別紙４（課程博士）
Date of Submission:

平成Department

Student ID Number

電気・電子情報工学専攻
Applicant’s name

氏名

髙橋

学籍番号第 115205 号

聡

２８年

２月

Supervisors

澤田

和明

指導教員

村上裕二

２５日

Abstract

論文内容の要旨(博士)

半導体技術と電気化学センサ技術を融合した増幅型酸化還元センサに関する研究
Title of Thesis
博士学位論文名(A study on an amplified redox sensor integrated with semiconductor technology
and electrochemical sensor technology)(Approx. 800 words)(要旨

1,200 字程度)

電気化学センサは，化学物質の種類や濃度に由来する電気化学信号を利用し化学物質の検出を行うセンサである．電気化学センサは，高感度，高速応答性，簡易性，小型化などの優れた特徴を持っている．
近年，測定場所の制限のない現場計測に適したセンサが望まれてきている．従来の分析手法として分光計測や吸光計測, 高速液体クロマトグラフィーを用いた化学物質の検出，定量評価が行われてきた．しかし，これらの分析手法は大きな光学系が必要であることや，加圧や分子修飾等の前処理が必要でとなり，現場計測には不向きである．一方，電気化学センサは，前処理や大規模な装置が必要なく現場計測装置を実現することが可能となる．電気化学センサは化学物質の濃度と測定電流の間に比例関係があることが知られており，低濃度計測の場合，非常に小さな電流を測定が必要となる．電流計は高感度になるほど装置の規模が大きくなってしまうため現場計測を実現する上で，課題になる．このような現状を鑑み本研究では半導体技術を利用し電気化学センサに増幅機能を付与することを提案した．増幅機能を付与することによって，小型で低感度な計測器による測定が達成できるようになるため，現場測定装置に適したセンサが実現可能になると考える．
本研究ではバイポーラトランジスタと酸化還元センサを融合した増幅型酸化還元センサを提案した．
増幅型酸化還元センサは電流増幅素子であるバイポーラトランジスタとセンシングエリアである作用電極を一体化した構造をしており，作用電極からの酸化還元電流を単素子で直接増幅できる特徴を有している．また，バイポーラトランジスタは一般的に金属酸化物半導体電界効果トランジスタに比べ，フリッカーノイズの影響が少ないことが知られており，低周波領域で行う測定が主である電気化学測定において検出限界の向上が期待できると考えた．また，増幅型酸化還元センサの検出限界を向上させるた
め，作用電極とバイポーラトランジスタのベースの間にバイアス電流源を挿入するシステムを提案した．このシステムを使用することで増幅型酸化還元センサのフェリシアン化カリウムの検出限界を 100μM から 1 μM へ向上させることに成功した．また，低ノイズ評価における検出限界の評価として，増幅型酸化還元センサと金属酸化物半導体電界効果トランジスタによって構築したトランスインピーダンス(TIA)回路の低周波ノイズの比較を行った．サイクリックボルタンメトリー法における測定周波数範囲である 0.061 Hz から 0.122 Hz の時の入力換算電流ノイズを比較した結果，増幅型酸化還元センサを使用した場合 19.1 pARMS，TIA 回路は 219.8 pARMS となりサイクリックボルタンメトリー法を用いた
電気化学測定において増幅型酸化還元センサによる増幅は 11.5 倍ほど TIA 回路に比べ最低検出感度向上が期待できる結果が得られた．
本研究では，現場計測に適したセンサを実現するため，半導体技術を利用し電気化学センサに増幅機能を付与することを提案し，小型で低周波ノイズの影響が小さい増幅型酸化還元センサを開発した．増幅型酸化還元センサは酸化還元電流を 100 倍程度に増幅することができ，低濃度の化学物質計測が可能である．応用例として，環境分野においては工場から排出される微量の重金属の測定，農業分野では植物の栄養分の分析，医療分野では介護用途での非侵襲型生体情報モニタリングなど幅広い活用が期待される．

別紙４（課程博士）
Date of Submission:

平成Department

Student ID Number

電気・電子情報工学専攻
Applicant’s name

髙橋

氏名

学籍番号

第 115205 号

聡

２８年

１月

Supervisors

澤田和明

指導教員

村上裕二

１５日

Abstract(博士)

論文内容の要旨

半導体技術と電気化学センサ技術を融合した増幅型酸化還元センサに関する研究
Title of Thesis
博士学位論文名(A study on an amplified redox sensor integrated with semiconductor technology
and electrochemical sensor technology)(Approx. 800 words)(要旨1,200 字程度)

