Engineering Science and Materials Commons^™

Soft Electronics And Sensors For Wearable Healthcare Applications, Li-Wei Lo

McKelvey School of Engineering Theses & Dissertations

Wearable electronics are becoming increasingly essential to personalized medicine by collecting and analyzing massive amounts of biological signals from internal organs, muscles, and blood vessels. Conventional rigid electronics may lead to motion artifacts and errors in collected data due to the mismatches in mechanical properties between human skin. Instead, soft wearable electronics provide a better platform and interface that can form intimate contact and conformably adapt to human skin. In this respect, this thesis focuses on new materials formulation, fabrication, characterization of low-cost, high sensitivity and reliable sensors for wearable health monitoring applications.

More specifically, we have studied the silver …

Synthesis And Consolidation Of Metal Oxide Nanocrystals Via Nonthermal Plasma, Austin Cendejas

McKelvey School of Engineering Theses & Dissertations

Nonthermal plasmas offer a unique nonequilibrium environment that has been leveraged in a wide variety of applications in the fields of material processing, lighting, and waste management to name a few. In all of these cases, the plasma serves as a source of high energy electrons, ions, reactive gas species, and radicals that interact in several ways with surfaces brought into contact with the plasma. Specifically, nonthermal plasmas have been shown to be very successful in achieving continuous, high-throughput, monodisperse nanocrystals of a wide variety of materials. The crystallinity of nanoparticles synthesized in nonthermal plasmas can be attributed to the …

Plasmonic Nanomaterials-Based Point-Of-Care Biosensors, Rohit Gupta

McKelvey School of Engineering Theses & Dissertations

Point-of-care (POC) biosensors, although rapid and easy-to-use, are orders magnitude less sensitive than laboratory-based tests. Further they are plagued by poor stability of recognition element thus limiting its widespread applicability in resource-limited settings. Therefore, there is a critical need for realizing stable POC biosensors with sensitivity comparable to gold-standard laboratory-based tests. This challenge constitutes the fundamental basis of this dissertation work– to expand access to quality and accurate biodiagnostic tools. At the heart of these solutions lies plasmonic nanoparticles which exhibit unique optical properties which are attractive for label-free and labelled biosensors.Firstly, we improve the stability and applicability of label-free …

Nucleation Studies In Barium Silicate Glasses And Soda-Lime Silicate Glass, Xinsheng Xia

McKelvey School of Engineering Theses & Dissertations

Controlling nucleation is key for the manufacture of glasses and glass-ceramics. It has been observed by different researchers in many silicate glasses that at low temperatures the critical work of cluster formation (i.e. the nucleation barrier) slowly rises rather than decreasing with decreasing temperature. However, this experimental observation is in contradiction with nucleation theories. In this dissertation, crystal nucleation was studied in BaO·2SiO2, 5BaO·8SiO2, and Na2O·2CaO·3SiO2 glasses. The main research topics include measurements of the nucleation rate, the structural evolution of the glass, and the low-temperature nucleation behavior. A special focus is given to the low-temperature nucleation anomaly. In total, …

Flexible Electronics For Neurological Electronic Skin With Multiple Sensing Modalities, Haochuan Wan

McKelvey School of Engineering Theses & Dissertations

The evolution of electronic skin (E-skin) technology in the past decade has resulted in a great variety of flexible electronic devices that mimic the physical and chemical sensing properties of skin for applications in advanced robotics, prosthetics, and health monitoring technologies. The further advancement of E-skin technology demands closer imitation of skin receptors' transduction mechanisms, simultaneous detection of multiple information from different sources, and the study of transmission, processing and memory of the signals among the neurons. Motivated by such demands, this thesis focuses on design, fabrication, characterization of novel flexible electronic devices and integration of individual devices to realize …

Novel Photothermal Materials And Thermally Engineered Membranes For Solar Desalination, Sisi Cao

McKelvey School of Engineering Theses & Dissertations

Although 71% of earth surface is covered with water, more than 97% of it is saltwater, and freshwater is limited to only about 2.5%. The freshwater shortage has been exacerbated due to the environmental pollution, increased agriculture needs, socio-economic development, and population growth. Among various desalination technologies, membrane distillation has gained wide attention due to its ability to treat highly saline water utilizing waste heat from industrial processes. However, the implementation of conventional membrane distillation is hindered in the remote regions and disaster-struck communities where the low-grade thermal energy from industrial plants and electricity are not readily available. To address …

