Enzymatic electrode based AC mode electrochemical technique for glucose detection and biofuel cell electrode development
Date Issued
2006
Date
2006
Author(s)
Lai, Wen-Ren
DOI
zh-TW
Abstract
Taking the research results on electrochemistry based detection methods developed in Nano-BioMEMS team of National Taiwan University, this dissertation proposed a fundamental theoretical model for the previously reported detection method and used this model to point out the potential advantages of using sine wave voltage as the primary power source. In order to prove the underlying advantage with respect to traditional electrochemical method, we developed a glucose enzymatic strip as the testing platform. The experimental data obtained indicated that higher linearity and lower than 5% coefficient of variation with respect to the glucose concentration rangking between 50 to 500 mg/dL can be obtained for 40% hematocrit whole blood test. Using different glucose concentrations standard solutions as the test samples, we compared the testing data obtained from our new voltage applied method and that of the traditional method. To determine right current sampling time, instant trigger voltage method was adopted, i.e., the response current created by dropping the glucose sample on strip was used to start the measurement process. By modulating the frequency and the amplitude of the applied sine wave voltage, a higher resolution and stronger response current can be obtained between measured voltage and the glucose concentration. Even at the high glucose concentration of 600 mg/dL, the new method achievees higher linearity when compared to traditional electrochemical method. To eliminate the non-Faraday current and to increase the signal-to-noise ratio this thesis proposed a new signal processing algorithm using the newly developed theoretical modeling. This approach recognized that non-Faraday current was induced by the double layer capacity effect created by applying the sine wave voltage and can thus be eliminated by proper signal processing algorithm. More specifically, it was identified that non-Faraday current can be integrated to zero if the integration time is set to be the integer times of the applied sine voltage period. The experimental data obtained clearly verified that this newly proposed integration signal processing algorithm and the newly proposed sine wave driving voltage method led to better singla to noise ratio and higher linearity when comparing the FFT spectrum of the signal at DC and at the applied driving voltage signal frequency. This research proves that the frequency of sine wave voltage can enhance the DC term of response current and this current is directly proportional to the sample glucose concentration and has higher sensitivity with respect to the glucose concentration. After several hundred measurements at the testing condition of 50Hz and 10mV amplitude sine wave voltage, it was found that this new approach can have better than 40% sensitivity when compared to the respone current obtained from the traditional method.
This thesis also attempted to develop biofuel cells, which can use biocatalysts to convert chemical energy to electrical energy. As the long-term vision of this biofuel is to be used as the power source for embedded biosensors, glucose was applied as the substrate for the oxidation processes at the anode and oxygen was uesd as the substrates for the reduction processes at the cathode. Taking the enzymatic strip of glucose sensor as the starting point, we used glucose oxidase (EC 1.1.3.4) and bilirubim oxidase(EC 1.3.3.5) to catalyze the processes on the anode and the cathode. The enzyme and mediator were entrapped by the polypyrrole on the Au electrode through electropolymerization. The Cyclic Voltammetry was used to polymerize the pyrrole, which control the scan cycles and the scan rate to determine the deposit of polypyrrole. For final testing of this newly attempted biofuel cell, the GOx-polypyrrole electrode and the BOD- -polypyrrole electrode were integrated and it was identified that for glucose concentration 200mg/dL, 0.15V maximum voltage and 0.242μW/cm2 output power can be obtained when connecting to a 50kΩ load.
Subjects
血糖檢測
電化學檢測法
生物燃料電池
glucose
biofuel cell
electrochemical
Type
thesis
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