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Full-Text Articles in Engineering

Top-Down And Bottom-Up Fabrication Of Key Components In Miniature Energy Storage Devices, Wenhao Li Oct 2019

Top-Down And Bottom-Up Fabrication Of Key Components In Miniature Energy Storage Devices, Wenhao Li

Doctoral Dissertations

The advent of miniature electronic devices demands power sources of commensurate form factors. This spurs the research of micro energy storage devices, e.g., 3D microbatteries. A 3D microbattery contains nonplanar microelectrodes with high aspect ratio and high surface area, separated by a nanoscale electrolyte. The device takes up a total volume as small as 10 mm3, allowing it to serve on a chip and to provide power in-situ. The marriage of nanotechnology and electrochemical energy storage makes microbattery research a fascinating field with both scientific excitement and application prospect. However, successful fabrication of well-functioned key components and the ...


Controlling Selectivities In Heterogeneously Catalyzed Aldol Reactions, Koushik Ponnuru Oct 2019

Controlling Selectivities In Heterogeneously Catalyzed Aldol Reactions, Koushik Ponnuru

Doctoral Dissertations

Aldol condensation is an important C-C bond formation reaction in chemical synthesis that finds versatile applications in bulk and fine chemical industries and has the potential for upgrading of biomass to fuels. However, aldol reactions pose a challenge for controlling the product selectivity by forming a mixture of desired and undesired self, cross, and poly-condensation products. Furthermore, a side reaction, the fission of aldol products resulting in an olefin and a carboxylic acid, has garnered attention recently as a route to isobutene from acetone. While a high level of selectivity control is achievable by homogeneous catalysis, selective solid catalysts, which ...


Bioinspired Complex Nanoarchitectures By Dna Supramolecular Polymerization, Laura A. Lanier Oct 2019

Bioinspired Complex Nanoarchitectures By Dna Supramolecular Polymerization, Laura A. Lanier

Doctoral Dissertations

Bioinspired nanoarchitectures are of great interest for applications in fields such as nanomedicine, tissue engineering, and biosensing. With this interest, understanding how the physical properties of these complex nanostructures relate to their function is increasingly important. This dissertation describes the creation of complex nanoarchitectures with controlled structure and the investigation of the effect of nanocarrier physical properties on cell uptake for applications in nanomedicine.

DNA self-assembly by supramolecular polymerization was chosen to create complex nanostructures of controlled architectures. We demonstrated that the supramolecular polymerization of DNA known as hybridization chain reaction (HCR) is in fact a living polymerization. The living ...


Engineering Nanomaterials For Imaging And Therapy Of Bacteria And Biofilm-Associated Infections, Akash Gupta Oct 2019

Engineering Nanomaterials For Imaging And Therapy Of Bacteria And Biofilm-Associated Infections, Akash Gupta

Doctoral Dissertations

Infections caused by multidrug-resistant (MDR) bacteria pose a serious global burden of mortality, causing thousands of deaths each year. The “superbug” risk is further exacerbated by chronic infections generated from antibiotic-resistant biofilms that are highly resistant to available treatments. Synthetic macromolecules such as polymers and nanoparticles have emerged as promising antimicrobials. Moreover, ability to modulate nanomaterial interaction with bacterial cellular systems plays a pivotal role in improving the efficacy of the strategy.

In the initial studies on engineering nanoparticle surface chemistry, I investigated the role played by surface ligands in determining the antimicrobial activity of the nanoparticles. In further study ...


Modeling And Simulation Of Driven Nanopatterning Of Bulk-Material And Thin-Film Surfaces, Ashish Kumar Oct 2019

Modeling And Simulation Of Driven Nanopatterning Of Bulk-Material And Thin-Film Surfaces, Ashish Kumar

Doctoral Dissertations

Material nanostructures such as nanowires, quantum dots, and nanorings have a wide variety of applications in electronic and photonic devices among numerous others. Assembling uniformly arranged and consistently sized nanostructure patterns on solid material surfaces is a major challenge for nanotechnology. This dissertation focuses on developing predictive models capable of simulation and analysis of such nanopattern formation on bulk material and strained thin film surfaces.

