GMR Sensor Research Articles

Handheld Biosensor System Based on a Gradient Grating Period Guided-Mode Resonance Device.

Handheld biosensors have attracted substantial attention for numerous applications, including disease diagnosis, drug dosage monitoring, and environmental sensing. This study presents a novel handheld biosensor based on a gradient grating period guided-mode resonance (GGP-GMR) sensor. Unlike conventional GMR sensors, the proposed sensor's grating period varies along the device length; hence, the resonant wavelength varies linearly along the device length. If a GGP-GMR sensor is illuminated with a narrow band of light at normal incidence, the light resonates and reflects at a specific period but transmits at other periods; this can be observed as a dark band by using a complementary metal oxide semiconductor (CMOS) underneath the sensor. The concentration of a target analyte can be determined by monitoring the shift of this dark band. We designed and fabricated a handheld device incorporating a light-emitting diode (LED) light source, the necessary optics, an optofluidic chip with an embedded GGP-GMR sensor, and a CMOS. LEDs with different beam angles and bandpass filters with different full width at half maximum values were investigated to optimize the dark band quality and improve the accuracy of the subsequent image analysis. Substrate materials with different refractive indices and waveguide thicknesses were also investigated to maximize the GGP-GMR sensor's figure of merit. Experiments were performed to validate the proposed handheld biosensor, which achieved a limit of detection (LOD) of 1.09 × 10-3 RIU for bulk solution measurement. The sensor's performance in the multiplexed detection of albumin and creatinine solutions at concentrations of 0-500 μg/mL and 0-10 mg/mL, respectively, was investigated; the corresponding LODs were 0.66 and 0.61 μg/mL.

Fabrication of GMR Sensors With Antiphase Magnetization Modulation and Closed-Loop Operation

Fabrication of GMR Sensors With Antiphase Magnetization Modulation and Closed-Loop Operation

Design, Development, and Performance Evaluation of GMR-Based Current Sensor for Industrial and Aerospace Applications

The article presents the development of an open-loop current sensor using indigenous multilayered giant magnetoresistance (GMR-ML) technology. The proposed current sensor consists of a magnetic core with an air gap, a GMR sensor chip, and a bias magnet. A GMR chip is biased with a permanent magnet to obtain linear bipolar output characteristics. The GMR chip measures the magnetic field produced in the air gap as a result of the current flowing through a conductor. The sensor design and characteristics were optimized and verified using both simulation and experiments. Several prototypes were fabricated and tested for the current range of ± 25 A. Experimental results indicate the sensitivity of the order of 0.165 mV/V/A with the temperature dependence of the sensitivity – 0.28 %/°C and bandwidth of 100 kHz. The fabricated prototypes were further compensated for temperature-dependent drift in sensitivity and offset in the temperature range of – 25 °C to 85 °C. The compensated sensor exhibits a sensitivity of 80 ± 0.5 mV/A with the temperature dependence of the sensitivity of 0.005 %/°C. The change in offset voltage of compensated sensor was less than 10 mV across the temperature range. The compensated prototype sensor shows a total output error of less than 1 % over the operating temperature range. Further, the performance of the sensor was evaluated for aerospace applications and compared with the existing current sensor. The comparative data shows an equivalent performance during the test.

New design of a commercial chip-based GMR sensor with magnetite nanoparticles for biosensing applications

New design of a commercial chip-based GMR sensor with magnetite nanoparticles for biosensing applications

Key Parameters for Detectivity Improvement of Low Noise Anisotropic Magnetoresistive Sensors Made of La2/3Sr1/3MnO3 Single Layers on Vicinal Substrates

The current trend in magnetoresistive sensors development is to increase the sensitivity of single sensing elements by using multilayer structures and to design them into arrays. Such arrays are designed to compensate the excess low frequency noise of individual elements, which limits their magnetic resolution. Here, we report the modeling, design, and fabrication of single layer anisotropic magnetoresistive (AMR) sensors using low noise epitaxial La2/3Sr1/3MnO3 (LSMO) oxide thin films deposited on vicinal SrTiO3 substrates. The fabrication process is simple, and the operation of the sensor is based on a step-induced uniaxial magnetic anisotropy, described using the Stoner–Wohlfarth model. A coherent magnetization reversal process is observed by magneto-optical Kerr effect imaging. A good agreement between experimental data and the expected sensor response confirms the correct operation of the device. Three main fabrication parameters, namely the vicinal angle of the substrate, the deposition temperature, the thin film thickness, and their effects on film anisotropy field and device detectivity have been studied. Detectivity levels as low as 1.4 nT Hz–1/2 at 1 Hz and 240 pT Hz–1/2 in the white noise region are achieved with a single Wheatstone bridge element operating at 310 K. Compared to GMR and AMR sensors, these results are promising for further development and for their use as single layer LSMO low field AMR sensors, including applications as implantable biomedical devices.

