Medical Test Strips made from plastics provide cheap and reliable analysis of body liquids. The underlying microsystem contains structured microchannels to adjust the filling time as an important parameter for chemical reactions. Columns or pins of some µm dimensons are being placed in the channel to define the fluidic resistance, which is influenced by the distance between these structure elements as well as by their geometry. As no analytic solution exists to describe the microfluidic interaction, the authors have been following approaches based on discrete partial differential equations and behavioural descriptions to obtain a simulation model. Model-based optimization has been performed to get useful sets of parameters to be handed to the industrial partner for manufacturing and therefore verification of the calculated results.