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In an ever expanding railway network all around the world, the need for track maintenance grows steadily. Traditionally, one major part of track maintenance is ramming large vibrating steel picks into the gravel between and under railway sleepers to compress the gravel and generate a safe substructure. Even today, maintenance personnel still have to manually locate the sleepers if they cannot be detected by computer vision systems or visually by the operator. Here we developed a first of its kind magnetic sleeper detector, even able to find sleepers, buried in gravel, undetectable by vision based systems. Our approach of magnetic detection is based on a DC magnetic field excitation and a detector moving with respect to the rail system, including the sleepers and fasteners for mounting the rails. Due to railway application constraints a large air gap between the sensor and the sleeper structure is required, which significantly complicates the magnetic sensing task for robust sleeper detection. The design and optimization of the magnetic circuit was based on extensive 3D simulation studies to ensure highest possible variation in magnetic flux density at the sensor locations for absence and presence of a sleeper. Furthermore, a low noise and high sensitivity electronic circuit has been realized to cope with sensor signal offsets from unknown or changing sensor orientations with respect to the earth's magnetic field, or magnetic interferences from other trains potentially passing by during active measurements. Since we only want to detect sleepers in close vicinity of the moving sensor system, digital signal processing of the acquired signals can easily compensate for disturbing slowly changing or static field components within real world application scenarios. We demonstrate that magnetic detection of even buried sleepers on railway tracks is possible for distances of up to 172 mm between the sensor and the sleeper. This enables an even higher level of railway maintenance automation previously impossible in certain scenarios. [ABSTRACT FROM AUTHOR]

Currently, the field of structural health monitoring (SHM) is focused on investigating non-destructive evaluation techniques for the identification of damages in concrete structures. Magnetic sensing has particularly gained attention among the innovative non-destructive evaluation techniques. Recently, the embedded magnetic shape memory alloy (MSMA) wire has been introduced for the evaluation of cracks in concrete components through magnetic sensing techniques while providing reinforcement as well. However, the available research in this regard is very scarce. This study has focused on the analyses of parameters affecting the magnetic sensing capability of embedded MSMA wire for crack detection in concrete beams. The response surface methodology (RSM) and artificial neural network (ANN) models have been used to analyse the magnetic sensing parameters for the first time. The models were trained using the experimental data obtained through literature. The models aimed to predict the alteration in magnetic flux created by a concrete beam that has a 1 mm wide embedded MSMA wire after experiencing a fracture or crack. The results showed that the change in magnetic flux was affected by the position of the wire and the position of the crack with respect to the position of the magnet in the concrete beam. RSM optimisation results showed that maximum change in magnetic flux was obtained when the wire was placed at a depth of 17.5 mm from the top surface of the concrete beam, and a crack was present at an axial distance of 8.50 mm from the permanent magnet. The change in magnetic flux was 9.50 % considering the aforementioned parameters. However, the ANN prediction results showed that the optimal wire and crack position were 10 mm and 1.1 mm, respectively. The results suggested that a larger beam requires a larger diameter of MSMA wire or multiple sensors and magnets for crack detection in concrete beams.

Since the release of MagSafe, which allows magnetic attachment of accessories to smartphones, many vendors have introduced various kinds of MagSafe accessories, including wireless chargers, wallets, car mounts, and coolers. In light of this trend, we introduce MagID, a novel interface to connect physical accessories with software functionalities. For example, when an accessory (e.g., a car mount) is attached, it automatically invokes a specific application (e.g., a navigation app) or performs a certain task that corresponds to the accessory. The main idea of MagID for supporting this functional connection is to identify when and which accessories are attached to or detached from a smartphone. More specifically, based on our observations that MagSafe accessories have different magnetic properties from each other, we design a magnetic sensing-based accessory identification method and further improve its robustness with the combined use of non-magnetic features, e.g., accelerometer, gyroscope, and battery state readings. Our extensive experiments with a prototype implementation of MagID demonstrate that MagID can identify MagSafe accessories with high accuracy on any MagSafe-enabled smartphone and even in noisy environments, while not compromising usability.

