Field Sensor Research Articles

Tunable Negative Permittivity and Magnetic Properties of Ag/BLM Ceramic Metacomposites

Abstract Percolation composites with tunable negative permittivity have garnered significant attention due to their potential use in the field of electromagnetic interference shielding, near field amplification, antennas, and sensors. However, studies on the magnetic property at a frequency range of 100 MHz to 1 GHz are relatively scarce. The objective of this study was to examine the magnetic property and adjustable negative permittivity of silver/La-doped barium ferrite(Ag/BLM) ceramic metacomposites. In this study, Ag/BLM ceramic metacomposites with varying Ag content were prepared using a simple impregnation-calcination method. We investigate the permittivity, reactance, and permeability of Ag/BLM ceramic metacomposites at 100 MHz ~ 1GHz. The findings indicate that the percolation threshold for Ag/BLM ceramic metacomposites with x wt% is between 10 wt% and 19 wt%. When Ag content reaches 19 wt%, it creates a conductive network that generates a high number of free electrons. This leads to low-frequency plasma states and results in negative permittivity. Meanwhile, the permeability of Ag/BLM ceramic metacomposites shows the frequency dispersion due to the magnetic resonance and eddy current. Therefore, this study's findings suggest that composites with tunable negative permittivity and permeability may be developed and utilised for microwave absorption, antenna design, and wireless power transmission.

Eccentric Core Photonic Crystal Fiber Magnetic Field Sensor Based on Surface Plasmon Resonance with Extremely High Linearity

Eccentric Core Photonic Crystal Fiber Magnetic Field Sensor Based on Surface Plasmon Resonance with Extremely High Linearity

Design and implementation of a low cost isotropic electric field sensor for SAR measurements

Design and implementation of a low cost isotropic electric field sensor for SAR measurements

Longitudinal (α33) and transverse(α31) dynamic magnetoelectric hysteretic response for CoFe1.88Dy0.12O4–K0.5Na0.5NbO3 lead-free multiferroic laminates

The magnetoelectric (ME) laminate structures of CoFe1.88Dy0.12O4 (CFDO, Ferrite) and K0.50Na0.50NbO3 (KNN, ferroelectric/piezoelectric) phases were fabricated by silver epoxy bonding technique and tested the ME response in longitudinal and transverse mode. The CFDO reveals the cubic spinel structure while KNN reveals the perovskite orthorhombic crystal structures having dense microstructure. The CFDO confirms the phase segregation of the DyFeO3ortho-ferrite phase, while the KNN lead-free ceramic showed the Curie temperature of 416 °C, 13µC/cm2 maximum polarization, 25,296 × 10-15 m2/N figure of merit, piezoelectric charge coefficient d33 of 47 pC/N. The longitudinal (α33) and transverse (α31) dynamic magnetoelectric response is studied to figure out the effective magnetic field direction to get better values of magnetoelectric voltage sensitivity i.e. αME. Both modes revealed the hysteretic behavior i.e. lagging of ME voltage response to an applied magnetic field which evidences a true multiferroic character of CFDO/KNN laminates. Remarkably, the (CFDO /KNN/ CFDO) structure demonstrated a substantial magnetoelectric coefficient in LT (α31) mode of approximately 38.5 mV/cm·Oe at a magnetic field of 400 Oe and −37.55 mV/cm·Oe at a magnetic field of −400 Oe. Thus, here we present the magnetoelectric laminate structure of CFDO /KNN/ CFDO phases beneficial for magnetic field sensors.

