Mixing process of ternary solvents prepared through microchannels in a microchip under laminar flow conditions

The mixing process of ternary solvents (water-hydrophilic/hydrophobic organic mixture) prepared in microchannels in a microchip was examined by fluorescence observation of the dyes dissolved in the solvents under laminar flow conditions. A microchip incorporating microchannels was used. In it, three narrow channels were combined to form one wide channel. Water-acetonitrile (hydrophilic) mixture containing relatively hydrophilic Eosin Y (green) was fed into the narrow center channel and an acetonitrile-ethyl acetate (hydrophobic) mixture containing hydrophobic perylene (blue) was fed into the two narrow side channels in the microchip. The mixtures in the narrow channels combined in the wide channel to prepare the ternary solvents of water-acetonitrile-ethyl acetate, causing the tube radial distribution of the solvents. We observed the mixing process of the ternary solvents in the wide channel through fluorescence of the green and blue dyes, including an aqueous-organic interface. For example, the green dye that was fed into the center channel was distributed near the inner side walls and the blue dye that was fed into the two side channels was distributed around the center area in the wide channel. Such specific mixing behavior was not observed for two-component solvents in the wide channel, such as water-acetonitrile mixture and water-ethyl acetate mixture.