Metal Oxide Nanoparticles Synthesized By Nonthermal Plasma For Electrochemical Applications, Qinyi Chen

McKelvey School of Engineering Theses & Dissertations

Metal oxide nanocrystals can be synthesized by colloidal processing and gas-phase processing routes. High-quality nanocrystals produced by colloidal routes typically have surface ligands. Transport of electrons and ions among nanocrystals is hindered by surface ligand, and degrades related electrical performance. Gas-phase processing, for example combustion and thermal plasma, can make free-standing nanocrystals. However, nanocrystals produced by combustion method are heavily agglomerated, which further limits the usage of nanoparticles in electrochemical applications. Nonthermal plasma, as an emerging attractive route, has been initially focused on the synthesis of elemental group IV materials, and extended to include the synthesis of multicomponent materials, such …

Metal Salt Hydrolysis For Electrochemically Active Conducting Polymer Nanocomposites, Hongmin Wang

Arts & Sciences Electronic Theses and Dissertations

The diversity of nanostructures obtained from organic polymerization is limited when compared to the vast amount of inorganic nanostructures. This dissertation will focus on a synergistic mechanism between organic polymerization and in situ inorganic salt hydrolysis for developing electrochemically active organic-inorganic hybrid nanostructures. The degree of polymerization, crystallinity and doping level of the conjugated polymer backbone is controlled using oxidative radical vapor-phase polymerization resulting in organic semiconductors featuring high crystallinity and superior electrical conductivity. An aqueous metal salt solution of iron (III) chloride serves as an oxidant for initiating the polymerization and interestingly, this inorganic salt hydrolyzes in situ producing …

Plasmonically-Enhanced Ultrasensitive Biodetection Technologies, Zheyu Wang

McKelvey School of Engineering Theses & Dissertations

Detection and quantification of biomolecules within biological fluids and tissues is of fundamental importance to biomedical research and clinical diagnostics. It is impossible to fully characterize complex, non-linear, biochemical systems without being able to accurately and quantitatively determine the component molecules. This problem is ubiquitous across all domains of biomedical research, and it is a major barrier to fully understanding health, ageing, and disease. Such bottlenecks are extremely challenging to be solved, especially for proteins and peptides, which do not have amplification schemes such as polymerase chain reaction for nucleic acids, because relevant concentrations of molecules related to diseases such …

Aerosol Vapor Synthesis Of Organic Processable Pedot Particles And Measuring Electric Conductivity Using A 3d Printed Probe Station, Yang Lu

McKelvey School of Engineering Theses & Dissertations

Conducting polymers are organic semiconductors characterized by conjugated backbones (alternating single-double bonds) that enable mixed ionic-electronic conductivity. Their polymeric nature, tunable band structure and reversible redox capability have demonstrated fundamental advances in the fields ranging from electrochemical energy storage, sensing, to electro/photo catalysis and neuromorphic engineering. Conjugated backbones, the origin of all the unique physical and chemical properties associated with conducting polymers, prevent their solubility due to high lattice energy which hinders processing. Current solution utilizes a long-chain polymer (PSS) as dopants to render conducting polymer water dispersible (PEDOT:PSS). Nonetheless, PSS is highly acidic and hydrophilic limiting applicability with acid-incompatible …

Converting Inorganic Rust To Organic Nanostructured Conducting Polymers: Synthesis And Applications, Yifan Diao

McKelvey School of Engineering Theses & Dissertations

Iron rust is a type of corrosion product, coming from the chemical reaction between iron and oxygen in the presence of water that first documented ca. 800 BCE. It is a heterogeneous inorganic solid-state material composed of multiple phases and is ubiquitous throughout the universe. Rust species such as Hematite (α-Fe2O3), Akaganeite (β-FeOOH), and ferrous hydroxide (Fe(OH)2), make up the solid-state chemical family composed of iron oxides, oxyhydroxides, and hydroxides that are typically recognized as chemical waste. Conducting polymer is a type of organic plastic composed of long chains with repeating subunits that bonding with strong interactions between neighboring molecules. …

Computational Design Of Two-Dimensional Transition Metal Dichalcogenide Alloys And Their Applications, John Douglas Cavin

