Vol. 29, Supplement A (2013)

1.

A solid electrolyte type sulfur dioxide (SO₂) gas sensor that can operate at moderate temperatures was fabricated by combining the Zr⁴⁺ ion conducting Zr_39/40TaP_2.9W_0.1O₁₂ solid electrolyte, 0.7La₂O₂SO₄-0.3(0.8Li₂SO₄+0.2K₂SO₄) auxiliary sensing electrode having large surface area, and Zr metal reference electrode. Since the present sensor showed a quantitative, reproducible and rapid response, which obeys the theoretical Nernst relationship even at 400 °C, it is expected to be a potential candidate for the on-site SO₂ gas sensing tool operable at moderate temperatures around 400 °C.

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2.

Response characteristics to NO₂ of zirconia-based amperometric-type sensors using La-based perovskite oxide sensing-electrode were examined. Powders with La_0.8Sr_0.2Mnx-₁MxO₃ (M = Ce : Mg = 1 : 1、x : 0.2 (LSMCM01), 0.4 (LSMCM02), 0.6 (LSMCM03), 0.8 (LSMCM04)) were synthesized by means of spray pyrolysis method. The response current to NO₂ of the sensors using LSMCM01 was two times higher than the original composition (LSM). The response had an almost linear relation with the logarithm NO₂ concentration of 50 - 750 ppm. The powder of LSMCM01 showed stronger adsorption of NO₂ as NO state from TPD measurement. We considered the improvement of sensor response has a connection with gas adsorption property on the oxide surface.

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3.

The sensing performances of Fe₂O₃ and Co₃O₄ electrodes attached on an yttria-stabilized zirconia (YSZ) were evaluated for utilization as a solid reference-electrode (RE) of oxygen sensors. Both electrodes were found to be insensitive toward 0.05~21 vol.% O₂ in the operational temperature range of 400-500℃ and 400-600℃ for Co₃O₄ and Fe₂O₃, respectively. In addition, the responses toward CO, NO, NO₂, C₃H₆, C₃H₈, NH₃, CH₄ and H₂ (100 ppm each, diluted with air) of these electrodes were minor or negligible in each temperature range. Thus, the YSZ-based sensors utilizing Pt sensing electrode (SE) and Fe₂O₃ (or Co₃O₄)-RE were fabricated and their sensing characteristics against oxygen were evaluated. As a result, it was found that the oxygen sensitivity of these fabricated sensors varied linearly with the logarithm of oxygen concentration, following Nernst's equation. In each case, the number of electron (n) for the electrochemical reaction of oxygen was calculated to be 4.1, which was almost close to the theoretical value (4.0).

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4.

　The improvement of gas selectivity toward volatile organic compounds (VOCs) was attempted for an yttria-stabilized zirconia (YSZ)-based sensor using NiO sensing-electrode (SE). It was found that the lamination of SnO₂ catalytic layer on NiO-SE drastically reduced interference from high concentration ethanol, while maintaining high toluene sensitivity. In addition, a gas-diffusion barrier layer composed of nano-Al₂O₃ particles which was formed on the SnO₂/NiO-SE ends further improved VOCs selectivity. Judging from SEM observation, the gas-diffusion barrier layer was confirmed to be rather dense, which helped the progress of ethanol oxidation reaction in the SnO₂ layer by hindering the direct gas penetration to the SE/YSZ interface from the exposed NiO-SE ends. The evaluation of catalytic activity of SnO₂ powder against the gas-phase reaction of various VOCs revealed that the SnO₂ layer facilitated the preferable oxidation of formaldehyde rather than toluene and m-xylene. This enabled the sensor to selectively detect aromatic VOCs.

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5.

A potentiometric sensor using yttria-stabilized zirconia (YSZ) as a solid electrolyte and ZnO(+ 84 wt.% Ta₂O₅) as a sensing electrode (SE) was developed and demonstrated the capability to detect H₂ sensitively and selectively. The sensitivity toward 100 ppm H₂ was found to be stabilized at 600 mV after about 40 days aging at 500℃. The sensor was capable of exhibiting sensitive responses toward H₂, with only minor responses toward other examined gases such as NOx and HCs. The sensor had lower detection limit of 10 ppm H₂ as well as 90% response time of approximately 70 s when exposed to 100 ppm H₂. The fabricated sensor exhibited a linear relationship between H₂sensitivity and concentration in the lower range (10-100 ppm) on a linear scale and in the higher range (100-400 ppm) on a logarithmic scale. The H₂ sensitivity was found to be hardly affected by a change of water vapor in the concentration range of 2.5-12.5 vol.%.

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6.

