Magnetoelectric Sensors Research Articles

Compressible and Stretchable Magnetoelectric Sensors Based on Liquid Metals for Highly Sensitive, Self-Powered Respiratory Monitoring.

Healthcare monitoring, especially for respiration, has attracted tremendous attention from academics considering the great significance of health information feedback. The respiratory rate, as a critical health indicator, has been used to screen and evaluate potential illness risks in early medical diagnoses. A self-powered sensing system for medical monitoring is critical and imperative due to needless battery replacement and simple assembly. However, the development of a self-powered respiratory sensor with highly sensitive performance is still a daunting challenge. In this work, a compressible and stretchable magnetoelectric sensor (CSMS) with an arch-shaped air gap is reported, enabling self-powered respiratory monitoring driven by exhaled/inhaled breath. The CSMS contains two key functional materials: liquid metals and magnetic powders both with low Young's modulus, allowing for sensing compressibility and stretchability simultaneously. More importantly, such a magnetoelectric sensor exhibits mechanoelectrical converting capacity under an external force, which has been verified by Maxwell numerical simulation. Owing to the air-layer introduction, the magnetoelectric sensors achieve high sensitivity (up to 17.73 kPa-1), fast response, and long-term stability. The highly sensitive and self-powered magnetoelectric sensor can be further applied as a noninvasive, miniaturized, and portable respiratory monitoring system with the aim of warning for potential health risks. We anticipate that this technique will create an avenue for self-powered respiratory monitoring fields.

A ball-in-ball type self-powered magnetoelectric inertial sensor for 3D multi-angle motion monitoring of humanoid robots

Abstract Motion monitoring stands as a powerful tool for humanoid robots to well adapt to nearby changing environment. However, despite the recent advance of inertial measuring units, both simplification of the sensors and free of power supply for 3D multi-angle monitoring remains elusive. Herein we demonstrate a facile & self-powered magnetoelectric inertial sensor for 3D multi-angle head motion monitoring of humanoid robots. A magnetic sphere could freely roll inside a smooth polymeric shell patterned with regionally distributed coils, allowing for monitoring the accelerations for 8 directions in the horizontal plane, the bowing angle for diverse directions in 3D space and rotations when tilting with multi-angle. It can detect an acceleration down to 0.06 m/s2 and a tilting angle of 2° in the vertical plane. Owing to these sensing capacities, the magnetoelectric inertial sensor can be placed inside a model head for detecting head bowing, head turning and even sudden strikes from diverse directions. Furthermore, when being placed in the humanoid robot’s head, it can monitor continuous motions like left-kicking, bending knees, standing on one leg and doing the splits. Such a single inertial sensor provides a building block for motion monitoring of humanoid robots and for future development of robotics.

Displacement Sensor With Nanometric Resolution Based on Magnetoelectric Effect

Micro-displacement measurement is essential in precision fields, such as precision positioning, micro-vibration control and biological engineering. Conventional sensors have disadvantages of susceptibility to environmental, high cost and difficulty in integration. To address these deficiencies, this paper developed a novel displacement sensor with nanometric resolution based on magnetoelectric effect. Combining equivalent magnetic circuit method and equivalent circuit method for magnetoelectric effect using the nonlinear constitutive parameters, an equivalent circuit model of the proposed sensor is established to analyse and predict the performance of displacement sensor. Then a prototype of sensor based on Terfenol-D/PZT composites is fabricated, and the performance of prototype for dynamic displacement amplitude and static position measurement are tested. The results not only validate the developed equivalent circuit model, but also evidence the potential of magnetoelectric displacement sensor. Especially for dynamic displacement amplitude measurement, the resolution of it is better than 13.27 nm, which is close to or even beyond commercial laser displacement sensor.

Surface microstructural design to improve mechanical and giant magneto-impedance properties of melt-extracted CoFe-based amorphous wires

The influence of surface microstructural regulation mechanisms on the mechanical and giant magneto-impedance (GMI) properties of as-cast melt-extracted CoFe-based wires has been systematically researched based on morphology, phase distribution and domain structure parameters. A series of statistical models were applied to analyze the mechanical properties and followed by mapping the curve of cumulative failure rate for wire application. It was found that the average and highest fracture strengths, average tensile strain increased with Cu substitution and reached peaks of ~3725 MPa, ~4250 MPa and ~2.7%, respectively. Verified structure-simulation experiments revealed that surface Rayleigh waves effectively split the main crack and the diffusely distributed nanocrystalline in surface area acted as a pinning point to impede the crack growth, enhancing the mechanical properties. The GMI ratio displayed similar variations and attained a maximum value of 700 ± 5% as well as the resistance and reactance ratios improved to ~687% and ~2206%, respectively. The enhanced relative dielectric permeability μs resulting from the increased domain wall energy density and the decreased surface domain width. The unique synchronous enhancement of CoFe-based wires satisfies the demand for emerging magnetoelectric sensor applications, e.g. flexible and wearable sensors, equipment self-monitoring sensors, and array robotic skin sensors under harsh working environments.

