AC Electrokinetically Enhanced Surface Reactions
Model ID: 507
This model studies the use of AC electrokinetic forces to enhance the rate of transport of electrolytic reactants to a reaction surface on the wall of a microchannel.
If transport was to be governed by flow alone, then the flow velocity perpendicular to the surface would be so small that the analyte would be transported mainly by diffusion. The reaction rate at the surface is large enough that the reaction is said to be transport limited. In order to increase this reaction rate, the system must increase the transport of molecules to the reaction surface.
AC electrokinetic forces can generate swirling patterns in the fluid and thereby enhance the transport of the analyte to the reaction surface. Biological immunoassays, which detect an analyte through their binding response to an antibody ligand, can use these flow patterns to great advantage.
The AC electrokinetic forces arise when the fluid absorbs energy from an applied nonuniform AC electric field by means of Joule heating. The temperature increase changes the fluid’s conductivity and permittivity. Consequently the fluid experiences an effective or time-averaged volume force, which depends on the conductivity and permittivity gradients and on the field intensity.
By changing the shape of the electric field it is possible to alter the fluid-flow pattern so that required amounts of analyte molecules reach the reaction surface. This model was originally developed by Gaurav Soni, Marin Sigurdson, and Carl Meinhart of the Department of Mechanical and Environmental Engineering, University of California, Santa Barbara.
|Flow streamlines and concentration profile in a fluid flowing through a microchannel after 1s. The fluid contains electrolyte that is influenced by an AC field.|