Mountain Scholar :: Browsing by Author "Bailey, Travis, committee member"

Browsing by Author "Bailey, Travis, committee member"

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Open Access
A rapid, point of need open cow test
(Colorado State University. Libraries, 2023) Mendez, Jacy, author; Dandy, David, advisor; Henry, Chuck, committee member; Bailey, Travis, committee member; Hansen, Thomas, committee member
In the dairy industry, maintaining non-pregnant (open) cows is expensive, and may require multiple rounds of artificial insemination (AI) for a cow to become pregnant. There is a need for early pregnancy detection in dairy cows, which allows the use of protocols such as prostaglandin F2-alpha (PGF) and gonadotropin releasing hormone (GnRH) to prepare a cow for another round of breeding via AI, with an emphasis on reduced time between each breeding attempt. The current gold standard method for confirming pregnancy in cows is a rectally-guided ultrasound at day 32 after AI. Interferon-tau (IFNT) is a biomarker that can be detected during days 7-28 of pregnancy in cattle, and is expressed by the cow conceptus. The goal of this work was to develop a cow-side test utilizing IFNT as the biomarker for early cattle pregnancy detection. A lateral flow assay (LFA) was chosen and investigated due to its simplicity and ease of use, but was later adapted to utilize the enzymatic oxidation of 3,3',5,5' – Tetramethylbenzidine to amplify the signal in the test line. C-reactive protein was used to develop protocols for aspects of device development involving nitrocellulose, including antibody striping, blocking, and nitrocellulose selection. These protocols were then utilized as optimization of the lateral flow assay was conducted. The resulting LFA has a limit of detection (LOD) of 10 μg/mL, with an LOD of 100 ng/mL in a half-strip format, with some limitations imposed by false positives. This work provides a novel method of detection for pregnancy in cattle and with further development, has the potential for use by dairy farmers in their respective industry.
Embargo
Advanced manufacturing of thermoset polymers and composites
(Colorado State University. Libraries, 2023) Ziaee, Morteza, author; Yourdkhani, Mostafa, advisor; Radford, Donald W., committee member; James, Susan, committee member; Bailey, Travis, committee member
Thermoset polymers and composites are lightweight materials extensively used in many industries from aerospace to automotive to prosthetics due to their excellent specific mechanical properties and high chemical resistance. However, these products are conventionally manufactured by labor-intensive processes using subtractive manufactured tooling or molds followed by thermal curing inside an oven or autoclave at elevated temperatures for several hours. Hence, conventional manufacturing approaches are energy- and time-consuming and require expensive equipment. Moreover, lack of design flexibility and poor repeatability are additional challenges, which limit the structural and functional capabilities of such products. In this dissertation, I present a novel approach to address the existing limitations in manufacturing thermosets and their composites by developing rapid curing resin systems and integrating them in additive manufacturing (AM) processes. In the first chapter, state-of-the-art manufacturing methods are reviewed and frontal polymerization (FP) as a promising curing strategy for rapid and energy-efficient manufacturing of thermosets and composites is introduced. In the second chapter, the effect of ambient conditioning and resin chemistry on thermal frontal polymerization of a high-performance resin system is explored. In the third chapter, FP is used to demonstrate, for the first time, simultaneous printing and curing of short carbon fiber-reinforced composites for high performance applications. In the following chapter, AM of a soft and stretchable elastomer with tunable thermomechanical properties manufactured via FP is discussed. In the fifth chapter, the printing process is further improved using an external localized heat source, instead of relying on the exothermic heat of polymerization of the resin, to accelerate the curing rate and make the printing process more robust and applicable to the manufacture of large-scale components. Finally in the last chapter, bubble-free frontal polymerization of polyacrylates is introduced for the developed 3D printing process.
Open Access
Brush-like surface using heparin/chitosan based nanoparticles for blood-contacting applications
(Colorado State University. Libraries, 2013) Nijjar, Rajvir Singh, author; Kipper, Matt, advisor; Bailey, Travis, committee member; Reynolds, Melissa, committee member
With increasing applications of biomedical implants, it is crucial to develop surfaces that are blood compatible, meaning they do not induce platelet or protein adhesion. Many implants that are currently used to treat a wide range of problems have one major drawback, they can induce thrombosis. The endothelial glycocalyx plays a crucial role in preventing thrombosis. Based on this idea, we set out to develop a surface that has a brush-like structure similar to that of the endothelial glycocalyx. We developed the surface by adsorbing negatively charged heparin/chitosan polyelectrolyte complex nanoparticles onto a heparin/tri-methylchitosan polyelectrolyte multilayer. The surface was then characterized using surface plasmon resonance (SPR), quartz crystal microbalance (QCM), atomic force microsocopy (AFM), scanning electron microscope (SEM), and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). Using these techniques we confirmed that we had created a surface with brush- like structure. Our hypothesis that the nanoparticles on the surface swell and form a brush-like structure when exposed to physiological conditions seems to be correct, as a result, we feel the surface we have developed could have a wide range of applications in the biomedical field.