Influence of the piezoelectric material on the signal and noise of magnetoelectric magnetic field sensors based on the delta-E effect

Magnetoelectric thin-film sensors based on the delta-E effect have widely been reported for the detection of low frequency and small amplitude magnetic fields. Such sensors are usually fabricated with microelectromechanical system technology, where aluminum nitride (AlN) is the established piezoelectric material. Here, we present aluminum scandium nitride (AlScN) for delta-E effect sensors instead and compare it with AlN using two sensors of identical design. The sensors are experimentally and theoretically analyzed regarding sensitivity, noise, limit of detection (LOD), and resonator linearity. We identify the influence of the dominating piezoelectric coefficients dij and other material parameters. Simulations and measurements demonstrate that, in contrast to the conventional direct operation of magnetoelectric sensors, a sensitivity increase ∝dij2 and a LOD improvement ∝dij−1 can be achieved if thermal–mechanical noise is dominant. In the present case, an 8× improved sensitivity and LOD are measured with AlScN at small excitation amplitudes. This factor decreases with increasing amplitude and resonator nonlinearities. The overall minimum LOD does not change due to an earlier onset of magnetic noise in the AlScN sensor. All in all, this study reveals the influence of the piezoelectric material on the signal and noise of delta-E effect sensors and the potential of AlScN to significantly improve sensitivity.

An analytical model for nonlinear magnetoelectric effect in laminated composites

This paper presents an analytical and explicit theoretical model for the nonlinear magnetoelectric (ME) effect in laminated composites, in which the multi-field coupled properties of magnetostrictive materials are taken into account. The adopted explicit nonlinear constitutive equation is equivalent to the one in series form through expanding the magnetostriction as a Taylor series in the vicinity of the applied bias field. Then the field-dependent materials’ parameters are derived as functions of bias field and stress. Analytical solutions of nonlinear ME voltages in various modes are obtained simultaneously using mechanical differential equations, boundary conditions, and electric equations. It is predicted that the frequency-multiplying behavior observed in the composites can be tuned by bias magnetic field. Only even harmonics occur in the absence of bias field, while odd harmonics appear once a bias field is applied. An optimal bias field corresponding to the maximum linear voltage and zero nonlinear voltage is obtained, where the highest piezomagetic effect generates. It is proved that the ME distortions under a fixed ac field is actually caused by the competition results between the linear piezomagnetic effect and high-order magnetostrictive effect. Moreover, pre-stress may enhance ME voltages and reduce the optimal field due to the multi-field coupled character, and control the resonance frequency via ΔE effect. Eventually, the origin of the observed dual-peak phenomenon around resonance frequencies is revealed and explained theoretically, indicating that strong ME effect may be achieved in a wider bias field range. The analytical solutions from this study can be applied to design tunable ME sensors, energy harvesters, and some other nonlinear devices via manipulating the external bias field and pre-stress.

Ultrasensitive flexible magnetoelectric sensor

Ever-evolving advances in flexible magnetic sensors are promising to fuel technological developments in the fields of touchless human–machine interaction, implantable medical diagnosis, and magnetoreception for artificial intelligence. However, the realization of highly flexible and extremely sensitive magnetic sensors remains a challenge. Here, we report a cost-effective, flexible, and ultra-sensitive heterostructural magnetoelectric (ME) sensor consisting of piezoelectric Pb(Zr0.52Ti0.48)O3 (PZT) thick films and Metglas foils. The flexible sensor exhibits a strong ME coefficient of 19.3 V cm−1 Oe−1 at low frequencies and 280.5 V cm−1 Oe−1 at resonance due to the exceptionally high piezoelectric coefficient d33 ∼ 72 pC N−1 of the constituent PZT thick films. The flexible ME sensor possesses not only ultrahigh sensitivities of 200 nT at low frequencies and 200 pT at resonance but also shows an excellent mechanical endurance. Through 5000 bending cycles (radii of ∼1 cm), the sensors showed no fatigue-induced performance degradation. This ultrasensitive flexible sensor provides a platform capable of sensing and responding to external magnetic fields and will find applications in soft robotics, wearable healthcare monitoring, and consumer electronics.