A boron-doped polycrystalline diamond (BDD) electrolyte solution-gate field effect transistor (SGFET) for the use of pH sensor has been investigated. In our previous works, a new-type pH sensor utilizing a non-doped diamond surface as a pH-sensitive/ pH-insensitive channel of field effect transistor (FET) sensor, where a hydrogen-termination induce p-type semiconductor property without extrinsic doping. The channel is directly wetted to liquid and the device is employed as so-called electrolyte-solution-gate field effect transistor (SGFET) sensor. Here, we report a partially oxygen-terminated BDD surface. The SGFET I-V characteristics were evaluated with bias voltages within potential window of diamond. The Ids-Vds characteristics showed pinch-off and saturation. In addition, they operated stably in electrolyte solutions with pH values from 2 to 12. The transfer characteristics showed pH sensitivity of approximately 30 mV/pH, which is comparable to a conventional oxygen-terminated non-doped SGFET. Furthermore, the polycrystalline BDD SGFET improved a longtime stability and its coefficient of variation (CV) of Ids for 10 months was up to 10%

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7.

Divalent cations can be reversibly inserted / extracted in vanadium oxides by an electrochemical process, which can be utilized as electrodes for ion-sensing. In this study, we examine vanadium oxides for the sensing of divalent cations, Mg^2＋ and Ca^2＋. The Pt/vanadium oxide electrodes show stable potential response to Mg^2＋ or Ca^2＋ ion in corresponding chloride salts aqueous solution. The vanadium oxide electrodes, covered with magnesium- or calcium-ion selective PVC membrane, Pt / vanadium oxides / PVC configuration, demonstrate quick and Nernstian response in a wide range of Mg^2＋ or Ca^2＋ ion activity, and better potential stability than the electrode without vanadium oxides (Pt/PVC). AC impedance analysis suggests that vanadium oxides as inner layers work as ion-to-electron transducer, and thus effectively reduces the resistance of the all-solid-state ion-selective electrodes, and thus improve the stability for ion-sensing.

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8.

In order to clear the mechanism of performance degradation based on the increase of impedance of electrolyte membrane, polarization curves of a working electrode and a counter electrode of a liquid electrolyte membrane type CO sensor were measured using Pt wire as a reference electrode. As a result, when the impedance of electrolyte membrane was increased, short-circuit current between both electrodes in the air containing CO is less than a half of the diffusion limited current of a CO oxidation reaction on the working electrode owing to the increase of IR drop between both electrodes. This mechanism of performance degradation based on the increase of impedance of electrolyte membrane can be described by using the model proposed by authors in a previous report.

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9.

An electrochemical gas sensor for the detection of hydrogen (H₂) gas was investigated based on electrolysis of H₂ gas. The sensor has been developed by using Au-black　particle electrode made by screen printed method. The sensor using a Au black working electrode showed a good sensitivity and selectivity for interference gases such as i-propyl alcohol. The good linear relationship between the oxidation current of H₂ gas and gas concentration was obtained from 50ppm to 4 vol.% . The response current for H₂ 400ppm was hardly changed for 1 year. The sensor has useful properties for practical usage.

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女性躍進賞受賞講演

Ubiquitous sensor network is one kind of tools for achieving a safe and secure society. Our aim is to develop a chemical sensor that can be applied to ubiquitous sensor networks. The requirements for such chemical sensors are high sensitivity, high selectivity, compact size, and low power consumption. We have focused on a porous glass as a chemical sensor's substrate, because their huge surface area is advantage for gas adsorption and their transparency in UV-vis region is good for an optical measurement with high precision. Moreover we have focused on a peculiar chemical reaction that is caused in pores of the porous glass. We have successfully developed a chemical sensor for detecting formaldehyde using the combination of the porous glass and a chemical reaction between formaldehyde, ß-diketone and ammonium ions.

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10.

A clean energy system which comes from sunlight, wind, biomass, etc. is required. This system needs hydrogen gas for the energy carrier. However, hydrogen is inflammable gas and easy to leak because of its smallest molecule. Therefore, hydrogen gas leak detection sensor is essential for wide spread use of the hydrogen energy system. The authors propose catalyst-type hydrogen gas sensor for the leak detection using Fiber Bragg Gratings (FBG). Sensing principle is based on the catalytic combustion heat which makes the shift of center wavelength of reflection spectra. It was found that this sensor is sensitive to low concentration of hydrogen under 0.5 vol.% in air at room temperature.

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11.

A catalytic combustion type methane gas sensor with super low power consumption using MEMS technology was developed for a battery drive type gas alarm. In this study, it is reported the actions of improvement for methane gas selectivity and sensitivity of the sensor from a viewpoint of the reliability satisfaction for practical use. As the method of improving gas selectivity, it was made to offset with constituting a reference element from a Pt-system oxidation catalyst. For the improvement of methane sensitivity, the amount of loaded Pd was made to optimize in order to increase gas reactive sites on a catalyst. And a slit-shaped through-hole was formed on the micro heater, as taking advantage of air bridge structure for promoting the gas contact from the heater backside. Methane sensitivity has improved drastically by these complex improvement effects.

