Presenter : Ahmad Hadadan Adviser : Dr.Nazari Shahrood University Of Technology 1/14

This flow is caused by the pressure gradient at up & down stream of channel. One of the basic laws of fluid mechanics for pressure driven laminar flow : no-slip boundary condition = velocity at the walls must be zero. This produces a parabolic velocity profile within the channel. 2/14 Pressure Driven Electrophoresis - Electrokinetic Pressure Driven Flows -Electroosmotic EDL Pumping

Electrokinetic phenomena are based on : - the interaction of the applied electric field + with a layer of electrical charges on a solid surface + in contact with an aqueous electrolyte solution + in microchannels. 3/14 Electrokinetically Driven Flows Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

fundamental assumption is : the linear response of the electrokinetic motion with respect to the applied electric field and the fixed static surface charges on non-conducting solid surface. 1 - Electrophoresis 2 - Electroosmosis 4/14 Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

A layer of mobile ions, known as an electrical double layer, forms in the region near the interface When an electric field is applied to the fluid (usually via electrodes placed at inlets and outlets), the net charge in the electrical double layer is induced to move by the resulting force. 5/14 EDL (Electrical Double Layer) Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

Electrophoresis is the motion of dispersed particles relative to a fluid under the influence of a uniform electric field 6/14 Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

Electroosmotic flow is : - the motion of liquid that includes ions - induced by an applied potential - across a porous material, capillary tube, membrane, microchannel, or any other fluid conduit Example ) Na Cl 7/14 Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

Generally, electrokinetically-driven flows in microchannels are laminar because of the slow velocity and small characteristic length scale and thus small Reynolds number. 8/14 No slip condition Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

The resulting flow from applying a voltage,Unlike a parabolic profile flow generated from a pressure differential, this flow’s velocity profile is approximately planar, with slight variation near the electric double layer. Velocity Profile of Electroosmotic Flow 9/14 Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping

10/14 Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping Comparison Between : Pressure Driven Flow & Electroosmotic Flow

Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping non-conducting hurdles conducting hurdles 11/14

An electrokinetic effect known as electroosmosis can be used to pump liquids at the microscale Electroosmotic Pumps (EOPs) Pressure Driven Electrophoresis - Electrokinetic -Electroosmotic EDL Pumping 12/14

[1] Yasaman Daghighia, Yandong Gao, Dongqing Li.umerical study of induced-charge electrokinetic motion of heterogeneous particle in a microchannel. Electrochimica Acta 56 (2011) 4254–4262 [2] Zhemin Wu,Dongqing Li. Micromixing using induced –charge electrokinetic flow. Electrochimica Acta 53(2008) /14

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