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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]

6.6 Summary [electroosmosis top]

In this chapter, we describe electroosmotic flow in the thin double layer limit, in which we are largely unconcerned with the details of the flow inside the electrical double layer, and care only about the net effect of the electrical double layer on the bulk flow. This is often applicable for microscale devices, since the electrical double layer is typically only nanometers in thickness. If the double layer is thin, the system can be solved using a matched asymptotic approach, in which the extrinsic electric field is assumed uniform inside the electrical double layer, and Coulomb forces are ignored outside the double layer. In this case, the electrical double layer can be replaced with an effective slip condition defined by the electroosmotic mobility:

microfluidics textbook nanofluidics textbook Brian Kirby Cornell

which, for uniform fluid properties, is given by

microfluidics textbook nanofluidics textbook Brian Kirby Cornell

For flows with uniform interfacial properties, uniform fluid properties, and no applied pressure gradients, the fluid flow in a purely electroosmotic flow is a potential flow in which the fluid velocity is proportional to the local electric field:
microfluidics textbook nanofluidics textbook Brian Kirby Cornell
(6.48)

These relations link the interfacial potential to the fluid velocity in the system; fluid flow in microdevices can be calculated with relatively straightforward simulations using effective slip boundary conditions.

[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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