Effect of Korteweg stress in miscible liquid two-layer flow in a microfluidic device

摘要

Miscible liquid two-layer flow in a Y-shaped microfluidic device, which consists of microchannels with 120 mu m in width and 35 mu m 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 x 1.5 mu m(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.