Arts & Sciences Electronic Theses and Dissertations

The discovery of bronze as an alloy of copper and tin is arguably the earliest form of material design, dating back thousands of years. In contrast, two-dimensional materials are new to the 21st century. The research presented in this dissertation is at the intersection of alloying and two-dimensional materials. I specifically study a class of two-dimensional materials known as transition metal dichalcogenides (TMDCs). Because of the large number of transition metals, there are many combinations of TMDCs that can be alloyed, making experimental exploration of the phase space of possible alloys unwieldly. Instead, I have applied first-principles methods to study …

Multifunctional Polydopamine Nanomaterials For Biomedical And Environmental Applications, Hamed Gholami Derami

McKelvey School of Engineering Theses & Dissertations

Polydopamine (PDA), a synthetic and organic material, has emerged as a promising materialplatform for various applications in energy, environmental, and biomedical fields. PDA, formed by self-polymerization of dopamine, is rich in catechol and amine groups, which facilitate covalent conjugation and/or other non-covalent interactions with organic and inorganic materials. It is highly biocompatible, biodegradable, has broadband light absorption spectrum and excellent light-to-heat conversion efficiency. Also, it is easy to synthesize and functionalize. The combination of excellent characteristics of polydopamine-based nanomaterials, make them a promising adsorbent agent for environmental wastewater treatment and photothermal agent for biomedical applications. In the first half of …

Nanoscale Enhancement Of Photosensitized Radionuclide Stimulated Therapy, Daniel Douglas Lane

McKelvey School of Engineering Theses & Dissertations

Photodynamic therapy (PDT) provides efficient tumor killing through the generation of reactive oxygen species (ROS) from the optical excitation of a photosensitizer (PS). Furthermore, this mechanism is highly immune stimulating, providing systemic tumor immunity with a reduction in metastasis. However, these materials had previously been limited by their dependence upon external light sources, allowing treatment of only laser-accessible malignancy. With the recent development of photosensitized radiation stimulated therapy (PRaST) this depth dependence is broken through co-localization of radionuclides and semiconducting photosensitizers. This dissertation focuses on the enhancement of titanium dioxide (TiO2) based PRaST agents through understanding of TiO2 material parameters …

Mechanical Strength Of Germanium Doped Low Oxygen Concentration Czochralski Silicon And The Effect Of Oxygen On Nitrogen Dissociation In Silicon, Junnan Wu

McKelvey School of Engineering Theses & Dissertations

During the Czochralski growth of silicon, it is inevitable for oxygen to be incorporated into the silicon crystal from the quartz crucible. Interstitial oxygen improves the mechanical strength of silicon by pinning and locking dislocations, but also generates thermal donors during device processes, shifting the electrical resistivity. For silicon wafers used in radio frequency (RF) applications, it is important to ensure the high resistivity of the substrates for good RF characteristics. Therefore, the oxygen level in these high resistivity silicon wafers is kept very low (< 2.5 × 1017 atoms/cm3) by carefully controlling the Czochralski growth conditions, in order to reduce the thermal donor concentration to an acceptable level. Silicon on insulator (SOI) substrates made from high resistivity wafers have been widely used for RF applications. SOI manufacturing includes multiple high temperature thermal cycles (1000 – 1100 °C), during which the high resistivity wafers are prone to slip and warpage. Therefore, it is technologically important to recover some of the lost mechanical strength due to the lack of oxygen by introducing electrically inactive impurities to suppress the dislocation generation and mobility in silicon. Germanium (Ge) as an isovalent impurity is 4% larger in size and forms a solid solution with silicon in the entire concentration range. Previous works have shown Ge doping at high concentrations above 6 × 1019 atoms/cm3 increased mechanical strength of silicon with high oxygen concentration (~ 1 × 1018 atoms/cm3). In this work, we explore the effect of Ge doping (7 - 9 × 1019 atoms/cm3) on the mechanical strength of low oxygen concentration (< 2 × 1017 atoms/cm3) silicon, where the oxygen associated dislocation locking and pinning are very low. A mechanical bending test was used to study the average dislocation migration velocity and the critical shear stress of dislocations motion at 600 – 750 °C for Ge doped, nitrogen doped, and undoped low oxygen samples, as well as nitrogen doped float-zone and un-doped high oxygen concentration samples. Next, we fabricated SOI substrates using these high resistivity wafers and compared their slip generation rates and the slip-free epitaxial grow temperature windows after the high temperature thermal cycles (> 1000 °C). Our results indicate at lower temperature Ge doesn’t affect the dislocation mobility …