In the current work, we illustrate the effect of adding a small amount of carbon to very common Co2MnSi Heusler alloy-based glass-coated microwires. A significant change in the magnetic and structure structural properties was observed for the new alloy Co2MnSiC compared to the Co2MnSi alloy. Magneto-structural investigations were performed to clarify the main physical parameters, i.e., structural and magnetic parameters, at a wide range of measuring temperatures. The XRD analysis illustrated the well-defined crystalline structure with average grain size (Dg = 29.16 nm) and a uniform cubic structure with A2 type compared to the mixed L21 and B2 cubic structures for Co2MnSi-based glass-coated microwires. The magnetic behavior was investigated at a temperature range of 5 to 300 K and under an applied external magnetic field (50 Oe to 20 kOe). The thermomagnetic behavior of Co2MnSiC glass-coated microwires shows a perfectly stable behavior for a temperature range from 300 K to 5 K. By studying the field cooling (FC) and field heating (FH) magnetization curves at a wide range of applied external magnetic fields, we detected a critical magnetic field (H = 1 kOe) where FC and FH curves have a stable magnetic behavior for the Co2MnSiC sample; such stability was not found in the Co2MnSi sample. We proposed a phenomenal expression to estimate the magnetization thermal stability, ΔM (%), of FC and FH magnetization curves, and the maximum value was detected at the critical magnetic field where ΔM (%) ≈ 98%. The promising magnetic stability of Co2MnSiC glass-coated microwires with temperature is due to the changing of the microstructure induced by the addition of carbon, as the A2-type structure shows a unique stability in response to variation in the temperature and the external magnetic field. In addition, a unique internal mechanical stress was induced during the fabrication process and played a role in controlling magnetic behavior with the temperature and external magnetic field. The obtained results make Co2MnSiC a promising candidate for magnetic sensing devices based on Heusler glass-coated microwires. [ABSTRACT FROM AUTHOR]

The identification of submarine cable locations is crucial for their operation and maintenance. Precise location data enables the monitoring of route changes and facilitates rapid fault detection. Magnetic sensing is commonly used for detecting buried submarine cables. However, current research seldom discusses the impact of mutual magnetic field interference among submarine power cables on location accuracy and considers only the magnetic field intensity for cable detection. In this study, the authors first establish a general magnetic field model for three parallel single-core submarine power cables carrying three-phase currents and thoroughly investigate the variations in the amplitude and phase difference of the magnetic field surrounding the cables. Based on this model, the authors introduce a gradient measurement method based on the phase difference for the first time and compare its location accuracy with that of the traditional extremum method. Our findings reveal that the phase difference method offers higher location accuracy at longer detection distances, whereas the extremum method is preferable for shorter distances because of its simpler device and criteria.

Identifying unbalanced phase currents is crucial for control and fault alarm rates in power grids, especially in urban distribution networks. The zero-sequence current transformer, specifically designed for measuring unbalanced phase currents, offers advantages in measurement range, identity, and size, compared to using three separate current transformers. However, it cannot provide detailed information on the unbalance status beyond the total zero-sequence current. We present a novel method for identifying unbalanced phase currents based on phase difference detection using magnetic sensors. Our approach relies on analyzing phase difference data from two orthogonal magnetic field components generated by three-phase currents, as opposed to the amplitude data used in previous methods. This enables the differentiation of unbalance types (amplitude unbalance and phase unbalance) through specific criteria and allows for the simultaneous selection of an unbalanced phase current in the three-phase currents. In this method, the amplitude measurement range of magnetic sensors is no longer a critical factor, allowing for an easily attainable wide identification range for current line loads. This approach offers a new avenue for unbalanced phase current identification in power systems. [ABSTRACT FROM AUTHOR]

Smart electromagnetic functional devices prepared based on electromagnetic wave responsive materials will provide more convenience for human life in the future. Here, we prepare oriented magnetic liquid metal droplet-filled polydimethylsiloxane films with micropillar array patterned surfaces, and further assemble them into bilayer films with interlocked structures. Once compressed, the increase in conductivity of the film due to the tunneling effect between microarrays and the elongation of liquid metal droplets leads to a rapid increase in electromagnetic interference shielding performance. Accordingly, a tunable electromagnetic interference shielding material with high sensitivity and wide control range is obtained, which has potential applications in electromagnetic wave control systems and intelligent electromagnetic protection systems. Meanwhile, we assemble a strain sensor and a magnetic sensor, which can precisely sense pressure and magnetic field according to changes in electromagnetic signal and electrical signal, respectively. [ABSTRACT FROM AUTHOR]

In recent years, magnetic nanoparticles (MNPs) have been widely used in many fields due to their advantageous properties, such as biocompatibility, easy modifiability, and high chemical stability. One of these areas is the detection of cancer. It is essential to use existing biomarkers, such as microRNAs (miRNAs), for the early diagnosis of this disease. miRNAs are challenging to distinguish and detect in biological samples because they are small, circulating molecules. It is necessary to use more sensitive and feature-rich systems. Thanks to their large surface areas and magnetic moments, MNPs allow easy separation of miRNA at low concentrations from complex samples (urine and blood) and rapid and specific detection in biosensing systems. Here, we discussed the synthesis and characterization methods of MNPs, their stabilization, and MNP-based biosensors in terms of miRNA detection. We considered the challenges and prospects of these biosensor systems in evaluating the development stages, sensitivity, and selectivity. [ABSTRACT FROM AUTHOR]

