Faculty Profiles - KIWA Toshihiko

Papers - KIWA Toshihiko

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Investigation of Cross-Section Measurement Method for All-Solid-State Batteries Using Terahertz Chemical Microscopy

Masashi Shimizu, Ryota Tomie, Kashu Hamada, Takashi Teranishi, Jin Wang, Kenji Sakai, Toshihiko Kiwa

2021 46TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ) 2021

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

In recent years, all-solid-state batteries have been attracting attention as secondary batteries to replace Li ion batteries. To improve the performance of all-solid-state batteries, measurement methods are required to evaluate electrode-solid electrolyte interfaces and electrochemical reactions between electrodes. In this study, we investigated a measurement method for the cross-section of all-solid-state batteries using terahertz chemical microscopy (TCM). We fabricated a model of all-solid-state battery and showed the possibility of using TCM to measure the cross-section of the all-solid-state battery by measuring the cross-section of a model of all-solid-state battery.

DOI： 10.1109/IRMMW-THz50926.2021.9567015

Development of Ion Concentration Measurement Method for Minute Volume of Blood Using Terahertz Chemical Microscope

Katsuya Taniizumi, Hiroki Nagata, Masaki Ando, Atsuya Mahana, Jin Wang, Kenji Sakai, Toshihiko Kiwa

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2021-August 2021

Electric Potential Distribution on Lithium Ion Battery Cathodes Measured Using Terahertz Chemical Microscopy

Toshihiko Kiwa, Yuki Akiwa, Hayato Fujita, Takashi Teranishi, Kenji Sakai, Hidetoshi Nose, Masaki Kobayashi, Keiji Tsukada

Journal of Infrared, Millimeter, and Terahertz Waves 41 ( 4 ) 430 - 437 2020.4

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. A terahertz chemical microscope has been developed to visualize electric potential distribution on lithium ion battery cathodes during battery operation. A sensing plate comprising a Si film grown epitaxially on a sapphire substrate was used as a terahertz emitter. The amplitude of terahertz radiation from the sensing plate could be related to the electric potential at the exact point where a femtosecond laser illuminated. Here, the sensing plate was integrated into a conventional can-type lithium ion battery and terahertz radiation from the sensing plate was observed during battery operation between 2.7 and 4.2 V. By scanning the laser, the distribution of terahertz amplitude radiated from the sensing plate was observed, which could be related to the electric potential distribution on the electrodes of the batteries. Localized electric potential could be visualized as the amplitude of terahertz radiation generated in the sensing plate, which was integrated beneath the battery electrode.

DOI： 10.1007/s10762-019-00640-x

Liquid-like dielectric response is an origin of long polaron lifetime exceeding 10 μs in lead bromide perovskites. International journal

Kiyoshi Miyata, Ryota Nagaoka, Masaki Hada, Takanori Tanaka, Ryuji Mishima, Taihei Kuroda, Sota Sueta, Takumi Iida, Yoshifumi Yamashita, Takeshi Nishikawa, Kenji Tsuruta, Yasuhiko Hayashi, Ken Onda, Toshihiko Kiwa, Takashi Teranishi

