Sandwich panels serve many purposes in engineering applications. Additive manufacturing opened the door for easy fabrication of the sandwich panels with different core structures. In this study, additive manufacturing technique, experiments, and numerical analysis are combined to evaluate the mechanical properties of sandwich panels with different cellular core structures. The sandwich panels having honeycomb, re-entrant honeycomb, diamond, square core topologies are printed with the vat photopolymerization technique. Uniaxial compression testing is performed to determine the compressive modulus, strength, and specific strength of these lightweight panels. Elasto-plastic finite element analysis having good similarities with the experimental results provided a preview of the stress distribution of the sandwich panels under applied loading. The imaging of the tested samples showed the fractured regions of the cellular cores. Dynamic mechanical analysis of the panels provided scope to compare the performance of panels and solid materials with the variation of temperature. Sandwich panels with the diamond structure exhibit better compressive properties and specific strength while the re-entrant structure offers high energy absorption capacity. The sandwich structures provided better thermo-mechanical properties than the solid material. The findings of this study offer insights into the mechanical properties of sandwich panels printed with vat photopolymerization technique which can benefit a wide range of engineering applications.

Tissue regeneration using in-vitro scaffold becomes a vital mean to mimic the in-vivo counterpart due to the insufficiency of animal models to predict the applicability of drug and other physiological behavior. Three-dimensional (3D) bio-printing is an emerging technology to reproduce living tissue through controlled allocation of biomaterial and cell. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material in bio-printing process. However, repeatable scaffold structure with good printability and shape fidelity is a challenge with hydrogel material due to weak bonding in polymer chain. Additionally, there are intrinsic limitations for bio-printing of hydrogels due to limited cell proliferation and colonization while cells are immobilized within hydrogels and don’t spread, stretch and migrate to generate new tissue. The goal of this research is to develop a bio-ink suitable for extrusion-based bio-printing process to construct 3D scaffold. In this research, a novel hybrid hydrogel, is designed and systematic quantitative characterization are conducted to validate its printability, shape fidelity and cell viability. The outcomes are measured and quantified which demonstrate the favorable printability and shape fidelity of our proposed material. The research focuses on factors associated with pre-printing, printing and post-printing behavior of bio-ink and their biology. With the proposed hybrid hydrogel, 2 cm tall acellular 3D scaffold is fabricated with proper shape fidelity. Cell viability of the proposed material are tested with multiple cell lines i.e. BxPC3, prostate stem cancer cell, HEK 293, and Porc1 cell and about 90% viability after 15-day incubation have been achieved. The designed hybrid hydrogel demonstrate excellent behavior as bio-ink for bio-printing process which can reproduce scaffold with proper printability, shape fidelity and higher cell survivability. Additionally, the outlined characterization techniques proposed here open-up a novel avenue for quantifiable bio-ink assessment framework in lieu of their qualitative evaluation.

