Characterization and analysis of micro channels and sub-micron surface roughness of injection moulded microfluidic systems using optical metrology

Precision injection moulding of miniaturized products with micro features such as channels for microfluidic applications poses the greatest challenges in terms of tooling technology and process optimization. The injection moulding process window of polypropylene was validated using a metrological approach for the production of a microfluidic substrate. Dimensional accuracy of micro channels 48 µm wide and 110 µm deep, as well as quality surface topography replication (surface roughness from 30 nm to 360 nm) were investigated using non-contact measuring instruments such as an optical coordinate measuring machine and a white light interferometer respectively. The effect of the dimensional scale range on the micro/nano features replication was evaluated and it was found to be the dominant parameter if compared with the effect of the other process-related parameters investigated (melt and mould temperature, injection speed).