The Journal of chemical physics 152 ( 8 ) 084704 - 084704 2020.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Lead halide perovskites are promising materials for optoelectronic applications because of their exceptional performances in carrier lifetime and diffusion length; however, the microscopic origins of their unique characteristics remain elusive. The organic-inorganic hybrid perovskites show unique dielectric functions, i.e., ferroelectric-like phonon responses in the 0.1-10 THz region and liquid-like rotational relaxation in the 1-100 GHz range. To reveal the role of the dielectric responses is of primal importance because the dielectric screening is a key to understanding the optoelectronic properties governed by polarons in the perovskites. Here, we conducted comparative studies of broadband dielectric spectroscopy on both all-inorganic CsPbBr3 and organic-inorganic hybrid (CH3NH3)PbBr3 single crystals to uncover the origin of the liquid-like dielectric relaxation in the 1-100 GHz range. We confirmed the absence of the dielectric response in the range of 106-1010 Hz in CsPbBr3, which was clearly present in the hybrid (CH3NH3)PbBr3. This suggests that the response is almost purely due to the rotational motions of the organic dipoles in the hybrid perovskites. We evaluated the lifetimes of the polarons using surface-free transient photoluminescence. The lifetime in CsPbBr3 was up to 1.6 µs, while the lifetime in (CH3NH3)PbBr3 was 18 µs. The lifetime in the hybrid (CH3NH3)PbBr3 was significantly longer than in CsPbBr3, also confirmed by transient infrared spectroscopy. We concluded that the liquid-like dielectric response inhibits polaron recombination due to the efficient separation of opposite charges by the additional dynamic disorder.

DOI： 10.1063/1.5127993

Laser monitoring of dynamic behavior of magnetic nanoparticles in magnetic field gradient

Kenta Tsunashima, Katsuya Jinno, Bunta Hiramatsu, Kayo Fujimoto, Kenji Sakai, Toshihiko Kiwa, Mohd Mawardi Saari, Keiji Tsukada

AIP Advances 10 ( 1 ) 2020.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

© 2020 Author(s). Manipulation of magnetic nanoparticles (MNP) by an external magnetic field has been widely studied in the fields of biotechnology and medicine for collecting and/or reacting biomaterials in the solutions. Here, dynamic behaviors of MNP in solution under changing gradient magnetic field were investigated using our newly developed laser transmission system (LTS) with a variable magnetic field manipulator. The manipulator consists of a moving permanent magnet placed beside the optical cell filled with MNP solution. A laser beam was focused on the cell and the transmitted laser beam was detected by a silicon photodiode, so that the localized concentration of the MNP at the focused area could be evaluated by the intensity of transmitted laser beam. In this study, the LTS was applied to evaluate dynamic behaviors of MNP in serum solution. Dispersion and aggregation of MNP in the solution were evaluated. While time evolution of dispersion depends on the serum concentration, the behavior during aggregation by the magnetic field was independent of the serum concentration. A series of measurements for zeta-potentials, distributions of particle size, and magnetization distributions was carried out to understand this difference in the behavior. The results indicated that a Brownian motion was main force to distribute the MNP in the solution; on the other hand, the magnetic force to the MNP mainly affected the behavior during aggregation of the MNP in the solution.

DOI： 10.1063/1.5130167

Magnetic characterization change by solvents of magnetic nanoparticles in liquid-phase magnetic immunoassay

Katsuya Jinno, Bunta Hiramatsu, Kenta Tsunashima, Kayo Fujimoto, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

AIP Advances 9 ( 12 ) 2019.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

© 2019 Author(s). Liquid-phase magnetic immunoassay (MIA) using magnetic nano-particles (MNPs) has been studied as a more rapid method compared to optical methods for inspecting proteins and viruses. MIA can estimate the number of conjugated antibodies without being washed differently from conventional optical immunoassay. However, in the case of the liquid phase, it is considered that the magnetic properties of MNPs are affected by physical properties such as viscosity and impurity substances such as biological substances contained in the blood. In this study, the effect of sodium chloride (NaCl) in buffer and serum solution was evaluated to reveal the effect of serum because the sodium (Na+) and chloride (Cl-) ions in the serum dominate ion balance of blood. The measurement results of AC magnetic susceptibility and a dynamic light scattering (DLS) showed that the aggregation of MNPs was largely affected by the concentration of NaCl. This effect of the NaCl could be explained by shielding of the surface charge of MNPs by ions in the solution. Although the concentrations of NaCl in the buffer and serum solution were almost same, we found that MNPs were aggregated more in their size for those in the serum solution because of other impurities, such as proteins. These results suggest evaluation of effects of the contaminants in serum and optimization of polymer coatings of MNPs could be important factors to realize measurements of magnetic immunoassay with high accuracy.

