Limits to feature size and resolution in ink jet printing

Ink jet printing is an attractive route for the manufacture of small ceramic parts and MEMS components. The attainable feature size of a component fabricated in this fashion is determined by both the generated droplet size and how the droplet interacts with the substrate. Here we present a study of the impingement and coalescence of drops to form beads, and linear deposits after a subsequent phase change. Experimentally, it is found that there is a minimum width of linear deposit produced in this way that is dependent upon droplet size and the surface energy interaction between droplet and substrate. A simple geometric model is presented that can accurately predict both the onset of limitation with changing droplet separation and the width of the deposit at a given droplet separation. A bulging instability is also found at small droplet separation that is explained in terms of competing pressure-driven axial flow and spreading flow driven by capillarity. The bulging of deposited nanoparticulate ink was found to agree qualitatively with previous observations, with the bulging being reduced with increasing print-head traverse velocity. The bulging of deposited solution-based ink did not agree with previous observations; this was explained in terms of evaporation of solvent as the instability was formed.