In recent years, there has been a significant amount of research into cellulose nanocrystals (CNCs). These materials are categorized as being between 5 and 10 nm wide and being 100-250 nm long. CNCs have several uses, but the most common is the reinforcement of polymer composites. Here I present 2 papers investigating CNC-based composites. By using standard bleaching procedures, pure cellulose was isolated from pistachio shells. Sulfuric acid was used to isolate cellulose nanocrystals from the purified cellulose. The obtained crystals were investigated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The CNCs were also added to thermoplastic polyurethane (TPU) to observe the reinforcement effects by dynamic mechanical analysis. Pistachio shells offered a high yield source material for CNCs, with a high aspect ratio but a low crystallinity. They did offer significant reinforcement of the TPU, but less than the commercially available wood-based CNCs. Wood-based CNCs were also mixed with TPU in structured composites to create a film which actuates when exposed to water. The method of actuation is based on the different amounts of absorption of water in the composite as opposed to the pure TPU. The actuation was modeled based on the absorption of water and the modulus of two components. Mechanical properties of the CNC/TPU composites were evaluated via dynamic mechanical analysis, and water absorption was measured gravimetricaly. The tests helped us to evaluate our model which we compared to the composites. / Master of Science / Composites are a category of materials where two or more materials are used together to enhance each of their strengths. Such materials are often used in airplanes, spacecraft, sporting equipment, and many high-end products. Cellulose nanocrystals (CNCs) have been research with the goal of improving the environmental sustainability and performance of composite materials. This newly utilized material is found in plants and some animals to provide them with their strength. Researches have already shown that CNCs can improve the performance of many materials while reducing their lifetime environmental impact. In order to increase the market for CNCs, we are looking at costreducing methods of producing them as well as finding exciting new uses for them once they are made. Right now, most CNCs are isolated from wood or cotton, which already have existing markets. This thesis presents a method of using pistachio shells, which are a waste product in many parts of the world including the United States. By finding new sources of CNCs, we hope to add to the body of knowledge and reduce the price of CNC production. This thesis also lays the groundwork for a material that changes shape when exposed to water. By integrating CNCs into only part of a polymer, when water is added, the part with the CNCs will increase in size, causing it to push on the polymer. Our hope is to create a new use for CNC composites to help to increase the market for them. We discuss potential methods and proofs of concept on how to create a 3D-printed part using CNCs and polyurethane.

This master's thesis deals with the challenges of undesirable thermal expansion in lightweight materials. Thermal expansion of parts or components can lead to malfunction or breakdowns of complete systems in demanding environment where a large temperature gradient often exists. This work investigates a class of lightweight materials of which the thermal expansion coefficient can be controlled. Moreover, an additive manufacturing approach to produce these thermal management materials with high fidelity and reliability are critical to reach this goal. To achieve these two major research objectives analytic predictions, simulations, and measurement of thermal expansion coefficient with respect to temperature changes are conducted. Design and optimization of a high precision multi-material manufacturing apparatus has been conducted, leading to significant increase in production quality including reliability, efficiency, and costs. / Master of Science

