Since the discovery in 1977 that conjugated polymers can be doped to achieve almost metallic electronic conduction, the research field of conducting polymers has escalated, with applications such as light emitting diodes, solar cells, thin film transistors, electrochemical transistors, logic circuits and sensors. The materials can be chemically modified during their synthesis in order to tailor the desired mechanical, electronic and optical properties of the final product. Polymers are also generally possible to process from solution, and regular roll-to-roll printing techniques can therefore be used for manufacturing of electronic components on flexible substrates like plastic or paper. On top of that, the nature of conjugated polymers enables the creation of devices with novel properties, which are not possible to achieve by using inorganic materials such as silicon. The work presented in this thesis mainly focuses on devices that utilize two rather unique properties of conducting polymers. Conducting polymers are generally electrochromic, i.e. they change color upon electrochemical oxidation or reduction, and can therefore be used as both conductor and pixel element in simple organic displays. As a result of the electrochemical reaction, some polymers also alter their surface properties and have proven to be suitable materials for organic electronic wettability switches. Control of surface wettability has applications in such diverse areas as printing techniques, micro-fluidics and biomaterials. The aim of the thesis is to briefly describe the physical and chemical background of the materials used in organic electronic devices. Topics include molecular properties and doping of conjugated polymers, electrochromism, surface tension etc. This slightly theoretical part is followed by a more detailed explanation of device design, functionality and characterization. Finally, a glance into future projects will also be presented. / <p>ISRN/Report code: LiU-TEK-LIC-2005:50</p>

At present there is an extraordinary need to overcome barriers in regards to discovering novel and enhanced biomaterials for various tissue engineering applications. The need for durable orthopaedic implants is on the rise to limit issues such as revision surgery. A promising pathway to enhance fixation is to accelerate the onset and rate of early cellular adhesion and bone growth through nanoscale surface topography at the implant surface. The main aim of this research project was to investigate cellular response to altered physical and mechanical characteristics of materials suitable for orthopaedic applications. Four injection moulded polymeric substrates were produced, each with varied compositional and topographical characteristics. The four materials fabricated are Polyether-ether-ketone (PEEK), PEEK with 30% glass fibre (GL/PEEK) composite, PEEK and GL/PEEK with grooved topography. SEM and AFM analysis was used to investigate the groove dimensions and surface roughness of all samples followed by mechanical testing using a nano indenter to detect the Young’s modulus, stiffness and hardness of all four substrates. These tests were performed to determine which material has similar characteristics to cortical bone. These tests were followed by wettability and surface energy testing. Cell-substrate adhesion was examined using a cell viability assay to identify if there is a significant difference (p<0.05) between the percentage of viable cells on all four PEEK based materials. Imaging of MG-63 osteosarcoma cells using immunohistochemistry staining kits was conducted to observe the relationship between cell length and surface topography followed by a comparison between HaCaT (skin) cells and MG-63 (bone) cells. Following experimental testing mechanical variations between PEEK and GL/PEEK were identified alongside physical characterization differences. The grooved topography increased the surface roughness of PEEK and GL/PEEK in comparison to the planar surface. After 72 hours a correlation between the increased surface roughness and the percentage of viable MG-63 cells could be identified. When assessing the effect surface topography has on the water contact angles and surface energy, all four substrates showed no correlation. However, the grooved topography did increase the water contact angle and reduced the surface energy of PEEK in comparison to planar PEEK. Images of the four substrates after cell culture observed the grooved topography to affect the cellular orientation of both MG-63 and HaCaT cells. Polycaprolactone (PCL) scaffolds with a concentration of 1, 3, and 5% triclosan (an antimicrobial and antifungal agent) were fabricated using electrospinning. In addition to PCL + Triclosan scaffolds PCL with a concentration of 1% silver (an antimicrobial agent that can reduce the risk of infection) and 1, 3, and 5% triclosan were also electrospun. The pore size and fibre diameters of the scaffolds were investigated using SEM and Image J software followed by wettability and surface energy testing. MG-63 cells were cultured on all PCL scaffolds to study cellular viability percentage after 24 and 72 hours. The findings obtained showed the physical characteristics of PCL scaffolds to affect cellular viability of MG-63 cells. The output from these findings aim to provide data at a proof of concept level in understanding the relationship between the mechanical and physical characteristics of biomaterials and cellular behaviour.

