Powder injection molding (PIM) is a net fabrication technique that combines the complex shape-forming ability of plastic injection molding, the precision of die-casting, and the material selection flexibility of powder metallurgy. For this study, the design issues related to PIM for fabrication of thin-walled high-aspect ratio geometries were investigated. These types of geometries are typical to the field of microtechnology-based energy and chemical systems (MECS). MECS are multi-scale (sizes in at least two or more different length scale regimes) fluidic devices working on the principle of heat and mass transfer through embedded micro and nanoscale features. Stainless steel was the material chosen for the investigations because of its high-thermal resistance and chemical inertness necessary for typical microfluidic applications. The investigations for the study were performed using the state-of-the-art computer aided engineering (CAE) design tool, PIMSolver��. The effect of reducing part thickness, on the process parameters including melt temperature, mold temperature, fill time and switch over position, during the mold-filling stage of the injection molding cycle were investigated. The design of experiments was conducted using the Taguchi method. It was seen that the process variability generally increased with reduction in thickness. Mold temperature played the most significant role in controlling the mold filling behavior as the part thickness reduced. The effects of reducing part thickness, process parameters, microscale surface geometry and delivery system design on the occurrence of defects like short shots were also studied. The operating range, in which the mold cavity was completely filled, was greatly reduced as the part thickness was reduced. The single edge gated delivery system designs, with single or branched runners, resulted in a completely formed part. The presence of microchannel features on the part surface increased the possibility of formation of defects like short shots and weld-lines when compared to a featureless part. The study explored some typical micro-fluidic geometries for fabrication using PIM. The final aspect of this study was the PIM experiments performed using a commercial stainless steel feedstock. Experiments were performed to study the mold-filling behavior of a thin, high aspect ratio part and also to study the effect of varying processing conditions on the mold-filling behavior. These experiments also provided correspondence to the mold filling behavior simulated using PIMSolver��. The PIMSolver�� closely predicted the mold-filling patterns as seen in the experiments performed under similar molding conditions. The study was successful in laying down a quantitative framework for using PIM to fabricate micro-fluidic devices. / Graduation date: 2005

Optical waveguides, quantum dot emitters, and flat top beam shapers were designed and fabricated by two soft lithographic techniques; micro transfer molding (microTM) and vacuum assisted microfluidics (VAM). Optical waveguides were fabricated through a microTM technique that utilizes a poly dimethylsiloxane (PDMS) stamp. Generation of the flexible stamp required development of a channel waveguide pattern mask, defined by maskless lithography, and followed by construction of a three dimensional channel waveguide master, acquired through contact lithography on a glass substrate coated with SU-8 photoresist. Creation of a positive imprint replicating mold was accomplished through prepolymer PDMS solution settling and curing around the master. Waveguide fabrication was achieved through PDMS conformal contact on, and subsequent curing of, ultraviolet (UV) polymer resins on a silicon substrate. A slight modification of the microTM PDMS stamp, whereby inlet and outlet tunnels were incorporated, resulted in a novel VAM structure and correspondingly waveguides. Waveguide propagation losses were determined to be 1.14 dB/cm and 0.68 dB/cm for the microTM and VAM fabricated waveguides, respectively. A lithographic approach employing quantum dots doped in SU-8 photoresist has led to the realization of a new quantum dot emitter. Uniform coating of a doped material on a silver coated substrate was followed by contact mask lithography. Evaporation of a thin silver layer, upon development of the resultant quantum dot doped channel waveguide structure, facilitates confined emission. Successful edge emitting was demonstrated with blue laser pumping. The lithographic fabrication of such quantum dot emitter is successfully replaced by soft lithographic VAM technique. A flat top beam shaper, whose profile was developed on cured UV polymer resins, was fabricated by microTM technique. The master used for the development of the PDMS stamp was produced through an iterative wet etching process capable of achieving etching depths as small as a few nanometers. Comparisons between the reference wet etched beam shaper and the microTM based beam shaper produced near identical output flat top beams from incident Gaussian beams. Through this research work, successful soft lithographic fabrication of optical waveguides, quantum dot emitters, and flat top beam shapers were demonstrated. The vast potential exhibited by these and other related technologies show great promise for cost-effective mass production of various micro optics and integrated photonic components.

