title: Anomalous effect of flow rate on the electrochemical behavior at a liquid|liquid interface under microfluidic conditions.
abstract: We have investigated the oxidation of ferrocene at a flowing organic solvent|aqueous electrolyte|solid electrode junction in a microfluidic setup using cyclic voltammetry and fluorescent laser scanning confocal microscopy. At low flow rates the oxidation current decreases with increasing flow, contrary to the Levich equation, but at higher flow rates the current increases linearly with the cube root of the flow rate. This behavior is explained using a simple model postulating a smallest effective width of the three-phase junction, which after fitting to the data comes to be ca. 20 μm. The fluorescence microscopy reveals mixing of the two phases close to the PDMS cover, but the liquid|liquid junction is stable close to the glass support. This study shows the importance of the solid|liquid|liquid junctions for the behavior of multiphase systems under microfluidic conditions.
authors: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors: Dawid
authors: D
authors: Kaluza
authors: Wojciech
authors: W
authors: Adamiak
authors: Tomasz
authors: T
authors: Kalwarczyk
authors: Krzysztof
authors: K
authors: Sozanski
authors: Marcin
authors: M
authors: Opallo
authors: Martin
authors: M
authors: Jönsson-Niedziolka