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Due to its flexibility and ease of patterning, ink jet printing has become a popular technique for the noncontact deposition of liquids, solutions, and melts on a variety of substrates at lateral resolutions down to 10 lm. This article presents a study of ink jet printing of homogeneous layers of Orgacon TM (Agfa-Gevaert, Belgium), a water-based dispersion of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonic acid) (PEDOT:PSS). The printed PEDOT:PSS layer can be used as a transparent electrode in organic light-emitting diodes (OLEDs). Fundamental aspects of the interaction between the ink jet ink and the substrate and the resulting homogeneity of the active layer in relation to OLED device performance are investigated. The optimized PEDOT:PSS ink formulation is shown to improve layer homogeneity, resulting in a uniform light output and device efficiency. Ink jet printing is shown to be capable of fabricating 25 Â 25 mm OLED devices that have equivalent efficiency and light uniformity to the ones produced by spin coating.

Due to its flexibility, inkjet printing has become a widespread technique for the non-contact deposition of liquids, solutions and melts on a variety of substrates with a lateral resolution down to about 10 μm. Because the patterns are formed via coalescence of many individual droplets, ripples and undulations can appear in the deposited layers, which gradually disappear if sufficient time before ink solidification is given. In this manuscript, we study this spontaneous leveling process of inkjet printed lines that is driven by surface tension and hydrostatic pressure gradients. We show that the process can be significantly retarded if the ink contains soluble or insoluble surfactants, which are common additives to improve print quality. We present qualitative experiments as well as theoretical and numerical models that allow estimation of the leveling time for arbitrary ripple amplitudes and realistic surfactant properties.

We report on dynamical observations of femtosecond-laser-generated bubbles in water using a single-laser-source pump/probe setup combined with stroboscopic imaging. With this simple setup, we accurately measure the transmission of a probe beam and simultaneously record images giving the size and lifetime of single-pulse-generated bubbles. Our experiments indicate that stable bubble nucleation can be obtained with pulses repetition rate up to 142 kHz, which offers promising perspectives for high-throughput jetting.

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