Husqvarna is a Swedish company producing products for forestry, park and gardens. Due to harder competition they wish to increase efficacy in production. This can be achieved by shorter lead-times in the complex process of making casting molds. Activities within this process have certain relations and dependencies between each other that can be analyzed by using a Dependence Structure Matrix. The Dependence Structure Matrix is a tool that can improve efficiency by rearranging activities according to how they are dependent of each other. The purpose is to make a Dependence Structure Matrix of activities that Husqvarna can use to analyze dependencies within the process of cast molding. The DSM Matrix will propose restructured activities of the process which can be evaluated to determine if greater efficacy can be reached. To determine the activities within the process of making cast molds a workshop at Husqvarna for the people involved was conducted. A matrix has been constructed based on the information of activities and their dependencies. This information has then been analyzed by the software Multiplan. The process of making casting molds could be analyzed by the DSM/DMM approach. A new order of how to carry out activities is the outcome of the analysis. The result can be analyzed by Husqvarna in order to determine if greater efficacy can be reached.

In later years polymer replication techniques have become a frequently employed fabrication method for microfluidic and micro-optical devices. This thesis describes applications and further developments of microstructures replicated in polymer materials. A novel method for homogenous amplified single-molecule detection utilizing a microfluidic readout format is presented. The method enables enumeration of single biomolecules by transforming specific molecular recognition events at nanometer dimensions to micrometer-sized DNA macromolecules. This transformation process is mediated by target specific padlock probe ligation, followed by rolling circle amplification (RCA) resulting in the creation of one rolling circle product (RCP) for each recognized target. Throughout this transformation the discrete nature of the molecular population is preserved. By hybridizing a fluorescence-labeled DNA detection oligonucleotide to each repeated sequence of the RCP, a confined cluster of fluorophores is generated, which makes optical detection and quantification possible. Spectral multiplexing is also possible since the spectral profile of each RCP can be analyzed separately. The microfluidic data acquisition process is characterized in detail and conditions that allow for quantification limited only by Poisson sampling statistics is established. The molecular characteristics of RCPs in solution are also investigated. Furthermore a novel thermoplastic microfluidic platform is described. The platform allows for observation of the microchannels using high magnification optics and also offers the possibility of on-chip cell culture and the integration of mechanical actuators. A novel fabrication process for the integration of polymer micro-optical elements on silicon is presented. The process is used for fabrication of a micro-optical system consisting of a laser and a movable microlens making beam steering possible. Such a micro-scanning system could potentially be used for miniaturized biochemical analysis.

This thesis focuses on the design, development, and evolution of a novel patent-pending plastic processing technology entitled “Rapid Rotational Foam Molding” with special emphasis on the processing of polyethylene (PE) integral-skin foamed core moldings. Rapid Rotational Foam Molding is a technology deliberately designed to address the intrinsic disadvantage of conventional rotational foam molding, i.e., its very long cycle times. In this context, a physical system that exploits the positive synergistic effects of innovatively combining extrusion melt compounding and rotational foam molding was designed and built. The fundamental processing steps of this system comprise (i) rotationally molding a non-foamable PE powder in a lab-scale oven while, (ii) simultaneously melt compounding and foaming a pre-dry blended foamable PE and chemical blowing agent (CBA) formulation in an on-line lab-scale extruder, and then (iii) filling the newly created foaming material into the non-chilled hollow article thereby created in the mold through a special interface. Two varieties of PE resins ranging from linear low density PE (LLDPE) to high density PE (HDPE) were selected for experimentation with melt flow rates (MFR) ranging from 2.0 to 3.6 g/10min. The implemented CBA was Celogen OT. The materials were characterized using thermal analysis techniques such as differential scanning calorimetery (DSC) and thermogravimetric analysis (TGA) to ensure their correct operating temperatures ranges. Scanning electron microscopy (SEM) was utilized for characterizing the quality of the foam samples and achieved skin-foam interface for the final moldings. Improvements to the achieved molding quality were accomplished through various system and process modifications described throughout this research work.

