The integration of multiple digitally driven processes is seen as the solution to many of the current limitations arising from standalone Additive Manufacturing (AM) techniques. A technique has been developed to digitally fabricate fully functioning electronics using a unique combination of AM technologies. This has been achieved by interleaving bottom-up Stereolithography (SL) with Direct Writing (DW) of conductor materials alongside mid-process development (optimising the substrate surface quality), dispensing of interconnects, component placement and thermal curing stages. The resulting process enables the low-temperature production of bespoke three-dimensional, fully packaged and assembled multi-layer embedded electronic circuitry. Two different Digital Light Processing (DLP) Stereolithography systems were developed applying different projection orientations to fabricate electronic substrates by selective photopolymerisation. The bottom up projection orientation produced higher quality more planar surfaces and demonstrated both a theoretical and practical feature resolution of 110 μm. A top down projection method was also developed however a uniform exposure of UV light and planar substrate surface of high quality could not be achieved. The most advantageous combination of three post processing techniques to optimise the substrate surface quality for subsequent conductor deposition was determined and defined as a mid-processing procedure. These techniques included ultrasonic agitation in solvent, thermal baking and additional ultraviolet exposure. SEM and surface analysis showed that a sequence including ultrasonic agitation in D-Limonene with additional UV exposure was optimal. DW of a silver conductive epoxy was used to print conductors on the photopolymer surface using a Musashi dispensing system that applies a pneumatic pressure to a loaded syringe mounted on a 3-axis print head and is controlled through CAD generated machine code. The dispensing behaviour of two isotropic conductive adhesives was characterised through three different nozzle sizes for the production of conductor traces as small as 170 μm wide and 40 μm high. Additionally, the high resolution dispensing of a viscous isotropic conductive adhesive (ICA) also led to a novel deposition approach for producing three dimensional, z-axis connections in the form of high freestanding pillars with an aspect ratio of 3.68 (height of 2mm and diameter of 550μm). Three conductive adhesive curing regimes were applied to printed samples to determine the effect of curing temperature and time on the resulting material resistivity. A temperature of 80 °C for 3 hours resulted in the lowest resistivity while displaying no substrate degradation. ii Compatibility with surface mount technology enabled components including resistors, capacitors and chip packages to be placed directly onto the silver adhesive contact pads before low-temperature thermal curing and embedding within additional layers of photopolymer. Packaging of components as small as 0603 surface mount devices (SMDs) was demonstrated via this process. After embedding of the circuitry in a thick layer of photopolymer using the bottom up Stereolithography apparatus, analysis of the adhesive strength at the boundary between the base substrate and embedding layer was conducted showing that loads up to 1500 N could be applied perpendicular to the embedding plane. A high degree of planarization was also found during evaluation of the embedding stage that resulted in an excellent surface finish on which to deposit subsequent layers. This complete procedure could be repeated numerous times to fabricate multilayer electronic devices. This hybrid process was also adapted to conduct flip-chip packaging of bare die with 195 μm wide bond pads. The SL/DW process combination was used to create conductive trenches in the substrate surface that were filled with isotropic conductive adhesive (ICA) to create conductive pathways. Additional experimentation with the dispensing parameters led to consistent 150 μm ICA bumps at a 457 μm pitch. A flip-chip bonding force of 0.08 N resulted in a contact resistance of 2.3 Ω at a standoff height of ~80 μm. Flip-chips with greater standoff heights of 160 μm were also successfully underfilled with liquid photopolymer using the SL embedding technique, while the same process on chips with 80 μm standoff height was unsuccessful. Finally the approaches were combined to fabricate single, double and triple layer circuit demonstrators; pyramid shaped electronic packages with internal multilayer electronics; fully packaged and underfilled flip-chip bare die and; a microfluidic device facilitating UV catalysis. This new paradigm in manufacturing supports rapid iterative product development and mass customisation of electronics for a specific application and, allows the generation of more dimensionally complex products with increased functionality.

abstract: This research work demonstrates the process feasibility of Ultrasonic Filament Modeling process as a metal additive manufacturing process. Additive manufacturing (or 3d printing) is the method to manufacture 3d objects layer by layer. Current direct or indirect metal additive manufacturing processes either require a high power heat source like a laser or an electron beam, or require some kind of a post processing operation to produce net-shape fully-dense 3D components. The novel process of Ultrasonic Filament Modeling uses ultrasonic energy to achieve voxel deformation and inter-layer and intra-layer mass transport between voxels causing metallurgical bonding between the voxels. This enables the process to build net-shape 3D components at room temperature and ambient conditions. Two parallel mechanisms, ultrasonic softening and enhanced mass transport due to ultrasonic irradiation enable the voxel shaping and bonding respectively. This work investigates ultrasonic softening and the mass transport across voxels. Microstructural changes in aluminium during the voxel shaping have also been investigated. The temperature evolution during the process has been analyzed and presented in this work. / Dissertation/Thesis / Masters Thesis Engineering 2016

No description available.

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

No description available.

No description available.

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)