Development of Magnetoelectric Speed Sensor for Engine with High Environment Adaptability

The high reliable environment adaptive magnetoelectric speed sensor developed by this project is mainly used in the field of engine measurement and control. This project can effectively improve the accuracy and reliability of sensor measurement by adopting a new output design of redundancy synchronous coil and transformer secondary amplification design. By optimizing the induction coil, magnetic steel and internal structure, the sensor has outstanding performance such as low speed work, high sensitivity and low noise; At the same time, the project also through the overall structure of the sensor, material design, packaging technology and other optimization design, to ensure that the sensor meets the wide temperature zone, vibration resistance, impact resistance and full seal protection and a series of high reliable environmental adaptability technical requirements.

Nanostabilization of tetragonal distorted FeCo variants in ultra-thin FeCo/TiN multilayer films

Composites of ultra-thin nanolayers of FeCo/TiN with individual layer thickness of a few unit cells offer stability at elevated temperatures and exhibit defined magnetic properties which can be tuned by variying the layers thickness making them interesting candiates as components for magnetoelectric (ME) sensors. Initial studies describing the nanostructure of such thin films, however, left uncertainty about their exact crystal structure. With aberration-corrected microscopes the characterization of the local structure down to the atomic scale is possible to address the real structure with high precision. Here, by means of atomic resolution TEM imaging together with X-ray diffraction analysis, we were able to describe the nanostructure to be composed of individual layers of FeCo and TiN forming a superlattice with a defined cube-on-cube orientation relationship. The simulation of electron diffraction pattern featuring superlattice reflections on basis of structural modeling together with geometric phase analysis verified a defined orientation relationship resolving in the nanostabilization of a tetragonal distorted FeCo unit cell with c/a < 1.

Carbon fabric-based self-powered magnetoelectric tactile sensors for soft robot's sensing with resistance to acidic/alkaline environments

The magnetoelectric tactile sensor prepared using carbon cloths and magnetic elastomers, exhibits softness resistance to harsh acid/alkali environments. Two C-METS can endow robot with multi-directional sensing and escape capability.

Influence of electric and magnetic poling on properties of Co/Nb codoped cobalt ferrite

Nb doped CoFe2O4 ferrites (Denoted: Co1.2Fe1.7Nb0.1O4) was prepared by conventional solid state reaction method at calcination temperature 1300 ͦ C. The tuning of both electrical and magnetic poling on the prepared samples shows suppression of (111) peak as observed in X-ray diffraction study implying that (111) is the easy magnetic axis in polycrystalline cobalt ferrite and it responds to both electric and magnetic field. Furthermore, the strain derivative of 84 × 10−9 Oe−1 at a field of 790 Oe is observed from magnetostriction measurement. Converse magnetoelectric effect was observed on an electrically poled sample where the sample got magnetized upon electrical poling. The value of linear magnetoelectric coefficient obtained was 150 mV/cm.Oe which is unusually high for a single phase material and at room temperature and this may be due to the d0 configuration of Nb. The observed linear magnetoelectric coefficient and room temperature PE loop was obtained suggesting that the Co1.2Fe1.7Nb0.1O4 material could be useful for magnetoelectric sensor applications.

Низкочастотный магнитоэлектрический датчик без смещения на основе слоистой структуры Metglas/кварц/Metglas

Tremendous progress has been made on boosting the performance of magnetoelecric sensor to detect low frequency magnetic field signal by frequency multiplication based on magnetolectric composites. In this paper, a novel magnetoelectric sensor based on the laminated Metglas/piezoelectric quartz crystal/Metglas composites structure is presented. The Metglas foils are bonded symmetrically on both sides of the X-cut quartz crystal plate with epoxy. Experiments showed that the ME composites sensor was able to achieved a limit of detection of 11 pT for a low frequency magnetic field 1 Hz without any bias field through frequency multiplication method. The noise power spectrum density of the sensor has also been tested to be 3.93·10-6 V/Hz−1/2 at 1 Hz. The results indicate that the proposed sensor has favorable features, which provides a cost-effective and high-performance approach for low frequency magnetic field measurement.

