Yes / There is an increased evidence for treating hypertension by a combination of two or more drugs. Increasing the number of daily intake of tablets has been reported to negatively affect the compliance of patients. Therefore, numerous fixed dose combinations (FDCs) have been introduced to the market. However, the inherent rigid nature of FDCs does not allow the titration of the dose of each single component for an individual patient's needs. In this work, flexible dose combinations of two anti-hypertensive drugs in a single bilayer tablet with a range of doses were fabricated using dual fused deposition modelling (FDM) 3D printer. Enalapril maleate (EM) and hydrochlorothiazide (HCT) loaded filaments were produced via hot-melt extrusion (HME). Computer software was utilised to design sets of oval bi-layer tablets of individualised doses. Thermal analysis and x-ray diffractometer (XRD) indicated that HCT remained crystalline in the polymeric matrix whilst EM appeared to be in an amorphous form. The interaction between anionic EM and cationic methacrylate polymer may have contributed to a drop in the glass transition temperature (Tg) of the filament and obviated the need for a plasticiser. Across all tablet sets, the methacrylate polymeric matrix provided immediate drug release profiles. This dynamic dosing system maintained the advantages of FDCs while providing a superior flexibility of dosing range, hence offering an optimal clinical solution to hypertension therapy in a patient-centric healthcare service.

Filament-based material extrusion additive manufacturing (MEAM) is an established technique in additive manufacturing (AM). However, semicrystalline polymers, such as polypropylene (PP), have limited commercial use in MEAM processes in the past due to their rapid crystallization kinetics and the subsequent effect on the integrity of the generated structures. The rapid crystallization of PP can be controlled by formulating blends of PP with hydrocarbon resins to enable longer re-entanglement times for interlayer adhesion. While the topic of formulating PP blends/composites with other materials to improve the printability has been investigated, variation in properties of commercial PP grades, of similar molecular weight (MW) and molecular weight distribution (MWD), on printability is still to be investigated. Those commercial PP grades can have wide variation in properties such as Melt Flow Index (MFI), additive content, and polymer architecture which can impact material properties relevant to printability. To investigate the effect of properties of commercial PP on their printability and mechanical performance, different commercial PP grades, with different properties, are blended with a fixed loading of hydrogenated resins, and the consequent effects on the mechanical properties of MEAM generated PP structures are studied via mechanical analysis. Tensile strength and the extent of interlayer adhesion in the 3D printed blends are characterized through rheological measurements. These measurements emphasize the importance of the relative location of the storage/loss modulus crossover point via small oscillatory frequency sweeps. We specifically show that a relatively higher crossover frequency will correlate with improved interlayer adhesion and reduced warpage in printed structures. However, this improvement is accompanied by a tradeoff, resulting in inferior tensile strength and an increased degree of print orientation anisotropy. / Master of Science / Additive Manufacturing (AM), commonly known as 3D printing, is a transformative technology with high potential to revolutionize the manufacturing landscape. Polymers are widely used in AM for various applications. As a result, extensive research is conducted to enhance the printability and properties of printed polymer structures. Polypropylene (PP) exhibits desirable mechanical, optical, and chemical properties that make its use in AM attractive. Despite this potential, optimizing the use of PP in 3D printing remains challenging. Consequently, extensive research is underway to improve the printability of PP. However, the effects of including additives to enhance the properties of commercial PP grades are often overlooked. We demonstrate that the choice of commercial PP grade is crucial to the mechanical and structural properties of structures generated via AM. This was established by developing a systematic experimental procedure to assess the printability of various PP grades and to measure their key mechanical and structural properties.

Yes / This paper presents an improved mathematical model for calculation of distortion vectors of two aligned surface meshes. The model shows better accuracy when benchmarked to an existing model with exceptional mathematical conditions, such as sharp corners and small radii. The model was implemented into a developed distortion compensation digital tool and applied to an industrial component. The component was made of Inconel 718 and produced by laser powder bed fusion 3D printing technology. The digital tool was utilised to compensate the original design geometry by pre-distortion of its original geometry using the developed mathematical model. The distortion of an industrial component was reduced from approximately ±400 µm to ±100 µm for a challenging thin structure subjected to buckling during the build process.

Additive manufacturing (AM) is used to create geometries otherwise impossible to machine. Topology optimization, microstructural texture control, and the use of lattices could be created through AM to increase performance of systems. Currently research focuses on solution aging of printed 17-4 PH, while other heat treatments are not as heavily studied. This study identifies different heat treatments applied to additively manufactured 17-4 precipitation hardened (PH) and the effects on mechanical properties. This study used quasi-static tension, quasi-static compression, and Charpy V-notch testing to analyze the effects of heat treatment as well as the effectiveness of additive manufacturing compared to traditional machining for wrought materials. Data during testing was taken with digital image correlation to identify changes in local strain. The effectiveness of heat treatment was demonstrated in this study and can be used to estimate performance on additively produced 17-4 PH.

