Nanoscience and Nanotechnology Commons^™

Nonuniformity In Lattice Contraction Of Bismuth Nanoclusters Heated Near Its Melting Point, A. Esmail, M. Abdel-Fattah, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 ± 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of ∼14 nm along the minor axis and ∼16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 ± 6 K along the [012] direction and 86 ± 9 K along the [110] …

Sub-Cooled Pool Boiling Enhancement With Nanofluids, Elliott Charles Rice

USF Tampa Graduate Theses and Dissertations

Phase-change heat transfer is an important process used in many engineering thermal designs. Boiling is an important phase change phenomena as it is a common heat transfer process in many thermal systems. Phase change processes are critical to thermodynamic cycles as most closed loop systems have an evaporator, in which the phase change process occurs. There are many applications/processes in which engineers employ the advantages of boiling heat transfer, as they seek to improve heat transfer performance. Recent research efforts have experimentally shown that nanofluids can have significantly better heat transfer properties than those of the pure base fluids, such …

Thermophysical Characterization Of Nanofluids Through Molecular Dynamic Simulations, John Shelton

USF Tampa Graduate Theses and Dissertations

Using equilibrium molecular dynamics simulations, an analysis of the key thermophysical properties critical to heat transfer processes is performed. Replication of thermal conductivity and shear viscosity observations found in experimental investigations were performed using a theoretical nanopthesis-fluid system and a novel colloid-fluid interaction potential to investigate the key nanofluid parameters. Analysis of both the heat current (thermal conductivity) and stress (shear viscosity) autocorrelation functions have suggested that the dominant physical mechanisms for thermal and momentum transport arises from enhancements to the longitudinal and transverse acoustic modes energy transfer brought about by the increased mass ratio of the nanopthesis to the …

Simulation Of Electrospun Nanofiber Deposition On Stationary And Moving Substrates, Linhua Liu, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Electrospinning produces continuous fibers with diameters from single nanometers to microns by jetting polymer solutions in high electric fields. Electrospun non-woven filamentary materials attract rapidly growing interest for broad range of applications. Properties of these materials depend on their nano- and microstructure that is determined in turn by the electric field and nanofiber collector. Despite critical importance, deposition of electrospun fibers on substrates has not yet been extensively studied theoretically and new methods of nanofiber collection continue to be developed mostly empirically. The objective of this Letter was to develop and demonstrate numerical simulation of electrospun nanofiber deposition on moving …

Achieving High Efficiency Laminated Polymer Solar Cell With Interfacial Modified Metallic Electrode And Pressure Induced Crystallization, Yongbo Yuan, Yu Bi, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

We report efficient laminated organic photovoltaic device with efficiency approach the optimized device by regular method based on Poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The high efficiency is mainly attributed to the formation of a concrete polymer/metal interface mechanically and electrically by the use of electronic-glue, and using the highly conductive and flexible silver film as anode to reduce photovoltage loss and modifying its work function for efficiency hole extraction by ultraviolet/ozone treatment, and the pressure induced crystallization of PCBM.

Intermediate Layers In Tandem Organic Solar Cells, Yongbo Yuan, Jinsong Huang, Gang Li

Department of Mechanical and Materials Engineering: Faculty Publications

Tandem structures can boost the efficiency of organic solar cell to more than 15%, compared to the 10% limit of single layer bulk heterojunction devices. Design and fabricating of intermediate layers plays a very important role to achieve high device performance. This article will review the main experimental progresses of tandem organic solar cells, and focus on the intermediate layers (charge recombination layers) in both thermal evaporated and solution processed organic tandem solar cell devices.

A Model Of Giant Vacuole Dynamics In Human Schlemm’S Canal Endothelial Cells, Ryan M. Pedrigi, David Simon, Ashley Reed, W. Daniel Stamer, Darryl R. Overby

Department of Mechanical and Materials Engineering: Faculty Publications

Aqueous humour transport across the inner wall endothelium of Schlemm’s canal likely involves flow through giant vacuoles and pores, but the mechanics of how these structures form and how they influence the regulation of intraocular pressure (IOP) are not well understood. In this study, we developed an in vitro model of giant vacuole formation in human Schlemm’s canal endothelial cells (HSCECs) perfused in the basal-to-apical direction (i.e., the direction that flow crosses the inner wall in vivo) under controlled pressure drops (2 or 6 mmHg). The system was mounted on a confocal microscope for time-lapse en face imaging, and cells …

In Vitro Models For Glaucoma Research: Effects Of Hydrostatic Pressure, Yuan Lei, Shadi Rajabi, Ryan M. Pedrigi, Darryl R. Overby, A. Thomas Read, C. Ross Ethier

Department of Mechanical and Materials Engineering: Faculty Publications

PURPOSE. The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressure and tension on cell migration, shape, and α-tubulin architecture in a transformed cell line (DITNC1 rat cortical astrocytes).

