A conductive ink for a rollerball pen comprises an aqueous solvent and conductive particles comprising one or more metals dispersed therein at a concentration of at least about 30 wt. %. The conductive particles include conductive flakes and conductive nanoparticles. A dispersant coats the conductive particles at a loading level of at least about 0.1 mg/m2 to about 0.8 mg/m2. A conductive trace deposited on a substrate from a rollerball pen comprises a percolative network of conductive particles comprising one or more metals. The conductive particles include conductive flakes and conductive nanoparticles. The conductive trace has a conductivity of at least about 1% of a bulk metal conductivity and a reflectance of greater than 40%.