electrokin_lec3

electrokin_lec3 - Key Concepts for section IV...

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1: Debye layer, Zeta potential, Electrokinetics 2: Electrophoresis, Electroosmosis 3: Dielectrophoresis 4: Inter-Debye layer force, Van-Der Waals forces 5: Coupled systems, Scaling, Dimensionless Number Goals of Part IV: (1) Understand electrokinetic phenomena and apply them in (natural or artificial) biosystems (2) Understand various driving forces and be able to identify dominating forces in coupled systems Key Concepts for section IV (Electrokinetics and Forces)
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Helmholtz model (1853) Guoy-Chapman model (1910-1913) Stern model (1924) + - + + + + + + + + + + + - - - - - - - - - - - 1 κ 1 0 Φ x + - + + + + + + + + + + + - - - - - - - - - - - 1 1 x 0 Φ + + + + + + + - + + + + + + + + + + + - - - - - - - - - - - 1 + + + + + + 1 0 Φ x - - - slip boundary (zeta potential) ξ
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The oxide or glass surface become unprotonated (pK ~ 2) when they are in contact with water, forming electrical double layer. When applied an electric field, a part of the ion cloud near the surface can move along the electric field. The motion of ions at the boundary of the channel induces bulk flow by viscous drag. Electroosmosis 1 2 3 4 Figure by MIT OCW.
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Concentration(c) ( ρ ) Maxwell’s equation Fick’s law of diffusion E and B field Navier-Stokes’ equation ρ e , J e : source Osmosis (aqueous) medium, Flow velocity (v m ) Convection Electrophoresis Streaming potential Electroosmosis
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Slip boundary, zeta potential 1 ~ κ x Φ ξ - + + + + - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + Stern layer Slip (shear) boundary z v x δ (0) Φ Zeta potential EEO v
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This note was uploaded on 11/11/2011 for the course BIO 2.797j taught by Professor Matthewlang during the Fall '06 term at MIT.

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electrokin_lec3 - Key Concepts for section IV...

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