Soft electronics have become increasingly necessary for the implementation and integration of novel technologies in a variety of environments including aerospace, robotics, and healthcare. In order to develop these soft electronic devices, materials and manufacturing strategies are required for these soft, stretchable, and flexible systems. Further, the ability to effectively tune not only these mechanical properties but also their thermal and electrical properties is key to developing multifunctional materials for soft electronic applications. In this thesis, we present a method of printing highly tunable flexible and stretchable composites consisting of elastomers with liquid metal (LM) inclusions. We analyze the mechanical and functional behaviors and highlight the anisotropic properties that can be created via our printing system, and we apply this understanding to the development of a multiphase material with a programmable crack propagation path. Throughout this work we describe the process by which we use Direct Ink Write (DIW) technology, a type of additive manufacturing, to print 2D and 3D LM composites with tunable properties. The design map used to control LM microstructure in-situ is first outlined in Chapter 2. This tuning ability is used to print materials with varied LM microstructures and study the impact on mechanical, thermal, and electrical properties (Chapter 2, Chapter 3). We further study the elongated LM droplet inclusions for how their orientation with respect to loading may impact mechanical properties (Chapter 3). We further utilize these findings to control crack propagation along a specified path using only variations in printing parameters (Chapter 3). We provide concluding statements and outlooks on future work in Chapter 4. We then summarize our findings and detail the implications for the soft electronics field (Chapter 5). / Master of Science / Soft electronics have become increasingly necessary for the successful implementation and integration of novel technologies in a variety of environments including the spaces of aerospace, robotics, and healthcare. In order to develop these soft electronic devices, a new class of materials with soft, stretchable, and flexible properties is critical. Further, the ability to effectively tune not only these mechanical properties but also their thermal and electrical properties is key to developing high-functioning materials for soft electronic applications. In this thesis, we present a method of printing highly tunable flexible and stretchable materials with liquid metal (LM), known as liquid metal embedded elastomers (LMEEs). We analyze the mechanical properties and their direction-dependent nature that can be tuned via our printing system, and we apply this understanding to the development of a 2D material with a programmable path along which the material will tear. Throughout this work we describe the process by which we use Direct Ink Write (DIW) technology, a type of additive manufacturing, to print 2D and 3D LMEE structures with tunable properties. The design map used to control the LM microstructure in-situ is first outlined in Chapter 2. This tuning ability is used to print materials with varied LM microstructures and study the impact on mechanical, thermal, and electrical properties (Chapter 2, Chapter 3). We further study the elongated LM droplet inclusions for how their orientation with respect to loading may impact mechanical failure (Chapter 3). We further utilize these findings to control crack propagation along a specified path using only variations in printing parameters (Chapter 3). We provide concluding statements and outlooks on future work in Chapter 4. We then summarize our findings and detail the implications for the soft electronics field (Chapter 5)

With the increase in popularity of virtual reality (VR) systems, haptic devices have been garnering interest as means of augmenting users' immersion and experiences in VR. Unfortunately, most commercial gloves available on the market are targeted towards enterprise and research, and are too expensive to be accessible to the average consumer for entertainment. Some efforts have been made by gaming and do-it-yourself (DIY) enthusiasts to develop cheap, accessible haptic gloves, but due to cost limitations, the designs are often simple and only provide feedback at the fingertips. Considering the many types of grasps used by humans to interact with objects, it is evident that haptic gloves must offer feedback to many regions of the hand, such as the palm and lengths of the fingers to provide more realistic feedback. This thesis discusses a novel, affordable design that provides haptic feedback to the intermediate and proximal phalanges of the fingers (index, middle, ring and pinkie) using a ratchet and pawl actuation mechanism. / Master of Science / Haptics, or simulation of the sense of touch, is already implemented in consumer devices such as smartphones and gaming controllers to augment users' immersive experiences. With the growing popularity of virtual reality, further advancements are being made, particularly in wearable haptic gloves, so users may physically feel the interactions with objects in virtual reality through their hands. Unfortunately, these products are currently inaccessible to the average consumer due to unaffordable pricing. To combat this issue, there have been efforts to develop cheap haptic gloves, but existing designs only provide feedback at the fingertips. Fingertip-only feedback can feel unnatural to users since other areas of the hand are typically also involved when grasping objects. To address the issue presented by low-cost fingertip haptic gloves, this thesis proposes a design which expands feedback to other areas of the hand while maintaining affordability and accessibility to average consumers.