Fluxgate sensors are key devices for magnetic field surveys in geophysics. In areas such as deep drilling, fluxgate sensors may have to operate steadily at high temperatures for a prolonged period of time. We present an accordant ring-core type fluxgate sensor that is stable up to 220   °C. The high temperature consistency is achieved by using an Fe-based nanocrystalline magnetic core, PEEK structural components, an epoxy resin wrapping, as well as a broadband short-circuited working mode. The sensor was characterized at various temperatures up to 220   °C by evaluating impedance, hysteresis, permeability and sensitivity. We found a sensitivity of approximately 24 kV/T at 25   °C with an acceptable temperature coefficient of 742 ppm/°C throughout the range. The variation law of magnetic characteristics and their influence mechanism on output amplitude and phase are discussed. [ABSTRACT FROM AUTHOR]

This work addresses the topic of magnetic linear position detection, a common method used in modern industries to determine linear displacement by magnetic means. One major shortcoming of this method is the inherent airgap instability, which puts strong constraints on mechanical construction tolerances and limits resolution and sensitivity. We propose a method to improve the airgap stability by adding a second magnet, which makes the field and by extension the system output (locally) independent of the distance from the source. It is shown that the measurement error for 1-D systems can be reduced by a factor of ~14 and for 2-D systems by a factor of ~5 by application of this method for a realistic example. [ABSTRACT FROM AUTHOR]

Integration of optically active diamond particles with glass fibers is a powerful method of scaling diamond's magnetic sensing functionality. We propose a novel approach for the integration of diamond particles containing nitrogen-vacancy centers directly into the fiber core. The core is fabricated by stacking the preform from 790 soft glass canes, drawn from a single rod dip-coated with submicron diamond particles suspended in isopropyl alcohol. This enables manual control over the distribution of nanoscale features, here – the diamond particles across the optical fiber core. We verify this by mapping the diamond distribution in the core using confocal microscopy. The particles are separated longitudinally by 12–29 μm, while in the transverse plane a separation of approximately 1.5–2.2 μm is observed, corresponding to the individual cane diameter in the final fiber, and without significant agglomeration. The fiber's magnetic sensitivity is confirmed in optically detected magnetic resonance recorded with a coiled, 60-cm-long fiber sample with readout contrast of 1.3% limited by microwave antenna coverage. Moreover, magnetic-field dependence of the NV─ fluorescence intensity is demonstrated in the absence of microwaves, allowing magnetometric applications with a large (from 0 to 35 mT) B-field dynamic range. [Display omitted] [ABSTRACT FROM AUTHOR]

Gold‐coated magnetic nanoparticles are key materials for the fast separation and ultrasensitive detection of analytes in magnetoplasmonic sensors. However, the synthesis of gold‐coated magnetic nanoparticles typically requires small‐scale, colloidal methods over hours or days and often results in incomplete shells with variable optical properties. A robust, rapid, and scalable synthesis method is still needed to reliably form a complete gold nanoshell around magnetic nanoparticles. Herein, a new methodology for the synthesis of gold‐coated magnetic nanoparticles via a flow‐based manufacturing system that can easily be scaled up is presented. The developed method first produces gold‐seeded silica coated magnetic nanoparticles and then a complete, tunable gold shell with relatively uniform size and shape. The flow‐based method can be performed in a total time of less than 2 min, enabling rapid and complete gold coating. The particles show both excellent magnetic and plasmonic properties, which facilitates application as biosensing agents in dark‐field microscopy and surface‐enhanced Raman scattering. [ABSTRACT FROM AUTHOR]

Underwater robot technologies are crucial for marine resource exploration and autonomous manipulation, and many breakthroughs have been achieved with key indicators (e.g., dive depth and navigation range). However, due to the complicated underwater environment, the state-of-the-art sensing technologies cannot handle all the needs of underwater observations. To improve the autonomous operating capacity of underwater robots, there is an urgent need to develop underwater sensing technology. Therefore, in this paper, we first introduce the development of underwater robot platforms. We then review some key sensing technologies such as underwater acoustic sensing, underwater optical sensing, underwater magnetic sensing, and underwater bionic sensing. Finally, we point out the challenges of underwater sensing technology and future directions in addressing these challenges, e.g., underwater bionic sensing, new underwater material development, multisource information fusion, and the construction of general test platforms.

