A simple method for insulating carbon-fiber microelectrodes using anodic electrophoretic deposition of paint.

We describe a simple method for the insulation of carbon-fiber microelectrodes (CFMEs). Using the technique of anodic electrophoretic deposition of paint (EDP), we deposited thin and uniform films of electrodeposition paint onto 10-μm-diameter carbon fibers. The polymer films were then heat cured, leading to an electrically insulating coat. The insulated carbon fibers were transected perpendicular to their axes to expose a 10-μm carbon disk and characterized using conventional electrochemical methods and scanning electron microscopy. As expected, cyclic voltammograms measured with electropainted CFMEs in solutions containing ferricyanide displayed a sigmoidal response without hysteresis. The insulating films had a low dielectric constant, resulting in low capacitance. In addition, the film thickness could be controlled simply by varying such deposition parameters as the applied voltage and the duration of treatment. Electrical noise of the transected fibers was determined principally by the cut surface of the fiber, not by the exposed insulated surfaces. Compared to electropolymerization of phenol compounds, another electrochemical method for insulating CFMEs, insulation by anodic EDP has the very significant advantages of greater simplicity, much shorter processing time, and much lower toxicity of the reagents involved, important considerations for those who work with the procedure on a daily basis. Furthermore, electrodeposition paints are commercially available and have long shelf lives.