<p>The phenomenon of radiation pressure has fascinated scientists since it was first proposed by Maxwell in the late 19th century. Numerous experiments involving optical forces have been carried out, however the optical force acting on a curved waveguide does not appear to have been previously investigated. An experiment to measure the force acting on a waveguide due to the optical power it contains is proposed here. This experiment takes advantage of the sensitivity of MicroElectroMechanical Systems (MEMS) and the performance of silicon integrated optics in a single hybrid device.</p> <p>Devices are fabricated from silicon-on-insulator (SOI) wafers using conventional micromachining techniques. Anisotropic alkali etches are used to produce smooth vertical side-walls for a mechanical structure and a rib waveguide. An analysis of the electrical systems and measurement techniques is provided. Using these techniques, the resonant operation of the devices is demonstrated by means of capacitive actuation and sensing. The application of this system to the measurement of radiation pressure is discussed.</p> / Master of Applied Science (MASc)

<p>Incorporating nanoparticles within a polymer to improve the mobility of the filmis one promising way of creating organic thin film transistors (OTFTs) with large mobilities that could be applicable in real world applications. Carbon nanotubes (CNTs)and graphene nanoplatelets (GNPs) are extensively studied for this application. In order to overcome their tendency to aggregate, a method for creating a stable dispersion within both the solution phase and the film is needed. Here an easy method is established for creating a stable dispersion of CNTs or GNPs within a polymer solution which results in excellent OTFT mobility.A non-percolating network of non-covalently functionalized single walled carbon nanotubes was embedded within poly[5,5’-bis(3-dodecyl-2-thienyl)-2,2’bithiophene](PQT-12) thin films for the purpose of enhancing field effect mobility in thin film transistors. The host polymer was used to stabilize the nanotubes in suspension by π orbital overlap caused by simple application of ultrasonication. The stable nanotube suspension was cast into two different device architectures both with excellent mobilities and on/off ratios. The effect of nanotube content on polymer interaction within suspension, film morphology and electrical properties are discussed. A CNT nanocomposite OTFT with enhanced mobility was also tested for applications in vapour sensing. A method is also presented for the creation of graphene nano-platelets (GNPs) for implementation in nano-composite films. Heat treatment of expandable graphite within a vacuum evaporation chamber yielded chemically pure GNPs of a few nanometer thickness. Exfoliating expandable graphite without heat treatment resulted in even higher concentrations but chemically impure GNPs. The material was non-covalently stabilizedwith PQT-12 in a similar method to CNTs and used to create OTFTs with enhanced mobility. The effect of heat treatment parameters and exfoliation conditions on GNP thickness, size and chemical purity are discussed, as well as effect of GNP content on mobility and on/off ratio.</p> / Master of Applied Science (MASc)

<p> Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert gas dynamics play a critical role on the catalyst morphology during CNT growth. A novel method for CNT catalyst activation by substrate manipulation is presented. Results of this study build upon prior knowledge of the role of the chemistry of the substrate supporting CNT catalysts. By bombarding sapphire, a substrate known to not support CNT growth, with an argon ion beam, the substrate is transformed into an active CNT growth support by modifying both the structure and chemistry of the sapphire surface. Finally, catalyst formation is studied with transmission electron microscopy by depositing an iron gradient film in order to identify a potential critical catalyst size and morphology for CNT growth. A relationship between catalyst size and morphology has been identified that adds evidence to the hypothesis that a catalysts activity is determined by its size and ability to properly reduce.</p>