Industries (food, beverage, petrochemical, etc.) normally use various gravitational separation echniques in their processes. Such separation processes often suffer from the deposition of undesirable material on the active surfaces of the process equipment, e.g. a high-speed separator or decanter, causing a slew of problems with the process or product quality. To restore operational efficiencies, additional cleaning steps using both water and chemicals are required, making the process more expensive and less environmentally friendly. Other than operating time and concentration of the process fluid there are several factors such as surface nature, surface roughness, type of material, surface charge, etc which influence the fouling deposition of surfaces. Fouling on the surfaces can grow following different mechanisms. The goal of this research work is to learn more about the nature of foulant interactions with stainless steel surfaces and eventually design some antifouling methodology. It is too difficult to study foulingfor all kinds of solutions and industries, so we tried to investigate the organic deposition in dairy and brewery industries by using lab-scale synthesized milk and beer solutions, For quantitative and statistical examination of these characteristics, several experimental approaches (FTIR, percent weight change, surface roughness, surface energy) were used. It was confirmed that fouling grows on the surfaces in a non-linear fashion irrespective of the time and concentration of the solution. The fouling of surfaces can be improved by producing more hydrophilic surfaces or by reducing surface roughness. Steric hindrance, electrostatic charge, and water barrier or hydration layer theories can be used to modify the surface nature and hence the fouling deposition. For antifouling purposes, PMMA (organic) and tungsten oxide (inorganic) coatings were employed. The PMMA was deposited using a dip-coating technique using (6%,10%, and 12%) PMMA solution, and the tungsten oxide coating was carried out by using a standard two electrode electrochemical system under different voltage (3.5V and 4.5V) and time (5min, 10 min, and 20 min) conditions. The coatings were characterized by using different techniques and their antifouling effects were studied in model milk and model beer solutions / Vid industriella processer (livsmedel, petrokemisk etc.) används ofta olika tekniker för separation med hjälp av gravitation. Sådana separationsprocesser drabbas ofta av oönskade beläggningar och påväxt på processutrustningens aktiva ytor så som t.ex. i en separator eller en dekanter, vilket orsakar problem med processen eller produktkvaliteten. För att återställa driftseffektivitet krävs särskilda rengöringssteg med både vatten och kemikalier vilket gör processen dyrare och mindre miljövänlig. Förutom drifttid och processvätskans sammansättning finns det flera faktorer såsom ytbeskaffenhet, ytjämnhet, materialtyp, ytladdning m.m. som påverkar mängden oönskade beläggningar på ytor. Föroreningarna på ytor kan tillväxa med olika mekanismer. Målet med detta forskningsarbete är att studera interaktionen mellan olika former av påväxt och ytan på rostfritt stål och senare utforma metoder för att förhindra bildandet av sådana oönskade beläggningar. Det är en stor utmaning att studera olika typer av påväxt för alla typer av flöden och industrier. I studien undersöktes organisk påväxt inom mejeri- och bryggeriindustrin genom att använda syntetiserade mjölk- och ölprodukter i laboratorieskala, för kvantitativa och statistiska undersökningar av dessa egenskaper. Flera olika experimentella metoder användes (FTIR, viktförändring, ytjämnhet, ytenergi). Det bekräftades att tillväxten på ytorna var olinjärt oavsett tid och lösningens koncentration. Bildandet och tillväxt av oönskade beläggningar kan minskas med hjälp av mera hydrofila ytor eller genom att minska ytans ojämnhet. Steriska hinder, elektrostatisk laddning och vattenbarriär eller hydratiseringsskal kan användas för att modifiera ytan och därmed fördröja bildandet av oönskade beläggningar. För att förhindra påväxt belades ytan med PMMA (organisk) och volframoxid (oorganisk). PMMA deponerades genom en doppbeläggningsteknik med användning av (6%, 10% och 12%) PMMA-lösning och volframoxidbeläggningen utfördes med ett elektrokemiskt tvåelektrodssystem med olika spänningar (3,5V och 4,5V) och tider (5min, 10min och 20min). Ytbeläggningarna karakteriserades genom att använda olika tekniker och deras förmåga att förhindra snabb påväxt studerades i modellösningar av mjölk och öl.