Single-layer atomic clusters (islands) of sizes larger than a critical size on crystalline conducting substrates undergo morphological instabilities when driven by an externally applied electric field or thermal gradient. We have conducted a systematic and ...


Amorphous-Crystalline Brush Block Copolymers: Phase Behavior, Rheology And Composite Design, Gayathri Kopanati Oct 2019

Amorphous-Crystalline Brush Block Copolymers: Phase Behavior, Rheology And Composite Design, Gayathri Kopanati

Doctoral Dissertations

Bottlebrush block copolymers are polymers with chemically distinct polymer side chains grafted onto a common backbone. The unique architecture induced properties make these materials attractive for applications such as photonic materials, stimuli responsive actuators and drug delivery vehicles to name a few. This dissertation primarily investigates the phase transitions and rheological behavior of amorphous-crystalline bottlebrush brush block copolymers and their composites. The temperature induced phase behavior is investigated using time resolved synchrotron X-ray source. Irrespective of volume fraction and backbone length, the samples display strong segregation even at high temperatures (200 °C) and there is no accessible order-disorder transition in ...


A Synthetic Human Brain Ecm Hydrogel For Tight Control Of Astrocyte Activation, Sualyneth Galarza Oct 2019

A Synthetic Human Brain Ecm Hydrogel For Tight Control Of Astrocyte Activation, Sualyneth Galarza

Doctoral Dissertations

Bioengineers have aimed to design instructive extracellular matrix (ECM) models that can tailor the protein composition and biomechanics of the brain in vitro in order to study how astrocytes remodel the brain during trauma and inflammation. However, these parameters cannot be independently controlled in protein-based models, and although tunable in synthetic systems, current astrocyte cultures fail to retain their characteristic stellate morphology without becoming activated. To this date, there is no biomaterial model that can retain astrocyte quiescence in vitro. This dissertation sought to develop such an in vitro model that would enable the study of specific ECM factors that ...


Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim Oct 2019

Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim

Doctoral Dissertations

Recent advances in the field of biomedical and life-sciences are increasingly demanding more life-like actuation with higher degrees of freedom in motion at small scales. Many researchers have developed various solutions to satisfy these emerging requirements. In many cases, new solutions are made possible with the development of novel polymeric actuators. Advances in polymeric actuation not only addressed problems concerning low degree of freedom in motion, large system size, and bio-incompatibility associated with conventional actuators, but also led to the discovery of novel applications, which were previously unattainable with conventional engineered systems.

This dissertation focuses on developing novel actuation mechanisms ...


Electrospinning Nanofibers From Chitosan-Hyaluronic Acid Complex Coacervates, Juanfeng Sun Aug 2019

Electrospinning Nanofibers From Chitosan-Hyaluronic Acid Complex Coacervates, Juanfeng Sun

Masters Theses

Electrospun nanofibers have been used for many applications, but a reliance on organic solvents limits their use in biomedical fields. In this study, we successfully electrospun nanofibers from aqueous chitosan-hyaluronic acid complex coacervates. We studied how solvent’ properties affected the average nanofiber diameter by using pure water as a solvent versus ethanol-water solutions. Experimentally, we investigated the effect of electrospinning apparatus parameters, such as how the applied voltage affected fiber formation and morphology. The smallest average nanofiber diameter was determined to be around 115 ± 30 nm when 3 wt% ethanol coacervate samples were electrospun using the applied voltage of 24 ...


Interfacial Interactions And Dynamic Adhesion Of Synthetic And Living Colloids In Flow, Molly Shave Aug 2019

Interfacial Interactions And Dynamic Adhesion Of Synthetic And Living Colloids In Flow, Molly Shave

Doctoral Dissertations

This thesis focuses on the interactions between flowing particles and a surface, where hydrodynamics couples with chemical interactions in order to modify the way they come into play.