Cyber physical systems (CPS) are an integration of computational and physical processes, where the cyber components monitor and control physical processes. Cyber-attacks largely target the cyber components with the intention of disrupting the functionality of the components in the physical domain. This dissertation explores the role of semantic inference in understanding such attacks and building resilient CPS systems. To that end, we present SIMON, an ontological design and verification framework that captures the intricate relationship(s) between cyber and physical components in CPS by leveraging several standard ontologies and extending the NIST CPS framework for the purpose of eliciting trustworthy requirements, assigning responsibilities and roles to CPS functionalities, and validating that the trustworthy requirements are met by the designed system. We demonstrate the capabilities of SIMON using two case studies – a vehicle to infrastructure (V2I) safety application and an additive manufacturing (AM) printer. In addition, we also present a taxonomy to capture threat feeds specific to the AM domain.

The purpose of this dissertation is to explore an entrepreneurial framework that this dissertation calls A First Principles Approach to Product Development in Entrepreneurship. The goal is to improve safety for bicycle riders. This research project identifies, applies, and assesses product development methodologies in a way that is grounded in qualitative research. The framework that encompasses those methodologies was created to bridge the gaps between entrepreneurship, engineering design, and industrial design, where the framework was specifically applied to bicycle helmets and examined as a case study. The framework is intended for entrepreneurs, product developers, and researchers who are developing physical, capital-intensive products, where the key stakeholder who is describing a problem is also close to the purchasing decision. Parts of this dissertation describe a framework that is generalizable to other startups and other parts of this dissertation are specific to developing bike helmets. Failure rates in entrepreneurship can often be between 30 to 75%. In addition, there are examples in motorcycling, football, and bicycling where companies are only designing and developing personal protective equipment (PPE) to the industry standard with little or no consideration for other relevant injury biomechanics. In response, this dissertation explores a series of product development methodologies, in a manner that is grounded in qualitative research, with the goal of improving safety for the rider and reducing the risk of failure for launching a new venture. The first principles approach described in this dissertation begins with Customer Discovery which is a process of conducting interviews with key stakeholders, in order to challenge and support evolving hypothesis about a potential new venture. The process begins with deconstructing an initial idea into product, market, and customer risk hypotheses. Next, a process for creating and organizing questions, conducting problem interviews, and pivoting is described. During the problem interviews I found a Severe Problem of bicycle helmet fit for US Bike Parents. Then, I examined other aspects for identifying if an opportunity is worth pursuing, namely finding a gap in the marketplace, and observing industry trends. After conducting the problem interviews, I developed and conducted brainstorming sessions with participants who experienced the Severe Problem. The goal for conducting the brainstorming sessions was to dislodge entrenched product ideas, explore the solution landscape, and find a solution that solved the problem the best and was the best opportunity for commercialization. For this dissertation I determined that a custom fit, 3D printed bicycle helmet was an appropriate solution. Next, I developed and conducted solution interviews to determine if the solution solved the participants problem, identify additional product features, and explore various pricing strategies. Once a product brief was created, the next step was product development. Product development can have many variables which can affect how a new venture team should approach development. For this dissertation initial product development began with designing (ideating), printing (prototyping), and impact testing (testing) 3D printed mesostructures. However, during development the strategy was adjusted in response to production issues (iterating). Now that some initial product development was underway, the next step for a first principles approach includes a critical reflection on different aspects of the new venture. A critical reflection can include a feasibility analysis, which is a formative assessment of the potential new venture, an assessment of Customer Discovery, and the application of the Abstraction Ladder to evaluate the problem driving product development. For this dissertation, a critical reflection also included an evaluation of other product development methodologies, as well as continued application of the Abstraction Ladder to direct the critical evaluation of other foundational elements that relate to bicycle helmets and safety. / Doctor of Philosophy / Startups can and do fail. For an entrepreneur, product developer, or researcher with a physical and capital-intensive product idea, this dissertation can serve as a resource to bridge the gaps between business, engineering, and design and reduce the risk of failure when trying to create a startup. The process described in this dissertation describes how to evaluate the key elements of an idea and conduct a series of interviews with potential customers to find evidence that supports pursing that idea further, challenge the startup team to change some aspect of the idea, or drop it altogether. Once the startup team has found a problem, as well as a solution to that problem, this dissertation describes an approach creating that solution. Then this dissertation describes an approach for critically evaluating the foundational elements of the problem and the solution. The goal for a critical evaluation is to identify additional foundational elements which relate to the product that may increase its value or decrease the risk of product failure.