DOI： 10.1063/1.5130168

One-Minute Joule Annealing Enhances the Thermoelectric Properties of Carbon Nanotube Yarns via the Formation of Graphene at the Interface Reviewed

Masaki Hada, Taisuke Hasegawa, Hirotaka Inoue, Makito Takagi, Kazuki Omoto, Daiki Chujo, Shogo Iemoto, Taihei Kuroda, Taiga Morimoto, Takuma Hayashi, Toru Iijima, Tomoharu Tokunaga, Naoshi Ikeda, Kazuhiro Fujimori, Chihiro Itoh, Takeshi Nishikawa, Yoshifumi Yamashita, Toshihiko Kiwa, Shin ya Koshihara, Satoshi Maeda, Yasuhiko Hayashi

ACS Applied Energy Materials 2 ( 10 ) 7700 - 7708 2019.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

© 2019 American Chemical Society. Interfaces in nanocarbon materials are highly important, as they determine the properties of carbon-based devices. In terms of carrier and thermal transport properties, the interfacial features are often more important than the intrinsic characteristics. Herein, we describe how 1 min Joule annealing of carbon nanotube (CNT) yarns can convert the interfacial amorphous carbon into graphene fragments. After 1 min Joule annealing, we have obtained multiwalled CNT yarns with extremely high Seebeck coefficients (±100 μV/K) and high thermoelectric power factor (400 and 1000 μW/mK2) at room temperature, both with or without polyethylenimine doping. Theoretical simulations and experimental measurements helped to determine the optimal annealing conditions in terms of a rapid transformation of the interfacial amorphous carbon between the bundled CNTs in the yarn into graphene fragments at â¼2000 K. The present approach represents significant progress in energy materials science, as it provides a guiding principle for the design of interfaces in nanocarbon materials with potential applications in energy-harvesting systems.

DOI： 10.1021/acsaem.9b01736

Influence of Viscosity on Dynamic Magnetization of Thermally Blocked Iron Oxide Nanoparticles Characterized by a Sensitive AC Magnetometer

Mohd Mawardi Saari, Nazatul Shareena Suhaimi, Mohd Herwan Sulaiman, Nurul Akmal Che Lah, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

Journal of Superconductivity and Novel Magnetism 32 ( 9 ) 2765 - 2772 2019.9

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. In this work, we show that the viscosity of carrier liquid affects the dynamic magnetization of thermally blocked multi-core iron oxide nanoparticles. The core size of the nanoparticles was determined from the magnetization curve measured by a specially developed high-Tc SQUID magnetometer and calculated to be 11.7 nm. Using an AC magnetometer developed based on induction coils, the dynamic magnetization of the multi-core iron oxide nanoparticle solution was measured from 3 Hz to 10.48 kHz. Later, we reconstructed of the hydrodynamic size distribution of the particles by assuming a log-normal distribution of particle size in an AC susceptibility model by Shliomis and Stepanov, which accounts for anisotropic directions of the easy axes of magnetic nanoparticles with respect to the excitation field direction. The reconstructed hydrodynamic sizes showed an average diameter of 130 nm and agreed with the size determined by dynamic light scattering method. In the case of increasing viscosity of the carrier liquids from 0.89 to 8.11 mPa s, the dynamic magnetization peaks of the imaginary component have shifted to a lower frequency region. We showed that the harmonics ratio and phase delay upon the magnetic field excitation at 30 Hz could also be used to determine the viscosity of carrier liquid independently.

