Affiliations: Department of Quantum Engineering and Systems Science,
University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. E-mail:
sugii@q.t.u-tokyo.ac.jp | Department of Applied Chemistry, University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan | Integrated Chemistry Project, Kanagawa Academy of
Science and Technology, 3-2-1, Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa
213-0012, Japan
Abstract: Miscible liquid two-layer flow in a Y-shaped microfluidic device,
which consists of microchannels with 120 μm in width and 35 μm in depth, is
investigated by particle image velocimetry (PIV) to clarify the flow
characteristics at fluid interfaces. The obtained velocities with a spatial
resolution of 5.9 × 1.5 μm^2 around the interface between water and ethanol
indicate an imbalance in shear stress at interface. The reason of the imbalance
is to be the Korteweg stress generated by interfacial tension gradient due to a
concentration gradient by diffusion in a miscible two-layer flow. The stress
may cause an interfacial instability and destroy a uniform mixing in two
flowing fluids in the case of large concentration gradient.
