Search

Model elastic inks were formulated, rheologically characterised in shear and extension, and printed via flexography to assess the impact of ink elasticity on print uniformity. Flexography is a roll-to-roll printing process with great potential in the mass production of printed electronics for which understanding layer uniformity and the influence of rheology is of critical importance. A new set of flexo-printable Boger fluids was formulated by blending polyvinyl alcohol and high molecular weight polyacrylamide to provide inks of varying elasticity. During print trials, the phenomenon of viscous fingering was observed in all prints, with those of the Newtonian ink exhibiting a continuous striping in the printing direction. Increasing elasticity significantly influenced this continuity, disrupting it and leading to a quantifiable decrease in the overall relative size of the printed finger features. As such, ink elasticity was seen to have a profound effect on flexographic printing uniformity, showing the rheological tuning of inks may be a route to obtaining specific printed features. [ABSTRACT FROM AUTHOR]

Functional model inks were formulated and printed using flexography in order to assess the influence of ink extensional elasticity and print velocity on the morphological and electrical properties of printed layers. Increased extensional elasticity and higher print velocity resulted in the printing of more isotropic prints, both morphologically and electronically. Furthermore, a correlation between the prints' morphological and electrical anisotropy strongly suggests that print uniformity has a considerable influence on functionality and that ink rheology may be used to control such characteristics. Image 1 • Ink rheology was used to control flexographic print properties. • Extensional elasticity of PEDOT:PSS inks was manipulated with polyacrylamide. • Increasing ink extensional elasticity and print velocity enhanced print isotropy. • Strong correlation was found between morphological and electrical print anisotropy. [ABSTRACT FROM AUTHOR]