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 weakened, promoting uniform deposition of the droplets.