Identifying unbalanced phase currents is crucial for control and fault alarm rates in power grids, especially in urban distribution networks. The zero-sequence current transformer, specifically designed for measuring unbalanced phase currents, offers advantages in measurement range, identity, and size, compared to using three separate current transformers. However, it cannot provide detailed information on the unbalance status beyond the total zero-sequence current. We present a novel method for identifying unbalanced phase currents based on phase difference detection using magnetic sensors. Our approach relies on analyzing phase difference data from two orthogonal magnetic field components generated by three-phase currents, as opposed to the amplitude data used in previous methods. This enables the differentiation of unbalance types (amplitude unbalance and phase unbalance) through specific criteria and allows for the simultaneous selection of an unbalanced phase current in the three-phase currents. In this method, the amplitude measurement range of magnetic sensors is no longer a critical factor, allowing for an easily attainable wide identification range for current line loads. This approach offers a new avenue for unbalanced phase current identification in power systems.

During surgical procedures, real-time estimation of the current position of a metal lead within the patient's body is obtained by radiographic imaging. The inherent opacity of metal objects allows their visualization using X-ray fluoroscopic devices. Although fluoroscopy uses reduced radiation intensities, the overall X-ray dose delivered during prolonged exposure times poses risks to the safety of patients and physicians. This study proposes a potential alternative to real-time visualization of a lead inside the human body. In principle, by making a weak current flow through the lead and measuring the related magnetic field generated outside the body, it is possible to trace the position of the lead. This hypothesis was verified experimentally via two tests: one carried out on a curved copper wire in air and one carried out on a real pacemaker lead in a saline solution. In the second test, a pacemaker lead and a large return electrode were placed in a tank filled with a saline solution that reproduced the mean resistivity of the human torso. In both tests, a current flowed through the lead, which consisted of square pulses with short duration, to avoid any neuro-muscular stimulation effects in a real scenario. A small coil with a ferrite core was moved along a grid of points over a plastic sheet and placed just above the lead to sample the spatial amplitude distribution of the magnetic induction field produced by the lead. For each measurement point, the main coil axis was oriented along the x and y axes of the plane to estimate the related components of the magnetic induction field. The two matrices of measurements along the x and y axes were further processed to obtain an estimate of lead positioning. The preliminary results of this study support the scientific hypothesis since the positions of the leads were accurately estimated. This encourages to deepen the investigation and overcome some limitations of this feasibility study. [ABSTRACT FROM AUTHOR]

The role of microbiome in shaping animal's behavior is well established. Accordingly, the use of antibiotics may have profound effects on behavior, which are seldom examined. Recently, the symbiotic magnetic-sensing hypothesis has been forwarded as a mechanistic explanation for the phenomenon of animal magnetoreception. It suggests a symbiotic relationship between magnetotactic bacteria (MTB) and the navigating host. To establish a research protocol for future behavioral studies, we examined the effect of a widely used antibiotic substance on migratory restlessness orientation and on magnetotactic bacteria. Using migrating Eurasian reed warblers, we show that in contrast to the control group, antibiotic treatment caused a lack of clear directionality in an Emlen funnel experiment. Accordingly, the antibiotic treatment group showed a significant increase in directional variance. This effect of antibiotics on behaviors associated with animal magnetic sensing might be considered as preliminary experimental support of the symbiotic magnetic-sensing hypothesis. Further, we lay a preliminary experimental protocol that could be implemented in experiments aiming to prove or refute the symbiotic magnetic sensing hypothesis. [ABSTRACT FROM AUTHOR]

Grid impedance is an important parameter in the impedance-based stability analysis method for analyzing the interaction between the power electronic inverters and the power grid. However, the existing measurement technique is deteriorated by narrow-bandwidth sensors, large perturbation injections, and inaccurate response components extraction based on the fast Fourier transform (FFT) algorithm. To overcome these problems, a magnetic-sensing-based wide-bandwidth grid impedance measurement technique with a small perturbation injection is proposed in this article. A novel impedance extraction algorithm based on the quadrature delay estimator (QDE) is developed to overcome the spectral leakages and frequency aliasing effect of the existing FFT-based impedance extraction algorithm. The proposed grid impedance measurement technique is implemented on a digitally controlled inverter system, and its effectiveness is verified through the experimental results. [ABSTRACT FROM AUTHOR]

In recent years, magnetic nanoparticles (MNPs) have been widely used in many fields due to their advantageous properties, such as biocompatibility, easy modifiability, and high chemical stability. One of these areas is the detection of cancer. It is essential to use existing biomarkers, such as microRNAs (miRNAs), for the early diagnosis of this disease. miRNAs are challenging to distinguish and detect in biological samples because they are small, circulating molecules. It is necessary to use more sensitive and feature-rich systems. Thanks to their large surface areas and magnetic moments, MNPs allow easy separation of miRNA at low concentrations from complex samples (urine and blood) and rapid and specific detection in biosensing systems. Here, we discussed the synthesis and characterization methods of MNPs, their stabilization, and MNP-based biosensors in terms of miRNA detection. We considered the challenges and prospects of these biosensor systems in evaluating the development stages, sensitivity, and selectivity.

