A Dimatix DMP-2831 ink-jet printer (Fujifilm)
was used to print 16 wt % CuO ink (Novacentrix, ICI-002HV) with an
average particle size of 126 nm onto silica-coated PET substrates
(Novacentrix, Novele IJ-220, thickness ≈ 150 μm), on which the silica
coating provides a porous morphology for improved droplet
absorption and wetting.22 Although the exact chemical ink formulation
is proprietary, Novacentrix provided that the CuO nanoparticles were
dispersed in a solution consisting of water and ethylene glycol. The
viscosity of the ink was around 9−12 cPs, which fits the recommended
viscosity parameters (10−12 cPs) provided by the printer
manufacturer. The printer cartridge utilizes a microelectro−mechanical
system based piezo-controlled nozzle to jet out highly controlled
droplet volumes. In the present study, we have used a 10 pL ink
cartridge that produces ∼30 μm diameter droplets. Nozzle voltages
and jetting waveforms were adjusted to achieve a drop velocity of 7−8
m/s. Drop spacing was kept constant at 20 μm to produce slightly
overlapping print lines to eliminate the potential gaps between the
tracks. We engineered the jetting waveform to eradicate the formation of satellite droplets, which create inconsistent droplet volumes and
have been shown to cause issues in print uniformity.