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12.

Platinum-titanium-oxygen (Pt-Ti-O) gate Si-MISFET hydrogen gas sensors have been found to show large sensing amplitude (ΔVg) of 624.4 mV with σΔVg of 7.27 mV for nine repeated measurements even under nitrogen-diluted 1.0% hydrogen gas, which are nearly the same values of 654.5 mV with σΔVg of 3.77 mV under air-diluted 1.0% hydrogen gas. The Pt-Ti-O sensor devices can work stably as hydrogen sensors up to about 250 ℃ and also show environmental hardness as follows: When nitrogen-diluted 10ppm HMDS (hexamethyldisiloxane) was exposed to the sensor FETs for 40 minutes at working temperature of 115 ℃, the sensing amplitude (ΔVg) little changed within repeating errors before and after HMDS exposures. The variations of ΔVg between relative humidity of 20% and 80% are very small within ± 6 % around 50 % under the 40 ℃ atmosphere. The radiation hardness of developed hydrogen sensor chips from γ ray (⁶⁰Co) and/or X-ray (Synchrotron Radiation) is sufficiently strong enough even at extremely high integral dose such as 1.8 MGy. It comes from the robustness of PN-junction between drain and p-well.

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13.

Thin film of Ni was deposited by vacuum evaporation on a sensor electrode. Multi walled carbon nanotubes (MWCNTs) array was directly grown on the electrode at 350 ℃ by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD). The MWCNTs array had about 752 nm in length and about 26.3 nm in diameter. Pd was deposited by vacuum evaporation on the surface of the MWCNTs array. The sensing properties of the MWCNTs and Pd-MWCNTs arrays was investigated to 1 ppm NO₂, C₈H₁₀, H₂S and CH₃SH at the operating temperatures from 100 to 250 ℃. In particular, Pd deposition was most effective to C₈H₁₀sub among other gases. The decomposition of C₈H₁₀ was accelerated by Pd. As the result, the decomposition gases such as H₂, H₂O, CO contribute to increasing the number of gas molecules relatively. This phenomenon was appeared as relative resistance change ratio of Pd-MWCNTs / MWCNTs.

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14.

Hot wire semiconductor gas sensors fabricated by Micro electro mechanical systems (MEMS) technology have been developed. The methane gas sensor consists of three-layer structure on a micro heater and electrode. The lower layer is a sintered SnO₂ thick film, and the middle layer is a Pd catalyst thin film, and the upper layer is an Al₂O₃ thick film for protection. The sensor showed a high sensitivity and selectivity to methane gas and showed good long term stability for about 2 years. The power consumption of this sensor is about 100μW. Moreover, the low power consumption gas sensors for liquefied petroleum gas, hydrogen, volatile organic compounds and carbon monoxide have been developed.

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15.

We have developed semiconductor alcohol sensor using MEMS technology. The micro heater has a new design for reducing heat distortion between layers at high temperature, and the adhesive between the layers is very durable. It has low heat capacity of membrane structure enabling quick temperature rise and very good stability of heater resistance at high temperatures. On the micro heater we formed a sensing element by a precision dispenser. The gas sensing material is palladium doped tin dioxide that we have been using. We report characteristics of developed alcohol sensor at continuous operation and characteristics of alcohol checker.

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16.

CO sensors using cerium oxide showed fast response but smaller response than that using tin oxide so that their response should be improved. Effects of noble metal addition (Pt, Pd, Au, and Ag particles) on response of sensor using ceria thick film for CO sensing application were investigated. The sensor using the ceria thick film with Au particles showed good response to CO and it was concluded that the addition of 5 wt% Au brought 40 times response increase to cerium oxide thick film. The response time was the same as the sensor without noble metal. In the case of the sensor having Ag particles, it showed response increase in the first measurement. However, the response decreased with increasing measurement number. In the case of Pd, the uneven responses were observed. In the case of the sensor having Pt particles, its response was approximately the same as the sensor without noble metal. Therefore, Pt did not show the response increase effect.

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17.

The CO sensing properties of Pt/SnO₂, Au/SnO₂, Ag/SnO₂, Pd/SnO₂, Ru/SnO₂, and Rh/SnO₂ sensors were investigated in wet H₂ atmosphere at 40-300 °C. Pt/SnO₂, Pd/SnO₂, and Rh/SnO₂ showed sensor response to CO at 40 °C. The sensor response of Rh(1wt%)/SnO₂ to 1000 ppm CO was 15.8 at 40 °C, which was higher than those of the other metal-loaded SnO₂ sensors. Good response and recovery behaviors of Rh(1wt%)/SnO₂ sensor were observed. In addition, the sensor response to other interference gases such as CH₄, CO₂, NH₃, and H₂S was much lower than that to CO gas. It is concluded that Rh/SnO₂ sensor has a potential candidate as CO monitoring in H₂ at room temperature.