Open Access
Cationic-doping of mayenite electride: synthesis, processing, and effect on thermal stability
(Colorado State University. Libraries, 2021) DeBoer, Brodderic, author; Ma, Kaka, advisor; Weinberger, Chris, committee member; Bailey, Travis, committee member; Bandhauer, Todd, committee member
Mayenite electride is an electrically conductive ceramic developed from its parent phase, oxy-mayenite (12CaO•7Al2O3, commonly referred to as C12A7). C12A7 has a unique unit cell that consists of a positively charged [Ca24Al28O64]4+ framework containing twelve cages and two extra-framework O2- ions located inside two cages. The extra-framework O2- ions can be replaced with electrons when C12A7 is heated in a reducing environment, and those extra-framework electrons act like anions, forming the mayenite electride phase, denoted as C12A7:e- hereafter. The anionic electrons enable peculiar properties of C12A7:e- such as high electrical conductivity and low work function, making it a promising material for field emission devices, thermionic-cooling, and as a hallow cathode for electrical propulsion. Compared to other electride materials such as Ca2N, which barely sustain their electride properties even at ambient conditions, C12A7:e- has been reported to be stable up to 400 °C. This temperature is yet not high enough to enable its applications in the technologies mentioned above. Doped derivatives of C12A7:e- emerged in recent years to improve its electronic properties, mainly electron density and electrical conductivity. However, the effects of doping on the oxidation resistance and thermal stability of C12A7:e- remained unclear. Experimental effort on cationic doping of C12A7:e- was particularly lacking in the literature. Therefore, the goal of this study is two-fold: (1) to develop processing routes for successful cationic doping of C12A7:e-, and (2) to test if cationic doping can improve the thermal stability of C12A7:e-. Copper (Cu) and niobium (Nb) were selected as cationic dopants in this study to elucidate how cationic doping affects the thermal stability of the mayenite electride. First, effort was focused on developing synthesis and processing methods to effectively dope Cu and Nb into C12A7:e-. Three different methods were investigated, including diffusion doping; in conventional furnace or via spark plasma sintering (SPS), single-step in-situ formation via SPS, and a solid-state reaction (SSR) synthesis followed by reduction. The phase constitutions, lattice parameters, and microstructure of the various C12A7:e- samples fabricated via the aforementioned methods were characterized to verify if cationic doping was successfully achieved. Electrical conductivity was measured to verify the electride phase is sustained after the doping. Thermal analysis was performed to determine the thermal stability of the cation-doped C12A7:e- compared to undoped counterparts, including onset temperature and peak temperature of oxidation, oxidation rate, mass gain percentage resulted from oxidation, and any decomposition reaction. The key findings of this study include: (1) both Cu-doping and Nb-doping improved the thermal stability of the C12A7:e- by increasing the onset temperatures of oxidation; (2) Cu-doping was effectively and efficiently achieved via the novel SPS diffusion doping method. SPS diffusion doping of Cu at 800 °C gave rise to a minimum lattice parameter (a = 11.942 Å) of C12A7:e-, the lowest oxidation rate, and the smallest mass gain percent at 1050 °C; (3) Using oxy-mayenite and Nb2O5 as precursor for reaction sintering and in-situ reduction in SPS led to successful Nb-doping into the C12A7:e-. Despite the increased onset oxidation temperature resulted from Nb addition, pest oxidation occurred in Nb-doped C12A7:e- samples, leading to high oxidation rate, high total mass gain percentage, and fracture of the solid samples at temperature above 700 °C. In conclusion, Cu-doping was experimentally proved to be an effective approach to improve the thermal stability of C12A7:e- and meanwhile increase the electrical conductivity.
Open Access
Chloride binding and desorption mechanism in blended cement containing supplementary cementitious materials exposed to de-icing brine solutions
(Colorado State University. Libraries, 2024) Teymouri Moogooee, Mohammad, author; Atadero, Rebecca, advisor; Fantz, Todd, advisor; Jia, Gaofeng, committee member; Bailey, Travis, committee member
Concrete, the most widely used construction material globally, faces significant challenges due to its porous nature, particularly from chloride-induced corrosion. This corrosion, primarily caused by chloride ions penetrating concrete, affects over 7.5% of U.S. concrete bridges, incurring annual costs ranging from $5.9 to $9.7 billion. Chlorides enter concrete from various sources, including de-icing salts. Maritime infrastructures also suffer from severe chloride-induced corrosion because seawater contains a high concentration of chloride ions. Irrespective of how chlorides enter the concrete, chlorides can exist in concrete in two forms: free and bound chlorides. While bound chlorides are beneficial, they can be released due to environmental factors like carbonation and chemical attacks, exacerbating corrosion rates. These attacks cause pH reduction in concrete and subsequently can result in the release of bound chlorides (chloride desorption).This dissertation aims to address three main objectives: (1) investigate factors influencing chloride binding measurements due to lack of a standardized method for chloride binding measurements, (2) study chloride desorption mechanisms in different cementitious systems exposed to de-icing brines, and (3) analyze pH and compositional changes in blended pastes under chloride contamination and carbonation. First, factors impacting chloride binding measurements were identified, such as sample form and saturation level, solution composition, and solution volume. Vacuum-saturated samples exhibited higher chloride binding than partially saturated or dried samples, with powdered samples showing the highest binding. Secondly, chloride desorption mechanisms were investigated in both Ordinary Portland Cement (OPC) pastes and pastes containing supplementary cementitious materials (SCMs) like fly ash, slag, and silica fume. Results indicated that the type of cation in the brine solution influenced bound chloride levels, with SCMs improving chloride binding capacity. Slag inclusion was effective in promoting chloride binding, while silica fume showed the least effect. The degree of chloride desorption under acid attack depended on the acid-to-paste mass ratio. The results reveal that inclusion of fly ash and slag is favorable in terms of chloride desorption, and silica fume is not recommended for use when chloride-induced corrosion is a concern. MgCl2 and CaCl2 de-icers demonstrated a lower chloride desorption compared to NaCl. Finally, the synergistic effects of chloride contamination and carbonation were examined in OPC and fly ash-containing pastes. Carbonation led to over 95% chloride desorption after two weeks, with fly ash-containing pastes exhibiting lower pH levels due to reduced portlandite content. Incorporation of fly ash is not recommended when carbonation is a concern. Therefore, caution should be exercised when considering fly ash inclusion in mixtures where both chloride contamination and carbonation are simultaneous concerns. This dissertation contributes to understanding chloride desorption in cementitious systems, essential for enhancing the durability and service life of concrete structures. This dissertation shed lights on primary factors influencing chloride binding measurements, enhancing the accuracy and comparability of chloride binding results. The results reveal that type of cation present in the solution and type of SCMs have significant influences on the pH, chloride binding capacity, and chloride desorption rates.