Surface Modification Of Ii-Vi Semiconducting Nanocrystals, Calynn Morrison

Arts & Sciences Electronic Theses and Dissertations

This dissertation presents the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES), a novel low-temperature shell growth precursor and installation pathway, and L-type for Z-type ligand exchange experiments conducted with four metal dithiocarbamate ligands. The techniques employed in the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES) have a profound influence on the accuracy and reproducibility of the results. In Chapter 3, we describe methods for sample preparation, calibration, standard selection, and data collection. Specific protocols are suggested for the analysis of II-VI compounds and nanocrystals containing the elements Zn, …

Structure, Thermophysical Properties Of Liquids, And Their Connection With Glass Formability, Rongrong Dai

McKelvey School of Engineering Theses & Dissertations

Metallic glasses have drawn significant attention due to their unique properties, such as high strength, excellent elastic energy storage capacity, and versatile processability. However, why some liquids can easily form metallic glasses while others donմ is still unclear. Since metallic glasses are formed when liquids are cooled fast enough to bypass crystallization, we hope to better understand glass formation by investigating the structural evolution and thermophysical properties of the liquids as they are cooled toward the glass transition. Multiple molecular dynamics simulations suggest a crossover temperature for the dynamics near the liquidus temperature, which corresponds to the onset of cooperative …

First-Principles Studies Of Anion Engineering In Functional Ceramics, Steven Timothy Hartman

McKelvey School of Engineering Theses & Dissertations

Ceramic materials display a wide variety of valuable properties, such as ferroelectricity, superconductivity, and magnetic ordering, due to the partially covalent bonds which connect the cations and anions. While many breakthroughs have been made by mixing multiple cations on a sublattice, the equivalent mixed-anion ceramics have not received nearly as much attention, despite the key role the anion plays in the materials’ properties. There is great potential for functional ceramics design using anion engineering, which aims to tune the materials properties by adding and removing different types of anions in existing classes of ceramic materials. In this dissertation, I present …

Spectroscopic Investigations Of Excited Charge Carriers In Ii-Vi Nanoparticles, William Matthew Sanderson

Arts & Sciences Electronic Theses and Dissertations

The large absorption cross sections and the tunability of the energetic spacings between the states in the conduction (CB) and valence band (VB) within a semiconductor nanoparticle (NP) make them promising media for capturing electromagnetic radiation and converting it into charge carriers, or electricity. In photovoltaic devices that incorporate semiconductor NPs, it would be ideal if every photon could be absorbed by a NP and the carriers could be collected with perfect efficiency and without loss of energy. The relaxation pathways of the carriers within the NPs down to the band edge and their fate at the band edge contribute …

Self-Assembly Of Conducting Polymer Nano- And Microstructures For Energy Storage, Luciano Matteo Santino

Arts & Sciences Electronic Theses and Dissertations

Plastics are materials composed of many long chains of molecules with repeating subunits; strong interactions between neighboring molecules lead to the material used throughout the world. Plastics are commonly thought to be insulating, in stark contrast to the conductivity of metals. However, certain polymer structures were discovered to exhibit semiconducting properties, the subject of the Nobel Prize in Chemistry in 2000. Conducting polymers have a unique molecular structure with an electronically conjugated backbone, allowing electrons to freely travel both across the chain and in between chains. This work focuses on controlling the kinetics of the reaction between the vapors of …

Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias

Arts & Sciences Electronic Theses and Dissertations

To induce a non-negligible spin-orbit coupling in monolayer graphene, for the purposes of realizing the Kane-Mele Hamiltonian, transition metal adatoms have been deposited in dilute amounts by thermal evaporation in situ while holding the device temperature near 4K. Electronic transport studies including measurements such as gate voltage dependent conductivity and mobility, weak localization, high field magnetoresistance (Shubnikov de Haas oscillations), quantum Hall, and nonlocal voltage were performed at low temperature before and after sequential evaporations. Studies of tungsten adatoms are consistent with literature regarding other metal adatoms on graphene but were unsuccessful in producing a spin-orbit signature, at least partially …

Defect Chemistry And Ion Intercalation During The Growth And Solid-State Transformation Of Metal Halide Nanocrystals, Bo Yin

McKelvey School of Engineering Theses & Dissertations

Abstract of the Dissertation

Defect Chemistry and Ion Intercalation During the Growth and Solid-State Transformation of Metal Halide Nanocrystals

Semiconductor metal halides as light-sensitive materials have applications in multiple areas, such as photographic film, antibacterial agents and photocatalysts. One focus of this dissertation is to achieve novel morphologies of ternary silver bromoiodide (AgBr1-xIx, 0

