Abstract
The intermediate state between microdroplets and microfluidics in two immiscible fluids is described. It was found that Y-shaped two-phase flow is formed with a stable liquid/liquid interface at a cross junction in a hydrophilic microchannel. A velocity vector map, obtained by microparticle image velocimetry, reveals the Y-shaped flow consists of aqueous phase flow along the edge of the channel and an acrylate monomer phase flow penetrating the center of the channel. The transition from the Y-shaped flow of other flow patterns can be characterized by a state diagram that depends on the capillary number and the Weber number of each injecting phase.
