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 cen- ter region, which could directly cause a capillary inward flow from the edge to the center. As a result, the outward capillary flow from the cen- ter region to the edge region of the droplets would be effectively weak- ened, promoting uniform deposition of the droplets.
compatibility