This master´s thesis is focused on design and manufacturing of prototype of central impression cylinder cleaning unit. This thesis contains explaining of basic principle of flexographic printing and preview of types of flexographic printing presses. There are explained patented cleaning units and main claims of every patented cleaning unit. In the next part of this thesis, there are some conceptual designs, from which was chosen the final design for manufacturing. In the next part of this work, there are detailly described each of the parts of cleaning unit. Prototype of the cleaning unit was manufactured and tested in the SOMA Engineering s.r.o. Lanškroun. Cleaning unit will simplify the work of operators and reduce time, needed to clean the central impression drum in comparison with manually cleaning.

With the technological progress of materials science, the palette of colours with which to print on textiles has expanded beyond those with previously known properties and expressions to a new generation, with more advanced functionality and expressive properties. This new range of colours is characterised by their ability when printed on textiles to change colour in relation to external factors and internal programmes; for example, leuco dye-based thermochromic inks generally change colour in response to temperature fluctuations. This research explores the design properties and potentials of leuco dye-based thermochromic inks printed on textiles, with regard to creating a wider range of colour-changing effects for textile applications. The significance of this for textile design is related to the development of a methodology for designing dynamic surface patterns. The research was conducted by creating a series of design experiments using leuco dye-based thermochromic inks, which resulted in different recipes and methods, along with a pedagogical tool. The results highlighted the diverse colour-changing properties of leuco dye-based thermochromic inks, which have the potential to create more complex patterns on textiles. The outcome of this research proposes a foundation for textile designers with which to approach new ways of thinking and designing.

Agglomeration of nanoparticles occurs in a number of colloidal systems related, for example, to material processing and drug delivery. The present work is motivated by the need to improve fundamental understanding of the agglomeration and structure formation processes that occur in catalyst inks used for the fabrication of polymer electrolyte fuel cells (PEMFCs). Particle dynamics simulations are performed to investigate agglomeration under various conditions. The interaction between particles is defined using realistic physical potentials, rather than commonly used potential models, and a novel analysis of the agglomeration and structure formation process is performed using network science concepts. The simulated systems correspond to catalyst inks consisting primarily of carbon nanoparticles in solution. The effect of various conditions such as different force magnitude, shape of the force function, concentration etc. are investigated in terms of network science parameters such as average degree and shortest path. An "agglomeration timescale" and a "restructuring timescale" introduced to interpret the evolution of the agglomeration process suggest that the structure, which has a strong impact on the performance of the eventual catalyst layer, can be controlled by tuning the rate at which particles are added based on the restructuring timescale. / Graduate

