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.

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>

Globally distributed additive manufacturing is a relatively new frontier in the field of product lifecycle management. Designers are independent of additive manufacturing services, often thousands of miles apart. Manufacturing data must be transmitted electronically from designer to manufacturer to realize the benefits of such a system. Unalterable blockchain legers can record transactions between customers, designers, and manufacturers allowing each to trust the other two without needing to be familiar with each other. Although trust can be established, malicious printers or customers still have the incentive to produce unauthorized or pirated parts. To prevent this, machine instructions are encrypted and electronically transmitted to the printing service, where an authorized printer decrypts the data and prints an approved number of parts or products. The encrypted data may include G-Code machine instructions which contain every motion of every motor on a 3D printer. Once these instructions are decrypted, motor drivers send control signals along wires to the printer's stepper motors. The transmission along these wires is no longer encrypted. If the signals along the wires are read, the motion of the motor can be analyzed, and G-Code can be reverse engineered. This thesis demonstrates such a threat through a simulated attack on a G-Code controlled device. A computer running a numeric controller and G-Code interpreter is connected to standard stepper motors. As G-Code commands are delivered, the magnetic field generated by the transmitted signals is read by a Hall Effect sensor. The rapid oscillation of the magnetic field corresponds to the stepper motor control signals which rhythmically move the motor. The oscillating signals are recorded by a high speed analog to digital converter attached to a second computer. The two systems are completely electronically isolated. The recorded signals are saved as a string of voltage data with a matching time stamp. The voltage data is processed through a Matlab script which analyzes the direction the motor spins and the number of steps the motor takes. With these two pieces of data, the G-Code instructions which produced the motion can be recreated. The demonstration shows the exposure of previously encrypted data, allowing for the unauthorized production of parts, revealing a security flaw in a distributed additive manufacturing environment. / Master of Science / Developed at the end of the 20th century, additive manufacturing, sometimes known as 3D printing, is a relatively new method for the production of physical products. Typically, these have been limited to plastics and a small number of metals. Recently, advances in additive manufacturing technology have allowed an increasing number of industrial and consumer products to be produced on demand. A worldwide industry of additive manufacturing has opened up where product designers and 3D printer operators can work together to deliver products to customers faster and more efficiently. Designers and printers may be on opposite sides of the world, but a customer can go to a local printer and order a part designed by an engineer thousands of miles away. The customer receives a part in as little time as it takes to physically produce the object. To achieve this, the printer needs manufacturing information such as object dimensions, material parameters, and machine settings from the designer. The designer risks unauthorized use and the loss of intellectual property if the manufacturing information is exposed. Legal protections on intellectual property only go so far, especially across borders. Technical solutions can help protect valuable IP. In such an industry, essential data may be digitally encrypted for secure transmission around the world. This information may only be read by authorized printers and printing services and is never saved or read by an outside person or computer. The control computers which read the data also control the physical operation of the printer. Most commonly, electric motors are used to move the machine to produce the physical object. These are most often stepper motors which are connected by wires to the controlling computers and move in a predictable rhythmic fashion. The signals transmitted through the wires generate a magnetic field, which can be detected and recorded. The pattern of the magnetic field matches the steps of the motors. Each step can be counted, and the path of the motors can be precisely traced. The path reveals the shape of the object and the encrypted manufacturing instructions used by the printer. This thesis demonstrates the tracking of motors and creation of encrypted machine code in a simulated 3D printing environment, revealing a potential security flaw in a distributed manufacturing system.