Open Access
Design of durable de-icing, superhydrophobic, superoleophobic coatings
(Colorado State University. Libraries, 2015) Beemer, Darryl Lewis, author; Kota, Arun K., advisor; Bailey, Travis, committee member; Popat, Ketul, committee member
This work looks at the issue of ice accretion on surfaces and efforts to reduce this ice accretion and the subsequent ice adhesion strength in order to make ice removal easier and more cost effective for wider implementation. Ice accretion on various surfaces is a major economic and safety issue for a variety of industries, including air travel, power production and transmission, maritime shipping, and more. While efforts have been taken to diminish ice accretion and subsequent ice adhesion strength, existing technology is limited in its ability to prevent ice accretion in a wide range of conditions and to then have a low ice adhesion strength once ice has accumulated on a surface. With the background of icing and solid mechanics of ice removal in mind, materials were developed to exhibit a low ice adhesion strength while maintaining the durability characteristic of a non-sacrificial coating. After development and testing, it was found that the developed materials exhibited an adhesion strength lower than any currently available technology, with extended durability under both ice removal and mechanical abrasion conditions. As a secondary effort, an initial exploration into the development of durable superomniphobic surfaces was performed in order to reduce and/or prevent adhesion of water-based paint and a low surface-tension fluid to various surfaces. Development of a variety of surface types (spray coated layered and mixed surfaces, etched stainless steel surfaces, and more) was performed, with initial results providing an encouraging path forward for future development of this durable coating work.
Open Access
Determination of spatial distribution, dissipation, and efficacy of insecticides used for control of citrus greening disease
(Colorado State University. Libraries, 2022) Rehberg, Rachelle Anne, author; Borch, Thomas, advisor; Henry, Chuck, committee member; Bailey, Travis, committee member; Trivedi, Pankaj, committee member
Citrus greening disease has devastated citrus production globally. While Florida growers explore management strategies, Asian citrus psyllids (ACP) continue spreading this detrimental disease. Determining the efficacy of insecticides applied in citrus groves is a necessity. In these field studies, the efficacies of foliar insecticide treatments to citrus trees were investigated with liquid chromatography tandem mass spectrometry. Insecticide spatial distribution, dissipation, degradation, and effectiveness at reducing ACP were quantified over time after commercial application at a field site in Florida. Citrus leaves, and sample discs attached to leaves, were collected at specific times and locations within individual citrus trees. ACP were inspected before and after treatments to quantify reductions associated with insecticide concentrations over time. We investigated several insecticides commonly used against ACP including malathion, imidacloprid, dimethoate, and one newer insecticide, afidopyropen. Our findings showed highly variable spatial distribution of insecticides throughout individual trees and rapid dissipation within 24 hours after application. Inadequate distribution to different sides of the leaf and tree canopy areas was observed for all aerial and ground spraying methods tested. Fast degradation rates were observed in sampling discs and citrus leaves with half-lives ranging from 0.6 to 4.0 hours while metabolite concentrations increased. Results showed faster dissipation rates during warmer months (July) and in younger-aged trees ground sprayed with the speed-sprayer. A wide range of insecticide efficacy was observed, with ACP reductions of 63 to 100%. When ACP remained after treatment, effectiveness decreased over time and ACP increased (e.g. from 6 to 172% after afidopyropen treatment). The observed variable spatial distribution, rapid insecticide dissipation, and inadequate efficacy allow remaining ACP or ACP from surrounding groves to continue spreading citrus greening disease, leaving citrus trees unprotected. For contact, or semi-systemic insecticides like afidopyropen, full coverage to both sides of the leaves and tree canopy is crucial to effectively manage ACP populations. ACP regeneration suggests lower metabolite toxicity or pest resistance development and reveals ineffective pest management. This research not only helps inform citrus growers of actual insecticide efficacy in the field, which may influence their pest and disease management strategies, but also provides better understanding of insecticide dissipation from citrus leaves, which assists those advancing predictive models for agricultural applications. Additionally, these results help inform insecticide manufacturers of their products' performance in field conditions which can be compared to laboratory studies. Lastly, this work reveals information on the fate of insecticides in the field which could be used to evaluate its impact on other species and the environment.
