Mixing in microchannels

Mixing is a key issue in microfluidic. For typical flow velocities of 5 cm/s, the Reynolds numbers related to the channel are on the order or smaller than 0.1 which means that inertia is negligible and flows are laminar (See above coflow example). The Reynolds number is a dimensionless number which relates inertial forces to viscous forces. More precisely Re=Rho*velocity*length/viscosity.
One of the easiest ways for achieving mixing is by making a drop go through a corner. Corners add an additional shear to the uniform flow and enhance mixing. Such a mixing is illustrated in the following movie. The flow tracers are 1 micron size polystyrene beads. A completely segregated drop gets mixed as it flows through a 90 degrees corner. Further in the channel, colloids segregate again.

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Last update 07/05/03

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