Faculty Profiles - KIWA Toshihiko

Papers - KIWA Toshihiko

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Characterization of new structural ion sensor for sodium ion Reviewed

Tatsuya Komori, Takafumi Yamamoto, Kazuyo Oda, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

IEEJ Transactions on Sensors and Micromachines 133 ( 7 ) 309 - 313 2013

Language：Japanese Publishing type：Research paper (scientific journal)

We developed a new structural ion sensor for measuring sodium ions without using a reference electrode. The ion sensor, which is all solid state, has a structure of double electrodes, which are integrated on the base plate, inside the sodium ion sensitive membrane. The ion sensitivity of the sensor was 41.4 mV/decade in the range of 10-1 to 10-4M. To investigate the response mechanism of the potential between two electrodes, the impedance characteristic was measured using the electrochemical impedance method. The impedance of the ion sensitive membrane changed by changing the sodium ion concentration in solution. These results suggest a correlation between the membrane potential and the membrane impedance. In conclusion, the potential difference between the electrodes is caused by the difference in ion concentration of the electrodes. © 2013 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejsmas.133.309

Improvement of sensitivity for a compact magnetometer using HTS-SQUID with rotating sample Reviewed

Daichi Hamasaki, Naohiro Okamoto, Mohd Mawardi Saari, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

2013 IEEE 14th InternationalSuperconductive Electronics Conference, ISEC 2013 134 ( 5 ) 347 - 351 2013

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

We previously reported a compact magnetometer using HTS-SQUID with a rotating sample for routine testing. In this study, we have improved the detection limit of the system to detect a very weak secondary magnetic field from diamagnetic material. The system consisted of a rotating sample table, a magnet with a pick-up coil, and an HTS-SQUID. The six sample cases can be fixed to a turntable using sample arms to enable multiple-detection. By rotating the sample, the velocity of the sample passing above the pick-up coil could be increased compared to the vibrating-sample method. The pick-up coil was directly coupled to a superconducting input coil of the HTS-SQUID to transfer the detected signal to the HTS-SQUID. The HTS-SQUID attached to a sensor probe was cooled by liquid nitrogen in a Dewar vessel, which was enclosed in a bilayer magnetically shielded cylindrical box. To improve the detection limit of the magnetometer's susceptibility, the noise of the applied magnetic fields was reduced, the pick-up coil shape optimized, and the accuracy of rotation speed was increased. As a result, the signal and noise ratio was improved and the magnetometer showed a high sensitivity and accuracy. © 2013 IEEE.

DOI： 10.1109/ISEC.2013.6604306

Development of a compact magnetometer with an AC/DC magnetic field using HTS-SQUID Reviewed

Ryuki Takagi, Mohd Mawardi Saari, Kenji Sakai, Toshihiko Kiwa, Keiji Tsukada

2013 IEEE 14th InternationalSuperconductive Electronics Conference, ISEC 2013 2013

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

Measuring the magnetic susceptibility of a material enable us to specify composition of the material. We have reported on development of a compact moving-sample magnetometer using high-temperature superconducting quantum interference device (HTS-SQUID). However, this magnetometer needs long time when we have to measure many samples. In order to solve this problem, we developed a compact magnetometer to analyze quantitative magnetic characteristics by our rapid measurement system using AC/DC functions. The optimal mounting position of pickup coils for the AC magnetic field measurement was optimized. The performance of the AC magnetic field measurement system was evaluated by measuring harmonic components of the AC magnetic response from a dispersion of iron oxide in styrene resin, when AC/DC magnetic field is applied. Using this system, the sample composition of ferromagnetic and diamagnetic substances can be evaluated from the mixed sample by measuring the harmonic components of the magnetic responses. © 2013 IEEE.

DOI： 10.1109/ISEC.2013.6604309

Visualization of the catalytic reactions in the fuel cells using THz chemical microscope Reviewed

T. Hagiwara, T. Kusaka, T. Kiwa, K. Sakai, K. Tsukada

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2013

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

THz Chemical Microscope can visualize the work function shift of the catalytic electrodes in fuel cells. We observed the variation of the terahertz wave intensity at the cathode and anode under fuel cell operation. From this result, TCM is a valuable tool for investigation and evaluation of the catalytic electrode and electrolyte in fuel cells. © 2013 IEEE.

