Fluid modelling in micro flow channels

Over the last few years there has been an increased level of interest in the development of miniaturised systems which require liquids to flow through narrow channels, often only a few microns across. Whilst much has been written on the design and fabrication of pumps, valves, flow channels and on their integration into useful systems, relatively little work has been done on modelling fluid flow behaviour on this scale. As micro-fluidic systems become more complex, the ability to model such flows will be seen as increasingly valuable. This paper begins by reviewing the limited amount of previous fluid modelling work which has been done on the micro-scale. The approach to Computational Fluid Dynamics modelling adopted by the authors and their use of the CFDS-FLOW3D package for this work are then described. Important assumptions and boundary conditions adopted in the analysis are outlined and a comparison given between code predictions and experimental results for fluid flows through a number of different channels of the order of tens of microns in width, showing good agreement. A more complex example in the use of CFDS-FLOW3D as a design tool for a micro-fluidic manifold structure is then given which, when compared with experimental observations, again shows that the methods employed give a valuable insight into flow behaviours on this scale. Finally, areas where future work is needed to improve microfluidic modelling are summarised.