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18.

Smell identification by using transient responses of SnO₂ semiconductor gas sensor was tried for four kinds of alcoholic gases. Heater of the sensor was heated by rectangular pulse current. The differences of the area of the transient responses are used for identification of the alcoholic gases. AVR microcomputer was used for identification of the alcoholic gases. Accuracy of the identification of two kinds of alcoholic gases was around 70-80%. The accuracy will go up by accumulating the date and increasing the factor for identification of the gases

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19.

Polymethylmethacrylate (PMMA) microspheres were synthesized in distilled water by ultrasonic-assisted emulsion polymerization. The PMMA microspheres are relatively uniform and the size was several tens of nanometer in diameter. Porous (pr-) In₂O₃ spherical particles with well-developed spherical macropores (ca. 30 nm in diameter) were prepared by ultrasonic spray pyrolysis of In(NO₃)₃ aqueous solution containing the PMMA microspheres synthesized. The NO₂ response of the pr-In₂O₃ sensors was much larger than that of conventional (c-) In₂O₃ sensors (c-In₂O₃sub: dense In₂O₃ spherical particle without macropores, which were prepared by the similar technique employing PMMA-free In(NO₃)₃ aqueous solution) at lower temperatures (≤ 300°C). In addition, the response speed of the pr-In₂O₃ sensors was faster than c-In₂O₃ sensor.

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20.

We report on spectroscopic study of H₂O/D₂O exchange on pure SnO₂ materials using modulation excitation DRIFTS. The study was performed on working sensors operating at 300 ℃ together with resistance measurements. Two SnO₂ materials have been compared. Evolution of resistance and band integrals as a function of CO concentration in humid air has been analyzed. It was found that material synthesized from tin(IV) hydroxide acetate manifests similar trend for band intensity (OD stretching vibrations) and resistance evolution upon increasing CO concentration from 0 to 500 ppm in humid air. No correlations between band intensity and resistance have been found for the material synthesized from tin(IV) chloride.

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21.

In order to enhance gas sensor response, Fe-modified SnO₂ nanoparticles were prepared and compared with neat SnO₂. Their gas sensing characteristics to H₂ were measured with dry and wet conditions at 250-350℃. It was found that the sensor response of 0.5Fe-SnO₂ was higher than that of neat SnO₂ because of the deeper depletion state by electron trapping of Fe ions. In addition, the DRIFTS spectra were investigated under the same conditions to analyze adsorption species and gas reaction on SnO₂ surface.

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特別講演1

Recently, new carbon materials such as boron-doped diamond and carbon nanotube have been employed for biochemical sensing. We have recently developed nanocarbon film electrodes formed by electron cyclotron resonance (ECR) sputtering. The ECR nanocarbon film has excellent electrochemical performances including wide potential window, low background current and less biomolecule adsorption. By utilizing this performance, we could improve detection limit and electrode stability for small biomolecules such as NADPH, neurotransmitters, oxidative stress markers. By combining enzymatic reaction, an electrochemical sensor for GABA has been developed. Each base in oligonucleotides (4~60 mers) can be quantified by voltammetric measurement. The amount of methylated cytosine in oligonucleotides could also be identified. The direct electron transfer of enzymes has also been improved by fabricating surface nanostructures by simply treated film with UV/ozone process.

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特別講演2

Global warming has recently become a major issue for the future of the global environment, and around the world, the reduction of the greenhouse gases causing global warming is required. Emission-regulations for motor vehicles are becoming more stringent around the world and fuel economy is also strongly required. In order to achieve such requirements, car manufacturers now focus on developing lean burn engines and diesel engines. However, exhaust gas from these engines has relatively higher NOx comparing to a conventional gasoline engine equipped with three way catalyst. Therefore, in order to reduce the NOx from those vehicles, NOx aftertreatment systems, such as NOx storage catalyst and selective catalytic reduction by urea dosing, are also aggressively being developed. For those systems, accurate direct measurement of NOx emission level is very important. NGK Insulators Ltd. has developed limiting-current-type NOx sensor with a zirconia thick-film technology. The NOx sensor is capable of measuring low levels of NOx concentration with high accuracy. The sensor contributes to control and diagnosis of the NOx aftertreatment systems in automotive application.

