Rapid prototyping of microfluidic chips for use in droplet formation and in-vitro compartmentalisation

The combined use of film transparency masks and dry film resist has allowed a rapid prototyping of designs and structures in chips for droplet generation. Patterning of the film resist has produced channels with smooth vertical sidewalls. The minimum feature dimension, δ, was reduced by increasing the resolution and spacing of the pattern geometries in the film mask. For a single layer of resist (~35 μm thick), a minimum feature width of ~60 μm was obtained using 2040 dpi transparency masks, 40 µm for 5800 dpi transparency masks and 25 μm using a Cr mask of equal size/ spacing of features. A doubling of the spacing between features in a 2400 dpi masks resulted in an attainable feature size of ~40 μm. The minimum feature dimension increased exponentially with thickness of 5038 resist. Microfluidic chips which were fabricated in PMMA by this method have demonstrated controlled characteristics in the generation of oil droplets in water.