DOI： 10.1109/IRMMW-THz.2013.6665916

Label free immune assay using terahertz chemical microscope Reviewed

Toshihiko Kiwa, Akira Tenma, Shinji Takahashi, Kenji Sakai, Keiji Tsukada

Sensors and Actuators, B: Chemical 187 8 - 11 2013

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

A terahertz chemical microscope (TCM) has been proposed and developed to visualize the distribution of the antibody-antigen bindings on the silicon based sensing plate without any labels and/or markers on the antibody. The sensing plate can emit the terahertz pulses by femtosecond laser pulses and the amplitude of the terahertz pulses can be related to the chemical or electric potential of the sensing plate surface at where the laser pulses are irradiated. Thus the potential distribution can be visualized as the map of the terahertz pulses amplitude. As the first demonstration of the label free immune assay, the mouse immunoglobulin G (IgG) was immobilized on the half part of the sensing plate and the mouse anti-IgG was combined with the IgG. The terahertz pulses were enhanced at where anti-IgG was combined with IgG on the sensing plate and the distributions of the IgG and anti-IgG bindings on the sensing plate were clearly seen as the TCM images. The amplitude of terahertz pulses as a function of the concentration of anti-IgG was also investigated. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2012.08.051

Development of a compact DC magnetometer using HTS-SQUID and a rotating sample Reviewed

K. Sakai, M. M. Saari, T. Kiwa, A. Tsukamoto, S. Adachi, K. Tanabe, A. Kandori, K. Tsukada

Superconductor Science and Technology 25 ( 4 ) 2012.4

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We developed a compact DC magnetometer using a high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) to measure very weak magnetic signals from samples such as paramagnetic and diamagnetic materials. The samples were rotated in the DC magnetic field that was detected by a normal conductive pick-up coil. The detected signal was transferred to an input coil that was inductively coupled to the SQUID. To clarify the basic characteristics of this system, the magnetic signal from a magnetic material was measured by varying the sample position and rotation speed. Then, the magnetic signal from pure water was measured under the optimized condition and a very weak magnetic signal from pure water was successfully detected. Therefore, the developed system could be applied to various non-destructive evaluation systems. © 2012 IOP Publishing Ltd.

DOI： 10.1088/0953-2048/25/4/045005

Electric characteristics of a loop in which two junctions between a catalytic metal and a noncatalytic metal are under different hydrogen gas concentrations Reviewed

Keiji Tsukada, Kenji Sakai, Toshihiko Kiwa

Applied Physics Express 5 ( 3 ) 2012.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

To investigate the localized electrochemical properties of an electrode composed of platinum (Pt), a thin-film loop containing two junctions between the catalytic metal Pt and the noncatalytic metal titanium was fabricated. When the loop was open and only one junction was exposed to 10% hydrogen in nitrogen gas, an output voltage change of about 30 nV was generated between these two junctions. The electron density change due to the equilibrium reaction of hydrogen dissociation along the part exposed to hydrogen induced a balance between the diffusion and drift caused by the electric field at both ends of the Pt film. © 2012 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.5.034102

Silver Gate Field Effect Transistor for Oxygen Gas Sensor Reviewed

Keiji Tsukada, Daisuke Kiriake, Kenji Sakai, Toshihiko Kiwa

PROCEEDINGS OF SENSORDEVICES 2011: THE SECOND INTERNATIONAL CONFERENCE ON SENSOR DEVICE TECHNOLOGIES AND APPLICATIONS 5 - 7 2011

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IARIA XPS PRESS

A silver gate field effect transistor (FET) integrated thermal controller was developed for a new type of oxygen gas sensor. It showed a threshold voltage change at a temperature as low as 80 degrees C. Oxygen response characteristics of the FET prepared with different productions of silver materials using a vacuum-evaporated membrane, printed material using silver-nanoparticles and silver epoxy were compared. The FET with a gate of silver epoxy showed the largest sensitivity of 135 mV/decade in the oxygen concentration range from 5% to 40% at 120 degrees C.

Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector Reviewed

Keiji Tsukada, Mitsuteru Yoshioka, Yoshihiko Kawasaki, Toshihiko Kiwa

NDT and E International 43 ( 4 ) 323 - 328 2010.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

We have developed a magnetic flux leakage (MFL) system using magnetic resistive (MR) sensors for detecting two dimensional magnetic field components, and an induction coil that generates low magnetic field strengths and extremely low frequencies. The signal at each scanned measurement point (i) was divided by the signal strength Mmes,i and phase αi by a lock-in amplifier. Using the strength Mmes,i and phase αi, we calculated the imaginary part of the signal using the common phase β. By optimization of the common phase β to the imaginary part, the analyzed scanning data curve was shown to be effective in estimating the size (depth and diameter) of back-side pits on a ferrous plate. Comparing the two dimensional magnetic field components of leakage, the imaginary part of the y-component parallel to the induced magnetic field was found to be suitable for detecting the back-side pits. © 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ndteint.2010.01.004