The results from this study, on a few commercial and model metastable beta titanium alloys, indicate that the growth restriction factor (GRF) model fails to interpret the grain growth behavior in the additively manufactured alloys. In lieu of this, an approach based on the classical nucleation theory of solidification incorporating the freezing range has been proposed for the first time to rationalize the experimental observations. Beta titanium alloys with a larger solidification range (liquidus minus solidus temperature) exhibited a more equiaxed grain morphology, while those with smaller solidification ranges exhibited columnar grains. Subsequently, the printability of two candidate beta titanium alloys containing eutectoid elements (Fe) that are prone to beta fleck in conventional casting, i.e., Ti-1Al-8V-5Fe (wt%) or Ti-185, and Ti-10V-2Fe-3Al (wt%) or Ti-10-2-3, is further investigated via two different AM processing routes. These alloys are used for high-strength applications in the aerospace industry,

The presented research explores the Wire-Laser Direct Energy Deposition of Fe17Co alloy for soft magnetic applications. Process parameters starting from power, feed speed, and feed/scan ratios were optimized where a high confidence multi-factor regression model was developed correlating the processing parameters to final bead dimensions. The model showed that increasing feed speeds led to an increase in bead height and a reduction in bead width while increasing feed/scan ratio resulted in an increase of bead height and width. Interlayer cooling time for multi-layer deposition was tested and revealed, through thermal camera measurement, that increasing interlayer cooling time leads to a higher cooling rate, and generally more stable printing process. Printed samples showed single phase BCC with fine equiaxed structure and high density (>98.5%) with no pores or cracks. ASTM A773 sample rings were printed and showed that for decreasing input energy (by decreasing power or increasing feed speed) leads to a finer grain structure. The average diameter grain size of the printed samples was 18.7 microns and grew to an average of 26.5 microns after a pre-anneal heat treatment at 700°C for 2 hours followed by 850°C for 10 hours. Furthermore, using interlayer cooling time, the thermal gradient of the samples throughout the printing was increased and lead to even finer grain structure. However, this lead to increased grain growth post annealing. Printed samples showed good magnetic properties, but slightly less than that of the commercial wrought material. / Master of Science / This research looks at the 3D printing of a cobalt-iron alloy for magnetic applications. This alloy is particularly interesting for Aerospace applications given its unique properties for high magnetic performance and ability to withstand high temperatures. Printing settings were adjusted to get the best results and the final samples were very dense without any holes or cracks, which is a common problem in 3D printing of metals in general. The printed samples had a uniform crystal structure and good magnetic properties, though a bit less than what the traditionally processed material is. Decreasing the energy or increasing printing cooling time made the grains in the material smaller. All the printed samples were sized in average 18.7 microns and grew to an average of 26.5 post heat treatment of a pre-anneal heat treatment at 700°C for 2 hours followed by 850°C for 10 hours. The heat treatment improved the material magnetic properties, but they were still not in-par with normally processed material.

<p>Polymer nanocomposites are a constantly evolving material category due to the ability to engineer the mechanical, thermal, and optical properties to enhance the efficiency of a variety of systems. While a vast amount of research has focused on the physical phenomena of nanoparticles and their contribution to the improvement of such properties, the ability to implement these materials into existing commercial or newly emerging processing methods has been studied much less extensively. The primary characteristic that determines which processing technique is the most viable is the rheology or viscosity of the material. In this work, we investigate the processing methods and properties of nanocomposites for thermal interface and radiative cooling applications. The first polymer nanocomposite examined here is a two-component PDMS with graphene filler for 3D printing via a direct ink writing approach. The composite acts as a thermal interface material which can enhance cooling between a microprocessor and a heat sink by increasing the thermal conductivity of the gap. Direct ink writing requires a shear thinning ink with specific viscoelastic properties that allow for the material to yield through a nozzle as well as retain its shape without a mold following deposition. No predictive models of viscosity for nanocomposites exist; therefore, several prominent models from literature are fit with experimental data to describe the change in viscosity with the addition of filler for several different PDMS ratios. The result is an understanding of the relationship between the PDMS component ratio and graphene filler concentration with respect to viscosity, with the goal of remaining within the acceptable limits for printing via direct ink writing. The second nanocomposite system whose processability is determined is paint consisting of acrylic filled with reflective nanoparticles for radiative cooling paint applications. The paint is tested with both inkjet and screen-printing procedures with the goal of producing a thermally invisible ink. Radiative cooling paint is successfully printed for the first time with solvent modification. This work evaluates the processability of polymer nanocomposites through rheological tailoring. </p><br>

Electroactive polymers are a class of materials capable of reallocating their shape in response to an electric field while also having the ability to harvest electrical energy when the materials are mechanically deformed. Electroactive polymers can therefore be used as sensors, actuators, and energy harvesters. The parameters for manufacturing flexible electroactive polymers are complex and rate limiting due to number of steps, their necessity, and time intensity of each step. Successful additive manufacturing processes for electroactive polymers will allow for scalability and flexibility beyond current limitations, advancing the field, opening additional manufacturing possibilities, and increasing output. The goal for this research was to use additive manufacturing techniques to print conductive and dielectric substrates for building flexible circuits and sensors. Printing flexible conductive layers and substrates together allows for added creativity in design and application.