Currently, the field of structural health monitoring (SHM) is focused on investigating non-destructive evaluation techniques for the identification of damages in concrete structures. Magnetic sensing has particularly gained attention among the innovative non-destructive evaluation techniques. Recently, the embedded magnetic shape memory alloy (MSMA) wire has been introduced for the evaluation of cracks in concrete components through magnetic sensing techniques while providing reinforcement as well. However, the available research in this regard is very scarce. This study has focused on the analyses of parameters affecting the magnetic sensing capability of embedded MSMA wire for crack detection in concrete beams. The response surface methodology (RSM) and artificial neural network (ANN) models have been used to analyse the magnetic sensing parameters for the first time. The models were trained using the experimental data obtained through literature. The models aimed to predict the alteration in magnetic flux created by a concrete beam that has a 1 mm wide embedded MSMA wire after experiencing a fracture or crack. The results showed that the change in magnetic flux was affected by the position of the wire and the position of the crack with respect to the position of the magnet in the concrete beam. RSM optimisation results showed that maximum change in magnetic flux was obtained when the wire was placed at a depth of 17.5 mm from the top surface of the concrete beam, and a crack was present at an axial distance of 8.50 mm from the permanent magnet. The change in magnetic flux was 9.50 % considering the aforementioned parameters. However, the ANN prediction results showed that the optimal wire and crack position were 10 mm and 1.1 mm, respectively. The results suggested that a larger beam requires a larger diameter of MSMA wire or multiple sensors and magnets for crack detection in concrete beams., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Graphene Hall-effect magnetic field sensors (GHSs) exhibit high performance comparable to state-of-the-art commercial Hall sensors made from III-V semiconductors. Graphene is also amenable to CMOS-compatible fabrication processes, making GHSs attractive candidates for implementing magnetic sensor arrays for imaging fields in biosensing and scanning probe applications. However, their practical appeal is limited by response heterogeneity and drift, arising from the high sensitivity of two-dimensional (2D) materials to local device imperfections. To address this challenge, we designed a GHS array in which an individual backgate is added to each GHS, allowing the carrier density of each sensor to be electrostatically tuned independent of other sensors in the array. Compared to the constraints encountered when all devices are tuned with the same backgate, we expected that the flexibility afforded by individual tuning would allow for the array's sensitivity, uniformity, and reconfigurability to be enhanced. We fabricated an array of 16 GHSs, each with its own backgate terminal, and characterized the ability to modulate GHS carrier density and Hall sensitivity within CMOS-compatible voltage ranges. We then demonstrated that individual device tuning can be used to break the trade-off between device sensitivity and uniformity in the GHS array, allowing for enhancement of both objectives. Our results showed that GHS arrays exhibiting >30% variability under single-backgate operation could be compensated using individual tuning to achieve <2% variability with minimal impact on the array sensitivity.

Fluxgate sensors are key devices for magnetic field surveys in geophysics. In areas such as deep drilling, fluxgate sensors may have to operate steadily at high temperatures for a prolonged period of time. We present an accordant ring-core type fluxgate sensor that is stable up to 220 °C. The high temperature consistency is achieved by using an Fe-based nanocrystalline magnetic core, PEEK structural components, an epoxy resin wrapping, as well as a broadband short-circuited working mode. The sensor was characterized at various temperatures up to 220 °C by evaluating impedance, hysteresis, permeability and sensitivity. We found a sensitivity of approximately 24 kV/T at 25 °C with an acceptable temperature coefficient of 742 ppm/°C throughout the range. The variation law of magnetic characteristics and their influence mechanism on output amplitude and phase are discussed.