A Magnetic Feedback-Based Δ–Σ Digitizing Interface for Giant Magnetoresistance Sensors

Giant magnetoresistance sensors are popular for measurement of low magnetic fields due to their low-cost, easy-to-use, high-sensitivity design. However, the GMR sensors exhibit omnipolar, non-linear, and hysteretic voltage versus field characteristics, and operate over a limited range of input fields. In this brief, a simple digitizing interface, based on magnetic-feedback-based Delta-Sigma modulation, is proposed to overcome the aforementioned limitations of GMR sensors. The proposed interface operates the sensor at a quiescent magnetic field and renders a linear direct-digital output. The scheme is designed to measure bipolar fields. The methodology, analysis, and performance verification of the proposed interface are brought out in this brief. Experimental results of the developed interface show a non-linearity (N.L.) of just 0.52% over an enhanced measuring field range and significantly reduced hysteresis.

Investigation of GMR Eddy Current Permanent Magnet System for Carbon Steel Corrosion Identification using IoT Unmanned Aerial Vehicles Drone Platform

Eddy current test (ECT) is one of the techniques for accurate testing as well as widely used in the aircraft and nuclear industry. Changes in thickness due to corrosion will affect the measurement of defects on pipes or plates. This will make an irrelevant decision as to whether the defect that occurs on the work piece is the thickness of the paint or corrosion. This problem can lead to the occurrence of leaking pipes, apart from the deterioration of the company’s productivity and most importantly endangering the safety of employees. Meanwhile, eddy current testing is one of the methods in NDT used to detect cracks or corrosion on the surface of carbon steel. In this work, GMR Eddy Current sensor is used to measure the corrosion on carbon steel pipes, and a permanent magnet is used to generate the magnetic field for corrosion detection. Also, this system is configured with an IoT Unmanned Aerial Vehicles (UAV) drone platform to facilitate access at different heights during the inspection process. The change of voltage amplitude at the GMR sensor on the test material proves the conditioning of the material either normal or corrosive. The result shows that when corrosion occurs on the pipe, the voltage amplitude increases up to 0.5% higher than normal. Finally, the metal loss is higher when the corrosion area is larger and at the same time it is directly proportional to the voltage amplitude

Retraction Note to: Preclinical diagnosis of asthma with GMR sensor and RADWT algorithm

Retraction Note to: Preclinical diagnosis of asthma with GMR sensor and RADWT algorithm

High-performance refractive index sensor by nano-cylindrical surface structure

In this work, a two-dimensional grating structure based on the metal assisted guided-mode resonance (MAGMR) effect is proposed, which can be used for near infrared band sensing in an aqueous environment. Following optimization by the finite-difference time-domain method, the structure is able to support MAGMR well, and has an excellent reflection dip. The electromagnetic field shows that the structure not only interacts well with the sensing medium but also has a large penetration depth. Results at different refractive indices of the sensing medium confirm the high sensing performance of the proposed MAGMR sensor, which achieves a sensitivity of 852 nm/RIU. Meanwhile, the sensor has a figure of merit up to 4813 RIU−1 (55 times typical GMR sensors) because of the full width at half maximum is only 0.177 nm. Furthermore, the shape and parameters of the MAGMR sensor have been analyzed in detail in order to gain a comprehensive understanding of its performance. This MAGMR sensor is promising for future applications in biomedicine, chemical measurements and environmental monitoring due to its polarization-independent, non-specific angle of incidence, high penetration depth and high sensing performance.

A GMR-based assay for quantification of the human response to influenza

Detecting and quantifying the host transcriptional response to influenza virus infection can serve as a real-time diagnostic tool for clinical management. We have employed the multiplexing capabilities of GMR sensors to develop a novel assay based on the influenza metasignature (IMS), which can classify influenza infection based on transcript levels. We show that the assay can reliably detect ten IMS transcripts and distinguish subjects with naturally acquired influenza infection from those with other symptomatic viral infections (AUC 0.93, 95% CI: 0.82–1.00). Separately, we validated that the gene IFI27, not included in the IMS panel, has very high single-biomarker accuracy (AUC 0.95, 95% CI: 0.90–0.99) in stratifying patients with influenza. We demonstrate that a portable GMR biosensor can be used as a tool to diagnose influenza infection by measuring the host response, simultaneously highlighting the power of immune system metrics and advancing the field of gene expression-based diagnostics.

Proof of concept of a two-stage GMR sensor-based lab-on-a-chip for early diagnostic tests.

