Formulation, Quality, Cleaning, and Other Advances in Inkjet Printing

This article describes a series of modern developments carried out by the inkjet community in its quest to improve material compatibility, printing quality, and reliability. Recent progress in rheology has advanced our understanding of liquids at time scales characteristic of inkjet printing processes. As a result, microsecond rheology now permits the formulation of inks with tailored viscosities that vary according to the time scale of their dynamics; that is low effective viscosity during jetting but high at breakup and landing. These advances have permitted the community to assess, and often predict, ink jetting behavior, at a given printing frequency, based on the linear or nonlinear viscoelasticity and other fluid characteristics. Advances in fluidic systems and in waveform design have now enabled the printing of high viscous inks that were previously impossible to jet on demand. This capability is opening up new markets and opportunities for inkjet, from the printing of glues to the use of heavily loaded ceramic inks. Advances in printhead design and the assessment of printing patterns using common standards now allow the verifiable and reliable operation of industrial-scale digital inkjet printing in a wide range of environments. Recent improvements on printhead cleaning protocols have contributed to an increase in printing speed and operating time by reducing the production of mist and satellite droplets neighboring the printhead region. Thanks to these improvements, inkjet is displacing traditional technologies such as offset and screen printing in large markets including graphics, packaging, and labeling.