The science behind inkjet technology



The next generation of inkjet applications is being investigated at a dedicated research unit at Cambridge University that could have a direct impact on the future of office printing.


The five-year project was created in collaboration with UK manufacturers to gain a greater understanding of the print process and to help further develop existing inkjet technologies.


Every process is under scrutiny from the dynamics of ink formation in the print head, nozzle design and performance through to droplet dispersal, flight and impact.


It is hoped the joint academic-industry programme, funded in part by the UK’s Engineering and Physical Sciences Research Council, will deliver new discoveries for the inkjet print sector and open up new markets for manufacturers.


Its aims are to "improve understanding, characterisation and modelling of fluid flow, fluid-nozzle and fluid-substrate interactions so that the inkjet process can be optimised".


The group is close to publishing new findings which they hope will provide designers with the help to create the future for inkjet printers. Director of the Cambridge University Inkjet Centre, Dr Graham Martin, told OPI that the higher accuracy and speeds required in the new applications of inkjet make demands beyond the current level of thinking.


He added: "In modern inkjet printing, jets and droplets are formed at extremely high speeds with the liquids experiencing very high shear rates. The fluids contain significant amounts of polymer and/or particulates and so have particularly complex properties. The combination of these two things leads to complex and inadequately-explained behaviour.


"We are looking at the ink and the delivery of the ink, some of these substances act in quite mysterious ways and we want to look at the detail of how that affects the performance of an inkjet print head as it comes out of the nozzle and breaks into drops, how to avoid contamination of the satellites that can sometimes form."


The Next-Generation Inkjet Technology project has been running for a year and involves several of the largest UK companies such as Sunjet, Sericol, Xaar, FFEI, Domino, Inca, Linx and CDT.


Dr Martin added: "We have got together with some of the directly competing companies to go back to basics and look at some of the fundamental things to do with inkjets.


"One of the issues we are looking at is where inkjet technology is going to be applied; clearly there is the office and home use of printers to create full colour images and printing from the web."


The team at Cambridge is currently focusing its research on eight areas: The characterisation of fluids, measurement techniques for inkjet fluids, droplet flight, droplet impact, fluid design, design rules for nozzles, measurement techniques for nozzles and manufacturing processes.


In his interview with OPI, Dr Martin added: "We want to achieve a better understanding of how to make inks, how to use them in print heads and engineer the polymers to best perform in the print heads. We are interested in paper as well as other substrates, we are concerned with how the ink spreads, dries and interacts with what’s around it.


"Over the next few years I think the spread of inkjet applications will change the most. Inkjets were first used merely to put sell-by dates on products and then that was followed by the office and high-end print market through the Eighties which is now pretty mature.


"There is always the push to increase the performance of inkjet print heads, more jets, faster-forming and finer drops. It requires high precision on how you form, deliver and deposit the drop.


"The work we do is pre-competitive but if it is advantageous to someone that will create a competitive edge, that will all be fed back into the office products market of the future."