Research

11 pages, 3523 KiB

Open AccessCommunication

Gradiometer Using Separated Diamond Quantum Magnetometers

by Yuta Masuyama, Katsumi Suzuki, Akira Hekizono, Mitsuyasu Iwanami, Mutsuko Hatano, Takayuki Iwasaki and Takeshi Ohshima

Sensors 2021, 21(3), 977; https://0-doi-org.brum.beds.ac.uk/10.3390/s21030977 - 02 Feb 2021

Cited by 8 | Viewed by 4112

Abstract

The negatively charged nitrogen-vacancy (NV) center in diamonds is known as the spin defect and using its electron spin, magnetometry can be realized even at room temperature with extremely high sensitivity as well as a high dynamic range. However, a magnetically shielded enclosure [...] Read more.

The negatively charged nitrogen-vacancy (NV) center in diamonds is known as the spin defect and using its electron spin, magnetometry can be realized even at room temperature with extremely high sensitivity as well as a high dynamic range. However, a magnetically shielded enclosure is usually required to sense weak magnetic fields because environmental magnetic field noises can disturb high sensitivity measurements. Here, we fabricated a gradiometer with variable sensor length that works at room temperature using a pair of diamond samples containing negatively charged NV centers. Each diamond is attached to an optical fiber to enable free sensor placement. Without any magnetically shielding, our gradiometer realizes a magnetic noise spectrum comparable to that of a three-layer magnetically shielded enclosure, reducing the noises at the low-frequency range below 1 Hz as well as at the frequency of 50 Hz (power line frequency) and its harmonics. These results indicate the potential of highly sensitive magnetic sensing by the gradiometer using the NV center for applications in noisy environments such as outdoor and in vehicles. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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19 pages, 4725 KiB

Open AccessArticle

A New Quaternion-Based Kalman Filter for Human Body Motion Tracking Using the Second Estimator of the Optimal Quaternion Algorithm and the Joint Angle Constraint Method with Inertial and Magnetic Sensors

by Yingbo Duan, Xiaoyue Zhang and Zhibing Li

Sensors 2020, 20(21), 6018; https://0-doi-org.brum.beds.ac.uk/10.3390/s20216018 - 23 Oct 2020

Cited by 13 | Viewed by 3565

Abstract

Human body motion tracking is a key technique in robotics, virtual reality and other human–computer interaction fields. This paper proposes a novel simple-structure Kalman filter to improve the accuracy of human body motion tracking, named the Second EStimator of the Optimal Quaternion Kalman [...] Read more.

Human body motion tracking is a key technique in robotics, virtual reality and other human–computer interaction fields. This paper proposes a novel simple-structure Kalman filter to improve the accuracy of human body motion tracking, named the Second EStimator of the Optimal Quaternion Kalman Filter (E2QKF). The new algorithm is the combination of the Second Estimator of the Optimal Quaternion (ESOQ-2) algorithm, the linear Kalman filter and the joint angle constraint method. In the proposed filter, the ESOQ-2 algorithm is used to produce an observation quaternion by preprocessing accelerometer and magnetometer measurements. The compensation for the accelerometer added in the ESOQ-2 algorithm is to eliminate the influence of human body motion acceleration included in the results. The state vector of the filter is the quaternion, which is calculated with gyroscope measurements, and the Kalman filter is to calculate the optimal quaternion by fusing the state quaternion and the observation quaternion. Therefore, the filter becomes a simple first-order linear system model, which avoids the linearization error of measurement equations and reduces the computational complexity. Furthermore, the joint angle constraint is considered in the proposed algorithm, which makes the results more accurate. To verify the accuracy of the proposed algorithm, inertial/magnetic sensors are used to perform the upper limb motion experiment, and the result of E2QKF (without joint angle constraint) is compared with an optical motion capture system and two traditional methods. Test results demonstrate the effectiveness of the proposed filter: the root mean square error (RMSE) of E2QKF is less than 2.0° and the maximum error is less than 4.6°. The result of E2QKF (with joint angle constraint) is compared with E2QKF (without joint angle constraint). Test results demonstrate the superiority of E2QKF (with joint angle constraint): the joint angle constraint method can further improve the accuracy of human body motion tracking. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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12 pages, 3290 KiB

