Analytical Sciences

Specific Distribution Behavior of a Ternary Mixture of Solvents Fed into Bent and Wound Microchannels in Microchips

Kei NISHIYAMA,* Masaharu MURATA,** Masahiko HASHIMOTO,* and Kazuhiko TSUKAGOSHI*,***

*Department of Chemical Engineering and Materials Science, Faculty of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan
**Department of Advanced Medical Initiatives, Kyushu University, Fukuoka 812-8582, Japan
***Tube Radial Distribution Phenomenon Research Center, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan

The tube radial distribution of ternary solvents (water–hydrophilic/hydrophobic organic mixture) fed into bent and wound microchannels in a microchip was examined by fluorescence observations of dyes dissolved in the solvents under laminar flow conditions. Four kinds of microchips incorporating bent microchannels were used, together with a microchip with a straight channel. The microchannels had different bending times (2, 4, or 12 times), bending radii (0.8, 2.3, or 3 mm), and total channel lengths (80, 120, 200, or 500 mm). A water–acetonitrile (hydrophilic)–ethyl acetate (hydrophobic) mixture containing relatively hydrophilic Eosin Y (green) and hydrophobic perylene (blue) was delivered into the bent microchannels in the microchips. The fluorescence of the green and blue dyes enabled us to observe the specific radial distribution behavior of the ternary solvents in the bent micro channels at 0°C, including liquid–liquid interfaces. Further, the radial distribution pattern of the solvents was clearly observed in the wound microchannel (bending radius, ca. 0.1 mm; real total channel length, 500 mm; and apparent straight channel length, 40 mm) at 20°C (room temperature) as well as 0°C. It was found that the radial distribution behaviors of the solvents were successfully generated in even specific microchannels including various types of curves under the present conditions.

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