Inkjet technology, a printing technique in which the digitally controlled drop formation affords accurate deposition at speed, is of great advantage for material preparation in several fields, such as printed biomaterials or electronics. However, there is a need to better understand the underlying fluid behaviour of colloidal dispersions, particularly when the solids content within the ink is increased, a highly desirable and cost-saving trait for industrial applications. More specifically, this applies to the speed and material diversity which can be attained, compared to conventional printing methods. Further, extensional deformation of colloidal particle dispersions has received little attention in the literature, despite the clear need to better understand the fluid response under these conditions. This holds particular relevance for inkjet printing, where the focus is to increase the material diversity.
To this end, high solids content sub 100 nm monodisperse model poly( methyl methacrylate) polymer particles have been prepared. These particle dispersions are normally prepared via complex polymerisation routes, requiring several sequential steps. However, research presented herein reports how a more straight forward chain transfer mediated emulsion polymerisation process is quite capable of preparing particle dispersions with these hard to attain properties. The developed method is a new route for high solids content latex preparation, and was fully explored and tuned to prepare particles in the 40-70 nm size range.
The particle dispersion shear rheology was then examined from a theoretical perspective. Moreover, the stability of particle dispersions at extremely high effective volume fractions is also explored, with the implications upon the shear rheology and jetting behaviour examined. Finally, extensional viscosity of the particle dispersions was determined using a bespoke microfluidic cross slot device. The jetting behaviour was then observed using a drop on demand micro-fab set-up.
