Theses and Dissertations from UMD
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Item ELECTROLYTE AND INTERPHASE DESIGN FOR HIGH-ENERGY AND LONG-LIFE LITHIUM/SULFURIZED POLYACRYLONITRILE (Li/SPAN) BATTERIES(2024) Phan, An Le Bao; Wang, Chunsheng; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Lithium/sulfurized polyacrylonitrile (Li/SPAN) recently emerged as a promising battery chemistry with theoretical energy density beyond traditional lithium-ion batteries, attributed to the high specific capacities of Li and SPAN. Compared to traditional sulfur-based cathodes, SPAN demonstrated superior sulfur activity/utilization and no polysulfide dissolution issue. Compared to batteries based on layered oxide cathodes, Li/SPAN shows two significant advantages: (1) high theoretical energy density (> 1000 Wh kg-1, compared to around 750 Wh kg-1 of Li/LiNi0.8Mn0.1Co0.1O2) and (2) transition-metal-free nature, which eliminates the shortcomings associated with transition metals, such as high cost, low abundance, uneven distribution on the earth and potential toxicity. The success of Li/SPAN chemistry with those two critical advantages would not only relief the range and cost anxiety persistently associated with electric vehicle (EV) applications, but also have great implications for the general energy storage market. However, current Li/SPAN batteries still fall far behind their true potential in terms of both energy density and cycle life. This dissertation aims to provide new insights into bridging the theory-practice gap of Li/SPAN batteries by appropriate interphase and comprehensive electrolyte designs. First, the effect of Li/SPAN cell design on energy density and cycle life was discussed using relevant in-house developed models. The concept of “sensitivity factor” was established and used to quantitatively analyze the influence of input parameters. It was found that the electrolyte, rather than SPAN and Li electrodes, represents the bottleneck in Li/SPAN development, which explains our motivation to focus on electrolyte study. Another remarkable finding is that although not well-perceived, electrolyte density has a great impact on Li/SPAN cell-level energy density. Second, design principles to achieve good electrode-electrolyte compatibility were explored. Novel approaches to promote the formation of more protective, inorganic-rich interphases (SEI or CEI) were proposed and validated with proper experiments, including electrochemical tests, material characterizations (such as SEM, XPS, NMR, IR, Raman), and their correlations. Finally, based on the principles discussed in previous chapters, we developed a new electrolyte that simultaneously offers good electrochemical performance (Li CE > 99.4%, Li-SPAN full-cells > 200 cycles), decent ionic conductivity (1.3 mS cm-1), low density (1.04 g mL-1), good processability (higher vapor pressure than conventional carbonates, b.p. > 140 °C), and good safety. Outlook and perspective will also be presented. Beyond Li/SPAN, we believe that our findings regarding cell design as well as electrolyte solvation structure, interphases chemistry, and their implications on electrochemical performance are also meaningful for the development of other high-energy battery chemistries.Item QUANTITATIVE UNDERSTANDING OF TEMPERATURE RISE AND SAFETY IN HIGH – ENERGY SOLID – STATE BATTERIES.(2024) Ogundipe, Taiwo Oladapo; Albertus, Paul; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The rising demand for renewable energy and electric transportation has increased the need for advanced and safer battery technologies. Conventional lithium – ion batteries face limitations in energy density and safety risks due to the reaction of oxygen from the decomposed cathodes with other battery components, which can cause thermal runaway, leading to fires or explosions. Solid – state batteries, which use a solid electrolyte, offer a promising solution by potentially improving both energy density and safety. This study focuses on the thermal behavior and heat generation of anode – cathode – electrolyte (ACE) (Li / LPSCl / NMC811) solid-state batteries using differential scanning calorimetry (DSC). The results show significant heat generation, ranging from 4000 to 5400 J/g NMC811, with a corresponding adiabatic temperature rise of 1300 – 1750 ℃. When small amounts of liquid electrolyte are added, the onset temperature is lowered, and the heat release shifts to higher temperatures. However, the total heat generation remains within a similar range. These findings provide insights into the thermal stability of all – solid – state batteries , and solid – state batteries with small amount of liquid electrolyte, contributing to the development of safer and higher energy density energy storage systems.Item INTEGRATED PROCESS MODELING AND EXPERIMENTAL ANALYSIS FOR OPTIMIZING CONTINUOUS MANUFACTURE OF DRUG SUBSTANCE CARBAMAZEPINE(2024) Kraus, Harrison; Choi, Kyu Yong; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation presents a comprehensive study on the continuous manufacture (CM) of the drug substance (DS) carbamazepine (CBZ), a widely used anti-epileptic medication, aimed at enhancing process efficiency and product