Microfluidic Particularities

When fluids are transported in miniaturized channels and structures they behave different than in normal dimensions like water tubes or hoses. This has mainly something to do with the fact that the drag forces become more and more irrelevant in comparison to the surface tensions of the liquids. As a result the mixing of liquids performs well in flow direction while the lateral mixing is dominated by diffusion, caused by concentration differences. This is a rather slow process in the order of a couple of micrometers per second and hence this effect can be used for the separation of liquids or particles in miniaturized structures.

Mixing in flow direction

Diffusion limited lateral mixing

The here presented case shows a microfluidic structure fabricated with help of laser ablation by an excimer laser. The structure splits up two inlet channels into several smaller channels in widths of 50µm. The three dimensional flow patterns are shown in a computational fluid dynamic (CFD) simulation and the flow pattern is illustrated with help of a fluorescent dye and a microscope.

Cell separation structure

This flow structure enables the user to separate and to align e.g. different cell types along to each other or to study the lateral diffusion to the sides. It can be used for the concentration driven extraction of dissolved compounds or for the controlled reaction of dissolved compounds in the liquid.