Open AccessArticle

Magnetic Micro Sensors with Two Magnetic Field Effect Transistors Fabricated Using the Commercial Complementary Metal Oxide Semiconductor Process

by Wei-Ren Chen, Yao-Chuan Tsai, Po-Jen Shih, Cheng-Chih Hsu and Ching-Liang Dai

Sensors 2020, 20(17), 4731; https://0-doi-org.brum.beds.ac.uk/10.3390/s20174731 - 21 Aug 2020

Cited by 7 | Viewed by 2737

Abstract

The fabrication and characterization of a magnetic micro sensor (MMS) with two magnetic field effect transistors (MAGFETs) based on the commercial complementary metal oxide semiconductor (CMOS) process are investigated. The magnetic micro sensor is a three-axis sensing type. The structure of the magnetic [...] Read more.

The fabrication and characterization of a magnetic micro sensor (MMS) with two magnetic field effect transistors (MAGFETs) based on the commercial complementary metal oxide semiconductor (CMOS) process are investigated. The magnetic micro sensor is a three-axis sensing type. The structure of the magnetic microsensor is composed of an x/y-MAGFET and a z-MAGFET. The x/y-MAGFET is employed to sense the magnetic field (MF) in the x- and y-axis, and the z-MAGFET is used to detect the MF in the z-axis. To increase the sensitivity of the magnetic microsensor, gates are introduced into the two MAGFETs. The sensing current of the MAGFET enhances when a bias voltage is applied to the gates. The finite element method software Sentaurus TCAD was used to analyze the MMS’s performance. Experiments show that the MMS has a sensitivity of 182 mV/T in the x-axis MF and a sensitivity of 180 mV/T in the y-axis MF. The sensitivity of the MMS is 27.8 mV/T in the z-axis MF. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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23 pages, 20076 KiB

Open AccessArticle

Enhancement of Diversity in Production and Applications Utilizing Electrolytically Polymerized Rubber Sensors with MCF: The Second Report on Various Engineering Applications

by Kunio Shimada, Ryo Ikeda, Hiroshige Kikura and Hideharu Takahashi

Sensors 2020, 20(17), 4674; https://0-doi-org.brum.beds.ac.uk/10.3390/s20174674 - 19 Aug 2020

Cited by 2 | Viewed by 2332

Abstract

We investigated the proposed hybrid skin (H-Skin) for the requirement of haptic sensibility in rubber using our proposed consummate fabrication process together with a multi-layered magnetic compound fluid (MCF) rubber and stocking-like porous rubber permeated by liquids, which was demonstrated in our previous [...] Read more.

We investigated the proposed hybrid skin (H-Skin) for the requirement of haptic sensibility in rubber using our proposed consummate fabrication process together with a multi-layered magnetic compound fluid (MCF) rubber and stocking-like porous rubber permeated by liquids, which was demonstrated in our previous report. The objective was to assess its applicability to sensing normal force and temperature, as well as fields dominated by shear force. For normal force, we investigated the piezo-electricity and electric current induced voltage, as well as the piezo-resistivity of the MCF rubber sensor under pressure. Additionally, we clarified the viability of measuring the softness and texture of materials using the MCF rubber sensor. For the shear motion, we clarified the characteristics of the friction coefficient using the MCF rubber sensor. The MCF rubber sensor can capture the reactions of paper, cloth, convex- and concave-shaped objects such as plant leaves and metal, and the skin of the human finger. Therefore, it is useful to investigate its texture and biological surfaces. Our obtained outstanding results indicated the feasibility of sensing the surface texture for any material in fields such as paper, fashion, apparel manufacturing, and cosmetic industries, which was impossible until now. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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26 pages, 13053 KiB

