Analytical Sciences

Stable Formation of Aqueous/Organic Parallel Two-phase Flow in Nanochannels with Partial Surface Modification

Hiroki SANO,*1 Yutaka KAZOE,*1,*2 and Takehiko KITAMORI*1,*3,*4

*1 Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
*2 Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama, Kanagawa 223-8522, Japan
*3 Collaborative Research Organization for Micro and Nano Multifunctional Devices, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
*4 Institute of NanoEngineering and MicroSystems, Department of Power Mechanical Engineering, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, R. O. C.

In microfluidics, various chemical processes can be integrated utilizing parallel multiphase flows. Our group has extended this research to nanofluidics, and recently performed the extraction of lipids using parallel two-phase flow in nanochannels. Although this was achieved in surface-modified nanochannels, a stable condition of parallel two-phase flow remains unknown due to difficulties in device fabrication, for a suitable method of bonding surface-modified substrates is lacking. Therefore, research on parallel two-phase flow in nanochannels has been limited. Herein, a new bonding method which improves the wash process for the substrates and increases the bonding rate to ∼100% is described. The conditions to achieve parallel organic/aqueous two-phase flow were then studied. It was revealed that in nanochannels, higher capillary numbers for the organic phase flow were required compared to that in microchannels. The newly developed fabrication process and flow regimes will contribute to realize integrated nanofluidic devices capable of analyzing single molecules/cells.

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