(565e) Microfluidic Free Flow Electrophoresis Using Conductive PDMS Polymer Membranes

Free flow electrophoresis (FFE) utilizes a combination of fluid flow and electric field-induced electrophoresis to deflect analyte in directions perpendicular to the flow stream for sample separation or concentration. Since the first miniaturized FFE device was reported in the early 1990s, several microfluidic-based FFE systems have been developed for biomedical, analytical and diagnostic applications. One major issue with miniaturized FFE systems is that the electric field-generating electrodes must be isolated from the main flow stream to prevent on-chip bubble generation and electrode damage from water electrolysis. Many strategies are used to isolate the electrodes from the main flow channel, including conductive gels and side channel electrode arrays. These techniques, however, suffer from poor mechanical strength and screen a significant portion of the electric field from entering the flow channel. In this talk, we demonstrate a new type of conductive PDMS microfluidic FFE technique. Our approach utilizes integrated metal electrodes, directly fabricated against conductive PDMS membranes and integrated into the microchannel sidewalls. The conductive membranes are fabricated using carbon black (CB) doped PDMS, and separate the electrophoresis channel from the gallium metal electrodes. These novel CB membranes are capable of preventing electrode contamination from electrolysis, while still providing sufficient electric field for FFE. The membranes also possess high mechanical strength and do not suffer from membrane break down caused by kilovolt/meter electric field strengths. We demonstrate the capabilities of these electrode-membrane systems for on chip microfluidic sample separation and enrichment using nanoparticle based FFE-isotachophoresis and FFE-zone electrophoresis.