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Articles 1 - 25 of 25
Full-Text Articles in Engineering
Nanoscience At Interfaces And Surfaces: From Jamming To Electrode Texturing, Mengmeng Cui
Nanoscience At Interfaces And Surfaces: From Jamming To Electrode Texturing, Mengmeng Cui
Doctoral Dissertations
This dissertation focuses on the nanoparticle self-assembly on the liquid/liquid interface and the nanomaterial modification on surface. The self-assembly of nanoparticles at the liquid/liquid interface was utilized to trap non-equilibrium morphology when the nanoparticles reach jamming state. The dynamics of jammed systems were further studied by X-ray photon correlation spectroscopy. For the surface part, the nanomaterials were modified on the electrodes to improve the performance of microbial electrosynthesis. Also, a novel and simple method was developed to prepare nanomaterials including nanoparticle surfactants and carbon nanotubes (CNTs).
Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang
Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang
Doctoral Dissertations
Polymer-based semiconducting materials are promising candidates for large-scale, low-cost photovoltaic devices. To date, the efficiency of these devices has been low in part because of the challenge of optimizing molecular packing while also obtaining a bicontinuous structure with a characteristic length comparable to the exciton diffusion length of 10 to 20 nm. In this dissertation we developed an innovative evaporation-induced nanoparticle self-assembly technique, which could be an effective approach to fabricate uniform, densely packed, smooth thin films with cm-scale area from home-made P3HT nanoparticles. Unlike the previous reports of nanoparticle-based film formation, we use a mixture of two solvents so …
Thermodynamic And Dynamic Models For Directed Assembly Of Small Ensembles Of Colloidal Particles, Raghuram Thyagarajan
Thermodynamic And Dynamic Models For Directed Assembly Of Small Ensembles Of Colloidal Particles, Raghuram Thyagarajan
Doctoral Dissertations
Self and directed assembly of finite clusters (10 to 1000) of colloidal particles into crystalline objects is an emerging area of scientific interest that finds applica- tions in manufacturing of photonic crystals and other meta-materials. Such assembly problems are also of fundamental scientific interest because they involve thermodynamically small systems, with a number of particles that is far below the bulk limit. Robust methods for assembling defect-free target structures will ultimately require reduced-dimension process models that link the particle-level dynamics of the colloids to the actuator states. We have developed a three-part strategy for developing such process models. First, we …
Biopolymer Electrospun Nanofiber Mats To Inactivate And Remove Bacteria, Katrina Ann Rieger
Biopolymer Electrospun Nanofiber Mats To Inactivate And Remove Bacteria, Katrina Ann Rieger
Doctoral Dissertations
The persistence of antibiotic resistance in bacterial pathogens remains a primary concern for immunocompromised and critically-ill hospital patients. Hospital associated infections can be deadly and reduce the successes of medical advancements, such as, cancer therapies and medical implants. Thus, it is imperative to develop materials that can (i) deliver new antibiotics with accuracy, as well as (ii) uptake pathogenic microbes. In this work, we will demonstrate that electrospun nanofiber mats offer a promising platform for both of these objectives because of their high surface-to-volume ratio, interconnected high porosity, gas permeability, and ability to contour to virtually any surface. To provide …
Cell Modulation Using Functionalized Nanoparticles, Rui Tang
Cell Modulation Using Functionalized Nanoparticles, Rui Tang
Doctoral Dissertations
Monolayer functionalized ultra-small gold nanoparticles (AuNPs) provide a versatile platform for applications in cell research. Through rational design of surface ligands, the chemistry of AuNPs are precisely regulated at atomic level. In this dissertation, applications of AuNPs in cell modulation are discussed. The topics are split into two categories. In the first category, functionalized AuNPs are harnessed to generate a robust monolayer on cell culture surface for cell modulation. The proliferation and behavior of different types of cancer cells and normal cells are modulated by tuning the surface ligands of AuNPs. Fate decision of mesenchymal stem cells are also modulated …
Fabrication Of Ultrafine Structures And Functional Surfaces Over Large Areas, Yinyong Li
Fabrication Of Ultrafine Structures And Functional Surfaces Over Large Areas, Yinyong Li
Doctoral Dissertations
Micro-/nanofabrication finds wide use in the preparation of patterned surfaces, which are of vital importance in the applications of functional surfaces, electronics, optics, and sensors. This dissertation will present the preparation of ultrafine structures and functional surfaces over large areas utilizing a combination of top-down lithography technique and bottom-up wrinkling method. First, a simple, scalable and cost-effective spacer lithography approach utilizing polydopamine coating technique was developed for the fabrication of well-controlled nanopatterns with feature size in the sub-20 nm scale. Briefly, a thin layer of polydopamine (PDA) was conformally deposited on the sidewalls of pre-patterned poly (methyl methacrylate) (PMMA) features …
