AFM The measurements and writing were performed using a Bruker Dimension Icon AFM, controlled through the Nanoscope software. The nanoelectrode AFM probes are obtained from Bruker (peakforce SECM) and are electrically insulated except for the platinum coated apex, which has a nominal radius of 50 nm . The AFM spring constant is obtained for each cantilever i) directly in the electrolyte, by doing a thermal tune at a distance of ˜1 mm from the substrate after obtaining the deflection sensitivity on the gold substrate inside the electrolyte, or ii) before filling the cell using the thermal tune method in air at a distance of ˜1 mm from the substrate, after obtaining the deflection sensitivity on the gold substrate. The deflection sensitivity of the cantilever is then re-calibrated on the gold substrate, inside the electrolyte. The measured f 0 , Q, and used k are reported in Supplementary file SI-7 as proposed in reference 55 . Ex-situ topography and data in figures 1b, 1c, and 2 are obtained in air using scanasyst-air tips (Bruker, nominal tip radius 2 nm). In-situ images and data in figures 1d and 3 are collected using the SECM tip, directly after deposition.