Preserving precision of inkjet-printed features with solvents of different volatilities

For printed micropatterns on plastic substrates, the decreasing volume because of solvent evaporation frequently leads to contact line receding and changes the original printed pattern. To prevent printing quality deterioration caused by contact line motions, an ink formulation method was developed. A nearly non-volatile solvent [polyethylene glycol (PEG)] with a low receding angle on polyethylene terephthalate (PET) sheets was added in water to hold the contact line. To understand the dewetting phenomena of inks, the geometrical evolution of circular liquid films under evaporation was recorded and analyzed. The results showed that the contact line receded as water evaporated for inks with low PEG concentrations but remained pinned at a moderate PEG concentration (~10 wt %). A simple model was proposed to explain the dewetting phenomena and can successfully predict the critical PEG concentration, beyond which the contact lines will be unconditionally pinned. The optimized water/PEG solvent can then be used to prepare dye- or particle-based inks, which preserved accurate features after solvent evaporation.