quality. The research progresses through a series of investigations, beginning with the development of kinetic models for CBZ synthesis from iminostilbene via two different synthetic routes using urea and potassium cyanate across various reactor setups, including batch and continuous flow systems. Discrepancies between batch and continuous models, particularly in yield prediction and impurity formation, are thoroughly examined and addressed through adjustments in reactant addition methods and system designs. This demonstrates the value of mechanistic modeling, a tool that has been undervalued in recent research particularly for its ability to compare between batch and continuous systems. Subsequently, the research delves into the crystallization processes, employing a population balance model (PBM) to study CBZ polymorph form III crystal formation, highlighting the influence of seed crystal size distribution on product crystal quality. It also provides novel strategies for modeling the evolution of crystal size distribution (CSD) due to nucleation and growth and evaluates the robustness of these strategies as seed CSD varies. Lastly, the scope is expanded to a holistic view of the integrated synthesis and crystallization process presenting one of the first studies of a complete DS CM system and emphasizing the development of a robust Quality-by-Control (QbC) framework. This includes the implementation of in-line Raman spectroscopy for real-time concentration monitoring, an active feedback level control system, dynamic modeling of impurity partitioning for enhancing disturbance mitigation across the CM process, and a retrograde design strategy that optimizes the upstream synthesis based on downstream purification capabilities/limitations. Through all these contributions, the dissertation aims to advance the modernization of continuous manufacturing practices in the pharmaceutical industry and promotes a shift towards more adaptive and controlled production environments.Item Sutureless Anastomosis: Electroadhering a Hydrogel Sleeve Over Cut Pieces of Tubular Tissue(2024) Grasso, Samantha Marie; Raghavan, Srinivasa R; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recently, our lab demonstrated that cationic gels could be adhered to animal tissues by applying an electric field (10 V DC, for ~ 20 s). This phenomenon, termed electroadhesion (EA), could potentially be used to repair injured tissues without sutures. An extreme injury is when a tube in the body (e.g., a blood vessel or an intestine) is cut into two segments. The surgical process of joining the segments is termed anastomosis, and thus far has only been done clinically with sutures. Here, we explore the use of EA for performing sutureless anastomoses in vitro with bovine aorta and chicken intestine. For this purpose, we make a strong and stretchable cationic gel in the form of a sleeve (i.e., a hollow tube). By using a custom plastic mold, we control both the sleeve diameter and wall thickness. A sleeve with a diameter matching that of the tubular tissue is slipped over the cut segments of the tube, followed by application of the DC electric field. Thereby, the sleeve becomes strongly adhered by EA to the underlying tube. Water or blood is then flowed through the repaired tube, and we record the burst pressure Pburst of the tube. We find that Pburst is > 80 mm Hg and close to the Pburst of an intact (uncut) tube. In comparison to the sleeve, a long strip of the gel attached around the cut tubular pieces allows a much lower Pburst. Thus, our study shows that gel-sleeves adhered by EA could enable anastomoses to be performed in the clinic without the need for sutures.Item Slow and Sustained Release of Hydrophilic Solutes from Capsules(2024) Cho, Hannah Yeonhee; Raghavan, Srinivasa R; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Capsules can be used to deliver solutes encapsulated in their aqueous core, including drugs. However, small, hydrophilic solutes tend to leak out of typical capsules in a matter of minutes. Solute release can be completely prevented if the capsule shell is made of a hydrophobic solid like paraffin wax. The goal of this study is to achieve release profiles between these extremes 3⁄4 i.e., release of solutes in a slow and sustained manner over a period of days. For this, we modify the wax-shell design above and include a nonionic surfactant (from the Brij series) along with the wax. Most of our studies have been done with Brij-C10, which has a polyethylene glycol (PEG) head and a hexadecyl (C16) tail. We show that capsules with a shell of 80/20 wax/Brij can release model dyes from the aqueous core over 20+ days. Such slow release has not been reported previously. The release rate can be tuned via the concentration of Brij in the shell (the higher the Brij, the faster the release) as well as the chemistry of the Brij (i.e., the size of the surfactant head or tail). The sustained release occurs because the Brij-bearing shell has microchannels through which the solute can permeate. Our approach can be used to slowly release many solutes, including dyes, drugs, and reactive reagents (such as H2O2). The simplicity and versatility of this approach make it highly suitable for controlled release applications across the pharmaceutical, agrochemical, and cosmetics industries.Item Chemically Fueled Transient Porous Hydrogels as Autonomous Soft Actuators(2024) Battumur, Sarangua; Woehl, Taylor J.