The field of implantology is centred around interfacial interactions with the surrounding bone tissue. Assessing the suitability of novel engineering materials as implants for clinical application follows a preliminary workflow that can be simplified into three main stages: (i) implant design, (ii) in vitro compatibility, and (iii) in vivo compatibility. This thesis is subdivided to mirror each of these three themes, with a specific focus on the multiscale features of the implant itself as well as appositional bone tissue. In Chapter 3, a biomimetic approach to generate porous metallic implants is presented, using preferential seeding in a 3D Voronoi tessellation to create struts within a porous scaffold that mirror the trabecular orientation in human bone tissue. In Chapter 4, cytocompatible succinate-alginate films are generated to promote the in vitro activity of osteoblast-like cells and endothelial cells using a methodology that could be replicated to coat the interior and exterior of porous metals. In Chapter 5, two types of porous implants with graded and uniform pore size are implanted into rabbit tibiae to characterize the biological process of osseointegration into porous scaffolds. In Chapter 6, these same scaffolds are probed with high-resolution 2D and 3D methods using scanning transmission electron microscopy (STEM) and the first-ever application of plasma focused ion beam (PFIB) serial sectioning to observe structural motifs in biomineralization at the implant interface in 3D. This thesis provides new knowledge, synthesis techniques, and development of characterization tools for bone-interfacing implants, specifically including a means to: (i) provide novel biomaterial design strategies for additive manufacturing; (ii) synthesize coatings that are compatible with additively manufactured surfaces; (iii) improve our understanding of mineralization process in newly formed bone, with the ultimate goal of improving the osseointegration of implants. / Thesis / Doctor of Philosophy (PhD) / Metallic implants are widely used in dental and orthopedic applications but can be prone to failure or incomplete integration with bone tissue due to a breakdown at the bone-implant interface as defined by clinical standards. In order to improve the ability of the implant to anchor itself into the surrounding bone tissue, it is possible to use novel three-dimensional (3D) printing approaches to produce porous metals with an increased area for direct bone-implant contact. This thesis examines strategies to design porous implants that better mimic the structure of human bone, possible coating materials to accelerate early bone growth at the implant interface, and the microscale-to-nanoscale origins of bone formation within the interior of porous materials.

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Additive Manufacturing (AM) provides a unique opportunity for fabrication of personalized medicine, where each oral dosage could be tailored to satisfy specific needs of each individual patient. Binder jetting, an easily scalable AM technique that is capable of processing the powdered raw material used by tablet manufacturers, is an attractive means for producing individualized pharmaceutical tablets. However, due to the low density of the printed specimens and incompatible binder-powder combination, tablets fabricated by this AM technology suffer from poor strength. The research is introducing an additional composition in the binder jetting powder bed (e.g., powdered sugar) could significantly enhance the compressive strength of the as-fabricated tablets, as compared with those tablets fabricated without the additional powder binding agent. However, no previous research demonstrated comprehensive approaches to enhance the poor performance of the 3D printed tablets. Therefore, the goal of this work is to identify processing techniques for improving the strength of binder jetted tablets, including the use of (i) novel jettable polymeric binders (e.g., 4-arm star polyvinylpyrrolidone (PVP), DI water, and different i) weight percentage of sorbitol binder) and (ii) introducing an additional powder binding agent into the powder bed (e.g.., different wt% of powdered sugar). / M.S. / Three-dimensional printing is well-known as 3D printing. 3D printing pills are printed from the 3D printer. As of today, we now stand on the brink of a fourth industrial revolution. By the remarkable technological advancements of the twenty-first century, manufacturing is now becoming digitized. Instead of using a large batch process as traditional, customized printlets with a tailored dose, shape, size, and release characteristics could be produced on- demand. The goal of developing pharmaceutical printing is to reduce the cost of labor, shorten the time of manufacturing, and tailor the pills for patients. And have the potential to cause a paradigm shift in medicine design, manufacture, and use. This paper aims to discuss the current and future potential applications of 3D printing in healthcare and, ultimately, the power of 3D printing in pharmaceuticals.