<p> Second cervical segment spinal cord hemisection (C2Hx) results in ipsilateral hemidiaphragm paralysis. However, the intact latent crossed phrenic pathway can restore function spontaneously over time or immediately following drug administration. </p><p> WGA bound fluorochromes were administered to identify nuclei associated with diaphragm function in both the acute and chronic C2Hx models. WGA is unique in that it undergoes receptor mediated endocytosis and is transsynaptically transported across select physiologically active synapses. Comparison of labeling in the acutely injured to the chronically injured rat provided an anatomical map of spinal and supraspinal injury induced synaptic plasticity. The plasticity occurs over time in the chronic C2Hx model in an effort to adapt to the loss of hemidiaphragm function. </p><p> Utilizing the selectivity of WGA, a nanoconjugate was developed to target drug delivery to nuclei involved in diaphragm function post C2Hx in an effort to restore lost function. Theophylline was selected due to its established history as a respiratory stimulant. Theophylline was attached to gold nanoparticles by a transient bond designed to degrade intracellularly. The gold nanoparticles were then permanently attached to WGA-HRP. Following intradiaphragmatic injection, the WGA portion was identified in the ipsilateral phrenic nuclei and bilaterally in the rVRGs. The location of WGA should reflect the location of the AuNP since the peptide bond between them is permanent. </p><p> The effectiveness of the nanoconjugate was verified with EMG analysis of the diaphragm and recordings from the phrenic nerves. All doses administered in the acute C2Hx model resulted in resorted hemidiaphragm and phrenic nerve activity. A dose of 0.14mg/kg had a significantly higher percent recovery on day 3, whereas 0.03mg/kg was significantly higher on day 14. The change in most effective dose over time is likely due to the availability or concentration of the drug and location of drug release. Administration of the nanoconjugate was also characterized in the chronically C2Hx model. The dose 0.06mg/kg resulted in significant recovery when injected 12 weeks post-C2Hx. This data suggests that WGA bound nanoconjugates are able to undergo endocytosis. In addition, the theophylline bound nanoconjugate is capable of restoring hemidiaphragm and phrenic nerve activity.</p>

<p>Printed electronics, including transparent conductors, currently rely on expensive materials to generate high conductivity devices. Conductive inks for thick film applications utilizing inkjet, aerosol, and screen printing technologies are often comprised of expensive and rare silver particles. Thin film applications such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) predominantly employ indium tin oxide (ITO) as the transparent conductive layer which requires expensive and wasteful vapor deposition techniques. Thus an alternative to silver and ITO with similar performance in printed electronics warrants considerable attention. Copper nanomaterials, being orders of magnitude cheaper and more abundant than silver or indium, solution-coatable, and exhibiting a bulk conductivity only 6 % less than silver, have emerged as a promising candidate for incorporation in printed electronics.</p><p> First, we examine the effect of nanomaterial shape on the conductivity of thick films. The inks used in such films often require annealing at elevated temperature in order to sinter the silver nanoparticles together and obtain low resistivities. We explore the change in morphology and resistivity that occurs upon heating thick films of silver nanowires (of two different lengths, Ag NWs), nanoparticles (Ag NPs), and microflakes (Ag MFs) deposited from water at temperatures between 70 and 400 °C. At the lowest temperatures, longer Ag NWs exhibited the lowest resistivity (1.8 × 10-5 Ω cm), suggesting that the resistivity of thick films of silver nanostructures is dominated by the contact resistance between particles.</p><p> This result supported previous research showing that junction resistance between Ag NWs in thin film conductors also dominates optoelectronic performance. Since the goal is to replace silver with copper, we perform a similar analysis by using a pseudo-2D rod network modeling approach that has been modified to include lognormal distributions in length that more closely reflect experimental data collected from the nanowire transparent conductors. In our analysis, we find that Cu NW-based transparent conductors are capable of achieving comparable electrical performance to Ag NW transparent conductors with similar dimensions. We also synthesize high aspect ratio Cu NWs (as high as 5700 in an aqueous based synthesis taking less than 30 minutes) and show that this increase in aspect ratio can result results in transparent conducting films with a transmittance >95% at a sheet resistance <100 Ω sq−1, optoelectronic properties similar to that for ITO.</p><p> Two of the major barriers preventing the further use of Cu NWs in printed electronics are the necessity to anneal the nanowires under H2¬ at higher temperatures and copper’s susceptibility to oxidation. The former issue is solved by removing the insulating oxide along the Cu NWs with acetic acid and pressing the nanowires together to make H2 annealing obsolete. Finally, several methods of preventing copper oxidation in the context of transparent conductors were successfully developed such as electroplating zinc, tin, and indium and electrolessly plating benzotriazole (BTAH), nickel, silver, gold, and platinum. While all of the shells lessened or prevented oxidation both in dry and humid conditions, it was found that a thin layer of silver confers identical optoelectronic properties to the Cu NWs as pure Ag NWs. These results are expected provide motivation to replace pure silver and ITO in printed electronics.</p> / Dissertation