METHODS. During the assay period, cells were exposed to one of four experimental configurations: (1) control pressure and control gas tension; (2) …

Precise Control Of Highly Ordered Arrays Of Nested Semiconductor/Metal Nanotubes, Diefeng Gu, Helmut Baumgart, Kandabara Tapily, Pragya Shrestha, Gon Namkoong, Xianyu Ao, Frank Müller

Electrical & Computer Engineering Faculty Publications

Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control of physical process parameters has not been fully realized with high precision resolution, and requires optimization in order to achieve a wider range of potential applications. Furthermore, the combination of composite insulating oxide layers alternating with semiconducting layers and metals can provide various types of novel applications and eventually provide unique and advanced levels of multifunctional nanoscale devices. Semiconducting TiO₂ nanotubes have potential applications in photovoltaic devices. The combination of nanostructured semiconducting materials …

Impact Of Elliptical Trainer Ergonomic Modifications On Perceptions Of Safety, Comfort, Workout, And Usability For People With Physical Disabilities And Chronic Conditions, Judith M. Burnfield, Yu Shu, Thad W. Buster, Adam P. Taylor, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

Background The popularity of elliptical training has grown in rehabilitation, fitness, and home settings as a means for improving fitness and walking, yet many people with physical disabilities and chronic conditions experience difficulties when trying to use elliptical trainers.

Objective The purpose of this study was to compare, for people with disabilities and chronic conditions, perceptions of safety, comfort, workout, and usability of 4 elliptical trainers before and after the development of a set of low-cost adaptations.

Design This study was a quasi-experimental repeated-measures investigation.

Methods Twenty adults with diverse medical conditions and functional abilities evaluated 4 elliptical trainers for …

Use Of Environmental Scanning Electron Microscopy For In Situ Observation Of Interaction Of Cells With Micro- And Nanoprobes, Alexander Goponenko, B. J. Boyle, K. I. Jahan, Maxim V. Gerashchenko, Dmitri E. Fomenko, Vadim N. Gladyshev, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Precision intracellular sensing, probing and manipulation offer unprecedented opportunities for advances in biological sciences. Next-generation ultra-fine probes will be capable of targeting individual cell organelles. Development of such probes as well as probes capable of penetrating through tough cell walls requires detailed knowledge of cell-probe interaction. This Letter evaluated the applicability of environmental scanning electron microscopy (ESEM) for cell and cell-probe interaction imaging. Several types of cells (plant and yeast cells as well as mouse spermatozoa) were successfully imaged in their natural state, with mouse spermatozoa observed by ESEM for the first time. Computerized stage applied to image was tough …

Modeling Of Solvent Evaporation From Polymer Jets In Electrospinning, Xiang-Fa Wu, Yury Salkovskiy, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Solvent evaporation plays a critical role in nanofiber formation in electrospinning. Here, we present a nonlinear mass diffusion-transfer model describing the drying process in dilute polymer solution jets. The model is used to predict transient solvent concentration profiles in polyacrylonitrile/ N,N-dimethylformamide (PAN/DMF) jets with the initial radii ranging from 50µm down to 100 nm. Numerical simulations demonstrate high transient inhomogeneity of solvent concentration over the jet cross-section in microscopic jets. The degree of inhomogeneity decreases for finer, submicron jets. The simulated jet drying time decreases rapidly with the decreasing initial jet radius, from seconds for microjets to single milliseconds for …

Moving Forward With Citizen Deliberation: Lessons And Inspiration From The National Citizens' Technology Forum, Jason Delborne, Jen Schneider

Jen Schneider

In his article on the National Citizens' Technology Forum (NCTF) in this chapter, Cobb notes that the NCTF was essentially a decendant of the "consensus conference," a form of political engagement that originated in Denmark and then traveled elsewhere. Sponsored by the Danish Parliament, the Danish Board of Technology was tasked with involving groups of citizens in making informed policy recommendations related to science and technology: these policy recommendations were and are considered by lawmakers in forming science policy. Cobb and others have noted that the consensus conference and related forms of public engagement have garnered significant academic interest in …

