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Copyright Brian J. Kirby. With questions, contact Prof. Kirby here. This material may not be distributed without the author's consent. When linking to these pages, please use the URL http://www.kirbyresearch.com/textbook.

This web posting is a draft, abridged version of the Cambridge University Press text. Follow the links to buy at Cambridge or Amazon or Powell's or Barnes and Noble. Contact Prof. Kirby here. Click here for the most recent version of the errata for the print version.

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Jump To: [Kinematics] [Couette/Poiseuille Flow] [Fluid Circuits] [Mixing] [Electrodynamics] [Electroosmosis] [Potential Flow] [Stokes Flow] [Debye Layer] [Zeta Potential] [Species Transport] [Separations] [Particle Electrophoresis] [DNA] [Nanofluidics] [Induced-Charge Effects] [DEP] [Solution Chemistry]

12.3 Microchip electrophoresis: motivation and experimental issues [microchip separations top]

Microchips are used for electrophoretic separations for a number of reasons, some of which are:

  1. Small amounts of fluid can be analyzed in small devices.
  2. Large electric fields can be used, both because the lengths are small and because microchips dissipateJoule heating better than capillaries.
  3. Techniques for injecting a sample bolus to create the initial condition (so far taken for granted) are more sophisticated in microfluidic devices.
  4. long pathlength separation channels can be compactly folded in microfluidic devices (if you know some tricks).

Some of these are discussed in the following sections.

12.3.1 Thermal dissipation

Thermal dissipation in microchips is typically good, simply because the microchip has a larger thermal mass than a capillary. Glass and silicon are relatively good conductors; polymers tend to be poor.

12.3.2 Compact, folded, long-pathlength channels

The separation resolution of an analyte band increases with 12; thus, the best separations occur over a long distance. One advantage of microchannels is the ease with which long microchannels can be designed with small footprint. For example, a channel that is 20 μm-wide and over 1 m long can be fabricated in a 1 cm×1cm footprint. The fabrication of such a channel takes no more time or money than to create a shorter channel.

This is a compelling advantage, but one that only can succeed through design oflow-dispersion turns with special geometries (see Section 12.4.2).

Related work on chemical separations from our research group can be found here.

[Return to Table of Contents]



Jump To: [Kinematics] [Couette/Poiseuille Flow] [Fluid Circuits] [Mixing] [Electrodynamics] [Electroosmosis] [Potential Flow] [Stokes Flow] [Debye Layer] [Zeta Potential] [Species Transport] [Separations] [Particle Electrophoresis] [DNA] [Nanofluidics] [Induced-Charge Effects] [DEP] [Solution Chemistry]

Copyright Brian J. Kirby. Please contact Prof. Kirby here with questions or corrections. This material may not be distributed without the author's consent. When linking to these pages, please use the URL http://www.kirbyresearch.com/textbook.

This web posting is a draft, abridged version of the Cambridge University Press text. Follow the links to buy at Cambridge or Amazon or Powell's or Barnes and Noble. Contact Prof. Kirby here. Click here for the most recent version of the errata for the print version.


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