Gyros AB, situated in Uppsala, builds microlaboratories (at micrometer scale). In doing so they experience many of the phenomena found in capillary theory such as stick-slip behaviour. In addition they find that the measured flow rates in their capillaries do not compare to the Washburn equation, frequently used to describe this. In this thesis the capillary flow problem is approached via a periodic surface roughness hypothesis, dynamic contact angle and perturbation analysis. A surface coefficient, for each material, describing the character of the interplay between the liquid and solid is produced. This coefficient could work as a complement to the contact angle.