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Issue 21 Winter 2003 Improved Ink-Jet Printing by Control of Ink-Media Interactions Digital ink-jet printing has huge potential as an alternative printing technology for many packaging and decorative applications. By its very nature, ink-jet printing provides 3 high added value since it meets the needs for the short 2 production run demands of today’s industrial and 4 commercial markets. These factors are summed up by the phrase ‘mass customisation’. In order to capture and exploit this huge potential capability, short comings of the 5 industrial ink-jet printing process must be overcome. Perhaps the most demanding of these factors is associated 1 with adaptation and tuning related to the key physical inputs: ink, media and media treatment. The introduction of new media or ink requires reformulation of the industrial Figure 1: Schematic representation of the challenges in industrial ink-jet printing processes being investigated by the IMAGE-IN printing parameters, which is both time consuming and project. wastes material and chemicals in setting up. Waste (1) determination of surface properties, € chemicals alone amount to approximately 29M annually, (2) effect of pre-treatment using plasmas, corona discharge, with similar figures for man-power effort lost in setting up. and/or surface coatings, (3) high speed multi-colour ink-jet printing using fixed matrix on Members of the Departments of Materials and Theoretical wide format variable media, (4) post-treatment using UV cure or heat fix and Physics are leading a new € multi-million initiative on (5) print quality feedback to stages (2), (3) and (4). improving ink-jet printing. By studying the whole digital ink-jet printing process the IMAGE-IN project (see www.imagein.org) is using a synergistic approach to achieve these objectives the IMAGE-IN consortium develop a complete understanding of the generic science includes 5 industrial companies (Agfa-Gevaert, Ardeje, that underpins the printing processes. This approach can be Dotrix, Coates Electrographics and Teich) and 2 universities understood schematically in figure 1, which summarises (Universities of Oxford and Joseph Fourier (Grenoble)) the key areas which are being addressed in the ink-jet who collectively possess core expertise in all the key printing process. components of the printing process such as inks, interface interactions, materials, benchmarking, characterization, Through a complete understanding of the print cycle, it modelling and print manufacturing. will be possible to extend the capability of industrial ink-jet printing to satisfy the commercial, economic and environ- The IMAGE-IN project, coordinated by David Bucknall, mental requirements of current and future markets. This Department of Materials, is funded for 3 years (from June will allow the EU to take a significant market lead over the 2002) through the European Union Framework 5 ‘Promoting current dominance of Asia and the USA. In order to Competitive and Sustainable Growth’ programme. Nanostructured Oxide Surfaces Production scale manufacture of novel electronic devices In figure 1 a series of scanning tunnelling microscope such as single electron transistors and quantum dot (STM) images shows the evolution of the nanostructures lasers will ultimately rely on the spontaneous growth of as a function of annealing temperature. The unpatterned nanometre sized structures. Research in this field has to surface in (a) develops nanolines in (b) which cover the date been dominated by semiconducting materials surface in (c) and eventually turn into nanodot arrays in systems and while there have been many successes, the (d). Figure 2 shows a 3D rendering of one of the nano- nanostructures that are grown are generally not well lines, which is thought to be due to strontium enrichment ordered and can have significant size distributions which of the surface region caused by the ion sputtering degrade their usefulness. As a possible solution to these process. In figure 3 an image of a nanodot array is shown. difficulties, studies on other materials systems have been The dots have the appearance of elongated crosses. initiated. Some oxide crystals are particularly attractive candidates because nanostructures grown on them will be The future electrically insulated from the substrate. Further research is currently in progress to clarify the SrTiO3 oxide surfaces relationship between the surface stoichiometry and the appearance of nanostructures. Work on other surfaces Martin Castell from the Department of Materials has and related materials is also being carried out. The major shown how modification of the SrTiO3 (001) surface can challenge ahead, and one that is faced by many give rise to growth of nanoline and nanodot arrays. These researchers in this field, is how to turn this nanoscience structures could be used as arrays of nanowires and into nanotechnology. quantum dots. The patterned surfaces might also act as a suitable substrate for the growth of new metallic or semi- conducting quantum structures. Figure 2: 3D rendering of a scanning