The electrochemical sensor can detect chemical substances from electrochemical signals derived fromsubstances type and concentration. In particular, a sensor for detecting chemical substances by using anoxidation-reduction reaction of chemical substances is a redox sensor. Redox sensor is attractive due to their fast
response, sensitivity, simplicity and miniaturization. Therefore, it does not require the measurement skills andknowledge once you build a measurement system. Redox sensor is used in medical field, environmental field,chemistry field, and also other field. Recently, study of redox sensor combined with semiconductor technology is
being actively conducted. Redox sensor is possible to integrate on one chip with signal processing circuits byusing semiconductor technology. Therefore, redox sensor is expected for application to onsite monitoring.
Onsite monitoring is required to be small size device, chemical substance with low concentrations detection
limits and real-time measurements. In conventional analysis method, the detection of chemical substances andquantitativeevaluationusedspectroscopy,absorption

measurement

andhighperformanceliquidchromatography. However, spectroscopy and absorption measurement require large optical system for measuring
the chemicals, chromatography requires a preprocessing. Therefore, they were not suitable for onsite monitoring.
However, the redox output current is reduced if the sensing area is small and/or the concentration of the sample islow. , It is necessary to measure a very small current for detecting species with low concentrations.
We have proposed the use of an amplified redox sensor (ARS), which combines the sensing area that perform
as a working electrode with a bipolar transistor. The proposed sensor can directly amplify a small current signal,and such amplification can be achieved with a single element, namely, the bipolar transistor. By applying anamplification function, the need for sensitive current measuring devices is eliminated. It is considered that thesensor suitable for field measurement can be realized. Moreover, most of the electrochemical measurements isbeing conducted under low frequency range. The less amplification of low frequency noise can be achieved.
Generally, flicker noise of bipolar transistor is smaller than MOSFET (Metal Oxide Semiconductor Field EffectTransistor). In other words, with the amplification by bipolar transistor, improvement of detection limit isexpected. As a result, ARS amplifies the oxidation current up to 75-100 times bigger. However, the drive voltageof bipolar transistor is influenced by redox current. When the redox current is small, it might not be amplified.
Moreover, when amplified in a single element, there is a problem that cannot amplify both current of theoxidation and reducing from the rectification of Bipolar Transistor.
To solve this problem, we propose a new measurement method in which both the redox current and a bias

current source that can stabilize the working voltage of Bipolar Transistor are being inserted into the baseterminal. Moreover, proposed measurement system can amplify the current of both oxidation and reduction andalso can measure the small current. In proposed measurement system, potassium ferricyanide of 1 μM can bedetected. Since this current source is possible for integration by using a semiconductor technology, increased
sensitivity without increasing the size of the measurement system can be expected. For the measurement of thelimit of low noise, we clarified our Bipolar Transistor is suitable for the measurement of low frequency bycomparing the low frequency noise of both sensor with Bipolar Transistor and sensor with transimpedance
amplifier (TIA) which is built from MOSFET.

From the result of cyclic voltammetry(CV) with a frequency of0.083 Hz, the effective value of noise range from 0.061 Hz to 0.122 Hz is calculated. The noise is 19.1 pARMS inthe ARS devices and 219.8 pARMS in the TIA. From this result, the improvement of detection sensitivity is
expected to be 11.5 times higher with the amplification by bipolar transistor. From the result of square wave
voltammetry (SWV) with a frequency range from 0.75 Hz to 15 Hz, where low frequency voltages are used togive rise to redox reactions, the noise is 46.6 pARMS in the ARS devices and 107 pARMS in the TIA. From thisresult, the improvement of detection sensitivity is expected to be 2 times higher with the amplification by bipolartransistor.Results of calculating the limit of detection of potassium ferricyanide from the effective value of thenoise in the CV method, the detection limit is 3 nM in the TIA circuit, whereas the possibility of measuring up
until 30 pM is indicated when using this sensor.
Finally, we conducted an experiment of glucose detection to check the applicable of this sensor inbiomeasurement. Glucose response was successfully detected by chronoamperometry using our ARS. ARS
showed that it is applicable to bio-measurement. As a result of the above, it is indicative of the possibility of theamplification type redox sensor as onsite monitoring device. Results show that this sensor can be used in a wide
range of applications. For example, in environmental field, the measurement of low concentration of heavy metal
discharged from factories is possible. It can also be used in the analysis of plants nutrition in agricultural field
and the monitoring of noninvasive organism for nursing use in medical field.