The development of rapid, sensitive, portable and inexpensive early diagnostic techniques is a real challenge in the fields of health, defense and in the environment. The current global pandemic has also shown the need for such tests. The World Health Organization has defined ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users) that field diagnostic tests must fulfill, which proves the real need in terms of public health. Giant magnetoresistance (GMR) sensors, which have flourished in a wide variety of spintronic applications (automobile industry, Information Technology, etc.), also have real potential in the field of health, particularly for the development of early diagnostic point-of-care devices. This work presents a new type of innovative biochip, consisting of GMR sensors arranged on both sides of a microfluidic channel which allow on the one hand to count magnetic objects one by one but also to better distinguish false positives (aggregates of beads, etc.) from labelled biological targets of interest by determining their magnetic moment. We present the operating principle of this new tool and its great potential as a versatile diagnostic test.

Synthesis of Fe3o4 at Different Reaction Temperatures and Investigation of its Magnetic Properties on Giant Magnetoresistance (Gmr) Sensors for Bio-Detection Applications

Synthesis of Fe3o4 at Different Reaction Temperatures and Investigation of its Magnetic Properties on Giant Magnetoresistance (Gmr) Sensors for Bio-Detection Applications

In-line detection of defects in steel pipes using flexible GMR sensor array

Steel pipes serve as the main source for transporting water, gas, and other petrochemical substances for longer distances. These pipes were able to withstand extreme weather conditions and hostile environments because of their remarkable properties such as higher strength, durability, lower cost, and improved wear and corrosion resistance. However, prolonged usage of these pipes in such environments may lead to the initiation of defects in their inner surface such as leak holes, cracks, corrosion, etc. In overtime, these defects may become more severe, resulting in component failure and property losses. Hence, earlier detection of defects is highly recommended to avoid these failures. In this work, an in-line robot system has been proposed for detecting the defects in the steel pipes. This robot utilizes a non-destructive way for evaluating the flaws by means of the magnetic flux leakage (MFL) technique. A 3D finite element model has been developed with the aid of ANSYS Maxwell 3D software for evaluating the generated magnetic field and optimizing the lift-off distance. The permanent magnet is preferred as the magnetizing material for implementing local magnetization in the inspection area. The magnetic flux leakage from the defect region is sensed by using a flexible GMR sensor array of six sensors. Artificial defects were introduced in a 6-inch diameter steel pipe in various shapes and the Arduino UNO controls the overall process. The data from the sensor array were collected using the Arduino and plotted as the waveform graph. From this graph, the voltage variations among the sensors represent the defect region. In addition, the higher peak in amplitude denotes that the flux is influenced by the defect’s depth. Thus, the waveform graph for the introduced defects was analyzed and all graph represents a better signal to noise ratio (SNR) for identifying the defects.

Extended micromagnetic model for the detection of superparamagnetic labels using a GMR vortex sensor

A self-consistent micromagnetic model is proposed for simulating interactions between a superparamagnetic label particle and a low-noise GMR vortex sensor, focusing on most common operations such as label detection and saturation. For this purpose, we evaluate the combined action of vortex stray field and the applied external field.By solving the Landau–Lifshitz-Gilbert equation we find that a superparamagnetic label with a diameter of 60 nm can be successfully detected by a magnetic vortex structure assisted with an external magnetic field of 100 mT. Subsequently, the self-consistent spin diffusion model is applied to calculate electric response of a standard low-noise GMR vortex sensor to the presence of magnetically-saturated label. It is shown that the stray field of the activated label produces a detectable potential difference in the GMR sensor of 27.1 to 27.8 mV, the magnitude of which depends on location of the label with respect to the sensor surface.

Effects of (Ni0.8Fe0.2)100−xCrx seed layer on microstructure, magnetic properties, and giant magnetoresistance of [FeCoNi/Cu] multilayer films

We studied the effect of the (Ni0.8Fe0.2)100−xCrx seed layer on the current-in-plane giant magnetoresistance (CIP-GMR) in Fe16Co66Ni18/Cu multilayer films. Both the GMR ratio (ΔR/R) and interlayer exchange coupling (IEC) between the FeCoNi layers showed strong dependences on the Cr concentration x in the seed layer. The highest ΔR/R of ∼30% was obtained for x = 38 (at. %) due to a comparatively strong antiparallel IEC resulting from a strong [111]-out-of-plane-texture of the [FeCoNi/Cu] multilayer. This confirms that a strong [111] texture is essential for the GMR in antiferromagnetically coupled multilayers as reported in previous works. However, we found that the strong [111] texture is not sufficient to obtain large ΔR/R. For x = 48, the [FeCoNi/Cu] multilayer showed a strong [111] texture as that for x = 38; however, the observed ΔR/R and antiparallel IEC for x = 48 were much smaller than those for x = 38. Detailed microstructural and chemical analyses by scanning transmission electron microscopy revealed that the fluctuation of the thickness of the Cu spacer layer can explain the reduction of antiparallel IEC that gave rise to the decrease in ΔR/R in the case of x = 48. We also discuss the effect of IEC energies on the sensitivity of GMR sensors.