This study provides, for the first time, an ex vivo comparative evaluation of formulations of budesonide with crystallised β-form mannitol, commercial DPI grade mannitol and lactose. The lactose-budesonide was the marketed Easyhaler® 200 g formulation. Ex vivo assessment of deposition using the Easyhaler® multi-dose high resistance inhaler with reservoir was compared with the RS01® single dose capsule low resistance inhaler at two different inhalation rates. Aerodynamic characteristics, flow and surface energies were investigated together with in vitro and ex vivo assessment of drug deposition. Dose emission was greater for all formulations with higher inhalation flow, indicating greater detachment of drug from carrier, and greater with the Easyhaler®, highlighting the importance of correct device for formulation. Emission was lowest at both inhalation rates for crystallised mannitol due to poor flowability associated with elongated particle shape which resulted in interception deposition. Surface energies were also implicated; closely matched polar surface energy of carrier and drug may be an important inhibiting factor. The promising aerodynamic characteristics of crystallised mannitol with the RS01® inhaler and lactose-budesonide from in vitro assessment were not supported by ex vivo results, highlighting the need for careful selection of device.

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Planar defects such as free surfaces and grain boundaries in metals and alloys play important roles affecting many material properties such as fracture toughness, corrosion resistance, wetting, and catalysis. Their interactions with point defects and solute elements also play critical roles on governing the microstructural evolution and associated property changes in materials. This work seeks to use atomistic modeling to obtain a fundamental understanding of many surface and interface related properties and phenomena, namely: orientation-dependent surface energy of elemental metals and alloys, segregation of solute elements at grain boundaries and their impact on grain boundary cohesive strength, and the controversial sluggish diffusion in both the bulk and grain boundaries of high entropy alloys. First, an analytical formula is derived, which can predict the surface energy of any arbitrary (h k l) crystallographic orientation in both body-centered-cubic (BCC) and face-centered-cubic (FCC) pure metals, using only two or three low-index (e.g., (100), (110), (111)) surface energies as input. This analytical formula is validated against 4357 independent single element surface energies reported in literature or calculated by the present author, and it proves to be highly accurate but easy to use. This formula is then expanded to include the simple-cubic (SC) structure and tested against 4542 surface energies of metallic alloys of different cubic structures, and good agreement is achieved for most cases. Second, the effect of segregation of substitutional solute elements on grain boundary cohesive strength in BCC Fe is studied. It is found that the bulk substitution energy can be used as an effective indicator to predict the embrittlement or strengthening potency induced by the solute segregation at grain boundaries. Third, the controversial vacancy-mediated sluggish diffusion in an equiatomic FeNiCrCoCu FCC high entropy alloy is studied. Many literature studies have postulated that the compositional complexity in high entropy alloys could lead to sluggish diffusion. To test this hypothesis, this work compares the vacancy-mediated self-diffusion in this model high entropy alloy with a hypothetical single-element material (called average-atom material) that has similar average properties as the high entropy alloy but without the compositional complexity. The results show that the self-diffusivities in the two bulk systems are very similar, suggesting that the compositional complexity in the high entropy alloy may not be sufficient to induce sluggish diffusion in bulk high entropy alloys. Based on the knowledge learned from the bulk alloy, the exploration of the possible sluggish diffusion has been extended to grain boundaries, using a similar approach as in the study of self-diffusion in bulk. Interestingly, the results show that sluggish diffusion is evident at a Σ5(210) grain boundary in the high entropy alloy due to the compositional complexity, especially in the low temperature regime, which is different from the bulk diffusion. The underlying mechanisms for the sluggish diffusion at this grain boundary is discussed. / Doctor of Philosophy / Human beings have utilized metals and alloys for over ten millennia and learned much from them. Based on the accumulated knowledge, they have countless applications in our current daily life. However, there is still much to learn for improving our current technology and even opening new opportunities. Throughout most of history, our understanding of these materials was largely obtained through empirical experimentation and refining them into theories and scientific laws. Nowadays, due to the advancements in computer simulations, we can learn more by modeling the behaviors of metals and alloys at the length and time scales that are