The development of slug flow channel microreactors is expected for new chemical production plants. The purpose of this study was to produce a device that could easily generate short steady slug flow. A fine stable slug flow (length ca. 1 mm) of aqueous and organic phases was successfully achieved in a microchannel for a wide range of flow rates (0-100 ml/h). This operation did not require complicated devices or a power source, and was achieved by the simple process of inserting a piece of glass bead into the microchannel. The generated slug flow was stable and ran through the microchannel without changing shape. The slug flow rapidly separated into aqueous and organic phases in a settler attached to the microreactor. The developed microreactor was applied to Cs+ extraction and resulted in rapid separation that compared favorably with conventional batch experiments. (C) 2010 Elsevier B.V. All rights reserved.