For the silver halide system, we demonstrate that the anion composition of AgBr1-xIx nanocrystals determines their shape through the introduction of twin defects as the nanocrystals are made more iodide-rich. AgBr1-xIx nanocrystals grow as single-phase, solid solutions with the rock salt crystal structure for anions compositions …

Multifunctional Nanocomposites Based On Bacterial Cellulose, Qisheng Jiang

McKelvey School of Engineering Theses & Dissertations

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to …

Multifunctional Nanocomposites Based On Bacterial Cellulose, Qisheng Jiang

McKelvey School of Engineering Theses & Dissertations

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to …

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Linking Structure And Dynamics In Metallic Liquids: A Combined Experimental And Molecular Dynamics Approach, Robert Ashcraft

Arts & Sciences Electronic Theses and Dissertations

A major outstanding problem in condensed matter physics is the nature of the glass transition, in which a rapidly cooled liquid can bypass the transition into a crystalline state and the liquid structure is "frozen-in" due to kinetic arrest. To characterize the fundamental features behind this transition the liquid, both in the high temperature (equilibrium) and supercooled state, needs to be better understood. By examining the relationship between structure and dynamics a better characterization of the liquid state and a determination of the mechanisms that are ultimately important for the formation of the glass can be gained. In this dissertation, …

Synthesis Of Crumpled Graphene And Titanium Dioxide Based–Nanomaterials And The Application To Carbon Dioxide Photoreduction, Yao Nie

McKelvey School of Engineering Theses & Dissertations

With the rapid development of the economy, increasing combustion of fossils fuels has caused an increase in the atmospheric carbon dioxide (CO2) level, and has led to global climate change. As a mitigation approach, CO2 capture and conversion (CCC) can not only capture CO2, but also convert it to useable products, such as hydrocarbon fuels. Photocatalytic reduction is an attractive CCC option that directly harnesses inexpensive and abundant solar energy. Titanium dioxide (TiO2) is a widely used semiconductor for photocatalysis, and graphene nanosheets are a promising material for use in fabricating graphene-TiO2 hybridized photocatalysts. To realize the application of these …

Functional Bio-Nano Hybrids Through A Precise Control Of Interfacial Interactions At The Nanoscale, Sirimuvva Tadepalli

McKelvey School of Engineering Theses & Dissertations

During the course of evolution, proteins have evolved to perform exquisite functions including structural support, signal transduction, actuation, sensing, catalysis, trafficking, gating, light-harvesting, charge transfer, molecular recognition, self-assembly, self-organization, or combinations of two or more of these functions. A precise control and manipulation of the structure and function of proteins is conceivable with the advent of nanotechnology, which has facilitated the integration of nanomaterials with functional biomolecules to realize bio-nano hybrids with synergistically enhanced functionalities.

At the genesis of bionanotechnology, a paucity in the fundamental understanding of the bio-nano interfaces is a grave impediment to the progress of the field. …

Characterization Of Structural Dynamics Of The Human Head Using Magnetic Resonance Elastography, Andrew Arun Badachhape

McKelvey School of Engineering Theses & Dissertations

In traumatic brain injury (TBI), the skull-brain interface, composed of three meningeal layers: the dura mater, arachnoid mater, and pia mater, along with cerebrospinal fluid (CSF) between the layers, plays a vital role in transmitting motion from the skull to brain tissue. Magnetic resonance elastography (MRE) is a noninvasive imaging modality capable of providing in vivo estimates of tissue motion and material properties. The objective of this work is to augment human and phantom MRE studies to better characterize the mechanical contributions of the skull-brain interface to improve the parameterization and validation of computational models of TBI. Three specific aims …

The Inter-Laminar Shearing Effect On Wrinkle Development In Composite Forming Processes, David Sundquist

McKelvey School of Engineering Theses & Dissertations

Composite materials are becoming prevalent in aerospace industries as the uniqueness of the composite structure allows the composite to be tailored specifically for individual applications. Many fabrication techniques produce defects in composite parts such as wrinkles, fiber waviness, fiber misalignment, and porosity. The driving mechanisms behind these defects occurring during forming processes are not fully understood and, thus, characterization formation of these defects in a uncured state is beneficial to optimize composite processing. This work primarily investigated the influence of how uncured pre-impregnated carbon ply properties affect the wrinkling behavior of a composite laminates. Several factors affecting composite ply forming …