Fabrication of a Three-Layer PDMS Pneumatic Microfluidic Chip for Micro Liquid Sample Operation.

The emphasis of this paper lies in the fabrication of a three-layer polydimethylsiloxane chip for micro liquid sample operation. In this paper, the microchannels with a rectangular control layer cross section are fabricated based on a dry-film negative photoresist mold, while the microchannels with a rounded liquid layer cross section are fabricated by a positive photoresist reflow mold. The relationships between temperature and the time of reflow and the arc level of the liquid layer mold are discussed. Different ratios, curing temperatures, and curing times are used to fabricate the two PDMS layers to improve their toughness and plasticity separately. The PDMS slabs with microstructure networks are treated with oxygen plasma to improve their surface properties. The improved surface properties serve to reduce the temperature and time, and improve the sealing strength, which is as effective as adding PDMS in varying ratios. The micro liquid sample operation experiments show that high levels of pinching off and mixing performances on pneumatic microfluidic chips are obtained more easily.