The overall goal of this work is to expand the materials library for the fused filament fabrication (FFF) material extrusion additive manufacturing (AM) process through innovations in the FFF process, post-process, and polymer composition. This research was conducted at two opposing ends of the FFF-processing temperature: low processing temperature (<100 °C) for pharmaceutical applications and high processing temperatures (>300 °C) for high-performance structural polymer applications. Both applications lie outside the typical range for FFF (190-260 °C). To achieve these goals, both the material and process were modified. Due to the low processing temperature requirements for pharmaceutical active ingredients, a water-soluble, low melting temperature material (sulfonated poly(ethylene glycol)) series was used to explore how different counterions affect FFF processing. The strong ionic interaction within poly(PEG8k-co-CaSIP) resulted in the best print quality due to the higher viscosity (105 Pa∙s) allowing the material to hold shape in the melt and the high-nucleation producing small spherulites mitigating the layer warping. Fillers were then explored to observe if an ionic filler would produce a similar effect. The ionic filler (calcium chloride) in poly(PEG8k-co-NaSIP) altered the crystallization kinetics, by increasing the nucleation density and viscosity, resulting in improved printability of the semi-crystalline polymer. A methodology for embedding liquids and powders into thin-walled capsules was developed for the incorporation of low-temperature active ingredients into water-soluble materials that uses a higher processing temperature than the actives are compatible with. By tuning the thickness of the printed walls, the time of internal liquid release was controlled during dissolution. This technique was used to enable the release of multiple liquids and powders at different times during dissolution. To enable the printing of high-temperature, high-performance polymers, an inverted desktop-scale heated chamber with the capability of reaching over 300 °C was developed for FFF. The design was integrated onto a FFF machine and was used to successfully print polyphenylsulfone which resulted in a 48% increase in tensile strength (at 200 °C) when compared to printing at room temperature. Finally, the effects of thermal processing conditions for printing ULTEM® 1010 were studied by independently varying the i) nozzle temperature, ii) environment temperature, and iii) post-processing conditions. The nozzle temperature primarily enables flow through the nozzle and needs to be set to at least 360 °C to prevent under extrusion. The environment temperature limits the part warping, as it approaches Tg (217 °C), and improves the layer bonding by decreasing the rate of cooling that allows more time for polymer chain entanglement. Post-processing for a longer time above Tg (18 hrs at 260 °C) promotes further entanglement, which increases the part strength (50% increase in yield strength); however, the part is susceptible to deformation. A post-processing technique was developed to preserve the parts' shape by packing solid parts into powdered salt. / Doctor of Philosophy / Fused filament fabrication (FFF) is the most widely used additive manufacturing (also referred to as 3D printing) process in industry, education, and for hobbyists. However, there is a limited number of materials available for FFF, which limits the potential of using FFF to solve engineering problems. This work focuses on material and machine modifications to enable FFF for use in both pharmaceutical and structural applications. Specifically, many pharmaceutical active ingredients require processing temperatures lower than what FFF typically uses. A low-temperature water-soluble material was altered by incorporating salt ions and ionic fillers separately. The differences in the printability were directly correlated to the measured variations in the viscosity and crystallization material properties. Alternatively, a technique is presented to embed liquids and powders into thin-walled, water-soluble printed parts that are processed using typical FFF temperatures, where the embedded material remains cool. The release time of the embedded material during dissolution is controlled by the thickness of the capsule structure. For structural applications, a machine was developed to allow for the processing of high-performance, high-temperature polymers on a desktop-scale system. This system uses an inverted heated chamber that uses natural convection to be able to heat the air around the part and not the electric components of the machine. The heated environment allows the part to remain at a higher temperature for a longer time, which enables a better bond between printed layers to achieve high-strength printed parts using high-performance materials. This machine was used to characterize the thermal processing effect for printing the high-performance polymer ULTEM® 1010. The nozzle temperature, environment temperature, and post-processing were tested where i) a higher nozzle temperature (360 °C) increases strength and prevents under extrusion, ii) a higher environment temperature (≥200 °C) increases the strength by slowing cooling and decreases warping by limiting the amount of shrinkage the occurs during printing, and iii) post-processing in powdered salt (18 hrs at 260 °C) increases part strength (50%) by allowing the printed roads to fuse.

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.

