Integration and characterization of solid wall electrodes in microfluidic devices fabricated in a single photolithography step

Abstract: We describe the fabrication and characterization of solid 3-dimensional electrodes in direct contact with microfluidic channels, implemented using a single photolithography step, allowing operation in high-dielectric constant media. Incorporation and self-alignment of electrodes is achieved by combining microsolidic approaches with exploitation of the surface tension of low melting point alloys. Thus the metal forms the walls flanking the channel. We show that this approach yields electrodes with a well-defined, reproducible morphology and stable electronic properties when in contact with biochemical buffers. By combining calibration of the electric field with free-flow electrophoresis we quantify the net solvated charges of small molecules.