DOI： 10.1007/s10948-019-5031-6

Development of a Highly Sensitive Magnetic Field Detector with a Wide Frequency Range for Nondestructive Testing Using an HTS Coil with Magnetic Sensors Reviewed

Tetsuro Hirata, Yuto Goda, Kenji Sakai, Toshihiko Kiwa, Seiji Adachi, Akira Tsukamoto, Tsunehiro Hato, Keiichi Tanabe, Keiji Tsukada

IEEE Transactions on Applied Superconductivity 29 ( 5 ) 2019.8

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2002-2011 IEEE. To perform an early stage detection of the deterioration of steel parts used in infrastructures, a nondestructive testing (NDT) method is required, which is capable of evaluating hidden parts such as a steel deck covered with an asphalt pavement. To achieve this, a magnetic field detector should be sufficiently large to detect magnetic fields over a wide range to account for high lift-off. In addition, the detector must be capable of functioning at high frequencies for a high-speed inspection of surface cracks, and at low frequencies to compensate for the skin effect during the inspection of inner or rear side cracks. In this paper, we developed a magnetic field detector for eddy current testing in a wide frequency range by combining a high-temperature superconducting (HTS) coil made using DI-BSCCO tapes with a tunnel magnetoresistive (TMR) sensor. The TMR sensor was attached on the inside of the loop of the HTS coil to maximize the shielding characteristic. We applied the developed system to NDT, which can detect a signal from an artificial crack with a lift-off of 75 mm, which is greater than the thickness of the asphalt pavement. In addition, inner cracks that are 2.7 mm beneath the surface can be detected with a 10 Hz applied magnetic field.

DOI： 10.1109/TASC.2019.2904485

Extraction Method of Crack Signal for Inspection of Complicated Steel Structures Using A Dual-Channel Magnetic Sensor. International journal

Minoru Hayashi, Taisuke Saito, Yoshihiro Nakamura, Kenji Sakai, Toshihiko Kiwa, Izumi Tanikura, Keiji Tsukada

Sensors (Basel, Switzerland) 19 ( 13 ) 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI

Conventional eddy current testing (ECT) using a pickup coil probe is widely employed for the detection of structural cracks. However, the inspection of conventional ECT for steel structures is difficult because of the magnetic noise caused by the nonuniform permeability of steel. To combat this challenge, we have developed a small magnetic sensor probe with a dual-channel tunneling magnetoresistance sensor that is capable of reducing magnetic noise. Applying this probe to a complicated component of steel structures-such as the welds joining a U-shaped rib and deck plate together-requires the reduction of signal fluctuation caused by the distance (liftoff) variations between the sensor probe and the subject. In this study, the fundamental crack signal and the liftoff signal were investigated with the dual-channel sensor. The results showed that the liftoff signals could be reduced and differentiated from the crack signals by the differential parameters of the dual-channel sensor. In addition, we proposed an extraction technique for the crack signal using the Lissajous curve of the differential parameters. The extraction technique could be applied to the inspections not only for flat plates but also for welded angles to detect cracks without the influence of the liftoff signal.

DOI： 10.3390/s19133001

Using Magnetic Field Gradients to Shorten the Antigen-Antibody Reaction Time for a Magnetic Immunoassay

Keiji Tsukada, Kenta Tsunashima, Katsuya Jinno, Bunta Hiramatsu, Shun Takeuchi, Kayo Fujimoto, Kenji Sakai, Toshihiko Kiwa, Mohd Mawardi Saari

IEEE Transactions on Magnetics 55 ( 7 ) 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 1965-2012 IEEE. The measurement of biological targets using nanoparticle magnetic markers has been extensively studied for its applications in magnetic immunoassays (MIAs). Compared with the optical immunoassay method, the MIA methods have some attractive characteristics such as a wash-free process that does not need bound/free marker separation and the ability to detect biological targets in a nebulous liquid. In addition, the wash-free process is very fast. In this paper, we tried to reduce the reaction time for the antigen-antibody reaction in order to make the MIA method more attractive. The reduction in reaction time and the detection characteristic of biological targets were demonstrated using C-reactive proteins (CRPs) as biological targets for diagnosing inflammation. To shorten the reaction time, a magnetic-shaking method using the magnetic field gradient from a neodymium magnet was developed. When comparing the reaction times with and without magnetic shaking, it was found that the reaction time decreased with magnetic shaking for all CRP concentrations. Even after the magnetic-shaking treatment, the dependence of the CRP concentration on the magnetic signal was observed. The number of surface modifications per magnetic marker and the magnetic marker concentration also affected the reaction time. In order to obtain the desired measurement range based on the CRP response characteristic, it is necessary to optimize the number of magnetic markers and polymer beads used.

