Fundamentals of mass transport in the microscale - Micromixers Fundamentals Design and Fabrication - page 55

FIGURE 2.28
The Wi-Re diagram (based on a planar 4:1 contraction flow); the gray area represents the operation region of
micromixers based on viscoelastic instabilities.
polymer solutions. Boger fluids are dilute solutions of a polymer and a solvent. The slopes of the
curves represent the elasticity numbers [36] .
2.6 ELECTROKINETIC EFFECTS
2.6.1 Electroosmosis
Electrokinetic effects are based on an electric double layer at the interface between a solid and a liquid
or between two liquids. This double layer is also called the Debye layer. This section focuses on the
interface between a solid and a liquid. In general, there are four basic electrokinetic effects:
Electroosmosis is the flow of a liquid in an electric field relative to a stationary charged surface.
Electrophoresis is the motion of a charged particle in an electric field relative to the surrounding
liquid.
Streaming potential is the opposite effect of electroosmosis. An electric potential is created when
a liquid is forced to flow relative to a charged surface.
Sedimentation potential is the opposite effect of electrophoresis. An electric potential is created
when charged particles are forced to flow relative to a surrounding liquid.
2.6.1.1 The Debye layer
The Debye layer is an electric double layer, which occurs due to interaction between an electrolyte
and a charged solid surface. Ions in an electrolyte solution are attracted to the charged surface and