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biomimetic materials take inspiration from biological systems to develop transformativereconfigurable synthetic materials. One example of a biological system is the contraction of muscle fibers driven by biochemical reactions. Actin filaments are crucial to cellular functions, facilitating movement, division, and structural integrity through ATP-driven polymerization and depolymerization. This ability to self-assemble and disassemble in response to biochemical signals provides a model for creating materials that mimic the sophisticated control found in biological systems. This thesis describes the use of a chemical reaction network to rapidly and autonomouslyreconfigure the size of a porous polymer hydrogels within tens of minutes. This hydrogel, composed of acrylic acid and acrylamide monomers, exhibits exceptional microporosity and an ability to expand approximately 150 times its original size within 15 seconds when exposed to water. The chemical reaction network utilizes a carbodiimide molecule, which transiently converts carboxylic acid moieties to anhydride bonds, causing transient shrinking of the hydrogel. The hydrogel spontaneously swelled due to hydrolysis of the anhydride bonds. We enhance the swelling rate of the porous hydrogels by adding polymer beads loaded with formaldehyde and sulfite buffer to the reaction vessel, which generate a time delayed pH increase that accelerates the hydrolysis of the anhydride bonds. This multi-reaction network forms porous hydrogels that contract and reswell autonomously in less than 10 minutes,compared to about 1 hour without the delayed pH change. This approach not only enables a faster reconfiguration of the porous gel induced by EDC through the hydrolysis of the anhydride due to a transient pH change, but also integrates this external stimulus into a single-step, autonomous process. This work also deepens our understanding of natural and synthetic actuation systems and how to couple different reactions to enhance their response. By harnessing the principles of bioinspired actuation, our work bridges the gap between the orchestrated movements of biological systems and the engineered behavior of synthetic materials, infusing our constructs with a level of adaptability and responsiveness that mirrors the natural world.Item HISTATIN 5 MODIFICATIONS IMPACT PROTEOLYTIC STABILITY IN THE PRESENCE OF FUNGAL AND SALIVARY PROTEASES(2024) Makambi, Wright Kingi; Karlsson, Amy J; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Candida albicans, found in the oral cavities of 30-50% of the global population, can lead to oral candidiasis, particularly in immunocompromised individuals like those with HIV or diabetes. The current treatments, small-molecule antifungals, often fall short due to drug resistance and toxicity. To address these challenges, histatin 5 (Hst5), a 24-amino-acid peptide naturally present in human saliva, has been studied as a potential antifungal therapy. Hst5, however, is susceptible to degradation by secreted aspartyl proteases (Saps) produced by C. albicans and salivary enzymes, limiting its potential efficacy as a therapeutic. We have engineered Hst5 variants utilizing rational design in order to understand the interactions with Saps and Saliva. We have also made advancements in developing a novel screening method utilizing the directed evolution technique yeast surface display. Our study employed rational design to modify Hst5, at its lysine residues (K5, K11, K13, and K17), substituting them with leucine or arginine to examine their influence on interactions with Saps (Sap1, Sap2, Sap3, Sap5, Sap6, Sap9, and Sap10). Sap5, Sap6, and Sap10 did not degrade Hst5 at the tested conditions, while Sap1, Sap2, Sap3, and Sap9 did. Some modifications, such as K13L, are particularly susceptible to proteolysis by Sap1, Sap2, Sap3, and Sap9. In contrast, K17L substantially increases the stability and antifungal activity of Hst5 in the presence of Saps. Additionally, although the K11RK17L variant was degraded more than the K17L variant, their antifungal activities were largely similar. The proteolysis products of were also identified by mass spectrometry identifying the [4-24], [1-17], and [14-24] Sap proteolysis products. We also evaluated the proteolytic stability of these variants in saliva. Both K17L and K5R showed improved stability; however, the enhancements were modest, suggesting that further engineering is required to achieve significant improvements. Further experiments evaluated how additional amino acid substitutions at K13 and K17 affect the peptide’s proteolytic stability in the presence of Saps (with and without zinc). Our findings suggest that the positive charge at K13 is important for the proteolytic stability of Hst5, as all other variants tested except K13R reduce overall proteolytic stability. Furthermore, many substitutions at K17, including tryptophan, significantly