First this thesis shows how electrostatic chemical heterogeneities on a flowing particle affect the interactions with a wall, using a highly tunable electrostatically heterogenous system produced by adsorbing small amounts of cationic polyelectrolytes onto silica particles in suspension and studying their behavior in flow over the fixed surface. By comparing this behavior to a system with equivalent chemical heterogeneity on a channel wall it was shown that the rotation of a particle ...


Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe Jul 2019

Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe

Doctoral Dissertations

This dissertation presents work focused on producing materials in non-equilibrium states by taking advantage of novel processing techniques. First, epoxy-based resins which can undergo radically promoted, cationic, thermal, frontal polymerization are investigated for their potential use as adhesives. These resins are found to be capable of sustaining propagating polymerization fronts between several different substrate materials, resulting in high levels of adhesion in some cases. In addition, a similar frontal resin was developed that can undergo sequential gelation and frontal polymerization. The gels are formed by radically crosslinking acrylate monomers within the epoxy resin. These gels can then be manipulated, and ...


Rheological Investigations Of Self-Assembled Block Copolymer Nanocomposites With Complex Architectures, Benjamin Yavitt Jul 2019

Rheological Investigations Of Self-Assembled Block Copolymer Nanocomposites With Complex Architectures, Benjamin Yavitt

Doctoral Dissertations

The self-assembly of block copolymers (BCP) into microphase separated structures is an attractive route to template and assemble functional nanoparticles (NP) into highly ordered nanocomposites and is central to the “bottom up” fabrication of future materials with tunable electronic, optical, magnetic, and mechanical properties. The optimization of the co-assembly requires an understanding of the fundamentals of phase behavior, intermolecular interactions and dynamics of the polymeric structure. Rheology is a novel characterization tool to investigate these processes in such systems that are not accessible by other means. With the combination of X-ray scattering techniques, structure-property relationships are determined as a function ...


Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu Mar 2019

Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu

Doctoral Dissertations

Oxygen vacancy and ion dynamics in functional oxides are critical factors influencing electrical conductivity and electrochemical activity of oxides assemblies. The recent advancements in deposition and fabrication of oxide heterostructured films with atomic-level precision has led to discovery of intriguing physical properties and new artificial materials. While still under debate, researchers most often attribute these observed behaviors to unique oxygen vacancy distributions in the substrate near heterointerfaces. In electroactive oxides devices such as solid oxide cells (SOCs), oxygen vacancy and ion transport at the triple-phase boundary determines the performance of the device. This complex process motivates numerous remaining questions regarding ...


Targeted Design Of Co-Continuous Nanostructures In Copolymers, Di Zeng Mar 2019

Targeted Design Of Co-Continuous Nanostructures In Copolymers, Di Zeng

Doctoral Dissertations

Microphase separated copolymers with nano-scale morphologies are critically important in designing next generation materials. Cocontinuous nanoscale structures, in which domains of multiple different phases each simultaneously percolate in three dimensions, provide opportunities to synergistically combine properties of the constituent polymers in a wide variety of contexts. While cocontinuous nanostructures are fabricated through equilibrium self-assembly of block or graft copolymers and kinetically trapped phase separation of polymer blends or crosslinked copolymer networks, their formation is highly sensitive to changes in chemical details, synthesis and/or processing conditions, bringing practical challenges to generalization to multiple systems.

In this dissertation, we focus on ...


Synthesis And Molecular Transport Studies In Zeolites And Nanoporous Membranes, Vivek Vattipalli Mar 2019

Synthesis And Molecular Transport Studies In Zeolites And Nanoporous Membranes, Vivek Vattipalli

Doctoral Dissertations

The advent of nanoporous materials such as zeolites and nanoporous membranes has provided cost-effective solutions to some of the most pressing problems of the 20th century such as the conversion of crude oil into fuels and valuable chemicals. Hierarchical zeolites and mesoporous inorganic membranes are showing great promise in addressing new problems such as the conversion of biomass into value-added chemicals and development of energy-efficient separation processes. The synthesis and fundamental aspects of molecular transport in these new materials with hierarchical porosities need to be better understood in order to rationally develop them for these desired applications.

