Abstract
We investigated shapes of the liquid-liquid interface in micro counter-current flows formed in microchannels. The pressure balance at the liquid-liquid interface was evaluated from the shapes of the liquid-liquid interface. Assuming steady laminar flow, the shape should be an arc. However, the shapes consisting of three arcs were observed. Around the center of the microchannel, Laplace pressure (171-450 Pa) was induced toward the aqueous phase. Contrastively, around the both wall sides, Laplace pressure (81-166 Pa) was induced toward the organic phase. This result suggested the mechanism of the loop-like flows reported previously. Furthremore, the opposite flow direction in each phase just around the liquid-liquid interface, namely a possibility of slip, was suggested.