Open AccessArticle

Enhancement of Diversity in Production and Application Utilizing Electrolytically Polymerized Rubber Sensors with MCF: 1st Report on Consummate Fabrication Combining Varied Kinds of Constituents with Porous Permeant Stocking-Like Rubber

by Kunio Shimada, Ryo Ikeda, Hiroshige Kikura and Hideharu Takahashi

Sensors 2020, 20(17), 4658; https://0-doi-org.brum.beds.ac.uk/10.3390/s20174658 - 19 Aug 2020

Cited by 6 | Viewed by 2304

Abstract

To satisfy the requirement of haptic sensibility in rubber such as in the proposed hybrid skin (H-Skin), the authors have demonstrated a new method for solidifying rubber using electrolytic polymerization together with configured magnetic clusters of magnetic compound fluid (MCF) incorporated into the [...] Read more.

To satisfy the requirement of haptic sensibility in rubber such as in the proposed hybrid skin (H-Skin), the authors have demonstrated a new method for solidifying rubber using electrolytic polymerization together with configured magnetic clusters of magnetic compound fluid (MCF) incorporated into the rubber by the application of a magnetic field. However, the rubber and magnetic fluid (MF) involved in the MCF rubber were water-soluble. In addition, the authors have demonstrated the practicability of using electrolytic polymerization with an emulsifier, polyvinyl alcohol (PVA), in which natural rubber (NR) or chloroprene rubber (CR) and silicone rubber (Q) can be mixed as water-soluble and water-insoluble rubbers, respectively. In this study, to enhance production, the feasibility of solidifying rubber by electrolytic polymerization is verified using varied water-insoluble rubber, varied water-insoluble MF, and varied surfactants to aid emulsion polymerization, except in the case of other kinds of rubber and MF which have been demonstrated until recent by the authors. Based on these diverse constituents, the authors propose a consummate fabrication process for multi-layered MCF rubber, which involves porous stocking-like rubber that can be permeated by any liquid. The investigation of this application is presented in the sequential second report. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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12 pages, 2678 KiB

Open AccessArticle

A Rapid and Sensitive Salmonella Biosensor Based on Viscoelastic Inertial Microfluidics

by Lan Yao, Lingyan Zheng, Gaozhe Cai, Siyuan Wang, Lei Wang and Jianhan Lin

Sensors 2020, 20(9), 2738; https://0-doi-org.brum.beds.ac.uk/10.3390/s20092738 - 11 May 2020

Cited by 15 | Viewed by 3314

Abstract

Salmonella is a main cause of foodborne illnesses and rapid screening of Salmonella is the key to prevent Salmonella outbreaks, however available detection methods either require a long time, or need complex pretreatment, or have low sensitivity. In this study, a microfluidic biosensor [...] Read more.

Salmonella is a main cause of foodborne illnesses and rapid screening of Salmonella is the key to prevent Salmonella outbreaks, however available detection methods either require a long time, or need complex pretreatment, or have low sensitivity. In this study, a microfluidic biosensor was developed for Salmonella detection using viscoelastic inertial microfluidics for separating magnetic bacteria from unbound magnetic nanoparticles (MNPs) and enzyme catalytic colorimetry for amplifying biological signals. The polyclonal antibodies and horseradish peroxidase (HRP) modified MNPs were first used to specifically capture Salmonella to form magnetic HRP-bacteria. Both magnetic HRP-bacteria and unbound MNPs were magnetically separated from background and resuspended in viscoelastic polyvinylpyrrolidone solution as sample flow. When sample flow was injected with polyvinylpyrrolidone sheath flow into a T-shaped microchannel, larger-sized magnetic HRP-bacteria could penetrate the sample flow, however smaller-sized MNPs remained in the sample flow due to weaker inertial lift force and elastic lift force, resulting in continuous-flow separation of magnetic HRP-bacteria. Finally, magnetic HRP-bacteria were collected and concentrated to catalyze tetramethyl benzidine, and absorbance was measured to determine the bacteria. This biosensor was able to detect Salmonella as low as 30 CFU/mL in 1 h and featured the advantages of shorter time due to a one-step immunoreaction, easier extension due to only one antibody and one label, and lower cost due to less expensive materials. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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Review

