Optimization of dispersant-free colloidal ink droplets for inkjet patterning without the coffee-ring effect using 1-octanethiol-coated copper nano-ink with a Standard Clean-1-treated substrate

Abstract

Inkjet-printed patterns and droplets were formed by the inkjet printing method on a Standard Clean-1 (SC-1)treated substrate using anti-oxidized copper nano-ink. The hydrophobicity of the substrate increased after the SC-1 treatment. Copper nanoparticles were coated with 1-octanethiol vapors via a dry coating method to produce anti-oxidized nanoparticles, which were dispersed in a solvent to form a nano-ink. Droplets of the 1octanethiol-coated copper nano-ink at 50 wt% concentration had a uniform morphology when printed on the SC-1-treated glass substrate. The minimum printed pattern line width was 55 mu m on the SC-1-treated glass and had a resistivity of 1.73 x 10(-7)Omega m. This resistivity was 4.3-times lower than that of the untreated substrate. Moreover, the pattern printed using the nano-ink made with 1-octanethiol-coated copper nanoparticles showed good adhesion and provided approximately 2.1-times lower resistivity. The dispersion of the nanoparticles within the droplet was more hydrophobic and formed uniform inkjet-printed patterns that had lower resistivity compared with those made with the uncoated nanoparticle-containing ink.