tunnelling microscope image of a 12 nm long nanoline. Figure 1: Following argon ion sputtering the samples are annealed in ultra high vacuum at increasing temperatures from 860°C to 1000°C. The scanning tunnelling microscope images show (a) straight step edges, with an insert of the c(2x4) atomic structure, Figure 3: STM image of a nanodot array. The typical horizontal (b) nanolines, (c) nanolines ordering, (d) nanodot arrays. separation between the dots is 1.6 nm. New NanoSIMS Arrives Figure 1: NanoSIMS maps of H (left) and Si (right) taken from a 25 µm square area of the surface of a squeeze cast Al-Si alloy. Concentration is indicated by a colour scale with red representing the highest concentration and dark blue representing the lowest concentration. The Department of Materials recently took delivery of a showing that the H can be located in discrete areas within state-of-the-art Secondary Ion Mass Spectrometry (SIMS) the eutectic regions of the microstructure but is not found facility, a Cameca NanoSIMS funded as part of the major in the α-Al matrix. Joint Infrastructure Fund grant awarded to the Department in 1999. For many years the power of SIMS in the precise New Investigations analysis of very dilute species has made it a vital tool for the semiconductor industry, but the technique has not been The intention is to investigate how the NanoSIMS may very widely used in other areas of Materials Science partly contribute to high resolution chemical analysis in as wide because of the poor spatial resolution of conventional SIMS a range of problem areas as possible. A key intent is to systems. Cameca have recently developed a machine that explore biological samples as well as metallurgical and combines the excellent chemical sensitivity of the SIMS polymeric materials. To this end collaborations have been technique with the ability to collect chemical information set up with colleagues in the Plant Science, Biochemistry, with a lateral resolution of about 100nm and a depth Chemistry and Medical Departments as well as within the resolution of 1nm. There are only five other of these Department of Materials. Areas being investigated already extremely sophisticated machines in the world (none in are as diverse as: Materials Science laboratories), and the Oxford NanoSIMS is currently the only one in the UK. • mechanisms for hyperaccumulation of trace heavy metals in plants Early results • location within human heart cells of metal-tagged drugs • diffusion mechanisms at polymer/polymer interfaces The particular power of the NanoSIMS lies in the ability • grain boundary segregation in polysilicon, high to detect and position all elements, including H, even at temperature superconductors and steels concentrations below 100ppm. Data from an early experi- ment carried out on the Oxford machine is shown in Chris Grovenor, leading work on the NanoSIMS, would be figure 1 which consists of H and Si maps taken from a 25 interested in discussing other potential areas with anyone µm square area of the surface of a squeeze cast Al-Si alloy with an interesting problem. Quantum Information Honorary Degree Processing IRC The University of Oxford has recently announced the award of the honorary The Engineering and Physical Sciences Research Council (EPSRC) has degree of Doctor of Science to Professor recently announced the appointment of Professor Andrew Briggs of the Dame Julia Higgins, DBE, FRS, FREng. Department of Materials to the position of Director of a new £9M Professor Higgins was an undergraduate Interdisciplinary Research Collaboration (IRC) in Quantum Information and graduate student at Somerville Processing (QIP). The basic aim of the QIPIRC (www.qipirc.org) is to under- College, Oxford. She has been Professor stand how the fundamental laws of quantum physics can be harnessed for of Polymer Science in the Department of the manipulation, storage and communication of information, opening up Chemical Engineering at Imperial College new possibilities in information processing. The IRC will create and since 1989, actively researching polymer coordinate a multidisciplinary team of researchers to address challenges behaviour, in terms of their molecular in QIP. The IRC will aim to establish new world-leading experimental structure, organisation and motion. activity in the UK, build on current world-leading theoretical activity and create a critical mass of coordinated QIP research. Professor Higgins became a Fellow of the Royal Society in 1995, and is currently Professor Briggs, who took up a new chair in Nanomaterials in August Foreign Secretary and Vice President of 2002, said, “The IRC provides a marvellous opportunity to create a critical the Royal Society. She has been awarded mass of coordinated research activity in the UK. We intend to establish the CBE and created DBE for her services world-leading experimental activity by building on the world-leading to science. She has a strong interest in the theoretical work of which the UK can be justly proud. We shall welcome participation of women in science and appropriate collaborations with industry and relevant organisations.