As an ultrastable material, single‐crystal diamond (SCD) has been proven to have extraordinary reliability in the application of microelectromechanical systems (MEMS). To satisfy the requirements of high sensitivity and high stability of magnetic sensors, SCD MEMS resonators integrated with TbDyFe thin film are successfully fabricated by radio‐frequency magnetron sputtering. The device is thermally stable and the sensing performance is improved after annealing at 550 °C for 3 h. A high magnetic sensitivity of 5.34 Hz mT−1 is achieved. The estimated minimum detectable force reaches 1.65 × 10−14 N due to the advantage of giant magnetostriction of the TbDyFe thin film. The realization of SCD MEMS magnetic sensor demonstrates a visible progress in the field of magnetic sensing and indicates a foreseeable potential of SCD MEMS in the application of fast, small, and energy‐efficient sensors. [ABSTRACT FROM AUTHOR]

Substituting the natural bladder with an artificial solution, after cancer and other pathologies, is an ambitious challenge in biomedical engineering. In this work we propose a fully implantable smart artificial bladder system (ABS) that collects urinary fluids and provides the subject with real-time feedback on the implant status. To achieve long term duration, the ABS was designed to be unstretchable in order to be treated with urine resistant coatings and included built-in passive check valves preventing reflux to kidneys. To estimate the amount of fluid collected, the ABS was provided with four electromagnetic distance sensing units and a control unit. An algorithm implemented on an embedded controller enabled the reconstruction of the bladder volume through sensors readings. A wireless data transfer system allows for providing a real-time feedback to the subject. Bench tests validated volume reconstruction accuracy and ex-vivo experiments verified the implantability of the proposed device on a human cadaver, proving the reliability of a Bluetooth data transmission system and paving the way towards an in-body/out-body communication. The proposed solution has the potential to overcome the limitations of currently available replacement strategies towards a new generation of implantable devices for lost organ functions replacement. [ABSTRACT FROM AUTHOR]

This paper presents a road vehicle recognition and classification approach for intelligent transportation systems. This approach uses a roadside installed low-cost magnetometer and associated data collection system. The system measures the magnetic field changing, detects passing vehicles, and recognizes vehicle types. We introduce Mel Frequency Cepstral Coefficients (MFCC) to analyze vehicle magnetic signals and extract it as vehicle feature with the representation of cepstrum, frame energy, and gap cepstrum of magnetic signals. We design a 3-dimensional map algorithm using Vector Quantization (VQ) to classify vehicle magnetic features to 4 typical types of vehicles in Australian suburbs: sedan, van, truck, and bus. In order to train an accurate classifier, training samples are selected using the Dynamic Time Warping (DTW). The verification experiments show that our approach achieves a high level of accuracy for vehicle detection and classification.

During surgical procedures, real-time estimation of the current position of a metal lead within the patient’s body is obtained by radiographic imaging. The inherent opacity of metal objects allows their visualization using X-ray fluoroscopic devices. Although fluoroscopy uses reduced radiation intensities, the overall X-ray dose delivered during prolonged exposure times poses risks to the safety of patients and physicians. This study proposes a potential alternative to real-time visualization of a lead inside the human body. In principle, by making a weak current flow through the lead and measuring the related magnetic field generated outside the body, it is possible to trace the position of the lead. This hypothesis was verified experimentally via two tests: one carried out on a curved copper wire in air and one carried out on a real pacemaker lead in a saline solution. In the second test, a pacemaker lead and a large return electrode were placed in a tank filled with a saline solution that reproduced the mean resistivity of the human torso. In both tests, a current flowed through the lead, which consisted of square pulses with short duration, to avoid any neuro-muscular stimulation effects in a real scenario. A small coil with a ferrite core was moved along a grid of points over a plastic sheet and placed just above the lead to sample the spatial amplitude distribution of the magnetic induction field produced by the lead. For each measurement point, the main coil axis was oriented along the x and y axes of the plane to estimate the related components of the magnetic induction field. The two matrices of measurements along the x and y axes were further processed to obtain an estimate of lead positioning. The preliminary results of this study support the scientific hypothesis since the positions of the leads were accurately estimated. This encourages to deepen the investigation and overcome some limitations of this feasibility study.

Scalable micro graphene Hall sensors (μGHSs) hold tremendous potential for highly sensitive and label-free biomagnetic sensing in physiological solutions. To enhance the performance of these devices, it is crucial to optimize frequency-dependent flicker noise to reduce the limit of detection (LOD), but it remains a great challenge due to the large contact resistance at the graphene-metal contact. Here we present a surface modification strategy employing persistent carbene on gold electrodes to reduce the contact resistivity by a factor of 25, greatly diminishing μGHS flicker noise by a factor of 1000 to 3.13 × 10 -14 V 2 /Hz while simultaneously lowering the magnetic LOD S B 1/2 to 1440 nT/Hz 1/2 at 1 kHz under a 100 μA bias current. To the best of our knowledge, this represents the lowest S B 1/2 reported for scalable μGHSs fabricated through wafer-scale photolithography. The reduction in contact noise is attributed to the π-π stacking interaction between the graphene and the benzene rings of persistent carbene, as well as the decrease in the work function of gold as confirmed by Kelvin Probe Force Microscopy. By incorporating a microcoil into the μGHS, we have demonstrated the real-time detection of superparamagnetic nanoparticles (SNPs), achieving a remarkable LOD of ∼528 μg/L. This advancement holds great potential for the label-free detection of magnetic biomarkers, e.g., ferritin, for the early diagnosis of diseases associated with iron overload, such as hereditary hemochromatosis (HHC).