DOI： 10.1109/TMAG.2019.2894904

Improvement of contrast of Terahertz Images of a Terahertz Chemical Microscopy using Adaptive Digital Filter

Feroz Ahmed, Tatsuki Kamiya, Yuki Maeno, Toshihiko Kiwa, Kenji Sakai, Keiji Tsukada

5th International Conference on Computer, Communication, Chemical, Materials and Electronic Engineering, IC4ME2 2019 2019.7

Publishing type：Research paper (international conference proceedings)

© 2019 IEEE. A Terahertz Chemical Microscope has been proposed and developed for the visualization of chemical reactions in the solutions. To visualize chemical reactions with higher imaging quality and higher scanning speed, it is required to improve the contrast of the images. In this study, we applied an adaptive filter to the TCM system and evaluate the imaging quality qualitatively. The contrasts without filter and with filter are 0.33 and 0.74 respectively. This result shows that our system with the filter could improve the imaging quality without losing the scanning speed of the microscope.

DOI： 10.1109/IC4ME247184.2019.9036485

High-sensitivity detection of metastatic breast cancer cells via terahertz chemical microscopy using aptamers Reviewed

Eman M. Hassan, Ahmed Mohamed, Maria C. DeRosa, William G. Willmore, Yuki Hanaoka, Toshihiko Kiwa, Tsuneyuki Ozaki

Sensors and Actuators, B: Chemical 287 595 - 601 2019.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

© 2019 Elsevier B.V. We demonstrate high-sensitivity detection of metastatic breast cancer cells using terahertz (THz) chemical microscopy (TCM) with aptamers as ligands. For the aptamers, we use previously developed synthetic single stranded (ss) DNA aptamers mammaglobin B1 (MAMB1) and mammaglobin A2 (MAMA2) that bind to mammaglobin B and mammaglobin A proteins, respectively, which are overexpressed on the surface of MCF7 and MDA-MB-415 breast cancer cells. Each aptamer was immobilized on the surface of a sensing plate, and the amplitude of the THz signal was measured upon the binding of each aptamer to different number (10–106) of its target breast cancer cells. A change in the THz amplitude was observed when MAMB1 and MAMA2 bind to MCF7 and MDA-MB-415, respectively. We find that this change was linear as a function of the log number of breast cancer cells used. No change in the THz amplitude was observed when the same number of normal breast cells (MCF 10A) were used. Moreover, MAMB1 and MAMA2 did not show binding to the counter breast cancer cells, indicating high selectivity. We have demonstrated that the TCM using aptamers as ligands has a limit of detection as small as 1 breast cancer cell in 100 μL of sample. Results described here indicate that the TCM could be a powerful tool to detect metastatic breast cancer cells.

DOI： 10.1016/j.snb.2019.02.019

Hybrid Magnetic Sensor Combined with a Tunnel Magnetoresistive Sensor and High-Temperature Superconducting Magnetic-Field-Focusing Plates Reviewed