Gelatin methacrylate (GelMA) is a ubiquitous biocompatible photopolymer used in tissue engineering and regenerative medicine due to its cost-effective synthesis, tunable mechanical properties, and cellular response. Biotechnology applications utilizing GelMA have ranged from developing cell-laden hydrogel networks to cell encapsulation and additive manufacturing (3D printing). However, extrusion based 3D printing is the most common technique used with GelMA. Mask projection microstereolithography (MPµSL or µSL) is an advanced 3D printing technique that can produce geometries with high resolution, high complexity, and feature sizes unlike extrusion based printing. There are few biomaterials available for µSL applications, so 3D printing GelMA using µSL would not only add to the repertoire materials, but also demonstrate the advantages of µSL over other 3D printing techniques. A novel GelMA resin was tested with µSL to create a porous scaffold with a height and print time that has not been displayed in the literature before for a scaffold of this size. The resin consists of GelMA, deionized water, lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP, photoinitiator), and 2-Hydroxy-4-methoxybenzophenone-5-sulfonic acid (sulisobenzone, UV blocker) and can be processed at room temperature. Four resins were tested (w/w %) and characterized for µSL printing: 20% GelMA 0.5% UV blocker, 20% GelMA 1.0% UV blocker, 30% GelMA 0.5% UV Blocker, and 30% GelMA 1.0% UV blocker. Swell testing, working curve, photo-rheology, photo-DSC (dynamic scanning calorimetry), 3D printing, and cell culture tests were performed and results showed that 30% GelMA 1.0% UV blocker had the best 3D print fidelity among resin compositions. / Master of Science / Three dimensional (3D) printing is a widely used technology to rapidly produce structures with varying degrees of complexity. 3D printing of biological components is of interest because as the world population increases, there is a lack of donors available to compensate for organ loss and tissue replacement. 3D printing offers a solution to great custom scaffolds and structures that mimic physiological geometry and properties. One printing technique is known as microstereolithography, or µSL, which uses a projector-like system to pattern ultraviolet (UV) light in specific arrangements to generate complex geometries and 3D parts. Gelatin is a material of interest for this technology because gelatin is derived from collagen, which is the most abundant protein found in the body. Gelatin can be modified so that it is reactive with UV light, and can be processed with µSL to generate 3D structures. In this work, gelatin was modified into the form of gelatin methacrylate (GelMA) in order to develop and test resin formulations for use with µSL. Four different resins were tested and characterized and the results indicated that one GelMA resin produced prints with greater fidelity and resolution than other formulations. This resin has been identified for potential applications in tissue engineering and 3D printed organ development.

Hybridizing additive manufacturing (AM) structures and direct write (DW) deposition of conductive traces enables the design and physical creation of integrated, complex, and conformal electronics such as embedded electronics and complex routing on a fully AM structure. Although this hybridization has a promising outlook, there are several key AM substrate-related limitations that limit the final performance of these hybridized AM-DW electronic parts. These limitations include low-temperature processability (leading to high trace resistivity) and poor surface finish (leading to electronic shorts and disconnections). Recently discovered ultraviolet-assisted direct ink write (UV-DIW) all-aromatic polyimide (PI) provides an opportunity to address these previous shortcomings previously due to its high-temperature stability (450C) and superior surface finish (relative to other AM processes). The primary goal of this thesis is to characterize the integration of this UV-DIW PI with DW-printed conductive inks as a means for obtaining high-performance hybrid AM-DW electronics. This goal has been achieved through an investigation into the increased temperature stability of AM PI on the conductivity and adhesion of DW extrusion and aerosol jet (AJ) silver inks, determining the dielectric constant and dissipation factor of processed UV-DIW PI, and determining the achievable microwave application performance of UV-DIW PI. These performance measurements are compared to commercially-available PI film and relative to existing AM substrates, such as ULTEM 1010. The temperature stability of UV-DIW PI enabled higher-temperature post-processing for the printed silver traces, which decreased DIW trace resistivity from 14.94±0.55 times the value of bulk silver at 160 °C to 2.16±0.028 times the resistivity of bulk silver at 375 °C, and AJ silver trace resistivity from 5.27±0.013 times the resistivity of bulk silver at 200 °C to 1.95±0.15 times the resistivity of bulk silver at 350 °C. The adhesion of these traces was not negatively affected by higher processing temperatures, and the traces performed similarly on UV-DIW PI and commercial PI. Furthermore, at similar thicknesses, UV-DIW PI was found to have a similar dielectric constant and dissipation factor to commercial Dupont Kapton PI film from 1 kHz to 1 MHz, indicating its ability to perform highly as a dielectric electronics substrate. Finally, the decrease in resistivity was able to decrease the gap in microwave stripline transmission line performance when compared with ULTEM 1010 processed at 200°C, with peak 10 GHz S21 loss differences decreasing from 2.46 dB to 1.32 dB after increasing the UV-DIW processing temperature from 200 °C to 400°C. / Master of Science / Due to the extensive potential benefits and applications, researchers are looking to hybridize additive manufacturing (AM) processes with direct write (DW) techniques to directly print a 3D part with integrated electronics. Unfortunately, there are several key substrate-related limitations that hinder the overall performance of a part fabricated by hybrid AM-DW processes. Specifically, typical AM materials are not capable of providing an electronics substrate with combined sufficient surface resolution, surface finish, and high-temperature processing stability. However, the recent discovery of a novel AM-processable all-aromatic polyimide (PI) presents an opportunity for addressing these limitations as its printed form offers a high surface resolution, superior surface finish, and mechanical stability up to 400 °C. The primary goal of this thesis is to evaluate the benefits and drawbacks of this PI, processed via ultraviolet-assisted direct ink write (UV-DIW) AM, as an AM-DW electronics substrate. Specifically, the author characterized the effect of the increased temperature stability of the printed PI on the resultant conductivity and adhesion of silver inks printed via direct ink write (DIW) and aerosol jetting (AJ) DW processes. These results were also compared to the performance of the inks on commercial PI. Furthermore, the dielectric performance of printed PI was evaluated and compared to commercial PI. To demonstrate and evaluate the hybridized approach in a potential end-use application, the author also characterized the achievable microwave application performance of UV-DIW polyimide relative to the existing highest performance commercially available printed substrate material. The experiments in this thesis found an 83% and 66% decrease in resistivity from extrusion and AJ printed inks due to the ability of the printed PI to be processed at higher temperatures. Furthermore, UV-DIW PI was found to have similar dielectric properties to commercial PI film, which indicates that it can serve as a high-performance dielectric substrate. Finally, the high-temperature processing stability was able to decrease the performance gap in microwave application performance between the higher performing dielectric substrate, ULTEM 1010. These results show that UV-DIW could serve as a dielectric substrate for hybridized AM-DW electronic parts with higher performance and the ability to be deployed in harsher environments than previous AM-DW electronic parts explored in literature.