Pore narrowing ...


Chemical Stability And Performance Influence Of Choice Substituents And Core Conjugation Of Organic Semiconductors, Jack Ly Mar 2019

Chemical Stability And Performance Influence Of Choice Substituents And Core Conjugation Of Organic Semiconductors, Jack Ly

Doctoral Dissertations

Realizing organic based active materials for electronic devices, such as thin film transistors and photovoltaics, has been long sought after. Advancement in the field driven by chemists, engineers, and physicists alike have bolstered organic based semiconductor performance levels to rival those of traditional inorganic amorphous silicon-based devices. Within the field of organic semiconductors (OSC), two categories of active materials may be generalized: (1) polymer and (2) small molecule semiconductors. Each class of OSC inherently have their own advantages and disadvantages. Polymer semiconductors (PSC) allow a wide range in tunability via choice monomers and side chain engineering to illicit desirable energy ...


The Investigation Of Surface Barrier During Molecular Transport In Hierarchical Zeolites, Xiaoduo Qi Mar 2019

The Investigation Of Surface Barrier During Molecular Transport In Hierarchical Zeolites, Xiaoduo Qi

Doctoral Dissertations

Hierarchical zeolites with micropore lengths on the order of nanometers have been synthesized with the aim of reducing mass transfer limitation. However, due to large external surface to volume ratios, the mass transport in these materials can be hindered by a secondary rate limitation step imposed on the external surface of the zeolites. This has led to the general phenomenon referred to as “surface barriers”, which cause the enhancement in mass transport being far lower than expected. In order to fully unlock the potential of hierarchical zeolites, it is imperative to fundamentally understand the molecular transport in these new types ...


Design Rules For Encapsulating Proteins Into Complex Coacervates, Whitney Blocher Mctigue, Sarah L. Perry Jan 2019

Design Rules For Encapsulating Proteins Into Complex Coacervates, Whitney Blocher Mctigue, Sarah L. Perry

Chemical Engineering Faculty Publication Series

We investigated the encapsulation of the model proteins bovine serum albumin (BSA), human hemoglobin (Hb), and hen egg white lysozyme (HEWL) into two-polymer complex coacervates as a function of polymer and solution conditions. Electrostatic parameters such as pH, protein net charge, salt concentration, and polymer charge density can be used to modulate protein uptake. While the use of a two-polymer coacervation system enables the encapsulation of weakly charged proteins that would otherwise require chemical modification to facilitate electrostatic complexation, we observed significantly higher uptake for proteins whose structure includes a cluster of like-charged residues on the protein surface. In addition ...


Designing Electrostatic Interactions Via Polyelectrolyte Monomer Sequence, Tyler K. Lytle, Li-Wei Chang, Natalia Markiewicz, Sarah L. Perry, Charles E. Sing Jan 2019

Designing Electrostatic Interactions Via Polyelectrolyte Monomer Sequence, Tyler K. Lytle, Li-Wei Chang, Natalia Markiewicz, Sarah L. Perry, Charles E. Sing

Chemical Engineering Faculty Publication Series

Charged polymers are ubiquitous in biological systems because electrostatic interactions can drive complicated structure formation and respond to environmental parameters such as ionic strength and pH. In these systems, function emerges from sophisticated molecular design; for example, intrinsically disordered proteins leverage specific sequences of monomeric charges to control the formation and function of intracellular compartments known as membraneless organelles. The role of a charged monomer sequence in dictating the strength of electrostatic interactions remains poorly understood despite extensive evidence that sequence is a powerful tool biology uses to tune soft materials. In this article, we use a combination of theory ...


Ionoelastomer Junctions Between Polymer Networks Of Fixed Anions And Cations, Hyeongjun Kim, Baohong Chen, Zhigang Suo, Ryan C. Hayward Jan 2019

Ionoelastomer Junctions Between Polymer Networks Of Fixed Anions And Cations, Hyeongjun Kim, Baohong Chen, Zhigang Suo, Ryan C. Hayward

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