A microwave (MW) resonator to provide frequency-tunable and circularly polarized MW fields is proposed. This technology enlarges the range of application in optically detected magnetic resonance (ODMR) systems based on the diamond negatively charged nitrogen-vacancy (NV) center and enable the selective excitation of its electronic spins. The characteristics of this resonator are simulated and discussed via a series of experimental studies. An adjustable MW frequency (${f}_{MW}$) can be provided in the 2.5-3.1GHz range and the value of the input return loss (S11) corresponding to ${f}_{MW}$ measures <−15 dB which mean at least 96.84% coupling efficiency between the microwave resonator and the microwave source. When ${f}_{MW}$ is equal to the resonance frequency of the NV center (${f}_{NV}$) for different external magnetic fields (${B}$), the results of the ODMR experiment indicate that the fluorescence increases upon an increase in $\vert {B}\vert $. Finally, the resonator provides a circularly polarized MW output with a purity of 97.17%. This study paves the way to novel applications and to the development of magnetic sensing devices based on the NV ensemble in diamond. [ABSTRACT FROM AUTHOR]

This study proposes a magnetic sensor design and application for monitoring the health of rotor magnets in permanent magnet (PM) electrical machines through in-situ observation of the air-gap magnetic flux density. The reported device employs the concept of Fibre Bragg Grating (FBG) strain sensing fusion with magnetostrictive material to deliver a machine stator slot wedge integrated sensor that allows straightforward installation and retrofit with no invasive action to core elements of the machine. The sensing theory, design, prototyping, calibration and installation of the proposed magnetic sensing scheme are detailed in the paper. The sensor was installed into an inverter driven surface mount PM synchronous machine (SPMSM) and its performance for in-situ observation of rotor PM magnetization conditions validated in a range of healthy and demagnetised PM conditions tests. The obtained experimental data demonstrate the reported device’s capability to enable recognition of rotor PMs’ magnetisation level and thus their health monitoring. Finally, a fault index is proposed and experimentally validated that allows the application of in-situ magnetic sensor measurements for relative quantification of PM demagnetization fault severity. [ABSTRACT FROM AUTHOR]

Fault classification of power distribution cables is essential for tripping relays, pinpointing fault location, and repairing failures of a distribution network in the power system. However, existing fault-classification techniques are not totally satisfactory because they may: 1) require the precalibration of responding threshold for each network; 2) fail to identify the three-phase short-circuit faults. since some electrical parameters (e.g., phase angle) are still symmetrical even in abnormal status; and 3) be invulnerable of electromagnetic interferences. In this paper, a fault-classification technique by detecting decaying dc components of currents in faulted phases through magnetic sensing is proposed to overcome the shortcomings mentioned above. First, the three-phase currents are reconstructed by magnetic sensing with a stochastic optimization algorithm, which avoids the waveform distortion in the measurement by current transformers that incurred by the dc bias. Then, the dc component is extracted by mathematical morphology (MM) in phase currents to identify the fault type together with the polarity of dc components. This method was verified successfully for various fault types on a 22-kV power distribution cable in simulation and also a scaled power distribution network experimentally. The proposed method can enhance the reliability of the power distribution network and contribute to smart grid development. [ABSTRACT FROM AUTHOR]

Attempts to improve the osteointegration, fixation and stability of Ti-base implants have been focused by producing a significative surface roughness that enhances the surface area available for bone/ implant apposition. In this research study, it shows the experimental data by synchrotron radiation X-ray diffraction (SR-XRD) of the main material surface properties (residual stress and cold work) that changed significantly during the application of different surface treatments such as grit blasting and laser shock peening in a biometallic Ti–6Al–4V alloy. The ratio of residual stress to cold work is primarily determined by the material and the specific surface treatment applied. In order to establish how they alter the recorded magnetic signatures and to validate that the residual stress and cold work effects govern the outcome of the magnetic measurements, we used a nondestructive magnetic method. It was displayed that the magnetic method provides the unique capability of nondestructively sensing the thermomechanical relaxation below the treated surface only calculating the normal and tangential magnetic intensities induced by thermocurrents using a fluxgate magnetometer. [ABSTRACT FROM AUTHOR]