Keiji Tsukada, Tetsuro Hirata, Yuto Goda, Kenji Sakai, Toshihiko Kiwa

IEEE Transactions on Applied Superconductivity 29 ( 3 ) 2019.4

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2002-2011 IEEE. Magnetoresistive (MR) sensors are widely used, particularly in consumer products. However, in applications requiring extremely sensitive magnetic sensors, superconducting quantum interference devices (SQUIDs) are primarily used. In this study, we develop a hybrid magnetic sensor by combining an MR sensor with two high-temperature superconducting (HTS) plates to achieve sensitivity that lies between those of MR sensors and SQUIDs. In addition, we apply a modulation method for measuring the absolute magnetic field. A nanogranular in-gap tunnel MR sensor is installed inside the slit between the magnetic-field-focusing HTS plates, and the magnetic response is evaluated. Using the magnetic-field-focusing characteristics of the HTS plates (made from YBa2Cu3O7-δ) and the MR sensor inside the slit between the two plates, the sensitivity and noise characteristics are improved. Adjustment of parameters, such as MR sensor height from the slit, slit width of the HTS plates, and plate size allow sensitivity control depending on the application. Moreover, the absolute magnetic response and low noise in low-frequency regions are obtained through ac modulation.

DOI： 10.1109/TASC.2018.2874354

Imaging of chemical reactions using a terahertz chemical microscope Reviewed

Toshihiko Kiwa, Tatsuki Kamiya, Taiga Morimoto, Kentaro Fujiwara, Yuki Maeno, Yuki Akiwa, Masahiro Iida, Taihei Kuroda, Kenji Sakai, Hidetoshi Nose, Masaki Kobayashi, Keiji Tsukada

Photonics 6 ( 1 ) 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI

© 2019 by the authors. This study develops a terahertz (THz) chemical microscope (TCM) that visualizes the distribution of chemical reaction on a silicon-based sensing chip. This chip, called the sensing plate, was fabricated by depositing Si thin films on a sapphire substrate and thermally oxidizing the Si film surface. The Si thin film of the sensing plate was irradiated from the substrate side by a femtosecond laser, generating THz pulses that were radiated into free space through the surface field effect of the Si thin film. The surface field responds to chemical reactions on the surface of the sensing plate, changing the amplitude of the THz pulses. This paper first demonstrates the principle and experimental setup of the TCM and performs the imaging and measurement of chemical reactions, including the reactions of bio-related materials.

DOI： 10.3390/photonics6010010

Integrated Magnetic Sensor Probe and Excitation Wire for Nondestructive Detection of Submillimeter Defects

Keiji Tsukada, Hiroto Shobu, Yuto Goda, Takumi Kobara, Kenji Sakai, Toshihiko Kiwa, Mohd Mawardi Saari

IEEE Magnetics Letters 10 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

© 2010-2012 IEEE. Eddy current testing with excitation and pickup coils is widely used to detect defects in metals. The detection of submillimeter defects is difficult because of limitations on pickup coil size. We have developed an integrated magnetic probe for detecting submillimeter defects in both nonmagnetic and ferromagnetic materials. The sensor probe consists of a tunneling magnetoresistance (TMR) device and an excitation wire. This probe can apply small, localized magnetic fields to a sample that is near the TMR sensor. The direction of the field excitation is perpendicular to the sensing direction of the TMR sensor to minimize magnetic coupling between the excitation wire and the sensor. A change in the line-scanned signal was detected when measuring pits from 0.5 mm to 1.0 mm in diameter at depths of more than 0.1 mm in both steel and aluminum plates. Signal changes depended on defect size. As the frequency was increased from 1 kHz to 50 kHz, the defect signal change for the aluminum plate increased due to an increase in eddy currents. A clear defect signal for the steel plate was obtained even at a low frequency of 1 kHz because the detected signal for steel consists of a frequency-dependent eddy-current component and a magnetization component even at low frequencies.