Hydrogen gas diffusion imaging using multiple FET type gas sensors Reviewed

T. Kiwa, T. Yamaguchi, K. Tsubota, W. Naruyama, H. Yamada, K. Tsukada

International Journal of Advanced Mechatronic Systems 2 ( 4 ) 219 - 224 2010

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

Imaging of hydrogen gas concentrations were demonstrated using arrayed sensors system in the cylindrical diffusion tank-shaped simulator. The field effect transistor type hydrogen sensors with platinum gate electrode were used. The sensitivity of the sensors was around -34.1 mV/dec. and the response time was 1.2 sec. in average. By applying a sensor drive circuit to each sensor, the diffusion processes of the hydrogen gas were successfully obtained in time domain and two different processes were demonstrated using 100% hydrogen gas. These results indicate that real-time monitoring of the hydrogen gas distribution can be possible. Additionally, the calibration method of the acquired data was proposed. © 2010 Inderscience Enterprises Ltd.

DOI： 10.1504/IJAMechS.2010.033594

Control of terahertz wave front using arrayed terahertz emission device Reviewed

K. Beppu, T. Sugimoto, T. Kiwa, K. Tsukada

IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide 2010

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

Arrayed THz emission device was proposed to control the wave front of THz. The simulation results indicated the THz wave front can be tilted by changing the emission pattern of the device. The 4×4 arrayed device was fabricated and the emission pattern was successfully controlled by the bias voltages.

DOI： 10.1109/ICIMW.2010.5612739

Chemical imaging of μ-TAS using terahertz chemical microscope Reviewed

Toshihiko Kiwa, Yuji Minami, Yusuke Kondo, Yohei Hashimoto, Iwao Kawayama, Masayoshi Tonouchi, Keiji Tsukada

IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide 2010

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

A terahertz chemical microscope (TCM) has been carried out to visualize the chemical potential distribution in μ-TAS. Since the TCM can detect the chemical potential at exactly where the femtosecond laser was irradiated, the spatial resolution less than 1μm, which is limited by the wavelength of the femtosecond laser, can be achieved. The μ-TAS was fabricated on the sensing chip and the distribution of chemical potential was successfully visualized using TCM. © 2010 IEEE.

DOI： 10.1109/ICIMW.2010.5613018

EXTREME LOW FREQUENCY MAGNETIC IMAGING METHOD FOR DETECTION OF DEFECT INSIDE WELDING PARTS OF IRON PLATE Reviewed

Keiji Tsukada, Teruki Hasegawa, Mituteru Yoshioka, Toshihiko Kiwa, Katsumi Inoue

10TH EUROPEAN CONFERENCE ON NON-DESTRUCTIVE TESTING 2010 (ECNDT), VOLS 1-5 82 - 93 2010

A Novel Ion Sensor Without a Reference Electrode Reviewed

Keiji Tsukada, Fumiyuki Kobayashi, Toyotaka Inoue, Toshihiko Kiwa

SENSOR LETTERS 7 ( 6 ) 1163 - 1166 2009.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SCIENTIFIC PUBLISHERS

We developed an ion sensor with a novel structure that does not require a reference electrode. The structure consists of a double electrode comprising an outer electrode with a hole and an inner electrode, a polymeric ion-selective membrane, and the sensor body. The ion sensitivity of a potassium ion sensor, where the hole of the outer electrode was the same size as the inner electrode, was 55 mV/decade. The sensor exhibited increased sensitivity according to the increment of the hole size The sensitivity was also dependent on the thickness of the outer membrane covering the outer electrode These phenomena were examined using a membrane potential gradient simulation

DOI： 10.1166/sl.2009.1240

Dual gate FET hydrogen gas sensor Reviewed

K. Tsukada, M. Kariya, T. Yamaguchi, T. Kiwa, H. Yamada, T. Maehara, T. Yamamoto, S. Kunitsugu

Proceedings of IEEE Sensors 517 - 519 2009

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

We developed a dual gate FET hydrogen gas sensor for application to hydrogen vehicles. The dual gate FET hydrogen sensor was integrated with Pt-gate FET to detect hydrogen and Ti-gate FET as the reference sensor in the same Si chip. Ti-gate FET has the same structure as Pt-FET except for the gate metal. The Pt-FET showed good response to hydrogen gas above 10 ppm in air, while the Ti-FET did not show any response to hydrogen gas. The differential output voltage between the Pt-FET and the Ti-FET was stable in the range of room temperature to 80° C because of the same temperature dependence of the I-V characteristic. ©2009 IEEE.

