Integrated multilayer flow system on a microchip

We utilized microchip technology and found that the multilayer flow of liqu ids can be formed in microchannels. Liquid/liquid interfaces were formed pa rallel to the side wall of the microchannels, because the surface tension a nd friction force are stronger than the force of gravity. A water/ethylacet ate/water interface was formed in a 70-mum-wide and 30-mum-deep channel. Th e interface was observed to be quite stable and to be maintained for a dist ance of more than 18 cm. As an example of a multilayer flow application, we demonstrated the liquid/liquid extraction of Co-dimethylaminophenol comple x in a microchannel. The solvent-extraction process of the complex into m-x ylene in the multilayer flow was found to reach equilibrium in 4 s, while i t took 60 s in a simple two-phase extraction.