Fluid Dynamics of Inkjet printing
Project funder: EPSRC
Project Lead and Collaborators: Oliver Harlen (University of Leeds), Mark Wilson (University of Leeds), Ian Hutchings (University of Cambridge), Malcolm Mackley (University of Cambridge), Colin Bain (Durham University).
Industrial Partners: Domino, Inca Digital Printers, GlaxoSmithKline, Linx Printing Technologies, Fujifilm Sericol, Xaar, Sun Chemical, Merck Chemicals, Ricoh
Inkjet printing is a rapidly advancing technology. The total market value of inkjet printing doubled between 2012 and 2015 and is predicted to exceed $90 billion by 2021. Inkjet technology uses one of two methods for generating ink droplets. Continuous-inkjet produces a continuous stream of droplets from the surface-tension-driven (Rayleigh-Plateau) instability of a liquid jet, whereas in drop-on-demand printing individual droplets are generated as required by applying a pressure wave to the ink in the print-head.
As part of a large interdisciplinary programme grant between the universities of Cambridge, Durham and Leeds and supported by a consortium of inkjet companies, at the University of Leeds we have developed experimentally verified simulation software for predicting jet ejection and droplet break-up in industrial inkjet applications. The software allows users to assess the effects of changes to nozzle design, jet modulation and the properties of printing fluids. This software has been used by print head manufacturers Xaar and Domino to reduce costs in developing new inks and print-head designs by reducing the need for physical experimentation.
The code uses a mesh embedded in the fluid and so naturally follows the evolution of the fluid surface. This makes it ideal for inkjet studies, where the simulations must determine the position of free surfaces very precisely to be able to predict accurately the break-up of the thin ligands that form behind the main drop in high-speed printing.
A particular focus of our research is the effect of non-Newtonian fluid ink properties such as viscoelasticity and shear-dependant viscosity on jetting performance, where we have shown that controlling the fluid rheology control can reduce or eliminate unwanted satellite drops.
Research in this area is continuing through a CDT PhD project funded by Ricoh UK.
Relevant Links:
Inkjet Research Centre – University of Cambridge https://www.ifm.eng.cam.ac.uk/research/irc/
Harlen OG; Morrison NF (2016) Simulations of drop formation in complex rheological fluids - Can rheology improve jetting performance? International Conference on Digital Printing Technologies, pp. 378-381. International Conference on Digital Printing Technologies.
Morrison NF; McIlroy C; Harlen OG (2015) Jetting Simulations, Fundamentals of Inkjet Printing: The Science of Inkjet and Droplets (ed. Hoath), Wiley. Doi: 10.1002/9783527684724.
Morrison NF; Harlen OG; Hoath SD (2014) Towards satellite free drop-on-demand printing of complex fluids International Conference on Digital Printing Technologies, pp. 162-165. International Conference on Digital Printing Technologies
McIlroy C; Harlen OG; Morrison NF (2013) Modelling the jetting of dilute polymer solutions in drop-on-demand inkjet printing. Journal of Non-Newtonian Fluid Mechanics, 201, pp. 17-28 DOI: 10.1016/j.jnnfm.2013.05.007 ·
Morrison NF; Harlen OG (2010) Viscoelasticity in inkjet printing. RHEOLOGICA ACTA, 49 (6), pp. 619-632. DOI: 10.1007/s00397-009-0419-z
Comparison between numerical simulations (insert) and experimental observations of the jetting of a 1000ppm solution of polystyrene (Molecular Weight 210K) in diethyl-phthalate in a drop-on-demand print-head.