Open Access
Development of LC-MS and degradation techniques for the analysis of fungal-derived chitin
(Colorado State University. Libraries, 2020) Allison, Christopher L., author; Reynolds, Melissa M., advisor; Farmer, Delphine, committee member; Bailey, Travis, committee member; Popat, Ketul, committee member
The research contained within this dissertation began with the following question: Can liquid chromatography-mass spectrometry (LC-MS) be used as a screening method for fungal infections? The ensuing projects investigated various aspects of that question, taking a ground-up approach that started with the analysis of the simplest constituents of the biomarkers used, chitin and chitosan. The complexity of the systems investigated was gradually increased, culminating in the extraction and detection of these biomarkers from pertinent fungal cells. Chitin constitutes 10-30% of the mass of filamentous fungi. While not found endogenously, it is the second most abundant naturally-occurring polysaccharide, next to cellulose. Chitin is composed of >50% N-acetylglucosamine (GlcNAc) and D-glucosamine (GlcN). In nature and in numerous applications, chitin can be deacetylated to produce chitosan. Chitosan is the deacetylated (>50% GlcN) counterpart to chitin and is also found in some species of fungi. This dissertation began with the development of electrospray ionization mass spectrometry (ESI-MS) methods to analyze GlcN and GlcNAc, as well as oligomers composed of both residues. The optimization of methods to analyze the components of chitin served as the foundation on which to advance the applicability of these methods. Following method optimization, the ability of mass spectrometry to analyze polymeric chitosan was explored. Detecting polymeric chitosan was determined to be infeasible using ESI-MS; hence, the focus of subsequent studies was turned to the use of degradation studies to generate low molecular weight chemical fingerprints that could be correlated to the presence of chitin and chitosan. The first experiments performed to study the degradation of chitosan evaluated the impact nitrosating conditions have on the structure of chitosan. Both mass spectrometry and spectroscopic methods were used to track the formation of a degradation product, 2,5-anhydro-D-mannose (2,5-AM), to demonstrate that nitrous acid-based conditions induce degradation in polymeric chitosan. Following these experiments, degradation studies were expanded to include a wider range of starting materials. Chitosan polymer was used again, in addition to two chitin polymers with varied degrees of deacetylation. In addition to examining the effect of nitrosating conditions on these polymers, degradation methods were expanded to include hydrochloric acid (HCl), hydrogen peroxide (H2O2), and enzymatic degradation agents (lysozyme, lipase, and hemicellulase). The susceptibility of each polymer to degradation protocols was assessed by ESI-MS or LC-MS analysis of degradation products generated. Results from these studies indicated that HCl, H2O2, HNO2, and lysozyme generate distinct products from chitin and chitosan polymers. Identification of unique chemical fingerprints produced from chitin and its derivatives provided the necessary information to apply these studies to pertinent fungal cells. The final experiments in this dissertation apply cleanup, cell lysis, degradation methods, and LC-MS to identify GlcN produced from Aspergillus niger fungi. Cumulatively, the following research contains a thorough overview of degradation methods for chitin and its derivates, along with the characterization of low molecular weight fingerprints that each protocol generates. ESI-MS or LC-MS methods were used to identify low molecular weight products formed during degradation. Finally, both degradation and LC-MS methods were applied to Aspergillus niger to validate that representative fungal species can be detected using the proposed techniques.
Open Access
Dynamics of protein interactions with new biomimetic interfaces: toward blood-compatible biomaterials
(Colorado State University. Libraries, 2019) Hedayati, Mohammadhasan, author; Kipper, Matt J., advisor; Krapf, Diego, committee member; Reynolds, Melissa, committee member; Bailey, Travis, committee member
Nonspecific blood protein adsorption on the surfaces is the first event that occurs within seconds when a biomaterial comes into contact with blood. This phenomenon may ultimately lead to significant adverse biological responses. Therefore, preventing blood protein adsorption on biomaterial surfaces is a prerequisite towards designing blood-compatible artificial surfaces.
Open Access
Electrochemically prepared metal antimonide nanostructures for lithium ion and sodium ion battery anodes
(Colorado State University. Libraries, 2016) Jackson, Everett D., author; Prieto, Amy, advisor; Rappe, Anthony, committee member; Dandy, David, committee member; Bailey, Travis, committee member; Henry, Charles, committee member
The use of energy fundamentally enables and globally supports post-industrial economies and is critical to all aspects of modern society. In recent years, it has become apparent that we will require superior energy technologies to support our society, including improved methods of generating, storing, and utilizing energy resources. Battery technology occupies a critical part of this new energy economy, and the development of electrochemical energy storage devices will be a critical factor for the successful implementation of renewable energy generation and efficiency strategies at the grid, transportation, and consumer levels. Current batteries suffer from limitations in energy density, power density, longevity, and overall cost. In addition, the inherent tradeoffs required in battery design make it impossible to create a single battery that is perfect for all applications. To overcome these issues, the development of low-cost and high-throughput methods, new strategies for materials design, and a comprehensive understanding of electrochemical mechanisms for battery performance is necessary. Herein, an in-depth study on the electrochemistry of a model anode system for rechargeable batteries based on metal antimony alloys produced through an electroplating approach is detailed. The first chapter of this dissertation provides a brief introduction of lithium ion and sodium ion battery technology. In the second chapter, a detailed review of the literature on antimony and metal antimonide alloys for battery anodes is provided. The third chapter details a study on copper antimonide thin films with varying stoichiometry produced through a facile electrodeposition process. In the fourth chapter, stoichiometric Cu2Sb thin films are studied as potential anodes for sodium ion batteries. The fifth chapter details the development of a process for electroplating zinc-antimony alloy thin films onto zinc and their electrochemical properties in sodium ion cells. The sixth and seventh chapters report the synthesis and characterization of copper-antimony alloy nanowire arrays produced through an alumina-templated process. These nanowire arrays are first used in an electrolyte-additive study to show the importance of surface stabilization for high surface area electrodes in chapter five. In chapter six, the rate performance is characterized under different thermal conditions for different compositions of copper-antimony alloy nanowire arrays as an assessment of the kinetic limitations of this electrode. The final chapter briefly describes some preliminary experiments that have been performed on characterizing the electrochemistry of metal salts in a deep eutectic solvent as a potential method for co-deposition of new metal antimonides.
