Multi-layer PMMA microfluidic chips with channel networks for liquid sample operation

The emphasis of this paper lies in the fabrications of an eight-layer chip for liquid mixing and a seven-layer chip for liquid sample dilution. In this paper, the microchannels, fabricated by CO2 laser, constructed three-dimensional serpentine channel networks for liquid sample operation. The eight-layer mixing chip used the “F”-shape mixing units to achieve splitting and recombination mixing. Furthermore, mixing was enhanced by chaotic flow induced by three-dimensional serpentine channel path. The seven-layer dilution chip created eight diluted fluid streams mixed in same volumetric proportions. Prior to thermal bonding, the polymethylmethacrylate (PMMA) substrates were treated by oxygen plasma to improve their surface properties. The increased surface properties served to reduce thermal bonding temperature and pressure, which minimized the deformation of microchannel. The mixing and diluting experiments showed high levels of mixing and diluting performances were obtained with the chips.