Low-power eddy current detection with 1-1 type magnetoelectric sensor for pipeline cracks monitoring

Pipeline systems, such as oil and natural gas pipelines, which are normally buried underground or distributed under the sea, are susceptible to corrosion and pressure destruction, and hence timely and reliable nondestructive testing (NDT) is necessary. Conventional nondestructive testing methods are generally based on ultrasonic, eddy current and magnetic flux leakage mechanism. With respect to eddy current testing (ECT) technologies, the current challenge is to develop magnetic sensors with high detection ability, extremely low power consumption and compatible with Internet of Things (IoT). Giant resonant magnetoelectric (ME) coupling has been previously reported in our proposed 1-1 ME composites. Here, we further presented an investigation on the eddy current testing (ECT) using 1-1 type ME sensor. The proposed ECT probe was built by integrating a small exciting coil surrounding the ME sensor. Simulation results indicate ECT based on ME sensors is especially applicable for non-ferromagnetic and low-conductivity materials, e.g. steel. One-dimensionally distributed cracks with varying crack sizes in a steel pipeline was then experimentally identified and located using ECT method. More importantly, the power consumption of our proposed ECT probe is as low as 0.625 uW, which shows 2–3 orders of magnitude improvement compared with other probes based on e.g. magnetoresistive (MR) sensors. Our research here provides a fundamental insight into NDT using ME sensors as a ECT probe and represents a crucial step towards online low-power monitoring of pipeline cracks.

Self-Biased Bidomain LiNbO3/Ni/Metglas Magnetoelectric Current Sensor.

The article is devoted to the theoretical and experimental study of a magnetoelectric (ME) current sensor based on a gradient structure. It is known that the use of gradient structures in magnetostrictive-piezoelectric composites makes it possible to create a self-biased structure by replacing an external magnetic field with an internal one, which significantly reduces the weight, power consumption and dimensions of the device. Current sensors based on a gradient bidomain structure LiNbO3 (LN)/Ni/Metglas with the following layer thicknesses: lithium niobate—500 μm, nickel—10 μm, Metglas—29 μm, operate on a linear section of the working characteristic and do not require the bias magnetic field. The main characteristics of a contactless ME current sensor: its current range measures up to 10 A, it has a sensitivity of 0.9 V/A, its current consumption is not more than 2.5 mA, and its linearity is maintained to an accuracy of 99.8%. Some additional advantages of a bidomain lithium niobate-based current sensor are the increased sensitivity of the device due to the use of the bending mode in the electromechanical resonance region and the absence of a lead component in the device.

Magnetoelectric response in lead-free Na0.4K0.1Bi0.5TiO3/NiFe2O4 laminated composites

Lead-free Na0.4K0.1Bi0.5TiO3 (NKBT) and NiFe2O4 (NFO) ceramics are synthesized by solid-state reaction, and the laminated NKBT/NFO composites have been prepared by gluing the sintered discs with silver-epoxy. The measured parameters, dielectric constant (ε′) ∼1450 at 1 kHz, remanent polarization (Pr)∼39 μC/cm2, coercive electric field (Ec)∼27 kV/cm and maximum strain (Smax)∼0.3 % of NKBT along with saturation magnetization (Ms)∼49 emu/g, coercive magnetic field (Hc)∼27 Oe and magnetostriction (λ)∼-30 ppm of NFO, makes them suitable materials to evaluate as laminated magnetoelectric (ME) composites. A maximum ME response of 37, 67 and 86 mV/cm Oe at Hdc∼350−400 Oe field and 1 kHz frequency is observed for NKBT/NFO, NKBT/NFO/NKBT and NFO/NKBT/NFO layered composites, respectively. The high ME response at reasonable fields implies that NKBT/NFO laminated composite is a worthy lead-free candidate for ME sensor and energy harvesting applications.

Structural, ferroelectric, magnetic and magnetoelectric properties of (1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 -x La0.67Sr0.33MnO3 lead-free magnetoelectric composites

The influence of an additional La0.67Sr0.33MnO3 (LSMO) magnetic phase on the structural, ferromagnetic, ferroelectric, and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ferroelectric phase was studied for composites of (1-x)BCZT -xLSMO (x = 0, 25, 50, 75 and 100%). The ferroelectric BCZT sample showed a perovskite single phase formation with a tetragonal crystal structure of the P4mm space group, and the magnetic phase of LSMO presented a rhombohedral crystal structure of R3c space group as shown by XRD. The composite sample with 25% LSMO exhibited large ferroelectric and piezoelectric properties with remnant, saturation polarization, and coercive electric field Pr ~7.74 μC/cm2, Ps ~11.69 μC/cm2 and EC ~12.22 kV/cm with a piezoelectric coefficient d33 ~ 231 pC/N. The magnetic characterization for the composites showed that the sample containing 75% of LSMO revealed the highest remnant, saturation magnetization, and coercive field of Mr ~1.358 emu/g, Ms ~19.17 emu/g, and HC ~33.19 Oe, respectively. Moreover, it revealed the largest magnetoelectric coupling coefficient αME ~2.51 mV/cm.Oe with high coupling quality at a lower applied magnetic field. The results highlight the value of these composites as lead-free room temperature magnetoelectric sensors and actuators.

