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Continuous Electrowetting in Passivating and Non-Passivating Systems" (2013)

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Continuous Electrowetting in Passivating and Non-Passivating Systems University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School January 2013 Continuous Electrowetting in Passivating and Non- passivating Systems Mehdi Khodayari University of South Florida, [email protected] Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Mechanical Engineering Commons Scholar Commons Citation Khodayari, Mehdi, "Continuous Electrowetting in Passivating and Non-passivating Systems" (2013). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/4708 This Dissertation is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Continuous Electrowetting in Passivating and Non-passivating Systems by Mehdi Khodayari A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Mechanical Engineering College of Engineering University of South Florida Co-Major Professor: Nathan B. Crane, Ph.D. Co-Major Professor: Alex A. Volinsky, Ph.D. Delcie Durham, Ph.D. Matthias Batzill, Ph.D. Alberto A. Sagüés, Ph.D. Date of Approval: July 3, 2013 Keywords: Reliable Electrowetting, Symmetric Electrowetting, Electrochemical Diodes, Electrostatic Force, Titanium, Aluminum Copyright © 2013, Mehdi Khodayari ACKNOWLEDGMENTS I would like to express my gratitude to Professor Nathan B. Crane and Professor Alex A. Volinsky for all of their scientific and financial support during my Ph.D. study at the University of South Florida. Professor Crane was my immediate advisor and from him I learned how a dedicated advisor would be. Professor Volinsky was my great mentor and advisor too. Their approaches to scientific problems have always aided me to do research and publish papers. I appreciate all of their kindness. TABLE OF CONTENTS LIST OF TABLES ......................................................................................................................... iv LIST OF FIGURES ........................................................................................................................ v ABSTRACT ................................................................................................................................. viii CHAPTER 1: INTRODUCTION ............................................................................................ 1 1.1. Technology Life-Cycle Path ..................................................................................... 1 1.2. Motivation for Electrowetting on Dielectric Process Research ................................ 1 1.3. Continuous Electrowetting........................................................................................ 2 1.4. Dissertation Goal ...................................................................................................... 4 1.5. References ............................................................................................................... 10 CHAPTER 2: BACKGROUND MATERIALS .................................................................... 12 2.1. Wetting Basics ........................................................................................................ 12 2.1.1. Surface Energy ........................................................................................... 13 2.1.2. Contact Angle (Young’s Equation) ............................................................ 13 2.2. Electrowetting ......................................................................................................... 14 2.2.1. Applications ................................................................................................ 18 2.2.1.1. Microprocessors Cooling ............................................................ 18 2.2.1.2. Micromechanical Systems ........................................................... 18 2.2.1.3. Electrowetting Lenses ................................................................. 19 2.2.1.4. Reflective Displays ...................................................................... 20 2.2.1.5. Energy Harvesting ....................................................................... 21 2.2.1.6. Lab on Chip ................................................................................. 21 2.2.2. Actuation Methods ..................................................................................... 22 2.2.2.1. Grounding from below ................................................................ 23 2.2.2.2. Conventional Electrowetting ....................................................... 23 2.2.2.3. Optoelectrowetting ...................................................................... 24 2.2.2.4. Bidirectional Electrowetting ........................................................ 25 2.2.2.5. Continuous Electrowetting (CEW) ............................................. 26 2.2.3. Materials Issues .......................................................................................... 26 2.3. Electrochemistry ..................................................................................................... 28 2.3.1. Basic Reactions .......................................................................................... 29 2.3.2. Basic Aluminum Electrochemistry ............................................................ 31 2.3.3. Incorporation of Anions in Aluminum Oxidation ...................................... 32 2.3.4. Porous Alumina .......................................................................................... 32 2.3.5. Barrier like Alumina ................................................................................... 32 i 2.3.6. Passivating Systems in EWOD .................................................................. 33 2.4. References ............................................................................................................... 35 CHAPTER 3: EXPERIMENTS ............................................................................................. 40 3.1. Dielectric Characterization ..................................................................................... 42 3.1.1. Resonant Methods ...................................................................................... 43 3.1.2. Electrochemical Impedance Spectroscopy ................................................. 43 3.1.3. Contact Angle versus Voltage .................................................................... 44 3.1.4. I-V Measurements ...................................................................................... 44 3.2. Experiments Setup .................................................................................................. 45 3.2.1. Electrochemical Impedance Tests Setup .................................................... 45 3.2.2. I-V Experimental Setup .............................................................................. 46 3.2.3. Contact Angle Measurement Methods ....................................................... 48 3.2.4. Test Setup of the Electrode Pair Measurement .......................................... 50 3.3. Microfabrication Methods ...................................................................................... 52 3.3.1. Reliability Tests Samples ........................................................................... 52 3.3.2. Test Samples of the Electrode Pair Measurements .................................... 55 3.3.3. Continuous Electrowetting Tests Samples ................................................. 55 3.4. Conclusion .............................................................................................................. 57 3.5. References ............................................................................................................... 57 CHAPTER 4: A MATERIAL SYSTEM FOR RELIABLE LOW VOLTAGE ANODIC D ELECTROWETTING .................................................................................... 60 4.1. Electrochemical Impedance Spectroscopy ............................................................. 60 4.2. Abstract ................................................................................................................... 62 4.3. Introduction ............................................................................................................. 63 4.4. Experiments ............................................................................................................ 64 4.5. Discussion ............................................................................................................... 65 4.6. Conclusion .............................................................................................................. 67 4.7. References ............................................................................................................... 69 CHAPTER 5: ELECTROCHEMICAL EXPLANATION FOR ASYMMETRIC D ELECTROWETTING RESPONSE ............................................................... 72 5.1. Abstract ................................................................................................................... 72 5.2. Introduction ............................................................................................................. 73 5.3. Discussion ............................................................................................................... 74 5.4. Conclusions ............................................................................................................
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