Extrusion compounding addresses such problems as the non-homogeneity of the mixture and separation of fiber from the polymer during rotational molding, which consequently affect the mechanical and physical properties of the resulting composites. <p>Using triethoxyvinylsilane as chemical pre-treatment on flax fibers and linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) as polymer matrices, this study focused on the effects of flax fiber content (0%, 12.5% or 25%) and extrusion parameters such as barrel zone temperatures (75-110-120-130-140°C or 75-120-130-140-150°C) and screw speed (110 or 150 rpm) on the extrudate and composite properties (extrudate color, extrudate density, extrudate melt flow index, extrudate morphology, composite color, composite density, composite morphology, composite tensile strength and composite water absorption). <p>A mixture of chemically pre-treated flax fibers and powdered polyethylene matrices underwent extrusion compounding using a twin-screw extruder. The extrudates were then pelletized, ground, rotationally molded and cut into test specimens (composites). The mechanical and physical properties of both the extrudates and the composites from different treatments were then measured and compared. <p>Using multiple linear regression, models were generated to show quantitatively the significant effects of the process variables on the response variables. Finally, using response surface methodology and superposition surface methodology on the preceding data, the following optimum values for fiber content and extrusion parameters were determined: for LLDPE composites, fiber content = 6.25%, temperatures = 75-117.3-127.3-137.3-147.3°C, screw speed = 117.5 rpm; for HDPE composites, fiber content = 5.02%, temperatures = 75-118.1-128.1-138.1-148.1°C, screw speed = 125.56 rpm.

Flax fibers are often used as reinforcement for thermoset and thermoplastic to produce biocomposite products. These products exhibit numerous advantages such as good mechanical properties, low density, and biodegradability. Thermoplastics are usually reinforced with flax fiber using injection molding technology and limited research has been done on compression molded thermoplastic biocomposite. Therefore, commercial thermoplastic high density polyethylene (HDPE) and polypropylene (PP) were selected for developing compression molded flax reinforced biocomposites in this research project. The main goal of this research was to develop compression molded biocomposite board using Saskatchewan flax fiber and investigate the effect of flax fiber and processing parameters (molding temperature and molding pressure) on the properties of biocomposite. <p>The fiber was cleaned and chemically treated with alkaline and silane solution that modified the fiber surface. Chemical treatments significantly increased the mechanical properties due to better fiber-polymer interfacial adhesion and also reduced the water absorption characteristics. The silane treatment showed better results than alkaline treatment. Differential scanning calorimetry (DSC) test and scanning electron microscopy (SEM) test were performed to study the thermal and morphological properties of the untreated and chemically treated flax fiber. Flax fiber and thermoplastic resin was mixed using a single-screw extruder to ensure homogenous mixing. HDPE- and PP-based biocomposites were developed through compression molding with three different pretreated flax fiber (untreated, alkaline, silane treated fiber), three levels of fiber content, two levels of molding temperature and two levels of molding pressure. <p>Increase in fiber content increased composite color index, density, water absorption, tensile strength, Youngs modulus, bending strength, and flexural modulus. However for the HDPE composites, tensile and bending strength decreased after 20% flax fiber loading. For the PP composites the, tensile and bending strength decreased after 10% flax fiber loading. Analysis of variance (ANOVA) was performed to quantitatively show the significant effects of the process variables (molding temperature, pressure, and fiber content) and their interactions on the response variables (physical and mechanical properties of biocomposites). The duncan multiple range test (DMRT) was also performed to compare the treatment means. Superposition surface methodology was adapted for both HDPE and PP composites to determine the optimum values of process variables.

Canadian grown oilseed flax is known for its oils that are used for industrial products. The flax fiber may also have a use as a potential replacement for synthetic fibers as reinforcement in plastic composites. It can also be utilized as a cost effective and environmentally acceptable supplement in the biodegradable composites. Tire rubber is a complex material which does not decompose naturally. As a result, many researchers have been trying to develop new applications for recycling scrap tires. The conversion of flax straw and scrap tire into a profitable product may benefit the agricultural economy, tire recycling market, and our environment. The main goal of this research was to develop a biocomposite material containing recycled ground tire rubber (GTR), untreated flax fiber, and linear low-density polyethylene (LLDPE).<p> In this study, the new biocomposite material was successfully prepared from flax fiber/shives, GTR, and LLDPE through extrusion and compression molding processes. The composites were compounded through a single-screw extruder. Then the pelletized extrudates were hot pressed into the final biocomposites. The properties of the flax fiber-GTR-LLDPE biocomposites were defined by using tearing, tensile, water absorption, hardness, and differential scanning calorimetry (DSC) tests. The effects of the independent variables (flax fiber content and GTR-LLDPE ratio) on each of the dependent variables (tear strength from tearing test, tensile yield strength and Youngs modulus from tensile test, and weight increase from water absorption test) were modeled. The properties of the composites can be predicted by using the mathematical model with known flax fiber content and GTR-LLDPE ratio.<p> The tensile yield strength and stiffness of the biocomposite were improved with the addition of flax fiber. The optimal composition of the biocomposite material (with strongest tensile yield strength or highest Youngs modulus) was calculated by using the model equations. The maximum yield strength was found to exist for a flax fiber content of 10.7% in weight and GTR-LLDPE ratio of one. The largest Youngs modulus was found for a fiber content of 17.7% by weight and the same GTR-LLDPE ratio. Both of these fiber contents were less than the amount that would give a composite with a 2% weight increase in water absorption.