Jump to: Research, Other

18 pages, 8286 KiB

Open AccessReview

Recent Progress of Fluxgate Magnetic Sensors: Basic Research and Application

by Songrui Wei, Xiaoqi Liao, Han Zhang, Jianhua Pang and Yan Zhou

Sensors 2021, 21(4), 1500; https://0-doi-org.brum.beds.ac.uk/10.3390/s21041500 - 22 Feb 2021

Cited by 34 | Viewed by 7653

Abstract

Fluxgate magnetic sensors are especially important in detecting weak magnetic fields. The mechanism of a fluxgate magnetic sensor is based on Faraday’s law of electromagnetic induction. The structure of a fluxgate magnetic sensor mainly consists of excitation windings, core and sensing windings, similar [...] Read more.

Fluxgate magnetic sensors are especially important in detecting weak magnetic fields. The mechanism of a fluxgate magnetic sensor is based on Faraday’s law of electromagnetic induction. The structure of a fluxgate magnetic sensor mainly consists of excitation windings, core and sensing windings, similar to the structure of a transformer. To date, they have been applied to many fields such as geophysics and astro-observations, wearable electronic devices and non-destructive testing. In this review, we report the recent progress in both the basic research and applications of fluxgate magnetic sensors, especially in the past two years. Regarding the basic research, we focus on the progress in lowering the noise, better calibration methods and increasing the sensitivity. Concerning applications, we introduce recent work about fluxgate magnetometers on spacecraft, unmanned aerial vehicles, wearable electronic devices and defect detection in coiled tubing. Based on the above work, we hope that we can have a clearer prospect about the future research direction of fluxgate magnetic sensor. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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Other

Jump to: Research, Review

10 pages, 4335 KiB

Open AccessLetter

Serial MTJ-Based TMR Sensors in Bridge Configuration for Detection of Fractured Steel Bar in Magnetic Flux Leakage Testing

by Zhenhu Jin, Muhamad Arif Ihsan Mohd Noor Sam, Mikihiko Oogane and Yasuo Ando

Sensors 2021, 21(2), 668; https://0-doi-org.brum.beds.ac.uk/10.3390/s21020668 - 19 Jan 2021

Cited by 38 | Viewed by 5687

Abstract

Thanks to high sensitivity, excellent scalability, and low power consumption, magnetic tunnel junction (MTJ)-based tunnel magnetoresistance (TMR) sensors have been widely implemented in various industrial fields. In nondestructive magnetic flux leakage testing, the magnetic sensor plays a significant role in the detection results. [...] Read more.

Thanks to high sensitivity, excellent scalability, and low power consumption, magnetic tunnel junction (MTJ)-based tunnel magnetoresistance (TMR) sensors have been widely implemented in various industrial fields. In nondestructive magnetic flux leakage testing, the magnetic sensor plays a significant role in the detection results. As highly sensitive sensors, integrated MTJs can suppress frequency-dependent noise and thereby decrease detectivity; therefore, serial MTJ-based sensors allow for the design of high-performance sensors to measure variations in magnetic fields. In the present work, we fabricated serial MTJ-based TMR sensors and connected them to a full Wheatstone bridge circuit. Because noise power can be suppressed by using bridge configuration, the TMR sensor with Wheatstone bridge configuration showed low noise spectral density (0.19 μV/Hz^0.5) and excellent detectivity (5.29 × 10⁻⁸ Oe/Hz^0.5) at a frequency of 1 Hz. Furthermore, in magnetic flux leakage testing, compared with one TMR sensor, the Wheatstone bridge TMR sensors provided a higher signal-to-noise ratio for inspection of a steel bar. The one TMR sensor system could provide a high defect signal due to its high sensitivity at low lift-off (4 cm). However, as a result of its excellent detectivity, the full Wheatstone bridge-based TMR sensor detected the defect even at high lift-off (20 cm). This suggests that the developed TMR sensor provides excellent detectivity, detecting weak field changes in magnetic flux leakage testing. Full article

(This article belongs to the Special Issue Magnetic Sensing/Functionalized Devices and Applications)

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