AAP and NaCl fluxes as the applied pressure increased from 4.8 to 7.6 bar, suggesting an insignificant influence of convection on solute transport. In addition, a 10-fold increase in NaCl concentration reduced the average AAP permeability coefficient of the NF membrane by 57% (i.e. from 2.8 × 10−5 m s−1 to 1.2 × 10−5 m s−1), highlighting the relevance of co-existing ions to AAP transport. Furthermore, organic fouling resulted in enhanced AAP rejection by both NF and RO membranes at neutral pH level and medium applied pressure (i.e. 5.8 bar). Overall, this study provided important insights into the separation mechanism of TFC membranes for neutral PhACs, as well as the complex effects of the water matrix on the solute permeation processes. [Display omitted] • Effects of water matrix on the rejection of neutral pharmaceuticals were studied. • Acetaminophen (AAP) rejection by NF and RO was pH-dependent. • Organic fouling significantly increased AAP rejection with only a minor flux decline. • Co-existing NaCl ions significantly impacted AAP permeation through the NF membrane. • Solution-diffusion was the dominant rejection mechanism for the TFC membranes. [ABSTRACT FROM AUTHOR]

• The selective removal of Sr2+ and Cs+ by P-MWCNT membranes were studied. • The P-MWCNT membrane showed superb selectivity to Sr2+ over other metal ions. • The selectivity of Cs+ was depressed by the presence of coexisted metal ions. • The selectivity of divalent cations resulted from inner-sphere complexation. • While the selectivity of monovalent cations resulted from electrostatic interactions. The need for high-performance and novel technologies for selective treatment of radionuclides in water has recently stimulated broad research. In this study, we examined the ability of carbon nanotube (CNT) membranes in selective removal of strontium (Sr2+) and cesium (Cs+) from water and wastewater. In single-metal systems that contained only Sr2+, Cs+ or their competitive metal ions, the distribution coefficients (K d) of functionalized CNT membranes for divalent cations, i.e., Sr2+, Ca2+, and Mg2+, were measured as 4.41 mmol g−1, 2.14 mmol g−1, and 1.30 mmol g−1, respectively, and those for monovalent cations, i.e., Cs+, K+ and Na+, were 0.81 mmol g−1, 0.79 mmol g−1, and 0.81 mmol g−1, respectively. When Cs+ or Sr2+ co-existed with a competing cation, both pristine and functionalized CNT membranes showed excellent selectivity to Sr2+ over Mg2+ and Ca2+ while their selectivity to Cs+ over K+ and Na+ diminished. Moreover, the CNT membranes remained their selectivity for Sr2+ in a wastewater effluent despite the complex water composition. Overall, the selectivity sequence of the CNT membranes for divalent cations support the occurrence of inner-sphere complexation on CNT surfaces, while that for the monovalent cations was probably determined by electrostatic interactions. This study demonstrates that Ar/O 2 plasma treatment is a greener technology for the production of CNT functionalized membranes for selective removal of contaminants from water to achieve "fit-for-purpose" treatment. [ABSTRACT FROM AUTHOR]

This study presents an innovative wirelessly powered stent rectenna system for endovascular aneurysm repair (EVAR), targeting abdominal aortic aneurysm (AAA) treatment. The system includes an on‐body flexible transmitter (Tx) antenna and an in‐body rectifier‐integrated stent receiver (Rx) antenna, operating in the industrial, scientific, and medical (ISM) band of 868 MHz. The Rx stent antenna, made from a biocompatible nylon‐coated metallic wire, ensures mechanical stretchability, biocompatibility, and precise current distribution. The flexible Tx antenna is designed for wearable use. A miniaturized rectifier on flexible polyimide, coated with biocompatible polydimethylsiloxane, converts received power into DC energy. The EVAR stent system's performance is validated through measurements using a saline‐filled American Society for Testing and Materials (ASTM) phantom. Magnetic resonance imaging (MRI) compatibility studies using Sim4Life simulations assess potential heating and image artifacts, confirming the proposed stent's MRI suitability. Wireless power transfer experiments demonstrate reliable power delivery to the Rx in various real‐world scenarios, achieving a power transfer efficiency of 3.6% at 18 cm inside the phantom. The flexible rectifier shows a peak efficiency of 87% at 15 dBm input power. The proposed system's exceptional performance and efficiency highlight its potential for effectively wirelessly powering advanced AAA stents. [ABSTRACT FROM AUTHOR]

Vigorous knowledge on the occurrence and distribution of toxic metals (TMs) in theenvironment is needed to assess their toxicological impacts on human health especially in developing countries like Pakistan. For the first time, the concentrations of TMs like Ni, Zn, Pb, Cr, and Cd in both ground and surface water and their potential health risk in the district Buner (Pakistan) were determined using Inductive Coupled Plasma Mass Spectrometry (ICP-MS, Agilent Technologies, 7500 CX, USA) and their results were compared with their safe limits defined by Pakistan Environmental Protection Agency (Pak-EPA) and World Health Organization WHO (2008). The concentrations of TMs, like Pb (43% and 86%), Ni (63% and 32%), Cr (41%), and Cd (1% and 20%) in drinking water samples exceeded their respective permissible limits set by Pak-EPA and WHO (2008), respectively. The mean concentrations of TMs were found in decreasing order Ni > Pb > Cr > Cd > Zn. The HRI values of TMs in drinking water samples for both adults and children were observed <1 indicating no health risk to the local population. Excessive marble industries are present in the study area; therefore, it is necessary to reduce metal contamination via proper disposal and treatment of marble wastewater, for which the government should take serious action in the study area. [ABSTRACT FROM AUTHOR]