Extrusion compounding addresses such problems as the non-homogeneity of the mixture and separation of fiber from the polymer during rotational molding, which consequently affect the mechanical and physical properties of the resulting composites. <p>Using triethoxyvinylsilane as chemical pre-treatment on flax fibers and linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) as polymer matrices, this study focused on the effects of flax fiber content (0%, 12.5% or 25%) and extrusion parameters such as barrel zone temperatures (75-110-120-130-140°C or 75-120-130-140-150°C) and screw speed (110 or 150 rpm) on the extrudate and composite properties (extrudate color, extrudate density, extrudate melt flow index, extrudate morphology, composite color, composite density, composite morphology, composite tensile strength and composite water absorption). <p>A mixture of chemically pre-treated flax fibers and powdered polyethylene matrices underwent extrusion compounding using a twin-screw extruder. The extrudates were then pelletized, ground, rotationally molded and cut into test specimens (composites). The mechanical and physical properties of both the extrudates and the composites from different treatments were then measured and compared. <p>Using multiple linear regression, models were generated to show quantitatively the significant effects of the process variables on the response variables. Finally, using response surface methodology and superposition surface methodology on the preceding data, the following optimum values for fiber content and extrusion parameters were determined: for LLDPE composites, fiber content = 6.25%, temperatures = 75-117.3-127.3-137.3-147.3°C, screw speed = 117.5 rpm; for HDPE composites, fiber content = 5.02%, temperatures = 75-118.1-128.1-138.1-148.1°C, screw speed = 125.56 rpm.

Flax fibers are often used as reinforcement for thermoset and thermoplastic to produce biocomposite products. These products exhibit numerous advantages such as good mechanical properties, low density, and biodegradability. Thermoplastics are usually reinforced with flax fiber using injection molding technology and limited research has been done on compression molded thermoplastic biocomposite. Therefore, commercial thermoplastic high density polyethylene (HDPE) and polypropylene (PP) were selected for developing compression molded flax reinforced biocomposites in this research project. The main goal of this research was to develop compression molded biocomposite board using Saskatchewan flax fiber and investigate the effect of flax fiber and processing parameters (molding temperature and molding pressure) on the properties of biocomposite. <p>The fiber was cleaned and chemically treated with alkaline and silane solution that modified the fiber surface. Chemical treatments significantly increased the mechanical properties due to better fiber-polymer interfacial adhesion and also reduced the water absorption characteristics. The silane treatment showed better results than alkaline treatment. Differential scanning calorimetry (DSC) test and scanning electron microscopy (SEM) test were performed to study the thermal and morphological properties of the untreated and chemically treated flax fiber. Flax fiber and thermoplastic resin was mixed using a single-screw extruder to ensure homogenous mixing. HDPE- and PP-based biocomposites were developed through compression molding with three different pretreated flax fiber (untreated, alkaline, silane treated fiber), three levels of fiber content, two levels of molding temperature and two levels of molding pressure. <p>Increase in fiber content increased composite color index, density, water absorption, tensile strength, Youngs modulus, bending strength, and flexural modulus. However for the HDPE composites, tensile and bending strength decreased after 20% flax fiber loading. For the PP composites the, tensile and bending strength decreased after 10% flax fiber loading. Analysis of variance (ANOVA) was performed to quantitatively show the significant effects of the process variables (molding temperature, pressure, and fiber content) and their interactions on the response variables (physical and mechanical properties of biocomposites). The duncan multiple range test (DMRT) was also performed to compare the treatment means. Superposition surface methodology was adapted for both HDPE and PP composites to determine the optimum values of process variables.