Addressable microelectrode arrays: Characterization by imaging with scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) was used to characterize addressable microelectrode arrays patterned with 25 regularly spaced (100 mum center to center) 10 mum diameter platinum microdisks. Both the feedback mode and the substrate generation/tip collection (SG/TC) mode were used where only the ultramicroelectrode (UME) tip current was recorded. A range of UME tip diameters (1, 2, 5, 10, and 25 mum) was used to image the surface of the arrays. The microdisks on the array were connected in parallel, kept electrically independent, or a predetermined combination of the two. The microelectrode array was also biased or unbiased. Combined, the SECM feedback and SG/TC modes gave valuable information regarding the conductivity, connectivity, and reactivity of the microdisks on the array. SECM was also found to be a unique method for screening the integrity of the insulator coating of the underlying tracks serving as connections to each microdisk in the array. Steady-state cyclic voltammetry and scanning electron microscopy were used to provide additional information regarding the nature of the microdisk surfaces on the array and the stability of the currents generated.