Morphology and deposit of picoliter droplet tracks generated by inkjet printing

Abstract

In this work, the morphological patterns of liquid tracks of droplets (~10 pl) wetting on a homogeneous surface were investigated analytically and experimentally. Using drop- on-demand inkjet printing, micro liquid tracks were formed from silver (Ag) nanoparticle suspension (~40 nm) ink under ambient environments. These liquid tracks in circular and polygonal shapes were intended to have different line widths (W) from 25 µm to 250 µm and droplet spacing (s) from 10 to 20 µm. The re-scaled ratio of volume (VR = V/W3) and aspect ratio of length (AR = Li/Lo) were calculated to construct one morphological diagram. The resulting morphological diagram generated from the inkjet printing formations clearly showed three distinct morphologies: the cap (C), bulge (B), and ring (R) phases. In other words, the morphological phase of the inkjet printing formations could be changed simply by varying the values of W and s. Also the looped liquid tracks clearly indicated that capillary (convective) flows were induced due to interfacial energy during the formation of nano-Ag deposits. Finally, we demonstrated the anchoring effect on suppression of bulges by the addition of one anchor in front of all segments. The findings in liquid track morphology here may be further developed for a variety of inkjet printing applications such as electric conductors and electrodes in micro-electro-mechanical systems (MEMS) in the future.