Book contents
- Frontmatter
- Contents
- Preface
- Nomenclature
- Introduction
- 1 Kinematics, Conservation Equations, and Boundary Conditions for Incompressible Flow
- 2 Unidirectional Flow
- 3 Hydraulic Circuit Analysis
- 4 Passive Scalar Transport: Dispersion, Patterning, and Mixing
- 5 Electrostatics and Electrodynamics
- 6 Electroosmosis
- 7 Potential Fluid Flow
- 8 Stokes Flow
- 9 The Diffuse Structure of the Electrical Double Layer
- 10 Zeta Potential in Microchannels
- 11 Species and Charge Transport
- 12 Microchip Chemical Separations
- 13 Particle Electrophoresis
- 14 DNA Transport and Analysis
- 15 Nanofluidics: Fluid and Current Flow in Molecular-Scale and Thick-EDL Systems
- 16 AC Electrokinetics and the Dynamics of Diffuse Charge
- 17 Particle and Droplet Actuation: Dielectrophoresis, Magnetophoresis, and Digital Microfluidics
- APPENDIX A Units and Fundamental Constants
- APPENDIX B Properties of Electrolyte Solutions
- APPENDIX C Coordinate Systems and Vector Calculus
- APPENDIX D Governing Equation Reference
- APPENDIX E Nondimensionalization and Characteristic Parameters
- APPENDIX F Multipolar Solutions to the Laplace and Stokes Equations
- APPENDIX G Complex Functions
- APPENDIX H Interaction Potentials: Atomistic Modeling of Solvents and Solutes
- Bibliography
- Index
10 - Zeta Potential in Microchannels
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Nomenclature
- Introduction
- 1 Kinematics, Conservation Equations, and Boundary Conditions for Incompressible Flow
- 2 Unidirectional Flow
- 3 Hydraulic Circuit Analysis
- 4 Passive Scalar Transport: Dispersion, Patterning, and Mixing
- 5 Electrostatics and Electrodynamics
- 6 Electroosmosis
- 7 Potential Fluid Flow
- 8 Stokes Flow
- 9 The Diffuse Structure of the Electrical Double Layer
- 10 Zeta Potential in Microchannels
- 11 Species and Charge Transport
- 12 Microchip Chemical Separations
- 13 Particle Electrophoresis
- 14 DNA Transport and Analysis
- 15 Nanofluidics: Fluid and Current Flow in Molecular-Scale and Thick-EDL Systems
- 16 AC Electrokinetics and the Dynamics of Diffuse Charge
- 17 Particle and Droplet Actuation: Dielectrophoresis, Magnetophoresis, and Digital Microfluidics
- APPENDIX A Units and Fundamental Constants
- APPENDIX B Properties of Electrolyte Solutions
- APPENDIX C Coordinate Systems and Vector Calculus
- APPENDIX D Governing Equation Reference
- APPENDIX E Nondimensionalization and Characteristic Parameters
- APPENDIX F Multipolar Solutions to the Laplace and Stokes Equations
- APPENDIX G Complex Functions
- APPENDIX H Interaction Potentials: Atomistic Modeling of Solvents and Solutes
- Bibliography
- Index
Summary
Previous chapters assert that a potential drop occurs over an EDL, consistent with the fact that chemical reactions occur at the surface to induce ionization of wall species. We now return to this subject in greater detail. Our goal is to be able to predict the equilibrium surface potential at microfluidic device interfaces as a function of the device material and solution conditions. This chapter frames the problem, describes associated parameters, and lists several models that can be used to attack this problem and interpret experimental data. We start by clarifying notation and terminology. We then discuss the chemical origins of surface charge for both Nernstian and non-Nernstian surfaces, discuss techniques for measuring and modifying electrokinetic potentials, and summarize observed zeta potentials for microfluidic substrates. Finally, we discuss how EDL theory is related to interpretation of zeta potential data and the relation between ζ and ϕ0.
DEFINITIONS AND NOTATION
Here we must define the distinct meanings of several terms, namely the zeta potential, the electrokinetic potential, the interfacial potential, the double-layer potential, and the surface potential. These terms have different meanings and are used differently by various authors. Further, some of these terms become equivalent if specific models are used to describe the interface, but have different meanings if other models are used.
Surface potential (or, equivalently, interfacial potential or double-layer potential) typically implies the difference between the potential in a bulk, electroneutral solution and the potential at the wall.
- Type
- Chapter
- Information
- Micro- and Nanoscale Fluid MechanicsTransport in Microfluidic Devices, pp. 225 - 249Publisher: Cambridge University PressPrint publication year: 2010
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