Patent ID: 7686907

Claim:
A method for forming capillaries in a substrate for a microfluidic device comprising: providing a substrate of a polymeric material; forming microchannels in a surface of the substrate; reversibly sealing a cover layer on the substrate surface over the microchannels enclosing the microchannels by the cover layer and the substrate; filling the enclosed microchannels with a liquid sacrificial material which becomes solid after the filling; removing the reversibly sealed cover layer from the substrate and microchannels filled with the solid sacrificial material; affixing by solvent bonding a top cover over the filled microchannel, the substrate and the top cover each of a polymeric material having properties that allow solvent bonding by bonding solvent of the substrate and the top piece; removing the sacrificial material from the microchannels to form microcapillaries free of the sacrificial material, the sacrificial material essentially non-reactive and non-soluble with the material of the substrate to the extent it does not bond with the material of the substrate, and essentially non-reactive and non-soluble with the bonding solvent for the solvent bonding, to not materially degrade the material of or bonding of the substrate and top cover, or materially degrade the integrity of the microchannels.