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This thesis presents work on the deposition of nanothermite using a piezoelectric inkjet printer, focusing on the effects of printing parameters and sample geometry on burning rate. The ability of the printer to produce consistent droplet size and spacing was shown to have repeatable droplet size and sub-millimeter precision in droplet spacing. The droplet-droplet interaction of the nanothermite ink was examined, and a printing frequency of 10 Hz was shown to produce smooth and consistent geometry in the printed samples. The primary printing parameter varied in this study was the pixel pitch (i.e., the distance between printed droplets). As pixel pitch decreased (i.e., the droplets are printed closer together) in both directions (x- and y-directions), the burning rate increased, and as sample width increased the burning rate increased. A significant number of samples (476) were printed and demonstrated consistent, energetic performance; this indicated favorable high-volume production capabilities. A thermal model was developed based on an energy balance for the printed nanothermite samples. The model accurately predicted the burning rate trends observed in the experimental results. This result indicated that the increase in heat generation in both the thicker (pixel-pitch studies) and wider samples decreased the significance of heat loss to the environment. The statistically significant results presented in this work, along with a descriptive thermal model, increase the fundamental understanding of the effects of printed geometry and droplet spacing on nanothermite energetic performance.

The aim of this work is to characterize the microstructural and mechanical behaviors of Additive Manufactured (AM) Inconel 718 and investigate the feasibility of using this material to produce thermal management devices. This was done in two parts: a literature review of AM phenomena that effect heat transfer rates and impede or benefit production using these methods, and a study that characterized Laser Engineered Net Shaping (LENS) Inconel 718 while investigating and manipulating the thermal history. The literature review provides evidence that while there are still many unsolved issues, it’s quickly becoming possible to use AM to produce thermal management devices that will exceed current limitations. The study showed that although LENS Inconel 718 exhibits nonstandard material behaviors, evidence indicate that it’s possible to control these behaviors to influence desired results. Overall, it is believed that the use of AM in producing thermal management devices will be inevitable and beneficial.

This study proposes a nitinol-based thin-walled arch wedge support (AWS) and validated its performance in shock absorbing by using finite element analysis (FEA) method. Five human movements, two boundary conditions, and three thicknesses were implemented in FEA models to systematically reveal how those parameters and factors affect the response of the AWS. Due to the lack of data, the FEA models were meshed with elements of different sizes and used for simulations until the results converged. The simulation results showed that the thin-walled nitinol AWS with the selected thicknesses can withstand different human movements under both boundary conditions. In another word, the AWS will retain its original shape give the force conditions with no permanent deformation. Based on the initial numerical results, the AWS design can be further optimized before experimentation and testing. The potential of replacing the plastic AWS with additive manufactured nitinol AWS is verified from this study.

Inconel 718 is a nickel-based superalloy with a series of superior properties, such as high strength, creep-resistance, and corrosion-resistance. Additive manufacturing (AM) is appealing to Inconel 718 because of its near-net-shape production capability to circumvent poor machinability. However, AM parts are prone to detrimental porosity, reducing their fatigue resistance. Thus, further understanding of AM fatigue behavior is required before widespread industrial use. The microstructural and fatigue properties of heat treated AM Inconel 718, produced using Laser Engineered Net Shaping (LENSTM), are evaluated at room and elevated temperatures. Fully reversed, strain-controlled fatigue tests were performed on cylindrical specimens at strain amplitudes of 0.001 to 0.01 mm/mm. Fracture surfaces were inspected using a scanning electron microscope (SEM). Heat treatment caused initial dendritic microstructure to mostly reorm into an equiaxed grain structure. AM specimens experienced reduced fatigue life in testing as compared to wrought material due to inclusions or pores near the surface

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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.

Carbon Fiber Reinforced Polymer (CFRP) composites exhibit exceptional specific stiffness and strength properties. However, their use in structural applications is often constrained with high safety margins out of concern for their brittle and sudden failures. This study proposes manipulating the tensile failure mechanism by utilizing a discontinuous overlapped architecture, which has been demonstrated in the literature to non-linearize the tensile stress-strain response of CFRP laminates. Continuous Carbon fiber 3D-printing provides freedom in building complex morphologies and adjusting the resin content, enabling intricate discontinuous patterns for further tuning the stress-strain response. This study characterizes the constituents and tensile properties of 3D-printed continuous UD laminates. Then, an investigation is conducted on the mechanical tensile response of a 3D-printed discontinuous laminates design and the effect of discontinuity pattern length, and post-processing.