Simple Fabrication Method of Needle‐Type Carbon‐Disk Microelectrodes Using Conductive Thermoplastics

Carbon‐based microelectrodes are extensively used for sensing applications and space‐resolved electrochemistry experiments like scanning electrochemical microscopy (SECM). For the later, needle‐type disk microelectrodes, having a thin layer of insulator around the conductive disk, are of great interest due to their mass transport characteristics and small dimensions, allowing them to be brought to close proximity of the substrate. Existing fabrication methods for carbon microelectrodes use carbon fibers or the deposition of pyrolytic carbon, which can limit the possible radii of the fabricated microelectrodes and reproducibility. A simple method is presented for fabricating needle‐type carbon‐disk microelectrodes using conductive thermoplastic filaments that are usually employed for 3D printing. Using the heat of a candle to melt the thermoplastic inside micro and nanopipettes, microelectrodes with radii smaller than 30 µm are fabricated. Through experiments, the electrodic surface is revealed to be partially blocked, with a complex relation between the size and interspacing of the conductive sites. Simulations clarify the surface properties and demonstrate the suitability of these electrodes for SECM. As a proof‐of‐concept, the carbon surface is evaluated for sensing, showing that the low capacitance of the electrodes and carbon surface can be used for dopamine sensing and voltammetric pH measurements.