Tunable polarization with enhanced multiferroic response of W/Co co-doped Bi4LaFeTi3O15 Aurivillius ceramics

A comprehensive investigation on structural, microstructural, optical, electrical, magnetic, and magnetoelectric (ME) properties of the single phase Bi4LaFeTi3−2x(WyCo2y)xO15 (0.00 ≤ x ≤ 0.15, y = 1.0) Aurivillius ceramics has been presented here. The preliminary x-ray diffraction and Raman spectroscopic studies reveal that a layered-structure perovskite Aurivillius phase of orthorhombic space group A21am. Furthermore, the surface morphology study provides a plate-like to spherical-like granules with increasing the dopant concentrations. The ferroelectric response prevails a slim P–E loop for pristine sample, whereas it provides the highest polarization (Ps) values of 7.21 and 13.25 μC/cm2 for x = 0.10 and 0.15 concentrations, respectively. At low temperature, magnetic measurements provide a weak antiferromagnetic ordering of pristine sample, whereas a strong FM (ferromagnetic) ordering of doped ceramics is attained. The observed strong FM behavior of the Aurivillius phase is attributed to either double exchange interactions between neighboring Fe3+–O–Fe3+, Co3+–O–Co3+, and Fe3+–O–Co3+ ions or antisymmetric Dzyaloshinskii–Moriya interactions for spin canting of adjacent sub-lattices via Co3+/2+–O–Co3+/2+, Fe3+–O–Fe3+, and Co3+/2+–O–Fe3+ ions. The temperature dependent dielectric broad-band spectroscopic study enlightened a dielectric relaxation. This is due to cationic disordering through the generation of oxygen vacancies, which yields a conduction mechanism at high temperature regions. Furthermore, a complex modulus spectroscopic technique is also adopted to investigate the dielectric relaxation at high temperature regimes. The observed magnetic ferroelectric polarization responses and magnitudes of ME coupling coefficients provided that this material could be useful for future magnetoelectric sensors.

Analysis of the Magnetoelectric Sensor's Usability for the Energy Harvesting

Analysis of the Magnetoelectric Sensor's Usability for the Energy Harvesting

Schematic modeling of functional units of a magnetoelectric current sensor

The article is devoted to circuit simulation of functional units of a magnetoelectric current sensor. The magnetoelectric current sensor is designed to measure the current in electrical circuits of direct or alternating current in electrical engineering. The advantages of the developed magnetoelectric current sensors over existing analogs are higher sensitivity, lower power consumption, wide dynamic range of the output voltage, and better linearity of the output characteristics. In the course of the simulation, a model of the OA MCP6024-E/ST microcircuit from Microchip Technology Inc. was used, which is used as a signal amplifier for a magnetoelectric sensing element in a current sensor. Simulation of the signal generation unit, peak detector and linear amplifier was carried out. Circuitry solutions were proposed to improve the parameters of existing current sensors. Solutions have been found to ensure the temperature stability of the sensor. The developed magnetoelectric current sensors can be manufactured using integral technology and become a significant competitor to the traditional Hall effect sensors.

Comparison of characteristics of variable magnetic field magnetoelectric sensors based on bidomain lithium niobate, with active magnetic mass and self-biased Ni / Metglas gradient structure

The article is devoted to a theoretical comparison of the characteristics of two magnetoelectric sensors of an alternating magnetic field, operating without an external magnetizing field. The first sensor uses a bending mode in a bimorph lithium niobate with an active magnetic mass at the free end. The second sensor consists of lithium bimorph niobate and a self-biased Ni-Metglas gradient structure. The performed estimates show that a sensor with an active magnetic mass is more than 4 times superior to a sensor with a self-biased gradient structure in sensitivity to an alternating magnetic field. However, it has the advantage that by changing the mass of the magnets, the resonant frequency of the sensor can be controlled. In turn, a sensor with a self-biased gradient structure wins in terms of mass and size characteristics. The results obtained can be used to build promising variable magnetic field sensors for use in biomedicine.