Today’s state of the art additive manufacturing (AM) systems have the ability to fabricate multi-material devices with novel capabilities that were previously constrained by traditional manufacturing. AM machines fuse or deposit material in an additive fashion only where necessary, thus unlocking advantages of mass customization, no part-specific tooling, near arbitrary geometric complexity, and reduced lead times and cost. The combination of conductive ink micro-dispensing AM process with hybrid manufacturing processes including: laser machining, CNC machining, and pick & place enables the fabrication of printed electronics. Printed electronics exploit the integration of AM with hybrid processes and allow embedded and/or conformal electronics systems to be fabricated, which overcomes previously limited multi-functionality, decreases the form factor, and enhances performance. However, AM processes are still emerging technologies and lack qualification and standardization, which limits widespread application, especially in harsh environments (i.e. defense and industrial sectors). This dissertation explores three topics of electronics integration into AM that address the path toward qualification and standardization to evaluate the performance and repeatable fabrication of printed electronics for resilience when subjected to harsh environments. These topics include: (1) the effect of smoothing processes to improve the as-printed surface finish of AM components with mechanical and electrical characterization—which highlights the lack of qualification and standardization within AM printed electronics and paves the way for the remaining topics of the dissertation, (2) harsh environmental testing (i.e. mechanical shock, thermal cycling, die shear strength) and initiation of a foundation for qualification of printed electronic components to demonstrate survivability in harsh environments, and (3) the development of standardized methods to evaluate the adhesion of conductive inks while also analyzing the effect of surface treatments on the adhesive failure mode of conductive inks. The first topic of this dissertation addresses the as-printed surface roughness from individually fusing lines in AM extrusion processes that create semi-continuous components. In this work, the impact of surface smoothing on mechanical properties and electrical performance was measured. For the mechanical study, surface roughness was decreased with vapor smoothing by 70% while maintaining dimensional accuracy and increasing the hermetic seal to overcome the inherent porosity. However, there was little impact on the mechanical properties. For the electrical study, a vapor smoothing and a thermal smoothing process reduced the surface roughness of the surfaces of extruded substrates by 90% and 80% while also reducing measured dissipative losses up to 24% and 40% at 7 GHz, respectively. The second topic of this dissertation addresses the survivability of printed electronic components under harsh environmental conditions by adapting test methods and conducting preliminary evaluation of multi-material AM components for initializing qualification procedures. A few of the material sets show resilience to high G impacts up to 20,000 G’s and thermal cycling in extreme temperatures (-55 to 125ºC). It was also found that coefficient of thermal expansion matching is an important consideration for multi-material printed electronics and adhesion of the conductive ink is a prerequisite for antenna survivability in harsh environments. The final topic of this dissertation addresses the development of semi-quantitative and quantitative measurements for standardizing adhesion testing of conductive inks while also evaluating the effect of surface treatments. Without standard adhesion measurements of conductive inks, comparisons between materials or references to application requirements cannot be determined and limit the adoption of printed electronics. The semi-quantitative method evolved from manual cross-hatch scratch testing by designing, printing, and testing a semi-automated tool, which was coined scratch adhesion tester (SAT). By cross-hatch scratch testing with a semi-automated device, the SAT bypasses the operator-to-operator variance and allows more repeatable and finer analysis/comparison across labs. Alternatively, single lap shear testing permits quantitative adhesion measurements by providing a numerical value of the nominal interfacial shear strength of a coating upon testing while also showing surface treatments can improve adhesion and alter the adhesive (i.e. the delamination) failure mode of conductive inks.