This paper develops an electromagnet-based position measurement system for industrial actuators which offers significant advantages compared with traditional position measurement systems. These advantages include low cost, non-contacting operation, easy installation, and robustness to magnetic disturbances. In the first embodiment of the sensor, the electromagnet is located on the stationary actuator housing while the sensor is mounted on the actuator’s moving piston rod. This requires power to be supplied to the electronics on a moving object, and therefore a second embodiment that eliminates this disadvantage is developed. The second embodiment locates both the electromagnet and the powered sensor on the stationary housing. A mu-metal film of high magnetic permeability is located on the moving piston. Due to its high magnetic permeability, a significant fraction of the magnetic field measured by the sensor is coupled through the piston of the actuator. Hence, as the piston position changes, the magnetic field measured by the sensor changes. This leads to an excellent position measurement system with high sensitivity. The experimental results show that the second position sensor embodiment can provide 1% accuracy in position measurement, can reject the influence of disturbances from magnetic objects and can measure positions for stroke lengths up to 20 cm. Longer stroke lengths can be handled using additional daisy-chained sensors. [ABSTRACT FROM AUTHOR]

Magnetic sensing based on nitrogen-vacancy (NV) center ensembles provides unique signal-to-noise ratio and sensitivity for physical and biological measurements at room temperature. However, inhomogeneous microwave (MW) coupling with NV ensembles and different field projections onto the NV axes lead to nonsynchronous spin dephasing and pose severe challenges to magnetic sensing. In this paper, we experimentally investigated the impact of the MW field uniformity on the DC magnetic sensing based on NV ensembles. We obtained different MW field uniformity between 42% and 93% in the same direction using a square split ring resonator. The uniformity and direction of the MW field was mapped using a wide-field magnetic imaging system. The magnetic sensing with the MW frequency modulation technology confirmed the consistence between the theoretical analysis and experimental results. The sensitivity was enhanced by nearly seven times with the best MW field uniformity. Our study can promote the further application and development of magnetic sensing devices based on solid-state spin ensembles. [ABSTRACT FROM AUTHOR]

Fluid accumulation in the lower extremities is an early indicator of disease deterioration in cardiac failure, chronic venous insufficiency and lymphedema. At-home wearable monitoring and early detection of fluid accumulation can potentially lead to prompt medical intervention and avoidance of hospitalization. Current methods of fluid accumulation monitoring either suffer from lack of specificity and sensitivity or are invasive and cost-prohibitive to use on a daily basis. Ultrasound velocity in animal and human tissue has been found to change with water content. However, previous prototype fluid monitoring sensors based on ultrasound are cumbersome and not wearable. Hence, in this research a compact water content sensor based on a wearable instrumented elastic band is proposed. A novel integration of magnetic sensing and ultrasonic sensing is utilized, where the magnetic sensor provides distance measurement and the ultrasonic sensor produces time-of-flight measurement. Magnetic field modeling with a Kalman filter and least squares linear fitting algorithms are employed to ensure robust sensor performance on a wearable device. The combination of the two measurements yields ultrasound velocity measurement in tissue. The water content sensor prototype was tested on a tissue phantom, on animal tissue and on a human leg. The error in velocity measurement is shown to be small enough for early detection of tissue edema. [ABSTRACT FROM AUTHOR]

The protection system of high-voltage direct-current (HVDC) system must detect, identify, and isolate the fault quickly to keep the system stable by only isolating the components that are under fault, while leaving the rest of the network in operation. However, the criteria of under-voltage and voltage-derivative protection systems may fail because there also arises a large voltage drop/variation on the healthy transmission line due to the electromagnetic coupling among HVDC transmission lines incurred by the sharp transient current in the faulty line. Thus, a fault-line identification technique of HVDC transmission lines by frequency-spectrum correlation was proposed in this paper, which is based on evaluating the similarity degree of frequency spectrum between the voltage of a line and the current of another. This technique was implemented and validated by simulation on a ±500 kV HVDC transmission system. The simulation model was integrated with a capacitive-coupling and magnetic-field-sensing-assisted platform comprised two paralleled induction bars, and an array of magnetic sensors to measure voltage and current. This identification technique can enhance the reliability of HVDC system by avoiding the unnecessary outages due to accidental shutdown of healthy lines, fostering the HVDC system development. [ABSTRACT FROM AUTHOR]