Modeling and Measurement of CMOS-Based Three-Axis Magnetic Field Sensors With Low Cross-Sensitivity

Modeling and Measurement of CMOS-Based Three-Axis Magnetic Field Sensors With Low Cross-Sensitivity

A Review on Resonant MEMS Electric Field Sensors

Electric field sensors (EFSs) are widely used in various fields, particularly in accurately assessing atmospheric electric fields and high-voltage power lines. Precisely detecting electric fields enhances the accuracy of weather forecasting and contributes to the safe operation of power grids. This paper comprehensively reviews the development of micro-electromechanical system (MEMS) resonant EFSs, including theoretical analysis, working principles, and applications. MEMS resonant EFSs have developed into various structures over the past decades. They have been reported to measure electric field strength by detecting changes in the induced charge on the electrodes. Significant advancements include diverse driving and sensing structures, along with improved dynamic range, sensitivity, and resolution. Recently, mode localization has gained attention and has been applied to electric field sensing. This paper reviews the performances and structures of MEMS resonant EFSs over recent decades and highlights recent advances in weakly coupled resonant EFSs, offering comprehensive guidance for researchers.

Numerical study of a tapered fiber magnetic field sensor based on ENZ mode

Numerical study of a tapered fiber magnetic field sensor based on ENZ mode

DESIGN AND FABRICATION OF SHAPE MORPHING MAGNETO-IMPEDANCE MAGNETIC SENSOR

The magnetoimpedance (MI) effect is characterized by the alteration in the impedance of soft magnetic materials when subjected to a magnetic field while a high-frequency alternating current flows through them. In this study, we engineered two distinct sensor architectures utilizing amorphous FeCSi magnetic ribbon: a single-bar structure with the dimension of 10 mm × 90 μm × 20 μm and a meander structure consisting of 13 parallel single bars. These structures were miniaturized through advanced techniques combining laser engraving and chemical etching. The magnetic analysis reveals that the meander structure exhibits a pronounced dependency on the angle θ between the magnetic field and the sensor orientation, enhancing its soft magnetic properties by up to fivefold compared to the single-bar design. This enhancement might be attributed to a reduction in the demagnetization effect and shape anisotropy energy within the meander sensor. Furthermore, the analysis of the MI effect indicates that the resonance frequency remains unaffected by external magnetic fields for both sensor types. Notably, the meander sensor demonstrates exceptional MI ratio values exceeding 82%, representing a remarkable 24-fold increase over the 3.5% observed in the single-bar sensor. Additionally, the isotropy - quantified as the MI ratio's dependence on angle θ, and magnetic field sensitivity are significantly improved in the meander configuration. These advancements in soft magnetic and physical properties are correlated to the domain structure of the sensor, particularly its transverse magnetic permeability, as evidenced by micromagnetic simulations conducted using Mumax3. With its superior MI ratio, isotropy, and heightened magnetic field sensitivity, the meander-type magnetic field sensor presents substantial potential for applications across diverse fields, ranging from biological systems to specialized practical missions.

Magnetic Field-Induced Polar Order in Monolayer Molybdenum Disulfide Transistors.

In semiconducting monolayer transition metal dichalcogenides (ML-TMDs), broken inversion symmetry and strong spin-orbit coupling result in spin-valley lock-in effects so that the valley degeneracy may be lifted by external magnetic fields, potentially leading to real-space structural transformation. Here, magnetic field (B)-induced giant electric hysteretic responses to back-gate voltages are reported in ML-MoS2 field-effect transistors (FETs) on SiO2/Si at temperatures <20 K. The observed hysteresis increases with |B| up to 12 T and is tunable by varying the temperature. Raman spectroscopic and scanning tunneling microscopic studies reveal significant lattice expansion with increasing |B| at 4.2 K, and this lattice expansion becomes asymmetric in ML-MoS2 FETs on rigid SiO2/Si substrates, leading to out-of-plane mirror symmetry breaking and the emergence of a tunable out-of-plane ferroelectric-like polar order. This broken symmetry-induced polarization in ML-MoS2 shows typical ferroelectric butterfly hysteresis in piezo-response force microscopy, adding ML-MoS2 to the single-layer material family that exhibits out-of-plane polar order-induced ferroelectricity, which is promising for such technological applications as cryo-temperature ultracompact non-volatile memories, memtransistors, and ultrasensitive magnetic field sensors. Moreover, the polar effect induced by asymmetric lattice expansion may be further generalized to other ML-TMDs and achieved by nanoscale strain engineering of the substrate without magnetic fields.