enhance proteolytic resistance and antifungal activity following incubation with Saps. The K17W variant showed improved stability and antifungal efficacy, maintaining its function even in the presence of zinc and exhibiting stronger antibiofilm activity than the parent Hst5. In addition to the rational design work, we have advanced the development of a directed evolution yeast surface display platform for screening peptides for proteolytic stability. This would allow for the expression of large peptide libraries on the surface of Saccharomyces cerevisiae. Through optimization of expression and display conditions, we determined an induction media at 30°C with a pH of 3.5 and devoid of glucose improved the expression and display of Hst5 peptides on the surface of S. cerevisiae. We also optimized the degradation conditions for Sap2 37°C, a pH not exceeding 7.4, and a Sap2 concentration of 0.78 µg/mL led to the best discrepancy between proteolytically stable variants. Additionally, we found that a 40 amino acid linker between the peptide and the yeast surface provided the best observing proteolytic degradation. Using the optimized system, we showed that yeast surface display can be used to discriminate between peptide variants with different levels of proteolytic stability. This lays the foundation for future work to screen large libraries of peptides for proteolytic stability. From these results, we have gained a deeper understanding of the interactions between Hst5 and Saps, showing that modification at different lysine residues greatly impacts the proteolytic stability of Hst5. Furthermore, we have shown that the yeast surface display platform can be used to screen the proteolytic stability of peptides. Looking forward, this peptide should be engineered for proteolytic stability in saliva. Furthermore, mock screens should be made before screening a library of peptides using the yeast surface display platform.Item DEVELOPMENT OF GLYCOSAMINOGLYCAN MIMICKING NANOGEL TECHNOLOGIES FOR CONTROLLED RELEASE OF THERAPEUTICS TO TREAT RETINAL DISEASES IN DIFFERENT AGE GROUPS(2024) Kim, Sangyoon; Lowe, Tao L.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Retinal diseases, such as diabetic retinopathy, glaucoma, macular degeneration, and retinoblastoma, affect around 13 million people worldwide, with projections indicating a rise to 20 million by 2030. These conditions lead to irreversible vision loss and significant impairment in both adults and children, with an annual economic burden of $139 billion in the United States alone. Aging significantly increases the risk of certain retinal conditions, and with improvements in healthcare leading to increased life expectancy, these conditions are becoming more prevalent due to the natural aging process and associated physiological changes in the eye. Current treatments are either destructive or have low efficacy and are not optimized for the younger population. While therapeutics including small molecular drugs, proteins and antibodies show promise in treating these diseases by reducing inflammation and neuronal apoptosis, their effectiveness is hindered by short half-lives and inability to cross the blood-retinal barrier (BRB). Nanoparticles offer a potential solution by improving drug delivery across biological barriers, yet no nanoparticles have been developed to effectively transport intact proteins or small molecules across the BRB to the retina without toxicity, slow clearance and stability. Therefore, there is an unmet need to evaluate the physical and physiological property changes of the eye along development and develop nanoparticle systems that can control and sustain the release of therapeutics across the blood retinal barrier (BRB) to treat the retinal diseases. In this project, the thickness, rheological property, permeability and morphological property changes of ocular barriers including sclera, cornea and vitreous humor in the developing eye from preterm to adult were evaluated using porcine ex vivo model. Two glycosaminoglycan mimicking nanogel systems, poly(NIPAAm-co-DEXcaprolactoneHEMA) nanogels with and without positive or negative charges and β-cyclodextrin based poly(β-amino ester) (CD-p-AE) nanogels were developed for sustained release of intact proteins including insulin and anti-TNFα, and small hydrophobic drugs, respectively across the ex vivo porcine sclera and in vitro BRB models: human fetal retinal pigment epithelial (hfRPE), adult retinal pigment epithelial (ARPE-19) and human cerebral microvascular endothelial (hCMEC/D3) cell monolayers. Completion of this project will have a significant impact on developing novel personalized nanotherapeutics to treat retinal diseases in different age groups.Item CATALYST DEVELOPMENT FOR NON-OXIDATIVE METHANE UPGRADING TOWARDS HYDROCARBONS AND HYDROGEN PRODUCTION(2024) LIU, ZIXIAO; Liu, Dongxia; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Methane, the main constituent of natural gas and biogas is deemed to be an alternative source to replace crude oil in the production of chemicals and fuel. Non-oxidative methane conversion enables methane coupling or splitting to produce hydrogen and more significant