Open Access
Enhanced surface functionality via plasma modification and plasma deposition techniques to create more biologically relevant materials
(Colorado State University. Libraries, 2013) Shearer, Jeffrey C., author; Fisher, Ellen R., advisor; Henry, Charles, committee member; Szamel, Grzegorz, committee member; Bailey, Travis, committee member; Buchanan, Kristen, committee member
Functionalizing nanoparticles and other unusually shaped substrates to create more biologically relevant materials has become central to a wide range of research programs. One of the primary challenges in this field is creating highly functionalized surfaces without modifying the underlying bulk material. Traditional wet chemistry techniques utilize thin film depositions to functionalize nanomaterials with oxygen and nitrogen containing functional groups, such as -OH and -NHx. These functional groups can serve to create surfaces that are amenable to cell adhesion or can act as reactive groups for further attachment of larger structures, such as macromolecules or antiviral agents. Additional layers, such as SiO2, are often added between the nanomaterial and the functionalized coating to act as a barrier films, adhesion layers, and to increase overall hydrophilicity. However, some wet chemistry techniques can damage the bulk material during processing. This dissertation examines the use of plasma processing as an alternative method for producing these highly functionalized surfaces on nanoparticles and polymeric scaffolds through the use of plasma modification and plasma enhanced chemical vapor deposition techniques. Specifically, this dissertation will focus on (1) plasma deposition of SiO2 barrier films on nanoparticle substrates; (2) surface functionalization of amine and alcohol groups through (a) plasma co-polymerization and (b) plasma modification; and (3) the design and construction of plasma hardware to facilitate plasma processing of nanoparticles and polymeric scaffolds. The body of work presented herein first examines the fabrication of composite nanoparticles by plasma processing. SiOxCy and hexylamine films were coated onto TiO2 nanoparticles to demonstrate enhanced water dispersion properties. Continuous wave and pulsed allyl alcohol plasmas were used to produce highly functionalized Fe2O3 supported nanoparticles. Specifically, film composition was correlated to gas-phase excited state species and the pulsing duty cycle to better understand the mechanisms of allyl alcohol deposition in our plasma systems. While these studies specifically examined supported nanoparticle substrates, some applications might require the complete functionalization of the entire nanoparticle surface. To overcome this challenge, a rotating drum plasma reactor was designed as a method for functionalizing the surface of individual Fe2O3 nanoparticles. Specifically, data show how the rotating motion of the reactor is beneficial for increasing the alcohol surface functionality of the nanoparticles when treated with pulsed allyl alcohol plasmas. Plasma copolymerization was used to deposit films rich in both oxygen and nitrogen containing functional groups using allyl alcohol and allyl amine plasma systems. Functional group retention and surface wettability was maximized under pulsed plasma conditions, and films produced under pulsed plasma conditions did not exhibit hydrophobic recovery or experience loss of nitrogen as the films aged. Plasma surface modification with N2/H2O and NH3/H2O, and plasma deposition with allyl alcohol and allyl amine, were used to increase the wettability of poly(caprolactone) scaffolds while simultaneously implanting functional groups onto the scaffold surface and into the scaffold core. While plasma deposition methods did not modify the internal core of the scaffold as much as modification methods, it afforded the ability to have higher water absorption rates after a three week aging period. Additionally, cell viability studies were conducted with N2/H2O plasma treated scaffolds and showed enhanced cell growth on plasma treated scaffolds over non plasma-treated scaffolds.
Open Access
Fabrication of slippery textured and slippery non-textured surfaces
(Colorado State University. Libraries, 2018) Cackovic, Matthew, author; Kota, Arun K., advisor; Popat, Ketul, committee member; Bailey, Travis, committee member
Slippery surfaces, i.e., surfaces that have high droplet mobility and low lateral adhesion for liquid droplets, have a wide range of application such as condensation heat transfer, anti-corrosion, lab-on-chip devices, etc. These surfaces can be categorized into smooth slippery surfaces and super-repellant textured slippery surfaces. In this work, we fabricated super-repellant textured superomniphobic paper surfaces. We developed a simple and facile method to fabricate superomniphobic paper surface by growing silicone nanofilaments on a glass microfiber paper surface before imparting low solid surface energy to give the surface the appropriate texture and chemistry. We characterized the performance of our surface and demonstrated our surfaces potential as a lab-on-chip type device. We showed high droplet transport rate, created a simple on-paper pH sensor, demonstrated weight bearing, and showed separation of water from ultra-low surface tension hexane demonstrating the utility of our superomniphobic paper surfaces. We also fabricated a smooth slippery copper surface by creating a chemically and physically homogenous surface. We developed a quick screening test to evaluate the performance of our surfaces in addition to the traditional tests. We showed smoother surfaces performed better and were more slippery.
Open Access
GPU-accelerated computational study of block copolymer self-assembly with advanced polymer theories
(Colorado State University. Libraries, 2024) He, Juntong, author; Wang, Qiang, advisor; Prasad, Ashok, committee member; Bailey, Travis, committee member; Gelfand, Martin, committee member
A high-performance GPU-accelerated software package for self-consistent field (SCF) calculations of block copolymer assembly, PSCF+, has been developed. PSCF+ allows various combinations of chain-connectivity models (including the continuous Gaussian chains, discrete Gaussian chains, and freely jointed chains), non-bonded isotropic pair (including the Dirac δ-function, soft-sphere, dissipative particle dynamics, and Gaussian) potentials and system compressibility (incompressible vs. compressible). The Richardson-extrapolated pseudo-spectral methods, the crystallographic fast Fourier transform, the "slice" algorithm, and the automated calculation-along-a-path are implemented in PSCF+, which not only speed up the SCF calculations and reduce the GPU memory usage significantly, but also make it very efficient in constructing phase diagrams. Given the wide use and great success of SCF calculations in understanding and predicting the self-assembled structures of block copolymer, PSCF+ will be an invaluable computational tool for the polymer community. Using PSCF+, we studied the stability of various Frank-Kasper phases formed by neat diblock copolymer (DBC) A-B melts using the "standard" model and the dissipative particle dynamics chain model and found that in general the SCF phase diagrams of these two models are qualitatively the same but with important differences. We also studied the stability of various Frank-Kasper phases formed by binary DBC blends using the "standard" model and found that the relative stability among the Frank-Kasper phases is dominated by their internal-energy densities. Finally, we performed high-accuracy SCF calculations to study the stability of all known tiling patterns formed by symmetrically interacting ABC miktoarm star triblock terpolymers.