<p> Mesoporous silicate have widespread potential applications, such as drug delivery, supports for catalysis, selective adsorption and host to guest molecules. Most important in the area of scientific research and industrial applications is their demand due to its extremely high surface areas (> 800<i>m</i>²<i>g</i>^&minus;1) and larger pores with well defined structures. </p><p> Mesoporous silicate (MCM-41) samples were prepared by hydrothermal method under various chemo-physical conditions and various experimental methods such as small angle X-rays scattering (SAXS), Nitrogen adsorption-desorption analysis at 77 K, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to investigate the changes in the structural morphology and subtle lattice parameter changes. With regards to the subtle changes in the structural characteristics of the synthesized mesoporous silicate, we seek to understand the electron density function changes as the synthesis parameter are varied from low molar concentration of ATAB/Si to higher concentration, the system becoming more acidity due to increase in the hydrolysis time of pH regulator as a result of increased production of ethanol and acetic acid and the changes due to extended reaction time. </p><p> This Ph.D. research tries to understand the influence of various parameters like surfactant-Si molar ratio, reaction time, and the hydrolysis of the pH regulator on the orderliness/disorderliness of the lattice order, lattice spacing and electron density function. The stages during synthesis are carefully selected to better understand where the greater influence on the overall structural morphology exist so as to be able to ne tune this parameter for any desired specification and application. </p><p> The SAXS measurement were conducted on a HECUS S3-Micro X-ray system at Rensselaer Polytechnic Institute, Troy, NY. while the data evaluation and visualization were carried in 3DView 4.2 and EasySWAXS software. The electron density functions were generated with a proprietary software called edens. </p><p> In this dissertation, the following observations have been revealed resulting from SAXS measurement. </p><p> 1. As one increases the hydrolysis duration of ethyl acetate, a gradual collapse of the lattice spacing of the mesoporous silcate MCM-41 is observed. We found from SAXS that there is a slight right shift of the spectra toward the higher q-values indicating that we are gradually losing orderliness in the lattice spacing and hexagonal structure of the mesoporous silica. Also, the intensity of the peak of second and third peaks are diminutive when compared to sample with shorter hydrolysis time. </p><p> 2. A comparison of the SAXS spectra for the different molar concentration sample reveals that the 0:5M samples shows a deteriorating structural characteristics as compared to the 0:25 and 0:75M samples respectively and a clear decrease in the (100) reflection planes. Also noticed is the slight rightward shift in the overall spectrum prole. This observation suggest that further analysis is needed so as to better understand the result. </p><p> 3. We establish that during MCM-41 synthesis, longer reaction time is needed to produce quality sample with well defined structurally characteristic for its intended application because according to spectrum for the sample with a longer reaction time (aging), a shift towards the lower q-values indicates that a sample with a larger lattice parameter and wall thickness but the intensities of its peak are diminishing when compared to the other of relatively shorter reaction time. </p><p> Other complementary techniques were used to corroborated the result obtained from SAXS. Nitrogen adsorption-desorption analysis at 77K was used to generate the isotherms while B.E.T method was used in conjunction with the isotherms to obtained the very important surface area information. SEM provide a visual structural morphology of the samples and FTIR gave the fingerprint detail of the bonds and vibration types between particle present.</p>