A photocurable ultra-tough eutectic gel with coordination crosslinking used for wearable sensors and TENG flexible electrodes

Flexible polymer molecular chains are of great interest to researchers in the field of flexible wearable electronics due to their unrivaled flexibility and ductility. However, achieving high toughness, high elasticity, environmental stability and easy machining of flexible electronic materials remains a challenge. In this study, we present a photocurable eutectic gel mainly composed of DMAPS, AAc, Zr4+ and deep eutectic solvents (DES). Due to the strong coordination between zirconium ions and polymer networks, the gel can be endowed with excellent properties, such as excellent tensile strength (1.14 MPa), low hysteresis (5 kJ·m−3) and good adhesion (above 40 kPa). DES can not only give the gel good electrical conductivity, but also maintain the stability of the gel to ensure that the leakage or volatilization of the solvent will not occur in use. The properties mentioned above allow the gel to achieve a sensitivity factor of up to 1.7 over a small strain range, demonstrating its potential applications in the field of flexible strain sensors and triboelectric flexible electrode materials. What’s more, the gel can be used to prepare complex geometric shapes with high precision through digital light processing (DLP) based 3D printing technology. Therefore, this work introduces a novel approach for the development of highly stable flexible wearable devices, which has the potential to expand the applications of eutectic gels.

Multi-Cavity Nanorefractive Index Sensor Based on MIM Waveguide

Within this manuscript, we provide a novel Fano resonance-driven micro-nanosensor. Its primary structural components are a metal-insulator-metal (MIM) waveguide, a shield with three disks, and a T-shaped cavity (STDTC). The finite element approach was used to study the gadget in theory. It is found that the adjustment of the structure and the change of the dimensions are closely related to the sensitivity (S) and the quality factor (FOM). Different model structural parameters affect the Fano resonance, which in turn changes the transmission characteristics of the resonator. Through in-depth experimental analysis and selection of appropriate parameters, the sensor sensitivity finally reaches 3020 nm/RIU and the quality factor reaches 51.89. Furthermore, the installation of this microrefractive index sensor allows for the quick and sensitive measurement of glucose levels. It is a positive contribution to the field of optical devices and micro-nano sensors and meets the demand for efficient detection when applied in medical and environmental scenarios.

Electrical liquid crystal integration with VCSEL arrays for tunable orthogonal polarization laser

Vertical-cavity surface-emitting laser (VCSEL) arrays that can emit orthogonally polarized light have shown broad application potential and market demand in the fields of optical communication, optical sensors, and biomedicine. Two kinds of polarization-switching VCSEL arrays based on anti-parallel (AP) oriented liquid crystal (LC) external cavities and twisted nematic (TN) oriented LC external cavities are proposed in this paper. The light is independently guided by the LC electrically, achieving uniform lasing of linearly polarized light with mutually orthogonal polarization modes and equal power. The uniformity and polarization tunable ability of the lasing orthogonally polarized light power is guaranteed by the integration of the LC external cavity and the VCSEL array.

Ultrasensitive optical electric field sensor with temperature compensation for point-wise and quasi-distributed sensing.

A point-wise and quasi-distributed optical sensing technique with the Vernier effect is proposed and achieved by multiplexing Fabry-Perot interferometers (FPIs). The FPIs are fabricated by LiNbO3 (LN) crystals of varying lengths to enable simultaneous measurement of electric field (E-field) and temperature. Compared to the traditional bulk-type optical E-field sensors, this innovative sensor enables E-field measurement without being limited by half-wave voltage and effectively avoids the influence of natural birefringence. By an algorithm based on the Fourier transform, sub-FPIs are addressable, and their interference spectra can be demodulated independently, where any two FPIs are paired to generate the fundamental Vernier effect (FVE) or harmonic Vernier effect (HVE). Thus, the measurement sensitivities of FPIs can be significantly improved by monitoring the spectral shift of the envelope in the superimposed spectra. The quasi-distributed sensing experiment is conducted using three cascaded FPIs, yielding E-field sensitivities of 2.84 nm/E (FVE) and 3.37 nm/E (HVE), with a standard deviation (STD) of spectrum variation after temperature compensation below 3.19 × 10-3. The proposed multiplexing method is significant for practical applications of the E-field quasi-distributed measurement.