Pamam Dendrimer-Based Therapeutic And Diagnostic Nanodevices, Admira Bosnjakovic

Wayne State University Dissertations

Dendrimers are ideal materials to be used in the emerging field of nanomedicine. Their nanoscale size and high density of functional groups on their peripheries allow them to be used for various biomedical applications. This work exploits dendrimers as drug delivery vehicles and a versatile platform for capturing biomarkers with improved sensitivity and specificity. Hydroxyl terminated poly(amidoamine) dendrimer (PAMAM-OH) was modified with a linker having amine group at the end and conjugated to two drugs, erythromycin (EM) and allopregnanonolne, respectively and evaluated in vitro. Both drugs were provided with a linker having carboxylic group required for conjugation reaction with dendrimer. …

Crystallite Phase And Orientation Determinations Of (Mn, Ga) As/Gaas-Crystallites Using Analyzed (Precession) Electron Diffraction Patterns, Ines Häusler, Stavros Nicolopoulos, Edgar F. Rauch, K. Volz, Peter Moeck

Physics Faculty Publications and Presentations

Outline of the presentation:

1. Material system: (Mn,Ga)As/GaAs-crystallites

2. Structure analysis using Nano-beam Diffraction (NBD) Precession Electron Diffraction Technique (PED) --> Structure type I + II

3. Phase and orientation mapping using ASTAR

4. Conclusion

Enhanced Field Emission From Vertically Oriented Graphene By Thin Solid Film Coatings, Michael Bagge-Hansen

Dissertations, Theses, and Masters Projects

Recent progress and a coordinated national research program have brought considerable effort to bear on the synthesis and application of carbon nanostructures for field emission. at the College of William and Mary, we have developed field emission arrays of vertically oriented graphene (carbon nanosheets, CNS) that have demonstrated promising cathode performance, delivering emission current densities up to 2 mA/mm2 and cathode lifetime > 800 hours. The work function ( & phis;) of CNS and other carbonaceous cathode materials has been reported to be &phis;∼4.5-5.1 eV. The application of low work function thin films can achieve several orders of magnitude enhancement of …

A New Method For The Removal Of Parasitic Capacitances From Sub-100nm Mosfets Using Low-Noise Split Capacitance-Voltage Measurements, Daniel R. Steinke

Legacy Theses & Dissertations (2009 - 2024)

The physical shape of MOSFETs and the processing involved in their fabrication give rise to parasitic capacitances. These capacitances are typically small compared to the intrinsic channel capacitance of the device, but as MOSFETs scale into the sub-100nm gate length range, the parasitic capacitances become a significant percentage of the overall measured capacitance, resulting in a source of error in the analysis of these devices. The purpose of this work is to describe these parasitic capacitances and their origin in MOSFET structures and to propose a method for their removal for analysis. The experimental devices used for this work are …

Energy Band Engineering Using Polarization Induced Interface Charges In Mocvd Grown Iii-Nitride Heterojunction Devices, Neeraj Tripathi

Legacy Theses & Dissertations (2009 - 2024)

Characteristics of III-nitride based heterojunction devices are greatly influenced by the presence of high density of polarization induced interface charges. Research undertaken in the current doctoral thesis demonstrates the effect of presence of one, three and six sheets of polarization induced charges in three different III-nitride based devices, namely in a photocathode, a high electron mobility transistor (HEMT) and a hyperspectral detector structure. Through a systematic set of experiments and theoretical modeling an in-depth study of the interaction between multiple sheets of polarization induced charges and their impact on energy band profile was undertaken. Various device designs were studied and …

Graphene-Based Interconnects : Electrical Performance And Reliability, Tianhua Yu

Legacy Theses & Dissertations (2009 - 2024)

According to the ITRS Roadmap, on-chip interconnects wire width and current density will reach 22 nm and 5.8×106 A/cm2 in 2020, respectively. The electrical resistivity of Cu increases with scaled critical dimensions due to exacerbated carrier scattering at grain boundaries and interfaces, resulting in signal speed degradation. Electronmigration (EM)-related failure due to intensified current distribution posts extra limits to ultra-scaled systems. Innovative interconnect solutions are needed to tackle performance and scaling challenges.

Cost-Effective Imprint Template Fabrication For Step And Flash Imprint Lithography, Adam Marc Munder

Legacy Theses & Dissertations (2009 - 2024)

The College of Nanoscale Science and Engineering (CNSE) is studying imprint template fabrication with the 100kV Vistec VB300 Gaussian E-Beam writer. The major goal is to develop and advance imprint template fabrication technology using low cost quartz wafers for proof-of-concept demonstrations.