Optimization of Experimental Parameters to Suppress Nozzle Clogging in Inkjet Printing

Abstract

Stable drop jettability is mandatory for a successful, technical scale inkjet printing, and accordingly, this aspect has attracted much attention in fundamental and applied research. Previous studies were mainly focused on Newtonian fluids or polymer solutions. Here, we have investigated the drop jetting for zinc oxide (ZnO) particulate suspensions. Generally, the inverse Ohnesorge number Z = Oh–1, which relates viscous forces to inertia and surface tension, is sufficient to predict the jettability of single phase fluids. For the inkjet printer setup used here, jetting was possible for Newtonian fluids with 2.5 < Z < 26, but in the identical Z-range, nonjetting and nozzle clogging occurred for certain suspensions. A so-called ring-slit device, which allows for simultaneous formation and detection of aggregates in strongly converging flow fields, and single particle detecting techniques, which allow for an accurate determination of the number and size of micrometer-sized aggregates in suspensions of nanoparticles, were used to study this phenomenon. Nozzle clogging is induced by heterocoagulation of micrometer-sized aggregates and ZnO nanoparticles in the elongational flow field at the nozzle exit. Clogging may occur even if the size of these aggregates is well below the nozzle diameter and their concentration is on the order of only a few hundred parts per million (ppm). Accordingly, increased colloidal stability of nanoparticles and reduced aggregate concentration result in better drop jettability. Also, a nozzle design resulting in a shorter exposure time of the ink to elongational flow and an increased flow velocity helps to avoid nozzle clogging.

Fabrication of lanthanum strontium cobalt ferrite (LSCF) cathodes for high performance solid oxide fuel cells using a low price commercial inkjet printer

“…The viscosity of the HP61 ink was identified as 4.38 mPa s, almost identical with the reported values of other commercially available HP inks [39]. The viscosity values of 0, 11, and 20 wt.% inks were measured as 2.83, 2.78 and 2.93 mPa s, respectively, which are lower than ones from the HP inks but in the range of values appropriate for inkjet printing [30,38]. Fig.…”

“…The 11 and 20 wt.% inks exhibited good dispersion stability without any severe sedimentation and maintained narrow distribution peaks similar to ones from freshly made materials. This result clearly confirms that the addition of suitable surfactants can improve the dispersion of the raw material particles in inks and prevent particle agglomeration [37,38].…”

Jet array driven flow on the nozzle plate of an inkjet printhead in deposition of molten nylon materials

“…Contamination may come from impurities in the ink or from the surrounding environment and could affect droplet formation by disturbing the oscillating meniscus. Jetting of particulate suspensions could be particularly challenging where the nozzle cloging is to be avoided by tailoring the ink formulation and also jetting parameters as reported by Lee et al (2012). de Jong et al (2006 studied the mechanism behind the failure of a single jet in the presence of a thin wetting ink layer on the nozzle plate of a DoD printhead.…”

Integration of additive manufacturing and inkjet printed electronics: a potential route to parts with embedded multifunctionality

“…For dissolved material; this is most likely to occur due to evaporation of solvent at the nozzle (and the solute coming out of solution) [58], and for particles is most likely to occur due to agglomeration of suspended particles at the nozzle or evaporation [59]. Care must therefore be taken in choosing the carrier solvent for inks, with relatively high boiling point solvents often used to counteract this [60].…”