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記念特別講演

Gases have been successfully sensed by gas phase induced polarization of metal/solid electrolyte/metal interfaces for many decades. The simplest operational mode occurs when the interfacial polarizations are fixed by a reversible reaction between the oxygen vacancies at the electrode-electrolyte interfaces and the partial pressure of oxygen gas at the interface. When the interfacial polarization is controlled by multiple triple-phase boundary reactions, the device is said to be a "mixed potential " sensor. The successful design of gas sensors of each of these types often requires different approaches to the engineering of the gas/electrode/electrolyte interface. Sensors that operate in mixed potential mode are particularly sensitive to electrode/electrolyte interfacial morphology as the devices rely on selective catalysis of desired reactions. Analysis of the requirements for mixed potential gas sensor design has led to the development of sensors with geometries that differ substantially from traditional solid electrolyte based sensors. We have found that it is often advantageous to design devices with porous electrolyte layers and dense electrodes rather than dense electrolytes and porous electrodes. We have fabricated and characterized mixed potential sensors for the detection of hydrogen, carbon monoxide, non-methane hydrocarbons and nitric oxides based on these principles. We have used these sensors for a variety of applications from workplace safety monitors, emission control systems and explosive detection.

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22.

Nanofibers have exceptional properties due to their minute diameter and large surface area to mass ratio. Thus, the potential of application of nanofibers as electrodes can provide high sensitive biosensing system, bio-fuel cells and high-power devices.

In this study, we have fabricated conductive polyurethane nanofiber composited FeCl3, which were prepared by electrospinning. We investigated the optical condition of electrospinning, and evaluated physical/chemical property of the nanofiber. As a result, conductive FeCl3/Polyurethane fibers with 700 nm in diameter were obtained. Its conductivity showed 2.4×103 Ω・cm.　Furthermore, the nanofibers have flexible property because the substrate of fiber was made of polyurethane.

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23.

We report a mediator-bonded glassy carbon-based electrode with a catalytic oxidation current for detecting hydrogen peroxide. The mediator-bonded glassy carbon-based electrode was fabricated by the stepwise electrolyses as follows. First, a glassy carbon electrode was electro-oxidized in ammonium carbamate aqueous solution at +1.1 V (vs. Ag/AgCl) for 60 minutes, next, the electrode reduction was carried out in 1.0 M H2SO4 at -1.0 V (vs. Ag/AgCl) for 20 hours at room temperature. In case of the cyclic voltammetry in pH 7.0 phosphate buffer solution, we found that the electrooxidation of hydrogen peroxide begins at +0.20 V (vs. Ag/AgCl) using the mediator-bonded glassy carbon-based electrode. The oxidation current of hydrogen peroxide with the rapid response time (~5 seconds) was obtained by the repetitive measurement. Linear caribration curve was observed in the concentration range of 0.025-6.0 mM with the detection limit of 50 μM (S/N=3). This indicates that our proposed amperometric sensor using the mediator-bonded glassy carbon-based electrode can be used for the determination of the hydrogen peroxide concentration.

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24.

Detection of amyloid proteins has an important role in early diagnosing the neurological diseases. In this study, we present a simple electrical detection of Sup35NM, known as a model amyloid protein, using field effect transistor (FET). The molecule congo red (CR), which is a representative molecule interacting with Sup35NM, was selected as a probe. The FET detects the intrinsic charge of Sup35NM, which bound to CR immobilized on the gate surface. As a result, specific binding of Sup35NM fibrils onto the CR-immobilized surface was detected as a shift in the drain current – gate voltage curve. In addition, the difference in FET responses to Sup35NM with different forms was examined.

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25.

Application of biosensors using field effect transistor (FET), of which usefulness for the sensitive detection of proteins we demonstrated, to the detection of amyloid β protein (Aβ) was investigated. Alzheimer's disease (AD) is attributed to nerve cell death caused by aggregates and deposits of Aβ in brain. Especially, the Aβ (1-42) isoform can easily aggregate and induce neuronal death. So, the detection of Aβ (1-42) and the determination of aggregation state of Aβ (1-42) by using FET biosensors can realize the early detection of AD. In this study, detection of Aβ (1-42) aggregate by using a FET having the gate modified with congo red, which can specifically interact with amyloid fibrils such as Aβ aggregate, was performed. In addition, the difference in FET responses to Aβ (1-42) with different aggregate morphology was examined.

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26.

Matrix metalloproteinase (MMP) is known to be involved in chronic inflammation, tumor invasion and carcinogenesis. To date, we have been investigating field effect transistor (FET) biosensors, which are capable of label-free detection, easy measurement, miniaturization and integration. Recently, we succeeded in the detection of MMP-2 based on degradation of fibronectin (FN) immobilized on the gate, which induces negative values of FET responses. In this study, to evaluate a possibility for a practical use of this system, we investigated the effect of reactive conditions on the detectability of MMP-2 and attempted to detect MMP-2 in the presence of fetal bovine serum (FBS). For pH 7.4, a stable negative value of FET response was observed compared with the case of other pH. With the increase in reaction time and reaction temperature, negative value of FET responses showed a tendency to increase. These results indicate that FET responses are affected by enzyme activity of MMP-2. In addition, this FET device successfully detected MMP-2 in the presence of FBS. However, the detectability was decreased compared with that in the absence of FBS, which is considered to be due to non-specific adsorption of negatively charged proteins.

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27.