Multifunctional composites have gained significant interest as they enable the integration of sensing and communication capabilities into structural, lightweight composites. Researchers have explored additive manufacturing processes for creating these structures through selective patterning of electrically conductive materials onto composites. Thus far, multifunctional composite performance has been limited by the conductivity of functional materials used, and the methods of integration have resulted in compromises to both structural and functional performance. Integration methods have also imposed limitations on part geometry due to an inability to adequately deposit conductive material over concave surfaces. Proposed methods of integrating functional devices within composites have been shown to negatively affect their mechanical performance. This work presents a novel method for integrating printed electronics onto the interior surfaces of closed, complex continuous fiber composite structures via the transfer of selectively printed conductive inks from additively manufactured sacrificial tooling to the composite surface. The process is demonstrated by creating multifunctional composites via embossing printed electronics onto structural composites without negatively affecting the mechanical performance of the structure. Additionally, this process expands the ability to pattern devices onto complex surfaces and demonstrates that the transferred functionality is well integrated (adhered) with the composite surface. The process is further validated through the successful completion of two separate case studies. The first is the integration of a functioning strain gauge onto an S-glass/epoxy composite, while a second process demonstration shows a composite surface featuring a band stop filter at the X-band, otherwise known as a frequency selective surface (FSS), to show the process' suitability for high performance, aerospace grade multifunctional composites. / Master of Science / Significant interest has been given in the past few decades to strong, lightweight materials for structural purposes. Among these materials, specific interest has been paid to fiber-reinforced composites, which are made of strong fibers and advanced resins. Recently, researchers have tried to use electrically conductive inks and 3D printing techniques to put antennas and other devices onto composites. These composites could possess additional functions beyond their structural purpose and are therefore called multifunctional composites. So far, the performance of multifunctional composites has been limited by the methods used to add additional functions. These methods often result in a weaker composite material and poor performance of the added devices. In this work, a new method for integrating devices onto complex-shaped composite structures is demonstrated. This is done by printing a mold for a composite, then putting a conductive ink onto the mold and transferring the ink to the composite surface. This process is demonstrated without weakening the composite. Additionally, this process allows researchers to put devices onto complex surfaces and demonstrates that the devices are secured to the composite surface. The process is used to make two separate devices and combine them with a composites surface. The first demonstration is the integration of a functioning strain gauge (used to measure a change in material dimension) onto a structural composite, while a second process demonstration shows a composite surface featuring an electromagnetic filter, otherwise known as a frequency selective surface (FSS), to show the process' suitability for high performance, aerospace grade multifunctional composites.

In an effort to save weight, transportation and aerospace industries have increasing investigated magnesium alloys because of their high strength-to-weight ratio. Further efforts to save on material use and machining time have focused on the use of additive manufacturing. However, anisotropic properties can be caused by both the HCP structure of magnesium alloys as well as by layered effects left by typical additive manufacturing processes. Additive Friction Stir (AFS) is a relatively new additive manufacturing technology that yields wrought microstructure with isotropic properties. In this study, Additive Friction Stir (AFS) fabrication was used to fabricate WE43 magnesium alloy, with both atomized powder and rolled plate as filler material, into multilayered structures. It was found that the WE43 alloy made by AFS exhibited nearly isotropic tensile properties. With aging these properties exceeded the base material in the T5 condition. The toughness measured by Charpy impact testing also showed an increase over the base material. The relationships among tensile properties, Vickers microhardness, impact toughness, microstructure and thermal history are developed and discussed. / Master of Science

<p dir="ltr">Printed Circuit Boards have become a vital component in the connected world in which we live in today. They can be found in all electronic devices, but their shape and function has been limited by the manufacturing capabilities of PCBs. The methods for manufacturing PCBs are well researched and optimized but have pitfalls as they are only capable of producing two dimensional, planar devices. As the demand for more integrated circuitry and electronics in devices like wearable technologies increases so will the need for a more flexible method for producing PCBs.</p><p dir="ltr">The purpose of this study was to create and analyze a method of creating PCBs using multi-material 3D printing and an electroplating process. The analysis includes an experimental procedure that will conclude whether the specimens created can conduct electricity at the same level of traditionally manufactured PCBs. This research proposed a procedure for manufacturing the PCBs and a testing apparatus designed to inject current at a specified level into the specimens so that the voltage could be measured. This allowed for the resistance of the specimens to be calculated and compared to known values for common materials used in PCB manufacturing.</p><p><br></p>