OBJECTIVE: To assess the effect of denture cleansers on the mechanical and optical properties such as color stability, surface hardness, surface roughness, and flexural strength of the 3D printed denture acrylics in comparison to heat polymerized denture acrylics. MATERIALS AND METHODS: A total of 216 disc specimens (12 mm × 2mm) were made from Lucitone Digital Print, DENTCA Denture Base II, Formlabs denture resin, and Lucitone 199. Each type of acrylic was divided into four sub-groups, Efferdent, Polident, dish soap and control group in water. Specimens of each material were exposed to a total of 28 cycles of immersion in denture cleanser, while being stored in water in an incubator at 37°C in between cycles to test for color stability, surface roughness, microhardness and biaxial flexural strength. Baseline values were obtained for color, hardness, surface roughness, and biaxial flexural strength using a CIE L*a*b* color space by spectrophotometer, Vickers microhardness in hardness tester, line Ra by profilometer, and ball-on-three-ball fixture with universal testing machine respectively. Color, surface roughness, and surface hardness values were obtained at the 8th, 16th, and 28th cycles in order to compare color stability along with changes in surface roughness and surface hardness. Biaxial flexural strength values were performed for specimens at the 28th cycle as a destructive test to compare values of treated and untreated specimens. SEM analysis was performed to assess fracture behavior and microstructural changes. The differences between the tested materials and the treatment effects were statistically analyzed using the Tukey HSD test (a=0.05) and MANOVA test (a=0.05) RESULTS: The greatest significant change in color was seen in Lucitone 199 specimens (P value <0.0001) when exposed to dish soap. Lucitone 199 and Lucitone Digital Print had the significantly lowest microhardness values (P value< 0.0001) after exposure to treatments, especially dish soap. Surface roughness was significantly higher for all 3D specimens initially (P value <0.001), however with exposure to Efferdent and Polident, Lucitone 199 specimens had the greatest significant increase in surface roughness. The surface roughness of 3D printed specimens did not significantly increase with exposure to treatments. The biaxial flexural strength of all materials decreased significantly with the exposure to all treatments (P value< 0.0001). Overall, Lucitone 199 had the lowest flexural strength in both treatment and control groups compared to all the 3D printed materials. Formlabs was significantly affected by exposure to treatments,and had the greatest decrease in biaxial flexural strength (P value <0.0001). CONCLUSION: Within the limitations of this study, we can conclude that 3D printed materials in this study are more color stable that the heat-polymerized Lucitone 199. In regards to microhardness, 3D printed materials except for Lucitone Digital Print have higher microhardness values than heat-polymerized materials. Although Lucitone 199 had a smoother surface as prepared, the 3D printed materials in this study maintained their roughness values throughout the study, whereas Lucitone 199 showed a significant increase in roughness. The properties of 3D printed materials show a promising future for their use in treating edentulous patients. Although there are limitations to this study, it is safe to say that denture cleansers are safe to use with 3D printed dentures as long as the manufacturer’s instructions are correctly followed.

This diploma thesis was focused on the preparation of self-cleaning and photocatalyticaly active titanium dioxide thin films. Transparent and porous thin layers of titanium dioxide were prepared from sol-gel containing titanium tetraisopropoxide (TTIP) as precursor with addition polyethylene glycol (PEG). Transparent thin layers of titanium dioxide were also prepared from colloidal solution titanium dioxide. The immobilization of thin titanium dioxide layers was performed by a sol-gel process on the soda lime glasses. Diffusion of sodium cation from soda lime glasses into titanium dioxide layer were blocked. Sol was deposited by printig method – micropiezo deposition. Sol and thin titanium dioxide layers were characterised by the physical-chemical method. For prepared sol viscosity, density and surface tension were measured. Thickness and hydrophilicity of titanium dioxide layers also were studied. The photocatalytic activity of the printed titanium layers were tested via the photocatalytic degradation of the 2,6-dichlorindophenol. The influence of addition PEG into the sol and influence of sol loading was studied. It was found that the addition of PEG into the sol significantly increased the photocatalytic activity of titanium dioxide layers.

The objective of this thesis is to prepare a business plan on establish a new company focused on technology low-volume printing self adhesive labels and other flexible materials with methods of UV flexo and digital printing. The author's method of digital printing holds a protected utility design (Úřad průmyslového vlastnictví, registration number 11001, dated March 19, 2001)

This master thesis summarizes the current knowledge about non-commercial 3D printing FDM technology. The goal of this thesis is to demonstrate the gained knowledge by building a 3D printer which can partially replicate itself, and to evaluate its technological parameters. The experimental part of this work is focused on the impact of the changes in technological parameters of printing on mechanical properties of printed parts.

The stability of inkjet print is influenced by a lot of factors. Mutual effects of these factors accelerate the print degradation. The surrounding environment in image stability plays an important role, when the prints degrade especially by the light. The degradation of inkjet prints is presented as a decrease of dye or multiple dyes. It is necessary to know the dye concentration for the dye decrease prediction in the time. This dissertation thesis deals with the study of kinetics and changes in electron and molecular structure of digital photography prints after accelerated ageing tests. The study of resistance of inkjet prints was realized on one type of media using three different sets of inks. Changes in printed colours were measured and evaluated in calibration (by PLS calibration and least squares method). On the basis of calibration the dye decrease prediction of real samples in receiving layer was evaluated. Changes in electron and molecular structure were analysed on KBr pellets by FTIR an UV-Vis spectroscopy.