Fine needle type glucose sensors were implanted in the veins of rabbits for ten days and the response to glucose were measured. Glucose sensors were implanted using cannula and the blood glucose levels were influenced by the injection of glucose and insulin. Definite glucose was hardly observed at the days of implantation, while clear response was obtained after several days. This may due to the recovery from the damage of blood vessel received on the process of sensor implantation. Good correlation between in vitro blood glucose levels was obtained at especially low glucose level. Although, the response current measured in phosphate buffer was lowered after the implantation in vein, satisfactorily response was confirmed. However, introduction of biocompatible materials such as heparin were essential for the sensor, which will practically perform in vivo measurement for longer than two days in vein.

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28.

There has been a considerable recent interest in paper-based biosensors, owing to low price, good flexiblity. In this study, we fabricated on a paper-based chromatographic electrochemical biosensor by screen printing. TTF (tetrathiafulvalene) and glucose oxidase (GOD) were immobilized in the paper. Catalytic oxidation current of glucose was observed clearly under glucose solution, indicating that the GOD and TTF immobilized in the paper works as an electrocatalytic system of the oxidation of glucose. Linear relationship was obtained from 0.001 mol dm^-3 to 0.1 mol dm^-3. The charactersitcs of the paper-based biosensor were investigated by electrochemical impedance spectroscopy.

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29.

A reactor containing catalase immobilized onto　carbon fibers　modified chemically was applied to a flow-injection system for determination of hydrogen peroxide. Performance characteristics as the enzyme sensor were examined.

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30.

Flow-injection determination of amounts of enthalpy changes in enzyme-catalyzed reactions was performed. Oxidative reactions of L-ascorbate solutions catalyzed by enzymes were monitored. Effects of ｆlow variables on the heat flows were examined.

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31.

We have developed a 2^nd generation Bio-LSI system for a highly sensitive and real-time amperometric bio-imaging platform with 400 sensor electrodes. In this study, we have estimated the improved functions for 2^nd generation. First, we checked the light shield effect of a top metal placed on a CMOS circuit to reduce a noise derived from a photocurrent. Only 800 fA of the photocurrent was produced even under the high intense (35000 lx) microscope light (below one hundredth of 1^st generation). Next, we demonstrated a mode select function. On the 2^nd generation, we can select the operation mode of the 400 electrodes individually from 4 modes; off, electrometer, V1 or V2. We used this function to image the behavior of 2 mM ferrocenemethanol (FcOH) on the Bio-LSI. The potential of a center electrode was stepped to +0.5 V, while the remaining 399 electrodes was kept 0.0 V. In the color map indicating the current of 400 electrodes, we can see the image of the flow streams of the oxidative form of FcOH (FcOH⁺) produced at the center electrode as reduction currents at the surrounding electrodes.

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32.

We developed the electrochemical lipopolysaccharide (LPS) detection system using a nanocarbon film electrode with an atomically flat surface. This film consists of nanocrystalline sp² and sp³ mixed bonds formed by employing the electron cyclotron resonance sputtering method. The LPS-recognition molecule was chemically modified on our nanocarbon film. After modification of the recognition molecule, LPS sample was cast on the surface followed by a rinse with the buffer. FcPMB was cast and rinsed in the same manner as described above. The obtained electrode was immersed into the acetate buffer (pH5.0) and cyclic voltammogram (CV) of the electrode was measured. The CV exhibited a anodic peak for oxidation of Fc-PMB adsorbed on the modified nanocarbon film electrode at 0.59 V vs Ag/AgCl. Moreover, the addition of Fe²⁺ ion caused a noticeable increase in the anodic current. These obtained current was obviously dependent on the LPS contents on the surface. Now this system achieved the LOD of 2 ng/mL for LPS, which was superior result to our previous report.

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33.

We have developed a bacterial immobilization technique using polypyrrole, which can be applied to imprinted polymer based bacterial sensors. Bacteria usually have negative charges at their cell surfaces, which allow one to prepare polypyrrole films doped with the bacteria. The bacteria were vertically immobilized against the film surfaces to show good viability after such incorporation. Imprinted polymers using these bacteria-immobilized films were prepared by electrochemical overoxidation of the polypyrrole films, which had been doped with bacilli as a template. The sensor was fabricated on a gold-coated quartz microbalance sensor, and the results of dielectrophoretic QCM measurements demonstrated that the greatest responses resulted from template bacilli rebinding.

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34.

We have developed the batch-type microbial sensors comprised of microorganisms and an oxygen electrode. The principle of the microbial sensor is based on the monitoring of current changes, which are caused by the inhibition of cellular respiration. Using this microbial sensor, the biological monitoring of toxicoids in water resources that are of significance in environmental research and industry has been achieved. In this study, we proposed miniaturized toxicity assay system consist of a microbial sensor and a microfluidic device towards high-throughput toxicity assay. We fabricated the toxicity assay system composed of the planar microbial sensor and the microchannel, which was useful for the evaluation of KCN toxicity to Candida albicans. Integration of the planar microbial sensor with the chemical gradient generator will contribute to develop a total system for microbial toxicity assay. This system will enable rapid and multiple toxicity assay in small volumes of samples.

