Spark-Engineered Microelectrode Arrays from Disposable Screen-Printed Macroelectrodes

A computer numerical control (CNC)-guided spark-assisted localized microelectrode patterning is used for the first time for the programmable fabrication of electrodes exhibiting microelectrode behavior with high spatial precision. A graphite wire serves as a spark probe to locally modify a disposable screen-printed carbon electrode (SPCE) overcoated with an insulating polydopamine (PDA) layer formed via electropolymerization. Localized spark discharge can be precisely positioned with three-dimensional (X, Y, and Z axis) CNC control and executed at a rate of ∼1 s per point, giving reproducible patterning of microscale features. While the PDA film effectively suppresses electron transfer, the spark treatment restores electrochemical activity only at predefined microscale positions. The sparked electrodes exhibit increased redox peak currents in cyclic voltammetry and reduced charge-transfer resistance in electrochemical impedance spectroscopy. Chronoamperometric measurements confirm a transition from Cottrellian behavior (unmodified SPCE) to a stable steady-state current (sparked microelectrode), confirming radial diffusion at the exposed micro-openings to the underlying electrode. Combined with precise spatial control, the fabrication of microelectrode arrays with tunable site density is demonstrated, resulting in amplified Faradaic responses and enhanced analytical sensitivity. This approach offers strong potential for advanced electrochemical sensing applications.