Cellulose-Templated Nanomaterials for Nanogenerators and Self-Powered Sensors.

Energy crisis inspires the development of renewable and clean energy sources, along with related applications such as nanogenerators and self-powered devices. Balancing high performance and environmental sustainability in advanced material innovation is a challenging task. Addressing the global challenges of sustainable development and carbon neutrality lead to increasedinterest in biopolymer research. Nanocellulose materials, derived from biopolymers, demonstrate potential as template candidates for advanced materials, due to their unique properties, including high strength, high surface area, controllable pore structures and high-water retention. In recent years, cellulose-templated nanomaterials enable delicate nano-/microscale structural construction, thus promoting developments in the field of nanogenerators and self-powered sensors. However, there is still a limited number of reviews focused on cellulose-templated nanomaterials for applications in nanogenerators and self-powered sensors. This review aims to fill this research gap by introducing various cellulose-templated nanomaterials and providing a detailed analysis of their fashionable applications in nanogenerators and self-powered sensors. The goal is to present cellulose-templated nanomaterials as highly promising template and guest materials for templating technologies, offering sustainable nano-/microscale control over advanced materials for the foreseeable future. This potential is promising for new applications in the fields of nanogenerators and self-powered sensors.

Performance of a Radio-Frequency Two-Photon Atomic Magnetometer in Different Magnetic Induction Measurement Geometries.

Measurements monitoring the inductive coupling between oscillating radio-frequency magnetic fields and objects of interest create versatile platforms for non-destructive testing. The benefits of ultra-low-frequency measurements, i.e., below 3 kHz, are sometimes outweighed by the fundamental and technical difficulties related to operating pick-up coils or other field sensors in this frequency range. Inductive measurements with the detection based on a two-photon interaction in rf atomic magnetometers address some of these issues as the sensor gains an uplift in its operational frequency. The developments reported here integrate the fundamental and applied aspects of the two-photon process in magnetic induction measurements. In this paper, all the spectral components of the two-photon process are identified, which result from the non-linear interactions between the rf fields and atoms. For the first time, a method for the retrieval of the two-photon phase information, which is critical for inductive measurements, is also demonstrated. Furthermore, a self-compensation configuration is introduced, whereby high-contrast measurements of defects can be obtained due to its insensitivity to the primary field, including using simplified instrumentation for this configuration by producing two rf fields with a single rf coil.

Adhesion layers between piezoelectric and magnetostrictive layers in a MEMS magneto-sensor stack: Influence on the phase transformation of deposited Co/Fe multilayers to magnetostrictive CoxFe1−x phase

Magnetoelectric MEMS devices, such as magnetic field sensors, may be composed of a multilayer stack as a magnetostrictive layer, which is mechanically coupled to a piezoelectric film. Good adhesion and a stable rigid interface have to be maintained for such a sensor. Certain electric and magnetic properties, especially the magnetostriction, have to reach sufficiently high values, which can be achieved by selected phases or mixtures of phases. In this study, Co/Fe multilayers with varied bilayer periods are deposited onto AlN or Sc0.14Al0.86N coated Si substrates by DC magnetron sputtering with the optional insertion of a 5 nm thick adhesion layer of Cr or Zr to investigate its influence on the formation of the desired mixture of bcc and fcc Co0.7Fe0.3 phases, which are expected to yield a high magnetostrictive strain, after an RTA at 800 °C. A qualitative phase analysis is made by XRD in Bragg-Brentano geometry and shows that the bcc + fcc mixture can be achieved with a Cr interlayer. A sharp, void free, and undamaged interface for that case was observed in SEM images of cross sections prepared with FIB.