DOI： 10.1109/LMAG.2019.2936392

Magnetic NDE system for detection of crack in steel deck with high lift-off using secondary differential detection coil

Yuto Goda, Hiroto Shobu, Takumi Kobara, Kenji Sakai, Toshihiko Kiwa, Akira Tsukamoto, Keiichi Tanabe, Keiji Tsukada

10th International Workshop NDT in Progress 2019

Publishing type：Research paper (international conference proceedings)

© International Workshop NDT.All rights reserved. Recently, the aging of buildings and infrastructure facilities is becoming a social problem. In the steel structure, the nondestructive evaluation with high lift-off is required to inspect the steel material under the asphalt or concrete, such as the steel floor slabs of roads. Under the high lift-off condition, the influence of the magnetic noise and applied magnetic field should be reduced because the signal from the crack is small. In order to reduce the influence of the magnetic noise, in this study, the detection of crack signal by eddy current testing was examined using a detection coil of a differential coil. This differential coil is a secondary differential coil combining two differential coils aiming for improving the signal to noise ratio (SNR) by reducing the influence of the magnetic noise and applied magnetic field. Using this secondary differential coil, the crack with high liftoff of 80 mm was detected, and it is expected to detect the cracks in steel structures located under the asphalt or concrete.

Design of eddy current testing probe for surface defect evaluation

M. M. Saari, N. A. Nadzri, A. M. Halil, M. Ishak, K. Sakai, T. Kiwa, K. Tsukada

International Journal of Automotive and Mechanical Engineering 16 ( 1 ) 6357 - 6367 2019

Publishing type：Research paper (scientific journal)

© Universiti Malaysia Pahang, Malaysia. Early detection of defects in metallic components used in infrastructure is crucial to ensure their safety and reliability. This paper presents a development of a small eddy current testing (ECT) probe for evaluation of sub-millimetre surface defects. The ECT probe is developed in a planar differential using sensitive anisotropy magnetoresistance sensors, and the signal amplification is achieved by a home-made instrumentation amplifier. The developed ECT probe is evaluated by performing phase sensitive measurement of the magnetic responses of sub-millimetre surface slits at the excitation field of 200 Hz and 10 kHz. Compared to the real component of the magnetic response, the imaginary component can be used to identify the existence and position of the slits based on the signal intensity change caused by the induced eddy current. The spatial distribution of the magnetic response measured by the ECT probe can be used to estimate the dimension of the slit. It is expected that the developed ECT probe can be utilised for assessment of sub-millimetre surface defect.

DOI： 10.15282/ijame.16.1.2019.19.0481

Detection of lung cancer cells using a terahertz chemical microscope

Kosuke Sato, Masahiro Iida, Hirofumi Inoue, Toshihiko Kiwa, Shinichi Toyooka, Keiji Tsukada

Optics InfoBase Conference Papers Part F146-JSAP 2019 2019

Optimization of inclined angle magnetic sensor probe to improve detection performance of corrosion near the ground using extremely low-frequency eddy current testing

Shunki Wakabayashi, Minoru Hayashi, Taisuke Saitoh, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

10th International Workshop NDT in Progress 2019

Publishing type：Research paper (international conference proceedings)

© International Workshop NDT.All rights reserved. As the aging of steel pipes used for sign pole is caused by the corrosion near ground, a quantitative evaluation of the corrosion location and thinning rate from the ground surface is required. Therefore, we have proposed a magnetic nondestructive testing for the steel pipes using two magnetic sensors, and it was possible to inspect the underground corrosion defects. However, in order to improve the accuracy of estimating the thinning rate and position of underground corrosion, the optimization of the inclination angle of the magnetic sensor probe and the distance between two magnetic sensors has been required. Therefore, in order to extract the signal change caused by the thinning rate of the test sample and the measurement distance, the distance dependence which is the relationship between the signal intensity and the measurement distance was measured and the measured value was normalized by the signal intensity measured at uncorroded area. As a result, the difference between the signal intensity at the uncorroded part and that near the corrosion defect could be clearly extracted. Furthermore, the rate of change of signal intensity increased by changing the tilt angle of probe and the distance between two sensors. Using the optimized magnetic sensor probe and applying the normalized distance dependence, we succeeded in the quantitative evaluation of the thinning rate and position of corrosion defects.

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