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2020-

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https://hdl.handle.net/10217/182111

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Browsing 2020- by Subject "3D printing"

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    Design, fabrication, and characterization of 3D printed ceramic scaffolds for bone regeneration
    (Colorado State University. Libraries, 2024) Baumer, Vail Olin, author; Prawel, David, advisor; McGilvray, Kirk, committee member; Heyliger, Paul, committee member
    Synthetic bone tissue scaffolds are a promising alternative to current clinical techniques for treating critically large bone defects. Scaffolds provide a three-dimensional (3D) environment that mimics the properties of bone to accelerate bone regeneration. Optimal scaffolds should match the mechanical properties of the implantation site, feature a highly porous network of interconnected channels to facilitate mass transport, and exhibit surface properties for the attachment, proliferation, and differentiation of bone cell lineages. 3D printing has enabled the manufacture of complex scaffold topologies that meet these requirements in a variety of biomaterials which has led to rapidly expanding research. Structural innovations such as triply periodic minimal surfaces (TPMS) are enabling the production of scaffolds that are stiffer and stronger than traditional rectilinear topologies. TPMS are proving to be ideal candidates for bone tissue engineering (BTE) due to their relatively high mechanical energy absorption and robustness, interconnected internal porous structure, scalable unit cell topology, and smooth internal surfaces with relatively high surface area per volume. Among the material options, calcium phosphate-based ceramics, such as hydroxyapatite and tricalcium phosphate, are popular for BTE due to their high levels of bioactivity (osteoconductivity, osteoinductivity and osteointegration), compositional similarities to human bone mineral, non-immunogenicity, tunable degradation rates, and promising drug delivery capabilities. Despite the potential for TPMS ceramic scaffolds in BTE, few studies have explored beyond the popular Gyroid topology. Of the many TPMS options, the Fischer Koch S (FKS) has been simulated to be stronger, be more isotropic, have higher surface area, and absorb more energy than Gyroid at high porosities. In this report, we present a method for photocasting any TPMS in hydroxyapatite which is used to 3D print the first FKS ceramic scaffold. Results indicated that the resolution and accuracy of the process is suitable for BTE, and the custom software for producing the scaffolds was made available to the open-source community. Then, FKS and Gyroid scaffolds were designed to match the properties of trabecular bone using this method for use in critical bone defect repair. The scaffolds were printed and characterized using compressive and flow-based testing to reveal that, while both designs could mimic the low end of natural bone performance, the FKS were 32% stronger and only 11% less permeable than Gyroid. These findings emphasized the need for further characterization of these scaffolds beyond mechanical analysis and into studies of cell growth. To accomplish this, a custom multi-channel perfusion bioreactor was designed to culture cells on these scaffolds to investigate differences in cell behavior with higher efficiency than current designs. The design, capable of culturing many samples simultaneously, was validated using computational fluid dynamics and cell growth assays to demonstrate osteogenic effects and repeatability. In this work, novel TPMS scaffolds were fabricated from hydroxyapatite with sufficient accuracy and quality for large defects, testing of these scaffolds matched trabecular bone performance and suggested that FKS may be superior to Gyroid, and lastly, a four-channel bioreactor system was designed and validated to enable researchers to further characterize scaffolds for BTE.
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    Fundamental and applied studies of polymeric photonic crystals: the role of polymer architecture and 3D printing
    (Colorado State University. Libraries, 2020) Boyle, Bret Michael, author; Miyake, Garret, advisor; McNally, Andrew, committee member; Menoni, Carmen, committee member; Prawel, David, committee member
    Block copolymers (BCP) provide a bottom-up, economical approach to synthesizing polymeric photonic crystals (PC) through the process of self-assembly. Photonic crystals (PC) are defined as periodic, dielectric nanostructures able to reflect certain wavelengths of light within a photonic band gap. The ability to directly tailor the synthesis, conformation, and self- assembly of a BCP to affect the properties of the resulting PC material creates a modular platform for PC materials design. Even though this platform exists for polymeric PC materials, the direct result of modulating the polymer architecture on the dynamics, self-assembly, and application of PC materials remains relatively unexplored. To help close this gap, this dissertation presents the polymer synthesis, characterization, and self-assembly of macromolecules within two unique classes of polymer architecture, dendritic block copolymers (DBCP) and bottlebrush block copolymers (BBCP). DBCPs were shown to possess many characteristics similar to those of bottlebrush polymers such as a rod-like conformation, a reduced capability for chain entanglement, and lower glassy moduli compared to non-rigid, linear polymers. Further, DBCPs possess high free energy parameters, as well as glass transition temperatures below melt extrusion 3D printing operating conditions, and were shown to self- assemble into PCs during the process of 3D printing. DBCP PCs represented the first example of 3D printing structural color. For BBCPs, the backbone composition's effect on the global BBCP conformation and in modulating self-assembly processes was examined. The backbone composition was shown to dramatically shift the wavelength of reflection of the PC material at similar molecular weights as well as improve the fidelity of the nanostructure morphology as the molecular weight increases from 50,000 g/mol to 2 million g/mol. The structure-property relationships illuminated herein have laid the groundwork for new research efforts into engineering BCPs for novel PC applications.
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    Mechanical and antimicrobial performance analysis of a shark skin bio-mimicked fabric swatch via 3D printing
    (Colorado State University. Libraries, 2020) Purandare, Saloni Prasanna, author; Li, Yan Vivian, advisor; Yan, Ruoh-Nan, committee member; Prawel, David, committee member
    Biomimicry is a long-practiced concept concerned with development of products with nature as the source of inspiration. Bio mimicked textiles is a branch of textiles wherein textile products are developed to replicate desirable elements of nature such as lotus-leaf inspired water repellent fabric, high-strength spider silk inspired by the spider web and shark skin biomimicry. The scaled texture on shark skin, known as riblet effect, exhibits drag reduction and antimicrobial properties. Accurate biomimicry of shark skin is an on-going continual process This study is concerned with 3D printing bio mimicked fabric swatches by replication of riblet effect followed by characterization of the developed fabric swatches. The swatches were printed using Autodesk Ember photopolymer 3D printer, allowing printing of minutely detailed denticles in the base. The materials used were polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and polyurethane (PU) material. PU allowed creation of rigid tough denticles embedded in flexible and soft base, indicating as a better raw material to 3D print bio-mimicked swatches for functional clothing. The PU swatches were studied further in morphological, mechanical, and antimicrobial analysis. The morphological analysis resulted into optical images exhibiting the developed texture resembling characteristic riblet effect of shark skin. Mechanical analysis in terms of tensile stress testing exhibited stronger and tougher fabric samples with thick (1.05mm) base in comparison with those having thin (0.75mm) base. Also, the mechanical analysis indicated good elastomeric properties for the fabric swatches suggesting potential in functional clothing. Lastly, the antimicrobial test conducted exhibited reduced antimicrobial growth for samples with riblet texture against untextured samples, copper foil as well as aluminum foil thus exhibiting potential use of the textured fabric swatches as non-toxic antimicrobial material. Shark skin biomimicry through riblet effect replication has been studied majorly for hydrodynamic properties while shark skin inspired material intended for antimicrobial properties such as by Sharklet® technology is not concerned with riblet effect replication. Thus, to our best knowledge study focusing on mechanical and antimicrobial analysis of shark skin biomimicry through replication of riblet effect is missing. This study will help determine potential of shark skin biomimicry by replication of riblet effect in functional clothing, through mechanical and antimicrobial analysis.