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
12 - Microchip Chemical Separations
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
Chemical separations are a critical component of analytical and synthetic chemistry. In microchip applications, a sample comprising multiple chemical species is separated spatially into individual components by inducing the components of a sample to move at differing velocities in a microchannel. This is shown schematically in Fig. 12.1 and a sample experimental result is shown in Fig. 12.2. Separations are achieved by inserting a sample fluid bolus into a microchannel, inducing motion of these species with velocities that differ from species to species, and detecting the concentration of species as a function of time as these species elute (i.e., arrive) at the location of the detector (Fig. 12.1). Many microfluidic separations are modified from capillary or column-based techniques, and draw advantages from more optimal fluid transport, thermal dissipation, or system integration. One example of a chemical separation is an electrophoresis separation, which can be used to separate species that have different electrophoretic mobilities. In this case, species motion is induced by an electric field aligned along the axis of the microchannel, which induces electroosmosis and electrophoresis. Because this technique requires only that electric fields be applied, it integrates easily into microsystem designs, and a large fraction of the microchip analyses developed since 1995 use microchip electrophoresis (see one example in Fig. 12.3). This is true for both protein analysis (Section 12.5) and DNA analysis and sequencing (Chapter 14).
- Type
- Chapter
- Information
- Micro- and Nanoscale Fluid MechanicsTransport in Microfluidic Devices, pp. 265 - 280Publisher: Cambridge University PressPrint publication year: 2010