either be too arduous, costly, or currently impossible experimentally. This work aims at using computer modeling to study some important surface/interface related physical behaviors and properties in metals and alloys at the atomistic scale. First, this work intends to develop a robust surface energy model in an analytical form for any crystallographic orientation. Surface energy is an important material property for many surface-related processes such as fracturing, wetting, sintering, catalysis, and crystalline particle shape. Surface energy is different at different surface orientations, and predicting this difference is important for understanding these surface phenomena. Second, the effect of solute segregation on grain boundary cohesive strength is studied. Most commonly used metallic materials consist of many small crystalline grains and the borders between them are called grain boundaries, which are weak spots for fracture. The minimum energy required to split a boundary is called the grain boundary cohesive strength. The presence of solutes or impurities at grain boundaries can further alter the cohesive strength. A better understanding of this phenomena will eventually help us develop more fracture-resistant materials. The third project deals with the possible sluggish/retarded diffusion in high entropy alloys, which contain five or more principal alloying elements and have many unique mechanical, radiation-resistant, and corrosion-resistant properties. Many researchers attribute these unique properties to the slow species diffusion in these alloys, but its existence is still controversial. This work studies the atomic-level diffusion mechanisms in an FeNiCrCoCu high entropy alloy both in bulk (grain interior) and at grain boundaries in order to determine if sluggish diffusion is present and its causes.

Yes / The Caleva UK single-screw Variable Density Extruder (VDE) is a continuous powder processing equipment known for spheronization and extrusion. Its suitability for granulation remains uncertain, a common challenge in powder processing industries that deal with granules, pellets, and tablets. This study investigates the VDE's potential for granulation, using 65 µm CaCO3 powder and PEG 4000 as a liquid binder. In order to replicate several experimental setups with varying binder concentrations and liquid-to-solid ratios (L/S) of 0.1 and 0.15, eight DEM simulations were run. Our results indicate that higher binder concentrations yield more consistent products with fewer fines, while lower concentrations result in inconsistent products with increased fines. Low L/S ratios produce fragile, fine-sized products with a broad particle size distribution (PSD). DEM simulations reveal a direct relationship between liquid binder content and contact forces. Analysis of bonds formed, and particle counts in simulations corroborates experimental observations of fines production. Additionally, granule strength appears to be directly proportional to contact force. / Special gratitude is given to Ghana Scholarship Secretariat for providing the necessary funding for this research. / The full-text of this article will be released for public view at the end of the publisher embargo on 23 Jan 2025.

The measurement of the work of adhesion is of significant technical interest in a variety of applications, ranging from a basic understanding of material behavior to the practical aspects associated with making strong, durable adhesive bonds. The objective of this thesis is to investigate a novel technique using an elastica loop to measure the work of adhesion between solid materials. Considering the range and resolution of the measured parameters, a specially designed apparatus with a precise displacement control system, an analytical balance, an optical system, and a computer control and data acquisition interface is constructed. An elastica loop made of poly(dimethylsiloxane) [PDMS] is attached directly to a stepper motor in the apparatus. To perform the measurement, the loop is brought into contact with various substrates as controlled by the computer interface, and information including the contact patterns, contact lengths, and contact forces is obtained. Experimental results indicate that due to anticlastic bending, the contact first occurs at the edges of the loop, and then spreads across the width as the displacement continues to increase. The patterns observed show that the loop is eventually flattened in the contact region and the effect of anticlastic bending of the loop is reduced. Compared to the contact diameters observed in the classical JKR tests, the contact length obtained using this elastica loop technique is, in general, larger, which provides potential for applications of this technique in measuring interfacial energies between solid materials with high moduli. The contact procedure is also simulated to investigate the anticlastic bending effect using finite element analysis with ABAQUS. The numerical simulation is conducted using a special geometrically nonlinear, elastic, contact mechanics algorithm with appropriate displacement increments. Comparisons of the numerical simulation results, experimental data, and the analytical solution are made. / Master of Science