In our the formation and suppression processes of “coffee ring” effect (b). (For interpretation of the experiments, the solvent in P(St-MAA) colloidal inks is water, so natu- rally the additives with higher boiling points and lower surface tensions than water attract our attentions. If the additive could be added into the inks to become a co-solvent dependent on the compatibility of water and the additive, water would preferentially evaporate more at the edge than the additive, leading to a higher concentration of the additive at the edge region than at the center region. Hence, a surface tension gradient would be produced from the edge of the droplet to its center, particularly the surface tension of the edge region is lower than the center region, which could directly cause a capillary inward flow from the edge to the center. As a result, the outward capillary flow from the center region to the edge region of the droplets would be effectively weak-ened, promoting uniform deposition of the droplets.