On the Origin of Signal and Bandwidth of Converse Magnetoelectric Magnetic Field Sensors

AbstractConverse magnetoelectric sensors enable the detection of low‐frequency and low‐amplitude magnetic fields over a bandwidth of several kilohertz by combining the electrical excitation of a magnetoelectric resonator via a piezoelectric layer with an inductive readout. Here, a comprehensive sensor model is presented to further foster the development of this promising sensor concept. The model relates the output signal to the device characteristics, taking into account the magnetoelastic and electromechanical properties, the resonator geometry, and operating conditions. The sensor system is thoroughly experimentally analyzed to validate the model. Based on the analysis, the sensor concept is explained in detail, including the origin of its loss and bandwidth and their connection with the magneto‐mechanical loss in the magnetostrictive layer. Significant advances have been made in the comprehensive understanding of converse magnetoelectric sensors, providing a solid basis for future improvements in magnetoelectric sensor systems.

Valorization of water hyacinth: Efficient extraction of nanofibrillated crystals using ultrasound-assisted TEMPO oxidation and their application in flexible piezoelectric films

This study presents an efficient extraction of nanocellulose crystals (CNCs) and nanofibers (CNFs) through ultrasound-assisted TEMPO oxidation method using deep-processed heavy metal-containing calabash as raw material. The extraction method, integrating TEMPO-mediated oxidation and ultrasound techniques, enhanced the yield of CNCs and CNFs. The results demonstrate that CNCs yielded 63 %, with a carboxyl content of 1.27 mmol/g, while CNFs yielded 31 %, with a carboxyl content of 1.21 mmol/g. CNCs and CNFs exhibited excellent mechanical properties, with CNCs having an average length of 214.4 nm, average diameter of 2.72 nm, and a length-to-diameter ratio of 78.8. CNFs had an average length of 437.8 nm, average diameter of 5.7 nm, and a length-to-diameter ratio of 76.8. X-ray diffraction (XRD) results showed crystallinity of 87.1 % for CNCs and 81.2 % for CNFs. The thermal stability of the fibers was confirmed up to 230℃. The film prepared by combining 10 % PVA with 90 % CNC exhibited a tensile strength of 32.11 MPa, Young's modulus of 2027.1 MPa, and could generate a maximum voltage of 0.83 V. This study provides an effective pathway for the value-added utilization of deep-processed calabash and highlights the broad application prospects of the composite film in the field of flexible sensors.

An Overview of Biochar Utilization Strategies for Screen-Printed Electrochemical Sensors

In this review, we address the utilization of biochar, a cost-effective material derived from renewable resources (biomass), for the construction of printable electrochemical devices. Key parameters influencing the final properties of biochar, including pyrolysis temperature, pyrolysis duration, heating rate, and activation treatments, are detailed. The role of biochar in the fabrication of electrochemical (bio)sensors is highlighted with emphasis on advancements in screen-printed electrochemical devices. Furthermore, this review showcases examples of using biochar in the construction of portable and flexible screen-printed electrodes, as well as humidity sensors. Future perspectives and challenges in the field of biochar-based electrochemical sensors and biosensors are also discussed, providing a comprehensive outlook on this promising area of research.

A Kernel-Based Calibration Algorithm for Chromatic Confocal Line Sensors.

In chromatic confocal line sensors, calibration is usually divided into peak extraction and wavelength calibration. In previous research, the focus was mainly on peak extraction. In this paper, a kernel-based algorithm is proposed to deal with wavelength calibration, which corresponds to the mapping relationship between peaks (i.e., the wavelengths) in image space and profiles in physical space. The primary component of the mapping function is depicted using polynomial basis functions, which are distinguished along various dispersion axes. Considering the unknown distortions resulting from field curvature, sensor fabrication and assembly, and even the inherent complexity of dispersion, a typical kernel trick-based nonparametric function element is introduced here, predicated on the notion that similar processes conducted on the same sensor yield comparable distortions.To ascertain the performance with and without the kernel trick, we carried out wavelength calibration and groove fitting on a standard groove sample processed via glass grinding and with a reference depth of 66.14 μm. The experimental results show that depths calculated by the kernel-based calibration algorithm have higher accuracy and lower uncertainty than those ascertained using the conventional polynomial algorithm. As such, this indicates that the proposed algorithm provides effective improvements.