Open Access
Hyaluronic acid enhancement of expanded polytetrafluoroethylene for small diameter vascular grafts
(Colorado State University. Libraries, 2014) Lewis, Nicole R., author; James, Susan P., advisor; Popat, Ketul C., committee member; Bailey, Travis, committee member
Cardiovascular disease is the leading cause of mortality and morbidity in the United States and other developed countries. In the United States alone, 8 million people are diagnosed with peripheral arterial disease per year and over 250,000 patients have coronary bypass surgery each year. Autologous blood vessels are the standard graft used in small diameter (<6mm) arterial bypass procedures. Synthetic small diameter grafts have had limited success. While polyethylene (Dacron) and expanded polytetrafluoroethylene (ePTFE) are the most commonly used small diameter synthetic vascular graft materials, there are significant limitations that make these materials unfavorable for use in the low blood flow conditions of the small diameter arteries. Specifically, Dacron and ePTFE grafts display failure due to early thrombosis or late intimal hyperplasia. With the shortage of tissue donors and the limited supply of autologous blood vessels available, there is a need for a small diameter synthetic vascular graft alternative. The aim of this research is to create and characterize ePTFE grafts prepared with hyaluronic acid (HA), evaluate thrombogenic potential of ePTFE-HA grafts, and evaluate graft mechanical properties and coating durability. The results in this work indicate the successful production of ePTFE-HA materials using a solvent infiltration technique. Surface interactions with blood show increased platelet adhesion on HA-modified surfaces, though evidence may suggest less platelet activation and erythrocyte lysis. Significant changes in mechanical properties of HA-modified ePTFE materials were observed. Further investigation into solvent selection, uniformity of HA, endothelialization, and dynamic flow testing would be beneficial in the evaluation of these materials for use in small diameter vascular graft bypass procedures.
Open Access
Improving hydrophilicity of silicone elastomer by IPN formation with hyaluronan
(Colorado State University. Libraries, 2016) Koch, Richard L., author; James, Susan P., advisor; Bailey, Travis, committee member; Popat, Ketul C., committee member
Soft contact lenses have been available to consumers for the past several decades. By far, the most popular form on the market today is the silicone hydrogel, with nearly 70% of the market share. However, many contact lens wearers still have issues which cause them to discontinue lens use. It is estimated that between 25-35% of people discontinue use permanently. This can be traced back to two main issues with modern hydrogel lenses: a lack of adequate oxygen permeability across the lens; and lens-induced dehydration of the cornea. The corneal epithelium lining the lens of the eye is an avascular environment. As such, the cells must get their oxygen by diffusion through the tear film, or any material covering the lens. The silicone hydrogel SCLs have reduced oxygen gas permeability compared to traditional silicone elastomers. Additionally, when the hydrogel lenses lose water to evaporation, they pull water from the wearer's eye, contributing to dryness. Beyond simple discomfort, these issues can lead to pathologies such as hyperemia and even corneal cell death in severe cases. It was determined that a solution to these issues would be a new ocular lens material which had superior oxygen gas permeability and was hydrophilic without containing water in its bulk. The aim of this research was to create an interpenetrating polymer network (IPN) materials of poly(dimethyl siloxane) (PDMS) and hyaluronan (HA) with such properties. The results in this work indicate the successful synthesis of these HA-PDMS IPN materials. These elastomeric materials had improved hydrophilicity compared to untreated PDMS. Additionally, new chemical species (ATR/FTIR and XPS spectroscopy) and surface morphologies (SEM imaging) indicated the introduction of HA into the PDMS. Furthermore, analysis of the oxygen gas permeability showed no significant change for the treated samples as compared to the PDMS base material. As silicone materials have use in many biomedical fields, the material was also tested for platelet adhesion/activation and whole blood clotting. However, studies showed unfavorable results as the treated samples still caused platelet activation and blood clotting. Additionally, overall optical transmittance of the treated materials was significantly decreased. Further refinement of the treatment methods may yield more favorable results in the areas of thrombogenicity and platelet adhesion.
Open Access
Investigation of adipose-derived mesenchymal stem cells interaction with electrospun demineralized bone matrix nanofiber scaffolds
(Colorado State University. Libraries, 2016) Yaprak Akgul, Selin, author; Kipper, Matt, advisor; Popat, Ketul, advisor; Bailey, Travis, committee member; Ehrhart, Nicole, committee member
Nanofiber demineralized bone matrix (DBM) scaffolds were fabricated by electrospinning, and their ability to support cell adhesion and cell viability of murine adipose-derived mesenchymal stem cells (AD-MSCs) for short-term in culture media was investigated. Poly (ε-caprolactone) (PCL) scaffolds were used as control surfaces. Live cell stain calcein-AM and CellTiter 96® Non-Radioactive Cell Proliferation assays were used for cell adhesion and cell proliferation, respectively. DBM scaffolds supported greater cell adhesion compared to PCL nanofiber scaffolds. For cell viability, the two types of scaffolds behaved similarly. The results led to further research on DBM scaffolds. The ability to support osteoblastic differentiation of AD-MSCs for long-term (three weeks) in osteogenic differentiation media was also investigated. Both PCL scaffolds and DBM scaffolds seeded with no cells were used as control surfaces. The total protein content of viable AD-MSCs on the scaffolds was assessed by bicinchoninic acid (BCA) assay. Nanofiber scaffolds displayed increased levels of alkaline phosphatase (ALP) activity for the first week for all cases. ALP activity dropped after one week. Scanning electron microscopy (SEM) and alizarin calcium staining techniques were used to examine mineralization patterns qualitatively on DBM and PCL nanofiber scaffolds. DBM scaffolds deposited more calcium mineral than PCL scaffolds during three-week experiments. Mineralization was quantified by energy-dispersive X-ray spectroscope (EDS). After three weeks of culture, EDS revealed high calcium and phosphorus deposition on DBM scaffolds compared to PCL controls. The DBM scaffolds exhibited increased mineralization over three weeks, both with and without cells. These results demonstrate that the adhesion, proliferation, and osteogenic differentiation of AD-MSCs were influenced by DBM scaffolds.
