Solvent and substrate effects on inkjet-printed dots and lines of silver nanoparticle colloids

The shape changes of inkjet-printed dots and lines were investigated by varying the primary solvent of nanosilver colloids, surface wettability and substrate temperature. The morphological changes in dots and lines in array patterns due to the interaction between neighboring dots or lines during evaporation was also examined for two different nanosilver colloids. In order to examine the effect of solvent evaporation rate, two different solvents with different boiling points (BP) were employed for nanosilver inks. With a fluorocarbon film coating and subsequent ultraviolet ozone (UV/O-3) treatment, various surface wettability conditions were obtained on silicon (Si) wafers. Substrate temperature was varied from room temperature to 80 degrees C, and droplets from a 50 mu m diameter nozzle were printed onto the substrate after optimizing the ejection of individual droplets. The results indicate that the shapes and sizes of dots and lines are sensitive to changes in both surface energy and substrate temperature, and the ink with a higher BP solvent produces larger dots under the same surface condition due to its slower evaporation. Dots and lines with better quality are achieved using the ink with a lower BP solvent. The morphological changes in dot and line arrays are dependent on the evaporation rate of the primary solvent as well as the distance between neighboring features. As a result, selecting a proper solvent for nanosilver ink is very crucial for controlling the shape and morphology of inkjet-printed patterns.