A thin-film micromanufactured oxygen microelectrode

i LIST OF TABLES. iii LIST OF FIGURES. iv ACKNOWLEDGEMENTS. vii CHAPTER 1 INTRODUCTION. 1 1.1 Historical Relevance.1 1.2 Basis for Biosensors. 3 1.3 Research Needed.3 1.4 Objectives of the Research. 5 1.5 Microelectrode Terminology.6 CHAPTER 2 RELATED RESEARCH. 8 2.1 Thin-Film Oxygen Sensors. 8 2.2 Needle-like Small Sample Volume Oxygen Microelectrodes.9 2.2.1 Basic Divisions by Manufacturing Technique. 12 2.2.2 Factors of Design Importance.15 2.3 The Whalen/Nair Oxygen Microelectrode.17 2.3.1 Whalen/Nair Electrode Applications.18 2.3.2 Whalen/Nair Electrode Characteristics. 19 2.3.3 Oxygen Sensitivity Theory. 21 2.3. 4 Construction of the Whalen/Nair Electrode.25 2.4 Micromanufacturing Processes. 26 2.4.1 Micromanufactured Oxygen Microelectrode Design.27 2.4.2 Benefits of Thin-Film Processing.28 2.4.3 Process Control and Application.29 2.5 Mathematical Modeling.31 2.5. 1 Past Modeling Efforts. 31 2.5. 2 Applied Mathematical Modeling. 33 2.5. 3 Applied Modeling Discussion. 35 CHAPTER 3 MICROELECTRODE DESIGN AND CONSTRUCTION.38 3.1 Electrode Design Considerations. 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3.1.1 Overall Tip Size Considerations.38 3.1.2 Recess Dimension Considerations.40 3.1.3 Electrode Design. 43 3.2 Construction o f the Micrornanufactured Oxygen Microelectrode.44 3.2.1 Substrate Preparation. 44 Results.45 Discussion.45 3.2.2 Catalytic & Insulation Layer Sputtering.45 Results.46 Discussion.48 3.2.3 Spin-on Glass Coating.50 Results.51 Discussion. 51 3.2.4 Focused Ion Beam Milling.53 Results. 53 Discussion. 54 3.2.5 Electrode Recess Generation. 54 Results. 55 Discussion. 57 3.3 Electrode Instrumentation System.58 3.3.1 Instrumentation System Response. 60 Results. 61 Discussion. 62 CHAPTER 4 ELECTRODE TESTING. 64 4.1 Preliminary Tests.64 4.1.1 Sputtered Metal Adhesion.65 Results.65 Discussion. 66 4.1.2 Sputtered Metal Catalytic Response.67 Results.67 Discussion.68 4.1.3 Insulation Layer. 69 Results.70 Discussion. 74 4.2 Microelectrode Testing. 77 4.2.1 Current/Voltage Plateau Generation.77 Results. 79 Discussion. 80 4.2.2 Dissolved Oxygen Response. 81 Results. 82 Discussion. 83 4.2.3 Stir Sensitivity.84 Results. 85 Discussion. 86 4.2.4 Drift. 86 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Results.86 Discussion.87 4.3 Electrode Production Yield. 87 CHAPTER 5 -CONCLUSIONS.90 CHAPTER 6 RECOMMENDATIONS. 91 6.1 Electrode Characterization Needs.91 6.2 Improvement of Current Thin-Film Process. 94 6.3 Development of New Micromanufacturing Processes. 95 APPENDIX A-GLOASSARY. 99 APPENDIX B HYBRID ELECTRICAL / MASS TRANSPORT MODEL 102 B.l Introduction.102 B.2 The Electrical Equivalent Circuit Model. 102 B.2.1 Modeling the Measurand.103 B.2.2 Modeling the Transduction Process. 105 B.2.3 Modeling the Signal Conditioning and Signal Output System. 107 B.2.4 Modeling the Complete System. 108 B.2.5 Model Simplification and Testing.110 B.3 The Mass Transport Model. 113 B.3.1 Species Mass Balance.114 B.3.2 Solving the System.116 B.3.3 Manipulation of the Model. 117 B.3. 4 Trends