Fabrication of microfluidic channels with various cross-sectional shapes using anisotropic etching of Si and self-alignment

A novel and simple fabrication method was proposed to produce microfluidic channels with various cross-sectional shapes, such as parallelogram, rhombus, pentagon and hexagon. The present study has the advantages of not only fabricating the microfluidic channel shapes that have not been reported before, but also the fabrication process is simple, flexible and robust. Microfluidic channels were fabricated using anisotropic wet etching of Si wafer and self-alignment between Si structure and PDMS mold. In this regard, (100) single crystal Si wafer was used to fabricate the Si microchannel and the master for PDMS mold using photolithography and anisotropic KOH etching. The Si structure for the microchannel and master were formed from the same Si wafer by KOH etching, and the PDMS mold was made from the Si master. Finally, the microchannels with various cross-sectional shapes could be easily formed through self-alignment of the Si microchannel and PDMS mold. They were permanently bonded using O₂ plasma treatment. It is expected that the fabricated microchannel with various cross-sectional shapes can be used in wide fields such as heat transfer, microscale transport of particle and fluid, and particle separation based on inertial focusing.