An efficient method for fabrication of disk-shaped scanning electrochemical microscopy probes with small glass-sheath thicknesses

This work describes a method for fabrication of disk microelectrodes for scanning electrochemical microscopy (SECM) tips. A sharpened platinum wire is sealed into a borosilicate glass capillary and is thermally projected out of the capillary as a tip. The disk microelectrode is obtained by mechanical polishing of the protruding glass-shrouded wire apex. What make this method distinctive are the following details: (1) The Pt-containing capillary is embedded into a polymer support to carry out a secure polishing of the tip apex; once the disk is exposed, the polymer is dissolved. (2) Disk exposure is revealed by an electrical detection method. (3) As no manual sharpening of the glass tip is required, very small glass-sheath thicknesses can be obtained (Rg = sheath radius/microelectrode radius < 3). The fabrication of tips with radii larger than 0.3 μm is relatively straightforward (success rate near 90%) with this method. SECM approach curves (positive and negative feedback), SEM and optical microscopy were used to characterize the described tips.