This thesis deals with design and productions of low-cost robot used for presentation and marketing purposes of companies CUTTER Systems spol. s r.o. and N-ROTE Mechanical s r.o. The main task of this robot is to serve beverages into glass containers.

This dissertation addresses the teaching of typography and book design in South Africa and how the literature relating to its education has changed during the course of the twentieth century. Several scholarly and educational book titles are compared to one another based on their approach to the subject and this is compared to the historical development of typographic technologies as they were developed in Europe. Based on the theoretical pool of the assessed books, a list of theoretical topics was drawn up and used to survey the current teaching intent of graphic design study programmes at South African tertiary education institutions. It was found that in spite of a less direct technical focus in the teaching and learning materials, training institutions within departments and faculties of arts have developed their graphic design programmes with the intent of developing students who are technologically proficient, readily employable, artistically fluent, and aware of industrial and historical conventions in their fields. However, they do not necessarily teach historical book design conventions, focussing rather on the skills and software required for contemporary design practice. / Dissertation(MIS)--University of Pretoria, 2016. / Information Science / MIS / Unrestricted

Orientador: Neri Alves / Resumo: Nesta tese de doutorado são apresentados resultados a respeito da fabricação e caracterização de dois tipos de transístores com eletrólito no gate (EGTs, do inglês Electrolyte Gated Transistors): Transístores eletroquímicos orgânicos (OECTs, do inglês Organic Electrochemical Transistors) e transístores de dupla camada elétrica (EDLTs, do inglês Electric Double Layer Transistor). Os dispositivos foram produzidos utilizando inkjet printing e screen printing para imprimir soluções à base de polímeros como o poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), precursores de óxido de zinco e de nanopartículas de óxido zinco. Como eletrólito de gate foram utilizadas faixas auto sustentáveis de íon gel à base de celulose. Esse último foi desenvolvido por pesquisadores do CEMOP/CENIMAT e combina a alta mobilidade iônica dos eletrólitos líquidos com a plasticidade dos eletrólitos sólidos. Sua estrutura em gel possibilita que o material seja moldado ou cortado de acordo com a aplicação. Os ECTs foram fabricados em arquitetura planar sobre substrato de vidro ou de papel, onde foram impressos: PEDOT:PSS como semicondutor e carbono como eletrodos. Os resultados mostram uma forte dependência de parâmetros como: corrente no estado ligado (Ion), no estado desligado (Ioff), transcondutância, razão Ion/Ioff, morfologia da superfície do substrato e a rugosidade. Os EDLTs foram fabricados usando síntese de auto combustão e foto-ativação química para produzir dispositivos com baix... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: On this doctoral thesis is presented results of the manufacture and characterization of two types of Electrolyte-gated Transistors (EGTs): Organic Electrochemical Transistors (OECTs) and electric double-layer transistors (EDLTs). Devices were manufactured using inkjet printing and screen printing to print solutions based on polymers such as poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS), zinc oxide precursors and zinc oxide nanoparticles. Self-sustainable bands of cellulose-based ion gel were used as gate electrolyte. The last was developed by researchers from CEMOP/CENIMAT and combines the high ion mobility of liquid electrolytes with the plasticity of solid electrolytes. This gel structure allows this material to be shaped or cut according to the application. The ECTs were manufactured in planar architecture over glass or paper substrates, where they were printed: PEDOT: PSS as semiconductor and carbon as electrodes. The results presents a strong dependence on parameters such as: on-state current (Ion), off-state current (Ioff), transconductance, Ion/Ioff ratio, surface morphology of the substrate and roughness. The EDLTs were manufactured using auto-combustion synthesis and chemical photo-activation process to produce devices with low processing temperatures in a way to be used in flexible, plastic or paper substrates. These devices are based on nanoparticles of zinc oxide as a semiconductor channel, fully printed and with heat treatment below 200 oC.... (Complete abstract click electronic access below) / Doutor