Engineering Polymers Through Impact Modification And Superheated Liquid Processing, Gregory Connor Evans
Engineering Polymers Through Impact Modification And Superheated Liquid Processing, Gregory Connor Evans
Doctoral Dissertations
A new approach to toughen anionically polymerized polyamide 6 (aPA6) was applied using reaction induced phase separation (RIPS). This method solved issues with particle dispersion, mixture viscosity, and additive concentration common with conventional rubber toughening thereby making it an ideal candidate for fiber reinforced aPA6 reaction injection molding (RIM). Octamethylcyclotetrasiloxane (D4) was used as a functional additive that undergoes RIPS during aPA6 polymerization and polymerizes to polydimethylsiloxane (PDMS). Controlled phase separation, modulus retention, and increased crystallinity were achieved at low additive concentrations. Optimal properties were achieved with 2 wt% D4. Fracture energy was measured at high …
Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem
Doctoral Dissertations
Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …
Cold Gas Dynamic Spray – Characterization Of Polymeric Deposition, Trenton Bush
Cold Gas Dynamic Spray – Characterization Of Polymeric Deposition, Trenton Bush
Masters Theses
When a solid, ductile particle impacts a substrate at sufficient velocity, the resulting heat, pressure, and plastic deformation can produce bonding at the interface. The use of a supersonic gas flow to accelerate such particles is known as Cold Spray deposition. The Cold Spray process has been commercialized for some metallic materials, but further research is required to unlock the exciting material properties possible with polymeric compounds. In this work, a combined computational and experimental study a) simulated and optimized the nozzle flow conditions necessary to produce bonding in a polyethylene particle, b) developed and fabricated an experimental device, and …
Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins
Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins
Doctoral Dissertations
Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions. In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these …
Synthesis And Applications Of Non-Migratory Metal Chelating Active Packaging, Maxine J. Roman
Synthesis And Applications Of Non-Migratory Metal Chelating Active Packaging, Maxine J. Roman
Doctoral Dissertations
Many packaged foods use synthetic chelators (e.g. ethylenediaminetetraacetic acid, EDTA) to inhibit metal promoted oxidation and/or microbial growth that may cause food spoilage. Consumer demand for foods without synthetic additives has prompted growing interest in alternative preservation methods. Our research group has previously developed non-migratory metal chelating active packaging materials by surface immobilization of polymeric chelators and demonstrated their ability to inhibit lipid oxidation in model food emulsions. The work presented in this dissertation investigates the synthesis, performance stability, and practical application of metal chelating surface modifications to optimize design of non-migratory metal chelating active packaging materials. Metal chelating active …
Enzyme Stabilization In Hierarchical Biocatalytic Food Packaging And Processing Materials, Dana Erin Wong
Enzyme Stabilization In Hierarchical Biocatalytic Food Packaging And Processing Materials, Dana Erin Wong
Doctoral Dissertations
The partnership of biocatalysts and solid support materials provides many opportunities for bioactive packaging and bioprocessing aids beneficial to the agricultural and food industries. Biocatalysis, or reactions modulated by enzymes, allows bioactive materials to assist in bringing a substrate to product. Enzymes are proteins which catalyze reactions by lowering the activation energy required to drive the production of a desired product. Enzymes are commonly utilized in food processing as catalysts with specificity in order to enhance product quality through the production of beneficial food components, and to break down undesirable components that may be harmful or may decrease product quality. …
Post-Wrinkling Behaviors In Layered Elastic Polymers, Anesia D. Auguste
Post-Wrinkling Behaviors In Layered Elastic Polymers, Anesia D. Auguste
Doctoral Dissertations
Surface instabilities include a variety of different modes such as wrinkles, folds, and creases. Such surface instabilities have been used in numerous contexts including changing the wetting, optical, and mechanical properties of different material surfaces for applications in flexible electronics, tissue engineering and biosensors. Interesting surface morphologies can arise due to differences in pre-strain, stiffness, and thickness between the film and substrate; however, the effects of these differences are not well understood. We have developed an experimental system, complemented by finite element simulations, to systematically vary the pre-stretch of the substrate, modulus contrast and thickness contrast to study the transitions …
Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz
Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz
Masters Theses
Solar technology has been a major topic in sustainable design for many years. In the last five years, however, the solar technology industry has seen a rapid growth in installations and technological advances in cell design. Combined with a rapidly declining overall system cost, the idea of introducing solar technology into a wider range of applications is becoming a focus for engineers and scientists around the world. So many variables which alter solar energy production, such as the sun and surrounding environment, determine whether a solar design is beneficial. This thesis presents a bridge deck surface integrated with solar cells …
Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang
Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang
Doctoral Dissertations
This thesis describes the solution behavior and interfacial properties of electronically active polymers. The performance of such polymers in devices is often determined by their chain conformation and morphology in solution and in thin films. For example, the intricate balance between polymer domain size and crystalline packing of electron donor and acceptor components, as well as the properties at the polymer-metal interface, are crucial for achieving optimal performance in devices, such as solar cells. Chapter 1 presents the current progress in polymer-based solar cells, their fundamental principles, and key factors to improve their efficiency. Literature precedents on the development of …
Diffusion Of Polymers In Polyelectrolyte Gels, Anand Rahalkar
Diffusion Of Polymers In Polyelectrolyte Gels, Anand Rahalkar
Doctoral Dissertations
Polyelectrolyte gels have the ability to undergo volume transitions in response to external stimuli. As a result, they are used in a wide variety of applications such as sensors, actuators, artificial implants, and controlled drug delivery. In addition, diffusion of trapped macromolecules inside gels is of tremendous significance in drug delivery systems. In this thesis, the dynamics of trapped polyelectrolytes in a polyelectrolyte gel is studied using dynamic light scattering technique. The effect of the crosslink density and the charge density of the gel, as well as of solvent quality and salt concentration are investigated. In general, two distinct diffusive …
Refractive Index Engineering And Optical Properties Enhancement By Polymer Nanocomposites, Cheng Li
Refractive Index Engineering And Optical Properties Enhancement By Polymer Nanocomposites, Cheng Li
Doctoral Dissertations
The major part of this dissertation discusses the engineering of the refractive index of materials using solution-processable polymer nanocomposites and their applications in building optical components and devices. Three particular polymer nanocomposites have been introduced to achieve materials with tunable refractive indices and enhanced optical properties, which can be used to manipulate the behavior of light or electromagnetic radiations. In the first system, polyhedral oligomeric silsesquioxane (POSS)/polymer nanocomposites are developed. Thin films with tunable, low refractive indicies were fabricated from the composites. The mechanical strength of these films was characterized, and their application in antireflective coatings is discussed. In the …
(I) Polymer Nanocomposites: Rheology And Processing For Mesoporous Materials And (Ii) Nanopatterning Of Metal Oxides Using Soft Lithography, Rohit Kothari
Doctoral Dissertations
The research in this dissertation is categorized into two parts. The first part is focused on investigation of order-to-disorder transitions (ODT) in nanocomposites of an amphiphilic block copolymer containing various hydrogen-bonded additives, and fabrication of novel mesoporous silica based materials by utilizing such nanocomposites as templates. Disordered Pluronic®, poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymer upon blending with small molecule additives containing hydrogen-bond-donating functional groups (carboxyl or hydroxyl) result into ordered nanoscale morphologies by preferentially interacting with the hydrophilic PEO chains in the Pluronic®. The dependence of ODT-temperature in these novel Pluronic®/small-molecule-additive complexes on composition, number and type of functional …
Theoretical Studies Of Atomic Transport In Ternary Semiconductor Quantum Dots And Charge Transport In Organic Photovoltaic Active Layers, Xu Han
Doctoral Dissertations
Ternary semiconductor quantum dots with thermodynamically stable structures are particularly important for achieving optimal performance in optoelectronic and photovoltaic applications. Ternary quantum dots (TQDs) are typically synthesized in the form of core/shell structures. However, misfit strain induced by the abrupt core/shell interface can change the nature of the TQDs dramatically, leading to unstable optoelectronic function. In this thesis, a transient species transport model is developed to predict species distributions in TQDs during their thermal annealing. Specifically, the interdiffusion kinetics is analyzed of group-VI species in ZnSe1-xSx and ZnSe1-xTex TQDs and of group-III species in …
Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella
Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella
Doctoral Dissertations
Polymer semiconductors hold great promise for the realization of inexpensive, flexible electronic devices. One of the greatest strengths of these materials, their low-cost processability from solution, results in a wide range of solid-state structures. The crystallinity and morphology of these materials strongly impacts their performance as charge carriers. Furthermore, the nature of polymerization inherently leads to the production of materials which are disperse in their molecular character, with regard to both coupling and molecular weight. Thus, it is difficult to deconvolute the intrinsic properties of polymer semiconductors from their synthetic and processing conditions. Polythiophenes are particularly susceptible to performance variations …
Controlling The Assembly Of Nanoparticles In Polymer Blends, Kyle C. Bryson
Controlling The Assembly Of Nanoparticles In Polymer Blends, Kyle C. Bryson
Doctoral Dissertations
While many novel methods have been devised for directing the assembly of nanoparticles in block copolymers, the topic has not reached the same level of sophistication for polymer blends. The assembly of particles at the interface between phase-separated domains can serve as a means to compatibilize polymer blends, reducing domain sizes and enhancing interdomain adhesion by impeding coalescence and decreasing interfacial tension. Compatibilization optimizes the performance of blended materials in applications where the properties of both components must be expressed synergistically, such as in plastics requiring both high strength and high toughness and in photovoltaic films. Thus, approaches to robustly …
Rational Development Of Solid Lewis Acid Catalysts For Biomass Conversion, Chun-Chih Chang
Rational Development Of Solid Lewis Acid Catalysts For Biomass Conversion, Chun-Chih Chang
Doctoral Dissertations
The need for sustainable production of everyday materials in addition to declining reserves of petroleum-based feedstocks has motivated research into the production of renewable aromatic chemicals from biomass. We have proposed a multistep pathway to produce renewable p-xylene from lignocellulosic biomass using heterogeneous catalysts. The pathway includes formation of glucose by saccharification of cellulose, isomerization of glucose into fructose, dehydration/hydrogenolysis for production of 2,5-dimethylfuran (DMF), and final step for producing p-xylene from reacting DMF with ethylene. Lewis acid zeolite catalysts (e.g. Sn-BEA, a tin containing molecular sieve with zeolite BEA structure) exhibited critical roles in the pathway because …
Patterns Around Us Presentation, Benny Davidovitch
Patterns Around Us Presentation, Benny Davidovitch
Patterns Around Us
No abstract provided.
Functional Droplets That Recognize, Collect, And Transport Debris On Surfaces, Ying Bai, Chia-Chih Chang, Umesh Choudhary, Irem Bolukbasi, Alfred J. Crosby, Todd Emrick
Functional Droplets That Recognize, Collect, And Transport Debris On Surfaces, Ying Bai, Chia-Chih Chang, Umesh Choudhary, Irem Bolukbasi, Alfred J. Crosby, Todd Emrick
Polymer Science and Engineering Department Faculty Publication Series
We describe polymer-stabilized droplets capable of recognizing and picking up nanoparticles from substrates in experiments designed for transporting hydroxyapatite nanoparticles that represent the principal elemental composition of bone. Our experiments, which are inspired by cells that carry out materials transport in vivo, used oil-in-water droplets that traverse a nanoparticle-coated substrate driven by an imposed fluid flow. Nanoparticle capture is realized by interaction of the particles with chemical functionality embedded within the polymeric stabilizing layer on the droplets. Nanoparticle uptake efficiency is controlled by solution conditions and the extent of functionality available for contact with the nanoparticles. Moreover, in an elementary …
A Comparison Of The Elastic Properties Of Graphene- And Fullerene-Reinforced Polymer Composites: The Role Of Filler Morphology And Size, Chang-Tsan Lu, Asanka Weerasinghe, Dimitrios Maroudas, Ashwin Ramasubramaniam
A Comparison Of The Elastic Properties Of Graphene- And Fullerene-Reinforced Polymer Composites: The Role Of Filler Morphology And Size, Chang-Tsan Lu, Asanka Weerasinghe, Dimitrios Maroudas, Ashwin Ramasubramaniam
Mechanical and Industrial Engineering Faculty Publication Series
Nanoscale carbon-based fillers are known to significantly alter the mechanical and electrical properties of polymers even at relatively low loadings. We report results from extensive molecular-dynamics simulations of mechanical testing of model polymer (high-density polyethylene) nanocomposites reinforced by nanocarbon fillers consisting of graphene flakes and fullerenes. By systematically varying filler concentration, morphology, and size, we identify clear trends in composite stiffness with reinforcement. To within statistical error, spherical fullerenes provide a nearly size-independent level of reinforcement. In contrast, two-dimensional graphene flakes induce a strongly size-dependent response: we find that flakes with radii in the 2–4 nm range provide appreciable enhancement …