System for transporting liquids in channels with dimensions from less than 1 µm to several hundred µm. The behaviour of liquids in such small channels differs in many aspects from their macromolecular behaviour. Purely laminar flows are possible for example, because the channels are too small for the formation of vortices. Used in medical, biological and chemical analysis, for example, to separate substances, isolate and treat individual cells. Microfluid structures can be etched with plasma etching processes for example in silicon. ätzen. The material PDMS (polydimethylsiloxane) is particularly important for microfluid systems. Thanks to its microscopic structures, whole laboratories can be implemented on a chip, complete with microchannels, pumps, valves, and microtiters (lab-on-a-chip).