A facile method for fabricating carbon fiber-based gold ultramicroelectrodes with different shapes using flame etching and electrochemical deposition

In this study, we developed a simple, cost-efficient, and time-saving approach for producing gold (Au) ultra-microelectrodes (UMEs) with different shapes and sizes ranging from one micron to several microns in diameter. A microneedle, in combination with a flame-etched carbon fiber (CF), acts as a template for electrochemical fabrication of Au electrodes. To fabricate spherical and disk-shaped electrodes, a small gap at the tip of the microneedle was formed using CFs whose tips were flame-etched to a size larger than that of the microneedle tip opening. The gap was then electrochemically filled with Au using chronoamperometry. However, to fabricate rod-shaped electrodes, the size of the CF tip was flame-etched to a size smaller than the microneedle tip opening, which resulted in CF to protrude from the microneedle tip opening. Then, the CF surface was electrochemically modified with Au. The whole fabrication process for each electrode took less than 15 min. The fabrication method is quite useful for researchers with limited resources, and the fabricated UMEs have great potential to be used in various applications ranging from constructing nano-/micro-biosensors to single-cell analysis.