Ag wire growth was performed in diH2O and applying varying electrical inputs with a high voltage stimulator (HVS -EC100SA, NF Instruments). As shown in Figure C+D, wire growth was imaged in real-time using a Nikon ECLIPSE TE300 fluorescent microscope equipped with a QImaging optiMOS Scientific CMOS camera. To improve electrical contact between the power source (HVS) and printed electrodes, silver paint (186-3600, RS components) was applied to the 3D printed samples and disposable 20 gauge steel needles (304827, BD) were used to attach samples to HVS. Au wires were grown using the same arrangement. The addition of gold chloride was required to facilitate growth; 10 mM AuCl in dH2O was used.