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35.

In this study, a large scale integration (LSI)-based amperometric sensor (Bio-LSI) is used for electrochemical evaluation and real-time monitoring of cell respiration activity. The Bio-LSI chip contained 400 measurement points for electrochemical bio-imaging. The sensor pitch was 250 µm. Since the temporal resolution of this device is less than 200 ms/400 points and the current detection range is 1 pA - 100 nA, a high-sensitive assay can be performed in real-time monitoring for cell analysis.

In this study, human hepatocellular carcinoma (HepG2) was used for preparing spheroids as a tissue-like sample. The HepG2 spheroids were placed onto the Bio-LSI chip and their oxygen consumption was electrochemically detected. The electrochemical images show that their oxygen consumption was successfully detected, indicating that the Bio-LSI can be used for analysis of tissue-like samples. We believe that the chip device can be applied various electrochemical bioassay including the cell screening.

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36.

A compact electrochemical ATP sensing system equipped with screen-printed electrode was developed on the basis of motility of unicellular flagellate Chlamydomonas reinhardtii. Change in the flagellar movement induced by ATP addition was monitored as changes in the redox current for a coexisting redox marker. The system responded to the ATP selectively. The linear relationship between ATP concentration and normalized redox current was obtained from 0.25 to 1.25 mM. Therefore, the present system is potentially applicable to new ATP sensing system.

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37.

This work　aims to develop the handheld electrochemical sensor system for practical use. The Au working electrode, the Au pseudo-reference electrode, and the Au auxiliary electrode are built in the sensor chip. In order to add the selectivity for uric acid, ferrocene terminated alkanethiol monolayer was formed on the Au working electrode by self-assembly method. It succeeded to detect uric acid in phosphate buffer (pH 7.4). However, this system did not work for the real urine sample, because sulfite ion in the sample disturbed the oxidation of ferrocene.

Thus, the fully automated pretreatment module was developed. First, sulfite ion and the organic impurities were removed from the real urine sample by the miniaturized NH2-terminated filter (Pore size is less than 10 m.). In addition, the electrochemical detection essentially requires controlling pH. In the pretreatment system, the filtered sample was mixed with phosphate buffer. The pH of the sample solution was adjusted to pH 7.4 in the sample pH range between 4.5 and 7.5. Then, the electrochemical sensor measured the sample without further pretreatment. The calibration curve shows a good linear relation with respect to the concentration of uric acid between 150 mM to 500 mM.

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38.

In our recent studies, we have developed a high-speed chemical imaging system which is capable of recording 'chemical movie' at 70 fps. In this study, the system was developed for a higher frame rate and a flexible definition of the measurement area. First, the number of measurement points was increased up to 64-points. As a result, high-speed measurement at 200 fps has been achieved. In addition, the bundled-fiber optics has been developed for the illumination in the measurement. By using the fiber optics as a light guide, the layout of the measurement points can be easily changed to fit the measurement area. As an example, the real-time measurement of the liquid flow in a micro channel was performed by changing the arrangement of the fibers along the channel. The system would be used to analyze the sample in a flow injection analysis.

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39.

A two dimensional surface plasmon resonance (2D-SPR) imager with high resolution was applied to novel cell-based biosensing system for drugs. Response of PC12　cells as a model nerve precursor cell, which were adhered on an Au sensor chip to acetyl choline receptor agonist such as dimethylphenylpiperazinium (DMPP) was observed by the reflection intensity change in the individual cell regions with the 2D-SPR imager at real-time without any probe reagents. The cell response in 2D-SPR imaging to agonist depended on the concentration of the agonist. It was further demonstrated that the reflection intensity change of cell regions might be based on intracellular recruitment of signal transduction proteins such as PKC to cell membrane because the reflection intensity increase of cell regions upon agonist stimulation was significantly suppressed in the presence of a PKC inhibitor. These results suggested future wide applications of label-free cell-based drug sensing with 2D-SPR imager.

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40.

We report the sequence-selective discrimination of the cytosine methylation status in DNA with anti methylcytosine antibody. This was realized by employing an affinity measurement involving the target methylcytosine in a bulge region and anti methylcytosine antibody, following hybridization with a bulge-inducing DNA to ensure that the only the target methylcytosine is located in the bulge. The affinity of the antibody for methylcytosine in the bulge was 79 % of that in a single strand of DNA, however the affinity for non-target methylcytosine in a double strand of DNA decreased greatly. By employing the difference between the affinity in the bulge and that in the duplex, we could determine selectively whether or not the target cytosine was methylated in MGMT promoter sequence with a single base level.

