Formulation of an Aqueous Titania Suspension and its Patterning with Ink-Jet Printing Technology

We present a general protocol for processing cost-beneficial, environmentally benign aqueous-type suspensions containing metal-oxide nanostructured particles, and their patterning with piezoelectric ink-jet printing technology. The critical issues relevant to ink-jet printing are the preparation and stabilization of nanosized particles in a fluid and adjusting its physical properties to the values appropriate for a particular ink-jet printer mechanism. We discuss and illustrate, on a model titania system, the processing of a highly stable, colloidal, water-based suspension containing particles not bigger than 570 nm, prepared by a ball-milling process. For the ink-jet printing experiments, the surface tension and the viscosity of the suspension were modified by the addition of a small amount of the appropriate non-ionic amphiphiles and glycerol. The formation of droplets, their positioning on the substrate, and the shape and uniformity of the dots on the substrate are discussed and correlated with the fluid properties via the inverse Ohnesorge number Z. It was shown successfully that uniform, regular-shaped TiO2 dots with a diameter of 30 mu m and a good positioning accuracy on Si/SiO2 substrates could be obtained by jetting a fluid with Z values of 5 and 9 using a piezoelectric ink-jet printer with a nozzle diameter of 21 mu m operating at an amplitude of 13 V and a frequency of 5 kHz.