Additive Manufacturing (AM, also known as 3D printing) can produce novel three-dimensional structures using low-loss dielectric materials. This enables the construction of dielectrics with complex shapes that enable innovative microwave applications such as resonators, filters, and metamaterial lenses. This thesis addresses the production and characterization of cellular structures of various designed densities created with a low loss ceramic material, alumina (aluminum oxide), via vat photopolymerization. The permittivity of these printed structures is variable over roughly an octave, with a range of relative permittivites from 1.78 to 3.60, controlled via part geometry. Two additional materials, ferrite and nickel, have been explored for inclusion within these dielectric structures to enable the production of multi-material electromagnetic structures with conductive, magnetic, and dielectric elements. / Master of Science

The inability to monitor the molecular trajectories of whole organs throughout the clinically relevant ischemic interval is a critical problem underlying the organ shortage crisis. Here, we report a novel technique for fabricating manufacturing conformal microfluidic devices for organ interface. 3D conformal printing was leveraged to engineer and fabricate novel organ-conforming microfluidic devices that endow the interface between microfluidic channels and the organ cortex. Large animal studies reveal microfluidic biopsy samples contain rich diagnostic information, including clinically relevant biomarkers of ischemic pathophysiology. Overall, these results suggest microfluidic biopsy via 3D printed organ-conforming microfluidic devices could shift the paradigm for whole organ preservation and assessment, thereby relieving the organ shortage crisis through increased availability and quality of donor organs. / Master of Science

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.

High performance communications, sensing and computing systems are growing exponentially as modern life continues to rely more and more on technology. One of the factors that are currently limiting computing and transmission speeds are copper wire interconnects between devices. Optical fiber interconnects would greatly increase the speed of today’s electronic devices. In this study it has been demonstrated that by using a new Direct Print Additive Manufacturing (DPAM) process of Fused Deposition Modeling (FDM) of plastic and micro-dispensing of pastes and inks, we can 3D print single and multi-mode optical fibers in a controlled manner such that compact, 3-dimensional optical interconnects can be printed along non-lineal paths. We are FDM printing the core materials from a plastic PMMA material. We are dispensing a urethane optical adhesive as the core material. These materials are available in many different refractive indices. During numerical simulations of these fibers, we were able to show through manipulation of the refractive indices of the core and cladding that we can also improve the bend performance of our fibers. As a result, they can perform better as an interconnect in tight routings between components as long as the interconnect fiber distances remain less than 1 meter. Fibers have been fabricated with diameters between 77 and 17 µm across an air gap with a surface roughness of less than 450 nm and cladded and tested with transmission rates of about 46%. 12 µm fibers have successfully been fabricated on a cladded surface as a proof of concept to test the small diameter and 3D shaping capability of this process.