Previous studies have considered an equivalent electrical circuit between an independently biased scanning probe and a substrate to describe the perturbation of a charged tip on the substrate-liquid EDL . This simple model consists of the EDL capacitances, CEDL, at both electrodes (tip and substrate) in series with a resistor R representing the solution resistance (Figure ). As such, the total system contains many RC-subcircuits that represent the current paths from the tip to different position on the substrate. As the solution resistance increases with distance, the associated charging time (i.e. RCtime) is longer for locations on the substrate farther away from the probe, since the larger solution resistance slows EDL charging through ion migration (Figure ). By applying a short potential pulse to the tip, the substrate-liquid interface is only significantly polarized close to the probe, which may locally enable an electrochemical reaction. In fact, due to the exponential dependence of the Faradaic current on the interface potential as described by Butler-Volmer kinetics, even modest potential differences near the probe are expected to result in sharp localization profiles for the electrochemical reaction rate .