Neat! I've occasionally looked into getting into DIY microfluidics, and one of the lowish-tech ideas I've seen is etching/engraving CD cases or other polystyrene sheets and baking them: this makes them shrink quite predictably, allowing for some really tiny channels. In arts & crafts they call them "Shrinky Dinks". PDMS is another interesting material, and could perhaps be somehow combined with 3D printing channels with alcohol-soluble polymers to print + dissolve the channels...