Open Access
Mechanisms of interaction between bentonite and anionic polymers in enhanced geosynthetic clay liners
(Colorado State University. Libraries, 2021) Norris, Anna, author; Scalia, Joseph, advisor; Shackelford, Charles, advisor; Borch, Thomas, committee member; Benson, Craig, committee member; Bailey, Travis, committee member
Polymer enhanced bentonites (EBs) are a potential solution to the chemical incompatibility of natural bentonite in many containment applications. Relative to conventional (natural or un-enhanced) bentonites, EBs have shown improved (lower) hydraulic conductivity to high strength waste liquids, but the mechanisms underlying these improvements are not well understood. The EB geosynthetic clay liners (EB-GCLs) evaluated in this study were produced with linear anionic polymers poly(acrylic acid) (PA) and sodium carboxymethylcellulose (CMC), as well as a covalently crosslinked PA (PAx), using multiple mixing methods (dry-sprinkle, dry mix, and wet mix) and percent polymer enhancements (5-10% by mass). The results of hydraulic conductivity tests based on permeation with concentrated inorganic solutions, viz., 500 mM NaCl and 167 mM CaCl2, indicated that specific combinations of polymer type and mixing methods in the EB-GCLs produced a low hydraulic conductivity (≤ 5.0×10-11 m/s) for a given applied hydraulic gradient and permeant solution. The use of a lower hydraulic gradient (i.e., 30 vs. 300) also was shown to have the potential to yield a lower hydraulic conductivity of EB-GCLs, suggesting that EB-GCLs are sensitive to the applied hydraulic gradient in a way that conventional GCLs containing unamended sodium bentonite (NaB) are not. The reason for this difference is that there is less likelihood of any hydrogel existing within the EB-GCL being flushed from the EB-GCL at the lower hydraulic gradient. Batch adsorption tests were conducted with 16.7 and 167 mM CaCl2, 500 mM NaCl, 12.3 mM CaSO4 and 167 mM Na2SO4 solutions to compare the adsorption behavior with respect to cation and anion species and concentration. Poly (acrylic acid) adsorption onto NaB increased with increasing Ca2+ concentration (12.5 mM CaSO4 < 16.67 mM CaCl2 < 167 mM CaCl2), resulting in increasing solid (adsorbed) phase concentration of PA. Sodium bentonite tested with NaCl exhibited limited adsorption capacity for PA. Total carbon (TC) analysis was confirmed to be an accurate technique for measuring polymer loading of both as-prepared and hydrated/permeated EB-GCLs. A multiple lines of evidence approach was used to determine the mechanisms controlling the hydraulic conductivity of EB-GCLs. The results of the hydraulic conductivity testing were paired with measurements of polymer retention and qualitative measurements of hydrogel formation to understand the variables controlling polymer migration within and through the EB-GCL and the relationship between polymer retention and hydraulic conductivity. The results indicated that the low hydraulic conductivity of EB-GCLs (≤ 5.0×10-11 m/s) is controlled by a combination of pore blocking (mechanical entrapment) and adsorption of polymer hydrogel. The reduction in long-term hydraulic conductivity of EB-GCLs relative to unamended GCLs in aggressive inorganic solutions was determined to be the result of several factors, including (1) the formation of hydrogel, (2) the clogging of the largest (most conductive) pores by the hydrogel, (3) the balancing of seepage forces that are sufficient to mobilize the hydrogel into the pores but not sufficiently high to untangle and mobilize the hydrogel due to shear thinning or dislodging by inertial forces, and (4) the kinetics of hydrogel formation and adsorption of polymer to the surface of bentonite. This study illuminates the myriad of interconnected factors that can and must be optimized for EB-GCLs to provide effective long-term containment of aggressive inorganic wastes.
Open Access
Mechanistically-guided advancement of photoinduced organocatalyzed atom transfer radical polymerization
(Colorado State University. Libraries, 2020) Buss, Bonnie Leigh, author; Miyake, Garret, advisor; Bailey, Travis, committee member; Shi, Yian, committee member; Herrera-Alonso, Margarita, committee member
Photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) is a promising polymerization methodology which leverages radical reactivity to afford macromolecular products with a high degree of control over polymer molecular weights and molecular weight distributions, paired with the added benefit of spatial and temporal control over polymerization. This process, a metal-free approach, relies on photoexcitation of an organic photoredox catalyst which stringently mediates the radical activation and deactivation steps of an oxidative quenching catalytic cycle. To successfully operate this cycle, and thus control the polymerization, the rate of deactivation must be faster than both the rates of radical activation and monomer propagation. Central to the initial development of O-ATRP has been the design and study of strongly reducing organic photocatalysts, particularly in the context of methacrylate monomer polymerizations. However, as a burgeoning methodology, the full scope of O-ATRP has not yet been established. In this dissertation, efforts in addressing three key challenges in O-ATRP, including reaction scalability, complex architecture synthesis, and polymerization of challenging monomers, through manipulation of features of the oxidative quenching mechanistic cycle is presented. To address these challenges diverse approaches were employed, including adaptation to continuous-flow reactors, implementation of multifunctional initiating systems, and rational design of a new family of organic photocatalysts, ultimately facilitating progression of O-ATRP to a scalable and efficient approach in the well-defined synthesis of industrially-relevant materials.
