How PEDOT:PSS solutions produce satellite-free inkjets

Abstract

Satellite droplets are unwanted in inkjet printing and various approaches have been suggested for their reduction. Low jetting speeds limit applications of the process. Added surfactants for wetting and conductivity enhancement may help but dynamic surface tension effects may counteract improvements. A higher fluid viscosity delays ligament break-up, but also leads to slower jets, while viscoelasticity reduces satellite formation only in certain cases. We show here that aqueous solutions of PEDOT:PSS (1:2.5 by weight) are strongly shear-thinning. They exhibit low viscosity within the printing nozzle over a wide range of jet speeds, yet rapidly (< 100 µs) recover a higher viscosity at the low shear rates applicable once the jet has formed, which give the benefit of delayed satellite formation. The delay over a 0.8 mm standoff distance can be sufficient to completely suppress satellites, which is significant for many printing applications.

Drop Speeds from Drop-on-Demand Ink-Jet Print Heads

“…There are significant delays in the creation of satellites from long ligaments trailing behind fast moving heads, proportional to the PEDOT:PSS concentration. 22 The long PEDOT:PSS tails behaved as if they had very rapidly regained the high viscosity normally associated with low shear rate conditions, thereby raising the effective Ohnesorge number and delaying the ligament break up. Figure 6 shows the effect of PEDOT:PSS content on the average production rates of satellites within 800 µm of a 40 µm diameter DoD nozzle, and data for two Newtonian liquids for comparison.…”

“…Highly shear thinning effects have been reported 22 for the complex fluid PEDOT:PSS commonly used in digital fabrication of organic electronics 23,24 . …”

Orodispersible films: Towards drug delivery in special populations

“…Beyond ink formulation, various inkjet printing related factors such as satellite drops, nozzle clogging, fast evaporation of volatile solvents, coffee ring effect have been an ongoing academic and industry R&D topic (Deegan et al, 1997;Hoath et al, 2008Hoath et al, , 2012Reis et al, 2005;Stringer and Derby, 2010). For example, an empirical effort to validate the regime of fluid "jettability" has been described by Kuang andcolleagues in 2014 (Nallan et al, 2014).…”

Comparison of Particle Number Counts Measured with an Ink Jet Aerosol Generator and an Aerodynamic Particle Sizer

“…The pressure is produced either by an electrical pulse applied to a piezoelectric element, which causes mechanical deformation of the piezoelectric element, or through momentarily electrically heating the liquid in the micro chamber, which causes some of the liquid to vaporize. The jet of liquid leaving a nozzle typically breaks down into a single droplet with the possible formation of one or more satellites (Bottiger and Deluca 1999;Hoath et al 2012, Hoath et al 2013. Because a single primary droplet is produced each time an electrical pulse is applied, ink jet cartridges have been used for aerosol generation (Bottiger et al 1998;Bottiger and Deluca 1999; 2000; Sergeyev and Shaw 2006;Yli-Ojanperä et al 2012;Iida et al 2013;Udey et al 2013).…”