Magnetic Nanoparticle Detection Using Wheatstone Bridge Giant Magnetoresistance (GMR) Sensor with Double CoFeB Spin-Valve Thin Films

The Wheatstone bridge-giant magnetoresistance (GMR) sensor with single and double spin valve thin film was successfully developed for potential biomolecular detection. The GMR sensor with spin valves structure of [Ta (2nm)/IrMn (10nm)/CoFe (3nm)/Cu (2,2nm)/CoFeB (10nm)/Ta (5nm)] was fabricated using DC Magnetic Sputtering method. The Fe3O4magnetic nanoparticles were synthesized by the co-precipitation method as a magnetic label. The magnetic properties of the Fe3O4nanoparticles measured are the saturation magnetization (Ms) of 77.7 emu/g, remanence magnetization (Mr) of 7.7 emu/g, and coercivity (Hc) of 49 Oe. The X-ray diffraction pattern showed the inverse cubic spinel structure with an average crystal size of about 20.1 nm. Fe3O4magnetic nanoparticles with various concentrations were used to be detected using a GMR sensor. The output voltage of the GMR sensor with the single and double spin-valve increased from 1.7 to 3.9 mV and 2.9 to 5.3 mV with the increase of the Fe3O4concentration from 0 to 20 mg/mL, respectively.

A tandem giant magnetoresistance assay for one-shot quantification of clinically relevant concentrations of N-terminal pro-B-type natriuretic peptide in human blood

We report a microfluidic sandwich immunoassay constructed around a dual-giant magnetoresistance (GMR) sensor array to quantify the heart failure biomarker NT-proBNP in human plasma at the clinically relevant concentration levels between 15 pg/mL and 40 ng/mL. The broad dynamic range was achieved by differential coating of two identical GMR sensors operated in tandem, and combining two standard curves. The detection limit was determined as 5 pg/mL. The assay, involving 53 plasma samples from patients with different cardiovascular diseases, was validated against the Roche Cobas e411 analyzer. The salient features of this system are its wide concentration range, low detection limit, small sample volume requirement (50 μL), and the need for a short measurement time of 15 min, making it a prospective candidate for practical use in point of care analysis.

Strain-induced control of magnetocrystalline anisotropy energy in FeCo thin films

We use density functional theory calculations to compute the lateral strain dependence of the magnetocrystalline anisotropy (MCA) energy of thin FeCo films. We investigate the effect of lateral strain on the MCA energy especially in the context of magnetostriction, which needs to be minimized for some applications like GMR sensors. The magneto-elastic coupling responsible for magnetostriction is a strain-derivative of the MCA energy, thus we concentrate to find extrema in the MCA energy vs. strain curves, which we find for both ordered Fe50Co50 films, as well as for disordered Fe10Co90 films modeled by special quasirandom structures. We show that using lateral strain we can switch the easy axis of magnetization from out-of-plane to in-plane in many cases. We can furthermore use lateral strain in combination with the film-thickness to minimize magnetostriction and change the MCA energy at the same time.

An Integrated Design of Planar Three-dimensional Magnetometers Powered by Novel Flux Guides

This paper presents a new framework for integrating a planar three-dimensional (3D) magnetometer, featuring high accuracy and reduced size. Sensing elements in this design are magnetoresistance (GMR) sensors, which generally exhibit good in-plane sensitivity but limiting performance when working out-of-plane. Therefore, to improve the out-of-plane sensing ability of the GMR sensors, we design a flux guide (FG) to redirect the out-of-plane magnetic field component to the sensitive plane of the sensors. In doing so, a Ni-Zn cubic FG, combined with a full-bridge of GMR, is exploited for z-sensing axis detection. The cross-detection minimization of in-plane magnetic fields is optimized by an FG rotated by 45o in the x-y axes. Moreover, for boosting the planar sensitivity, two half-bridge GMRs are incorporated into a cross-shaped flux concentrator, working as a fullbridge sensor. The performance of the proposed design is simulated, as well as estimated the sensing features.

Measuring technology and quality assurance in packaging steel production

Tinplate, being used primarily for packaging purposes, went through a considerable development over the last decades. Its quality was continuously improved enabling significant savings in material consumption and production economy and ecology. A premise for that progress is the development of advanced measurement and inspection equipment. It utilizes different physical principles to allow an online monitoring of important material parameters for regulation feedback or quality control. One of the latest developments is an online inspection system for non-metallic inclusions. It is based on magnetic flux leakage which is contactless detected by arrays of differential GMR sensors. The sensors are mounted to compact sensor modules containing all required peripheral equipment. Multiple sensor modules are connected to hubs which convert their data stream to the GigE camera standard. The resulting device resembles a magnetic line camera covering the whole surface of the inspected strip. The recorded images are processed by a software to detect and classify defects from the material noise.