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41.

Processing of solutions in the form of liquid droplets was carried out and sensing of analyte molecules was conducted based on surface plasmon resonance (SPR). Two types of devices were fabricated. Performance of the device was characterized to optimize the structure of the sensing region and microfluidic channel. The sensor responded to concentration changes of glucose. A linear relationship was observed between the change in reflectivity and the concentration of compounds. Thiol terminated single stranded DNA was modified on the gold surface of the sensing region. The device function was tested by detecting streptavidin (SA) complex accompanying DNA hybridization. Sequential detection of multi sample plugs was carried out.

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42.

In practical aspect of the sensing, multiple pretreatment steps such as filtering, purification, separation, and sometimes condensation process, are required before a user injects the sample into the sensing system. We believe that the total sensing system should equip those functions, and simplify the manual handling process. Hence, this work proposes the total Surface Plasmon Resonance (SPR) sensor system with immunosensor chip using thiol compounds, aiming to minimize the manual handling process. This work also reports the various pretreatment modules assembled in the flow system.

It is well known that thiol compounds easily forms well-ordered monolayer on Au surface by immersion method. However, in fact, it is difficult to make the high-quality monolayer of thiol compound on Au surface, because Au surface is often covered with contamination from air pollutants. This work also proposes the cleaning system using Exima light to achieve a good reproducibility in the sensor chip production process. In order to optimize the SPR sensing performance, various thiol compounds were examined. The surface structures in molecular scale were characterized by electrochemical methods, scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and FT-IR RAS.

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43.

Alfa fetoprotein (AFP) is known as a diagnostic marker of hepatocellular carcinoma and determined by enzyme linked immune sorbent assay (ELISA) using microtiter plate. ELISA needs time consuming procedure. We have developed a microfluidic disc to perform rapid and high-throughput detection of AFP based on ELISA. In this study, the anti AFP mouse monoclonal antibody was immobilized on the micro beads with carboxyl groups by the carbodiimide method. After immobilization, antibody-immobilized beads are introduced into a microchamber on a microchannel in the disc. Sandwich ELISA was carried out in the microchamber using HRP labeled anti AFP antibody. After the ELISA step, HRP was detected through chemiluminescence of luminal. All the steps were finished within 40 min, with 5 l of reagent and sample per chamber. AFP was detected at the range of 2 – 250 ng/ml by the microfluidic disc method. Using microfluidic disc, high-throughput ELISA for AFP was performed rapidly with reduced reagent and samples.

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44.

An informational interface between neural system and electrical circuit is very important for artificial sense organs. The interface using chemical stimulation would be more physiologically friendly than electrical stimulation. We have developed an electrochemical micropump for rapid micro-administration of neurotransmitters toward neurons by using electrolysis of water. This micropump is feasible for real-time control of neuronal signals. However high-speed refilling system was not yet to be developed. Then, we developed a novel micro- electrochemical diaphragm pump which has automatic refilling function. The pump is composed from a flow path of the fluid for administration and a chamber filled with electrolytic solution with interdigitated array (IDA) of platinum—black electrodes. A diaphragm made of polydimethylsiloxane (PDMS) was between the flow path and the chamber. Electrolysis of the water produced bubbles in the chamber and jetted out the fluid in the flow path with the diaphragm. The time lag from the voltage-application on the electrode to the start of jetting out is 50 ms. The finish of the voltage-application, the bubbles disappeared by the platinum catalysis and diaphragm was flattened. Then, the jetting stopped and the fluid was refilled from the back of the flow path. The time lag was from stop of the application and that of jetting was less than 100 ms. The micropump using electrochemically-powered diaphragm would be able to administration neurotransmitter to the neurons rapidly and control neuronal signal in almost real-time. The pump would realize the new neuron-machine interface based on chemical stimulation.

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45.

In this study, a metabolite sensor gel sheet has been developed for skeletal muscle cell-based assay system. In vitro assay of exercise-mediated myokine (such as Interleukin 6) secretion from skeletal muscle cells are essential for revealing the mechanism of glycemic control in muscle cells because their myokines have significant effects on self-regulation of skeletal muscle glucose metabolism. Previously, we have established a hydrogel-supported contractile myotube micropatterns integrated with a hydrogel-based conducting polymer microelectrode arrays to afford a bioassay system. Contractile activity of each myotube line pattern was site-specifically controlled with microelectrode arrays, enabling clear comparison of exercise effects on cellular metabolic activity. To integrate metabolite sensing elements into the bioassay system, we used a sensor molecule-functionalized microbead, which has advantages for easily patterning of soluble sensor molecules even on a wet hydrogel sheet. The gel sheet sensor with an antibody-functionalized microbead successfully displayed an increase of IL6 secretion from contracting myotubes by about 3-fold larger than that of resting cells.

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