Open Access
Metal organic frameworks as heterogenous nitric oxide catalysts for use in the development of therapeutic polymer materials
(Colorado State University. Libraries, 2014) Harding, Jacqueline L., author; Reynolds, Melissa, advisor; Prieto, Amy, committee member; Crans, Debbie, committee member; Bailey, Travis, committee member; Worley, Deanna, committee member
Implantable polymeric medical devices are subject to surface biofouling due to the deposition of microbial agents and the accumulation of proteins at the material interface. Consequently, medical devices which are intended for beneficial functions can become a potentially fatal threat. As a result biofouling resistant materials are vigorously sought through the manipulation of material surface properties and by eluting therapeutics on the material surface. Nitric oxide (NO) is a bioactive agent generated by most nucleated cells in the human body and is known to mediate antimicrobial and antithrombus effects while maintain the capacity to promote the proliferation of healthy tissues. As such, the development of NO releasing biomaterials is known to reduce incidences of surface biofouling. However, current NO releasing materials are limited to short lifetimes of used based on limited capacity of exogenous NO which can be incorporated into the material. In order to circumvent this problem the goal of this research is to develop a biomaterial which generates NO from an endogenously supplied source. Metal organic frameworks (MOFs) were selected for investigation as heterogeneous catalysts for the generation of NO from bioavailable NO donors, S-nitrosothiols (RSNOS). MOFs were evaluated as NO catalysts based on their capacity to react with various RSNO substrates and their maintained structural integrity under reaction conditions. Presented herein is the successful demonstration of a Cu-MOF for the catalytic generation of NO from bioavailable RSNOs donors. However, the limited stability of this proof of principle MOF in aqueous solution prompted the development of a MOF-NO catalyst that is suitable for physiological applications through tuning the organic ligands used in the construction of the framework. Finally a two-fold demonstration of the feasibility towards designing composite MOF based biomaterials is presented as blended materials prepared via commercial manufacturing processes and via surface growth of MOFs on flexible polymeric substrates.
Open Access
Modifying electronic and solid-state properties of fullerenes, polycyclic aromatic hydrocarbons, and perylene diimides
(Colorado State University. Libraries, 2015) Clikeman, Tyler T., author; Strauss, Steven H., advisor; Rumbles, Garry, advisor; Shores, Matt P., committee member; Chen, Eugene Y.-X., committee member; Bailey, Travis, committee member; Sites, Jim, committee member
The growing world energy demand necessitates the development of novel, cheap, and efficient energy sources and low energy consumption electronics devices. Organic photovoltaics, transistors, and light-emitting diodes are actively being developed as replacements for traditional energy sources and electronic devices. Strong electron acceptors are required to increase the efficiency and air stability for many of these applications. Studying how the incremental introduction of strong electron-accepting moieties onto electron-accepting substrates can affect performance is essential for systematically developing new devices. Furthermore, synthetic methodologies and characterization of these molecules are essential before incorporation into real world applications. This dissertation focuses on synthesizing families of strong electron acceptors via modification with strong perfluoroalkyl or cyano electron-withdrawing groups for fundamental studies in the development of advanced electronics. The first chapter focuses on the synthesis and characterization of new trifluoromethylfullerene derivatives. Synthetic methods for adding CF3 groups to C60, C70, and M3N@C80 are discussed and new CF3 addition patterns are revealed by single crystal XRD. Then the addition of electrophiles, nucleophiles, and cycloadducts to these trifluoromethylfullerene derivatives are discussed. Adding single nucleophiles and electrophiles to the cages along with collaborative DFT studies show which cage carbon atoms are most susceptible towards additional attack. The variations in electron accepting behavior were studied by adding a combination of electron-withdrawing and electron-donating groups at these specific locations on the fullerene cage. The studies revealed that these groups can modify electronic behaviors incrementally and somewhat unexpectedly by disrupting the fullerene π system. Understanding where and why new groups add to the fullerene cages and how they affect electronic behaviors could be used as the foundation for synthesizing new fullerene molecules to be used in advanced electronic devices. The second chapter concentrates on substituting electron-withdrawing fluorinated groups onto polycyclic aromatic hydrocarbon substrates. A family of poly(trifluoromethyl)azulene derivatives was synthesized and characterized for the first time. Trifluoromethylation of azulene systematically increases the electron-withdrawing strength and affects solid-state packing motifs. The molecular structures and solid-state packing of four other families of fluorine-modified polycyclic aromatic hydrocarbon substrates, corannulene, phenazine, triphenylene, and anthracene, were studied using single crystal XRD. Not only did XRD reveal previously unknown substitution patterns, but it was able to show where close π- π interactions existed within the packing structure, which could be extrapolated to solid-state charge transport in future applications. The third chapter focuses on developing a new series of perylene diimide acceptors and their use in organic photovoltaic active layers. Perylene diimides with previously unknown substitution patterns were synthesized with CF3 and CN groups and then isolated to isomeric purity using HPLC. Substituting with these strong electron-withdrawing groups at specific positions modified absorption, emission, solid-state packing, and solution- and gas-phase electron-accepting strength. These properties were compared within the entire series and solution reduction potentials were compared with a comprehensive list of literature reported perylene diimide acceptors. It was found that these properties were dependent on position and were not constant for each substituent. The series of poly(trifluoromethyl)perylene diimides were then blended with polymer donors and tested in photovoltaic active layer films. The systematic tuning of electron-withdrawing strength was used as a handle for fundamental studies on how increased electron affinity and fluorination affect charge transfer in the solid-state. All of the perylene diimides were able to accept charge from the polymer donors, but increasing the electron- withdrawing strength by introducing more fluorine atoms did not improve the charge separation yield.