hydrocarbons, but catalyst deactivation has been a challenge in past research. This dissertation addresses catalyst deactivation issues in non-oxidative methane conversion by inventing novel catalyst systems. For direct non-oxidative methane coupling, a pathway for methane upgrading into hydrogen, olefin, and aromatic products, the silica-supported catalysts were synthesized by flame fusion of a mixture of quartz silica and metal silicate precursors. Compared to the cristobalite silica-supported catalysts reported previously, vitreous silica-supported catalysts have disordered Si-O bonds and structural defects, enabling better metal dispersion and more vital metal-support interaction. The as-prepared vitreous silica-supported iron catalyst had a shorter induction period in methane activation and lower coke yield. The increase in iron concentration elongated the catalyst induction period and promoted aromatics and coke formation. Among different transition metal catalysts, the cobalt supported by vitreous silica had the best methane conversion, hydrocarbon product yield, and catalyst stability. For catalytic methane pyrolysis, a pathway producing COx-free hydrogen and valuable carbon product, a siliceous zeolite-supported cobalt catalyst was invented. In comparison to the methane pyrolysis catalysts in literature, the siliceous zeolite support in the invented catalyst has limited Brönsted acidity and increased mesoporosity, which limited the acid-catalyzed deactivation mechanism and facilitated the mass transport, and thus significantly increased the catalyst lifetime. The cobalt sites change the cluster sizes and coordination structures with the loading concentrations in the zeolite support, which leads to carbon products with different properties.Item Nature-Inspired Polymeric Materials: Unveiling Unique Responsive Properties(2023) Rath, Medha; Woehl, Taylor J.; Raghavan, Srinivasa R.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In nature, biological systems are able to respond autonomously to environmental cues. Drawing inspiration from nature, scientists have been creating materials that change their appearance, shape, or properties (e.g., optical or mechanical) in response to various stimuli. This work is our contribution to the field - we have designed a range of nature-inspired polymeric materials that reconfigure their properties in response to either physical cues (e.g., temperature) or chemicals in the external medium. In our initial study, our point of inspiration is the natural pearl, which displays a bright sheen (called ‘pearlescence’) due to light reflection from plate-like particles. We show, for the first time, that pearlescence can be reversibly induced in soft capsules that contain no plate-like particles. Our millimeter-sized capsules have an outer shell (~ 500 µm thick) of N-isopropylacrylamide (NIPA) gel, which shrinks above its lower critical solution temperature (LCST) of ~ 32°C. When a transparent capsule is heated above this LCST, it turns pearlescent, and the transparent state is recovered upon cooling. Specular reflectance measurements confirm that the pearlescence of the capsules is comparable to that of natural pearls. We attribute the pearlescence to light reflection from nanoscale domains in the shrunken NIPA shell above the LCST. Next, we draw inspiration from the skin of chameleons - the brilliant colors of the skin are due to ordered arrays (photonic crystals) of particles within the skin cells. To mimic this structure, we first create ‘photonic capsules’ with silica nanoparticles (NPs) in their liquid cores. When the capsules are placed in a polymer solution, the shell is impermeable to the polymer chains but is permeable to water. The resulting osmotic gradient induces the silica NPs to form close-packed arrays, i.e., photonic crystals, which deposit on the inner wall of the capsule. The capsules thereby show brilliant colors (iridescence), with the exact color depending on the NP size. We then further use these capsules as building blocks and fuse them together to form a free-standing sheet. The sheet is thus analogous to a tissue, with the capsules analogous to the constituent cells. We are thereby able to create a sheet of colored capsules, resembling the chameleon skin. Lastly, we take a step towards creating an ‘artificial muscle’. The muscles in our body are nature’s ideal machines as they can expand and contract at will. To mimic this ability, materials that change their size autonomously are of interest. With this goal in mind, we start with an anionic hydrogel with microscale pores - the gel expands by 300% when placed in water. When a carbodiimide is added to the water, it converts the carboxylates on the gel strands to anhydrides, and the loss of charge makes the gel shrink by 50%. The anhydrides are metastable, however, and hydrolyze over time - thereby, the charge on the chains is restored and the gel expands back to its initial size. A cycle of gel expansion and contraction is completed in ~ 40 min, which is ~ 10x faster than any previous soft autonomous material. The rapid response moves our gels closer to the timescales required for use in practical actuators or soft robots.