In this work, we present the design, fabrication and characterization of a novel micro-extractor which performs on-line extraction-detection of target molecules flowing in a carrier liquid. The system comprises a primary microchannel containing a flowing aqueous carrier liquid and a secondary organic storage fluid circulating in an adjacent channel. The interfaces between the two immiscible fluids are stabilized by vertical micro-pillars. The system encompasses three functions: (i) extraction of the target molecules from the carrier fluid through the pillar-stabilized interfaces, (ii) concentration of the targets in the secondary organic solvent due to its very low—or zero—velocity, (iii) on-line detection via optical spectrometry.

We successively present the analysis of the physics of the system which has led us to a specific design, then the microfabrication of the chip, and finally we demonstrate the extraction, concentration and detection of lead ions (Pb2+) from a water flow.

Key words: liquid-liquid extraction, microflow, interface stability, Monte-Carlo modeling, lead detection