Electroosmosis involves the onset of flow due to the application of an external electric field. It can also be induced by an electric field created by, for example, ion transport in membranes. Electroosmosis can be used for mixing and separating ions contained within electrolytes and solvents. In the past decade, electroosmosis has found applications in microfluidic devices such as pumps and mixers.
Modeling electroosmosis involves coupling the physics describing mass transport, fluid flow, and electromagnetics. Electric fields cause migration of ionic species, and the mass transport is further affected by diffusion and convective flow. Ion transport can in turn drag solvent species along, which affects the system's fluid dynamics and the electric field.
Passive mixers, common in microfluidics applications, often require very long mixing channels to ensure that the molecular diffusion between the different fluids is adequate. An alternative design uses electroosmotic effects to achieve a mixing effect. Perpendicular to the main direction of the flow, such effects add to the diffusion mixing in the system.