Thin film copper indium gallium selenide (CIGS) solar cells have exhibited single junction power conversion efficiencies above 20% and have been commercialized. The large scale production of CIGS solar cells, however, is hampered by the relatively high cost and poor stoichiometric control of coevaporating tertiary and quaternary semiconductors in high vacuum. To reduce the overall cost of production, CIGS nanocrystals with predetermined stoichiometry and crystal phase were synthesized in solution. Colloidal nanocrystals of CIGS provide a novel route for production of electronic devices. Colloidal nanocrystals combine the well understood device physics of inorganic crystalline semiconductors with the solution processability of amorphous organic semiconductors. This approach reduces the overall cost of CIGS manufacturing and can be used to fabricate solar cells on flexible and light-weight plastic substrates. As deposited CIGS nanocrystal solar cells were fabricated by ambient spray-deposition. Devices with efficiencies of 3.1% under AM1.5 illumination were fabricated. Examining the external and internal quantum efficiency spectrums of the devices reveal that in nanocrystal devices only the space charge region is actively contributing to the extracted photocurrent. The device efficiency of the as-deposited nanocrystal films is presently limited by the small crystalline grains (≈ 15 nm) in the absorber layer and the relatively large interparticle spacing due to the organic capping ligands on the nanocrystal surfaces. Small grains and large interparticle spacing limits high density extraction of electrons and holes from the nanocrystal film. A Mott-Schottky estimation of the space charge region reveals that only 50 nm depth of the nanocrystalline absorber is effectively contributing to the photogenerated current. One strategy to improve charge collection involves increased space charge region for extraction by vertical stacking of diodes. A much longer absorption path for the photons exists in the space charge region with the stacked devices, increasing the probability that the incident radiation is absorbed and then extracted. This method enables an increase in the collected short circuit current. The overall device efficiency, however, suffers with the increased series resistance and shunt conductance of the device. Growth of nanocrystal grains was deemed necessary to achieve power conversion efficiencies comparable to vapor deposited CIGS films. Simple thermal treatment of the nanocrystal layers did not contribute to the growth of the crystalline grain size. At the same time, because of the loss of selenium and increased trap density in the absorber layer, there was a measurable decrease in device efficiency with thermal processing. For increased grain size, the thermal treatment of the absorber layer took place in presence of compensating amounts of selenium vapor. The process of selenization, as it is called, took place at 500°C in a graphite box and led to an increase of the grain size from 15 nm to several microns in diameter. Devices with the increased grain size yielded efficiencies up to 5.1% under AM1.5 radiation. Mott-Schottky analysis of the selenized films revealed a reduction in doping density and a comparable increase in the space-charge region depth with the increased grain size. The increased collection combined with the much higher carrier mobility in the larger grains led to achieved Jsc values greater than 20 mA/cm2. Light beam induced current microscopy (LBIC) maps of the devices with selenized absorber layers revealed significant heterogeneity in photogenerated current. Distribution of current hotspots in the film corresponded with highly selenized regions of the absorber films. In an effort to improve the overall device efficiency, improvements in the selenization process are necessary. It was determined that the selenization procedure is dependent on the selenization temperature and processing environment. Meanwhile, the reactor geometry and nanocrystal inks composition played important roles in determining selenized film morphology and the resulting device efficiency. Further work is necessary to optimize all the parameters to improve device efficiency even further. / text

Baigiamajame magistro darbe ištirtas ofsetinių dažų poveikis skirtingų popierių struktūrinėms, optinėms ir mechaninėms savybėms. Atliktas palyginimas tarp balto popieriaus, nepadengto dažų sluoksniu, su atspaudais, padengtais keturiais skirtingais dažų sluoksnio storiais. Nustatyta, kurie popieriai esant tam tikram dažų sluoksnio storiui turi mažiausią bei didžiausią atsparumą mechaninėms savybėms, blogiausias ir geriausias optines savybes. Eksperimentiškai ištirtos šešių popierių, ofsetinių atspaudų trinties savybės ir nustatyti statinės ir kinetinės trinties koeficientai. Nustatytos šių koeficientų vertės tarp popieriaus ir popieriaus, tarp popieriaus ir atspaudo ir tarp atspaudo ir atspaudo. Darbo apimtis – 67 teksto be priedų, 45 iliustracijos ir 2 lentelės. / The thesis investigated inks effects of the different papers structural, optical and mechanical properties. Performed comparison between the white paper, uncoated inks layer, with printed, coated in four different inks thickness. It was found which papers and with which kind of coated inks thickness have minimum and maximum resistance of mechanical properties, the best and the worst optical properties. Experimentally investigated six different papers and offset prints friction properties and determined the static and kinetic coefficients of friction. These coefficients determined between the paper and the paper, the paper and print, and the print and print. Space of works – 67 pages of text without additions, 45 figures, 2 tables.