DOI： 10.1109/ICSENS.2009.5398290

Hydrogen gas diffusion imaging using multiple FET type gas sensors Reviewed

T. Kiwa, T. Yamaguchi, K. Tsubota, W. Naruyama, H. Yamada, K. Tsukada

Proceedings of the 2009 IEEE International Conference on Networking, Sensing and Control, ICNSC 2009 282 - 286 2009

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

Imaging of hydrogen gas concentrations were demonstrated using arrayed sensors system in the cylindrical diffusion tank-shaped simulator. The field effect transistor type hydrogen sensors with platinum gate electrode were used. The sensitivity of the sensors was around -34.1 mV/dec. and the response time was 1.2 sec. in average. By applying a sensor drive circuit to each sensor, the diffusion processes of the hydrogen gas were successfully obtained in time domain and two different processes were demonstrated using 100% hydrogen gas. Theseresults indicate that real-time monitoring of the hydrogen gas distribution can be possible. Additionally, the calibration method of the acquired data was proposed. © 2009 IEEE.

DOI： 10.1109/ICNSC.2009.4919287

Evaluation of the catalytic metal for the hydrogen sensor using terahertz chemical microscope Reviewed

Takeshi Sugimoto, Yosuke Kondo, Toshihiko Kiwa, Iwao Kawayama, Masayoshi Tonouchi, Keiji Tsukada

34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009 411 - + 2009

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

To develop the hydrogen sensor, the chemical potential due to the catalytic reaction of the metals are required to evaluate. The platinum and titanium layered electrode on the insulator/semiconductor layered device are fabricated as the test chip. The catalytic reaction of platinum and hydrogen gas were successfully visualized. © 2009 IEEE.

DOI： 10.1109/ICIMW.2009.5325729

Redox reaction imaging using THz chemical microscope Reviewed

Y. Minami, T. Kiwa, I. Kawayama, M. Tonouchi, K. Tsukada

34th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2009 272 - 274 2009

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

Terahertz chemical microscope was carried out to visualize the distribution of the redox reaction of the immobilized-enzyme. The urease films with the spot size of 3, 2, 1 mm in diameter were immobilized on a SiO2/Si/ Sapphire layered device and the laser-excited terahertz radiation from the Si layer was observed, which can be related to the chemical potential shift of the SiO2 surface. The redox reaction between the urease and the urea solution was successfully measured. © 2009 IEEE.

DOI： 10.1109/ICIMW.2009.5324691

Laser terahertz emission microscope Reviewed

Hironaru Murakami, Naotsugu Uchida, Ryotaro Inoue, Sunmi Kim, Toshihiko Kiwa, Masayoshi Tonouchi

Proceedings of the IEEE 95 ( 8 ) 1646 - 1657 2007.8

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Developments of laser terahertz (THz) emission microscope (LTEM) systems are reviewed. Femtosecond lasers can excite the THz wave emission from various electronic materials, such as semiconductors, high-temperature superconductors, manganites, multiferroic oxides, etc., due to ultrafast current modulation. Limiting the topic to semiconductors, the current modulation is realized by acceleration or deceleration of photoexcited carriers due to the local electric field extrinsically or intrinsically induced at the laser illumination spot. Thus, LTEM has a potential to visualize the local electric field distribution and photoresponse without any contacts or damages. We have ever constructed prototype free-space type and scanning fiber-probe (SFP) type LTEM systems with transmission or reflection mode. The system performance of the SFP-LTEM has been greatly improved compared with that for the prototype one. The spatial resolution of the SFP-LTEM system has a minimum spatial resolution less than 3 mum , which is defined by the laser beam diameter. The compact SFP-LTEM system, in particular the reflection system, has the potential to be utilized for wide applications as well as various materials. In this review paper, we introduce the details of the LTEM systems and example applications for the evaluation of electric field distribution in integrated circuits and supercurrent distribution in high-temperature superconductors. © 2006 IEEE.

DOI： 10.1109/JPROC.2007.898829

Terahertz emission from catalytic-metal/semiconductor interface of hydrogen sensors

T. Kiwa, K. Tsukada, M. Suzuki, M. Tonouchi, S. Migitaka, K. Yokosawa

Optics InfoBase Conference Papers 2005

Publishing type：Research paper (international conference proceedings)

Terahertz emission properties of catalytic-metal/semiconductor structures under hydrogen gas were investigated for non-contact and non-destructive test of hydrogen sensors. The peak amplitude of terahertz from the samples decreases with increasing the hydrogen concentration.©2005 Optical Society of America.

DOI： 10.1364/otst.2005.tud7

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