i Fundamental Studies of AC/DC Electrokinetic Phenomena for the Realization of Microchip Capillary Electrophoresis for Single-Cell Analysis A Thesis Submitted to the Faculty of Drexel University by Doh-Hyoung Lee in partial fulfillment of the requirements for the degree of Doctor of Philosophy March 2011 ii © Copyright 2011 Doh-Hyoung Lee. All Rights Reserved iii ACKNOWLEDGEMENTS I would like to acknowledge the support and help of numerous people, without whom this thesis would not have been possible. I would like to express my deepest gratitude to my two advisers, Dr. Hongseok (Moses) Noh, and Dr. Bakhtier Farouk for their invaluable guidance and support throughout this research work. I am also grateful to Dr. Young I. Cho, Dr. Joe Foley, and Dr. Elisabeth Papazoglou for serving on my thesis committee and for their many helpful comments. I would like to thank my graduate student friends for their help, friendship and support: Temitope Sodunke, Jorge Capurro, Rob Hart, Jonghyun Oh, Joseph Cirillo, Kewei Liu, Chengjie Yu, and many others. Finally a special thanks to my parents, wife Soyoung and son Benjamin for their love and support. iv TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................................ iii TABLE OF CONTENTS ................................................................................................................ iv ABSTRACT .................................................................................................................................... ix CHAPTER 1. INTRODUCTION & MOTIVATION ................................................................... 1 1.1 . Motivation ............................................................................................................ 1 1.1.1. Needs for Single Cell Analysis ...................................................................... 1 1.1.2. Challenges in Single-cell Analysis ................................................................ 3 1.1.3. Current Techniques for Single-cell Analysis ................................................. 4 1.1.4. Challenges of Microchip Capillary Electrophoresis ...................................... 8 1.1.5. AC/DC Electrokinetic Phenomena for Single-cell Analysis Microchips ...... 9 1.2 . Research Objectives ........................................................................................... 10 1.3 . Outline of the Thesis .......................................................................................... 16 1.4 . Summary ............................................................................................................ 19 CHAPTER 2. BACKGROUND ............................................................................................... 21 2.1 . Microfluidics, BioMEMS and Lab-On-A-Chip ................................................. 21 2.2 . Microfabrication Techniques ............................................................................. 23 2.3 . DC Electrokinetics Theory ................................................................................. 29 2.3.1. Electrophoresis ............................................................................................. 29 v 2.3.2. Electroosmosis ............................................................................................. 30 2.4 . AC Electrokinetics Theory ................................................................................. 34 2.4.1. AC Electroosmosis....................................................................................... 34 2.4.2. Dielectrophoresis ......................................................................................... 37 2.4.3. Electrothermal Flow ..................................................................................... 40 2.5 . Cell Manipulation in Microchannels .................................................................. 44 2.6 . Cell Lysis in Microchannels ............................................................................... 53 2.6.1. Chemical Lysis............................................................................................. 53 2.6.2. Mechanical Lysis ......................................................................................... 55 2.6.3. Electrical Lysis (irreversible electroporation) .............................................. 56 2.6.4. Osmotic Lysis .............................................................................................. 60 2.6.5. Other Cell Lysis Methods ............................................................................ 61 2.7 . Sample Concentration Techniques ..................................................................... 62 2.8 . Separation Methods ............................................................................................ 68 2.9 . Detection Methods ............................................................................................. 75 CHAPTER 3. INTERACTION BETWEEN DC AND AC ELECTROKINETICS ................. 81 3.1 . Introduction ........................................................................................................ 81 3.2 . Microfabrication Method: PDMS Replica Molding .......................................... 83 3.3 . Experiment Procedure ........................................................................................ 84 3.4 . Measurement of DC Electroosmotic Mobility ................................................... 84 vi 3.5 . Numerical Methods: AC Electroosmosis ........................................................... 85 3.5.1. Geometry and Boundary Conditions............................................................ 86 3.5.2. Electrostatics Simulation ............................................................................. 86 3.5.3. Incompressible Navier-Stokes Simulation ................................................... 87 3.6 . Experimental Results ......................................................................................... 87 3.6.1. AC and DC Electroosmotic Flow Interaction .............................................. 87 3.6.2. Dielectrophoresis under DC Electroosmotic Flow ...................................... 88 3.7 . Numerical Simulation Results ............................................................................ 89 3.8 . Conclusions ........................................................................................................ 92 CHAPTER 4. DIELECTROPHORETIC PARTICLE-PARTICLE INTERACTION UNDER AC ELECTROHYDRODYNAMIC FLOW CONDITIONS ........................................................ 93 4.1 . Introduction ........................................................................................................ 93 4.2 . Theory ................................................................................................................ 95 4.2.1. Dielectrophoresis ......................................................................................... 95 4.2.2. AC Electroosmosis....................................................................................... 97 4.2.3. Electrothermal Flow ..................................................................................... 98 4.2.4. Van der Waals Force and Double Layer Interaction .................................... 99 4.3 . Experimental Method ....................................................................................... 100 4.3.1. Device Fabrication and Materials .............................................................. 100 4.3.2. Experimental Procedure ............................................................................. 102 4.4 . Simulation Method ........................................................................................... 103 vii 4.5 . Results and Discussion ..................................................................................... 106 4.5.1. Particle Behaviors under ACEO Flows ..................................................... 106 4.5.2. Particle Behaviors under Electrothermal Flows ......................................... 112 4.6 . Conclusions ...................................................................................................... 116 CHAPTER 5. 3-D SIMULATION OF ELECTROOSMOTIC SAMPLE INJECTION AND MIGRAION IN MICROCHANNELS : EFFECTS OF NON-RECTANGULAR CROSS SECTION……… ......................................................................................................................... 118 5.1 . Introduction ...................................................................................................... 118 5.2 . Problems Considered ....................................................................................... 120 5.2.1. Effects of Non-rectangular Cross Section .................................................. 120 5.3 . Governing Equations ........................................................................................ 124 5.4 . Numerical Methods: DC Electrokinetics ......................................................... 125 5.5 . Model Validation ............................................................................................. 128 5.6 . Effects of Non-rectangular Cross Section ........................................................ 129 5.6.1. 3-D Characteristics in Sample Loading ..................................................... 129 5.6.2. 3-D Characteristics in Sample Dispensing ................................................. 132 5.6.3. 3-D Characteristics of Sample Dispersion during