Casting of PDMS microfluidics into 3D printed moulds and their application in capillary electrophoresis

Stereolithography (SLA) 3D printing is used for the fabrication of PDMS microfluidics. Moulds with a system of stretched filaments are made using SLA, which are filled with a polymerisation mixture and the PDMS is left to thermally cure. Subsequently, the mould is removed, the fibres are pulled out and the inner channels of microfluidics are surface treated by ozonisation. The proposed process can be used to fabricate two-, three-, four-, and multi-way couplings, mixers, or flow gating interfaces (FGI), which find applications in CE and in the laboratory treatment of microliter sample volumes. The PDMS microfluidics ensures easy connection of capillaries and tubing in a wide range of sizes and the internal diameters of the channels can be continuously varied from a few millimetres up to a minimum size of 100 μm. The microfluidics connection to the capillaries is watertight and tested for pressures up to 56.7 kPa. In addition, the integrated PDMS microfluidics is used as a cross-FGI to construct an on-line connection of the flow-through sampling technique with the CE instrument, which is fully automated, software controlled and fills a gap in the market with CE instruments. The coupling is tested for sequential analysis of a mixture of Gly and Ala and also in combination with microdialysis of human serum. The proposed fabrication process is characterized by rapid prototyping and is designed for mass production.