Ce projet vise à développer de nouvelles encres à base de nanofils d’argent et de nanocellulose pour des applications conductrices et transparentes. Les nanocelluloses, nanoparticules issues de la cellulose, sont de deux types : les nanocristaux de cellulose (NCC) et les nanofibrilles de cellulose (NFC) et possèdent des propriétés bien spécifiques. Ce travail a consisté d’une part (i) à utiliser la forme tubulaire et rigide des NCC pour produire des nanotubes d’argents par synthèse chimique, avant leur formulation en encre et d’autre part (ii) à utiliser les propriétés d’enchevêtrement des NFC flexibles pour stabiliser des nanofils d’argent commerciaux, habituellement instables en suspension. Les divers résultats de ce projet ont permis d’aboutir à la formulation brevetée et à la commercialisation d’une encre conductrice à base d’une faible quantité d’argent et de NCC et de deux encres conductrices et transparentes à base de NFC et de nanofils d’argent. Les interactions physico-chimiques et la stabilité colloïdale de ces suspensions hybrides ont été étudiée de manière fondamentale, tout en développant des formulations adaptées à divers procédés d’impression, que ce soit à échelle laboratoire mais aussi industrielle. / This project aims at developing new conductive inks based on nanocellulose and silver nanowires for transparent and conductive applications. Nanocellulose are nanoparticles extracted from the cellulose and two kinds currently exist: the cellulose nanocrystals (CNC) and the cellulose nanofibrils (CNF). This project have evaluated on one hand the ability of using tubular rigid CNC as template for producing silver nanorods, prior their formulation into conductive inks. On the other hand, the ability of using flexible and entangled CNF to stabilize commercial silver nanowires, usually unstable in suspension, was investigated. The results of this project lead to the patented formulation and commercialization of one low silver content conductive ink based on silver and CNC and two conductive transparent ink based on CNF and silver nanowires. Physico-chemical interactions and colloidal stability of such hybrid suspension have been scientifically studied meanwhile printing process adapted formulation have been successfully designed and tested at laboratory scale but also industrial scale.

Isotropically conductive adhesives (ICAs) and inks are potential candidates for low cost interconnect materials and widely used in electrical/electronic packaging applications. Silver (Ag)filled ICAs and inks are the most popular due to their high conductivity and good reliability. However, the price of Ag is a significant issue for the wider exploitation of these materials in low cost, high volume applications such as printed electronics. In addition, there is a need to develop systems compatible with temperature sensitive substrates through the use of alternative materials and heating methods. Copper (Cu) is considered as a more cost-effective filler for ICAs and in this work, Cu powders were treated to remove the oxide layer and then protected with a self-assembled monolayer (SAM). The coating was found to be able to limit the re-oxidation of the Cumicron particles. The treated Cu powderswerecombined with one of two different adhesive resins to form ICAs that were stencil printed onto glass substrates before curing. The use of conventional and microwave assisted heating methods under an inert atmosphere for the curing of the Cu loaded ICAs was investigated in detail. The samples were characterised for electrical performance, microstructure and shrinkage as a function of curing temperature (80-150°C) and time. Tracks with electrical conductivity comparable to Ag filled adhesives were obtained for both curing methods and with both resins. It was found that curing could be accelerated and/or carried out at lower temperature with the addition of microwave radiation for one adhesive resin, but the other showed almost no absorption indicating a difference in curing mechanism for the two formulations.

abstract: This paper details ink chemistries and processes to fabricate passive microfluidic devices using drop-on-demand printing of tetraethyl-orthosilicate (TEOS) inks. Parameters space investigation of the relationship between printed morphology and ink chemistries and printing parameters was conducted to demonstrate that morphology can be controlled by adjusting solvents selection, TEOS concentration, substrate temperature, and hydrolysis time. Optical microscope and scanning electron microscope images were gathered to observe printed morphology and optical videos were taken to quantify the impact of morphology on fluid flow rates. The microscopy images show that by controlling the hydrolysis time of TEOS, dilution solvents and the printing temperature, dense or fracture structure can be obtained. Fracture structures are used as passive fluidic device due to strong capillary action in cracks. At last, flow rate of passive fluidic devices with different thickness printed at different temperatures are measured and compared. The result shows the flow rate increases with the increase of device width and thickness. By controlling the morphology and dimensions of printed structure, passive microfluidic devices with designed flow rate and low fluorescence background are able to be printed. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-04-10T14:21:53Z No. of bitstreams: 0 / Made available in DSpace on 2015-04-10T14:21:53Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP