Artificial tactile recognition systems can provide valuable information about the surroundings and would enable artificial systems like prostheses and robotics to protect themselves against damage. However, making the desired geometry of sensing elements in flexible and stretchable sensors is a problem to be addressed. To overcome these hurdles, 3D printing technology can introduce advantages such as ease of design and rapid prototyping of complex geometries for soft sensors. Here, we report a conductive, biocompatible and antimicrobial 3D printed electronic skin (e-skin) based on a combination of platinum-cured silicone inks alongside carbon nanofibers (CNF). We adapted and standardized 3D printing parameters to obtain consistent CNF-based structural patterns and geometries. We explored the influence of printing angles and infill density on the mechanical properties of the printed structure, and utilized them to build complex resistive sensors with conductivity values of up to 120 S m-1, stretchability of up to 1000%, and 1200% increased pressure sensitivity in comparison to bulk sensors. We investigated the biocompatibility and antibacterial action of our material, and developed relieved pigmented e-skin sensor parts that can be integrated into robotic limbs to measure touch and a wide range of human motions demonstrating its promising integration in smart robotic sensing.

No description available.

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.

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.

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.

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

This thesis constitutes the final part of studies for a Bachelor’s degree in Mechanical Engineering. The report presents an investigation of radar-absorbing materials with a focus on the effects of magnetic layers in 3D-printed materials. This work is conducted at the Swedish Defence Research Agency (FOI), a leading entity in defense and security research in Europe. The project aims to improve the understanding of radar-absorbing materials and develop techniques to reduce the signature when exposed to radar. The purpose of the work includes analyzing different material compositions to identify the one that minimizes radar reflection and exploring gradient effects with multiple layers at the bottom and fewer at the top of the material. Additionally, the study aims to develop a mathematical model to describe the dependency of permittivity or loss tangent on the number of PLA-M layers compared to the base material PLA from the 3D printer. The method used in the project is derived from ”Product Design and Development” [1] with some adjustments. The work began with an extensive preliminary study that combined both theoretical and practical elements. A literature review and microscopic analyses of 3D-printed samples in PLAMwere conducted to understand the material behavior. Subsequently, various concepts were developed using a functional analysis conducted after creating a list of needs and requirements. Four concepts were developed, three of which were constructed and produced for further testing of radar properties in an NRL arch. The results of the work show that concept four, with a combination of PLA-M and PLA-E materials, proved to be the most promising for radar absorption. Unfortunately, I was not able to develop a mathematical model based on the test results. Despite this, the results provide valuable insights into how different parameters affect radar absorption in multilayer panels.

The primary intention behind performing this thesis is to identify possibilities of implementing Metal Additive Manufacturing (MAM) in automotive industries in spare part manufacturing. This project tries to analyse the differences between conventional and contemporary manufacturing techniques. The industrial partner we worked with, Frauenthal Gnotec AB, specializes in traditional manufacturing techniques for making automobile spare parts primarily by stamping. Hence, a large building area is required to store the die and materials. Automobile spare parts are manufactured by demand. The organization has to have the die and material ready to go, forcing it to expand its inventories, workforce, and transportation, causing substantial financial liabilities.  The projects include a wide range of information from the different scientific articles, Journals, and consultations with AM services, Professors, and Technicians. The thesis studied the various available options in MAM and compared its specification with our client's requirements. The project estimates the cost, time for printing the components, thermo-mechanical properties, and structural properties of the component and its feasibility.   The project helped us put our theoretical knowledge about MAM into practice. It was very significant for us to have the opportunity to work with Frauenthal Gnotec AB, one of the leading automobile spare parts manufacturers in Sweden. Examine and evaluate their manufacturing and production strategies, which was very helpful for us in determining the efficacy of our efforts. Our scientific study, based on various simulations, optimizations, mechanical tests, and cost estimates, found MAM to be a promising future technology for the automotive industry.