Carbon nanotubes (CNTs) are known to exhibit outstanding mechanical, electrical, thermal, and coupled electromechanical properties. CNTs can be employed towards the design of an innovative strain sensor with enhanced multifunctionality due to their load carrying capability, sensing properties, high thermal stability, and outstanding electrical conductivity. All these features indicate the prospect to use CNTs in a very wide range of applications, for instance, highly sensitive resistance-type strain/force sensors, wearable electronics, flexible microelectronic devices, robotic skins, and in-situ structural health monitoring. CNT-based strain sensors can be divided into two different types, the individual CNT- based strain sensors and the ensemble CNT-based strain sensors e.g. CNT/polymer nanocomposites and CNT thin films. In contrast, to individual CNT-based strain sensors with very high gauge factor (GF) e.g. ~3000, the ensemble CNT-based strain sensors exhibit very low GFs e.g. for a SWCNT thin film strain sensor, GF is ~1. This research discusses the mechanisms and the optimizing principles of a SWCNT thin film piezoresistive sensor, and provide an experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like alignment, network density, bundle diameter (effective tunneling area), and SWCNT length is studied. The tunneling effect is significant in SWCNT thin films showing higher degrees of alignment, due to greater inter-tube distances between the SWCNTs as compared to random oriented SWCNT thin films. It can be concluded that SWCNT thin films featuring higher alignment would have a higher GF. On the other hand, the use of sparse network density which comprises of aligned SWCNTs can as well intensify the tunneling effect which can result to a further increase in the GF. In addition, it is well-known that percolation is greatly influenced by the geometry of the nanotubes e.g. bundle diameter and length. A study on the influence of bundle diameter of SWCNTs on the piezoresistivity behavior of mechanically drawn SWCNT thin films showed the best performance with an improved GF of ~10 when compared to the randomly oriented SWCNT thin films with GF of ~1. The non-linear piezoresistivity of the mechanically drawn SWCNT thin films is considered to be the main mechanism behind the high strain sensitivity. Furthermore, information about the average length and length distribution is very essential when examining the influence of individual nanotube length on the strain sensitivity. With that in mind, we use our previously developed preparative ultracentrifuge method (PUM), and our newly developed gel electrophoresis and simultaneous Raman and photolumiscence spectroscopy (GEP-SRSPL) to characterize the average length and length distribution of SWCNTs respectively. / A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / September 28, 2015. / Alignment, Gauge Fcator, Network density, Piezoresistivity, Single Walled Carbon nanotubes, Strain sensor / Includes bibliographical references. / Tao Liu, Professor Directing Dissertation; Sachin Shanbhag, University Representative; Mei Zhang, Committee Member; Okenwa Okoli, Committee Member; William Oates, Committee Member.

Cells sense and respond to topographical cues in their microenvironment that influence growth, development, and migration. Cell migration and outgrowth assays have been used to study cellular movement or changes in cellular morphology and topography. Such assays are promising tools in drug discovery, especially when implemented with high-throughput and high-content imaging systems. These techniques have also been useful for screening and analyzing the effect of different compounds on neurite outgrowth and topography which in turn may lead to the discovery of beneficial targets for regeneration of nervous tissue. Typically, high-throughput screening of large chemical libraries is employed during the early stages of discovering new drug entities. However, these screening assays do not utilize different topographical surfaces. Many common techniques such as the scratch wound assay are limited in their compatibility with patterned surfaces. Therefore, there is a need to develop novel technologies capable of identifying potentially therapeutic compounds in early stage of drug discovery processes that can regulate cell behaviors and are not limited in their throughput and compatibility with patterned surfaces. A potentially scalable approach is the “fence” assay in which cells are cultured on topographical surfaces which are partially covered by a removable barrier. Upon removal of the barrier, cells are free to spread and migrate on the freshly uncovered topographies. In this thesis, a novel technique called evaporative edge lithography (EEL) is demonstrated as an approach to miniaturize the fence assay and can be used for high-throughput screening (HTS) in early stages of drug discovery. Furthermore, EEL is a new method to fabricate lipid-based drug delivery microarrays. Lipid multilayer micro-patterns offer a promising approach to applications such as drug screening and biosensing that require well defined patterns and fluidity. It is shown in this thesis that the factors that govern stability and instability of lipid multilayer nanostructures upon immersion using fluorescence microscopy and observed the following four mechanisms of lipid multilayer instability and strategies are derived to control immersion stability based on these findings: (1) Dissolution by the air/water interface; (2) Disruption by shearing from flowing solution; (3) Spreading at the solid-liquid interface; (4) Diffusion into solution. Based on these studies, a lipid multilayer microarray was developed that is suitable for cell-based assays without detectible cross-contamination by culturing cells on lipid patterns. It is shown in this thesis that this assay is compatible with poorly soluble lipophilic drug compounds that pose a challenge for HTS microarray assays. EEL was demonstrated for topographically patterned surfaces for screening compounds on adherent cells. Lipophilic compounds including docetaxel and BFA were screened using EEL with cultured HeLa cells to test if migration is affected and can be quantified with this approach. These results indicate that docetaxel and BFA were delivered locally into cells locally from surface supported lipid films and significantly inhibited cellular migration. Subsequently, EEL was used to screen docetaxel on cultured primary olfactory bulb neuronal cells to test the effect on neurite outgrowth. EEL is a novel approach that allows delivery and subsequent study of the effects of poorly water-soluble drugs on cell migration as well as in vitro screening of different drugs for their effects on cell structures and functions. In addition, this migration assay is a scalable and promising approach for high throughput drug screening microarrays since multiple drug compounds at different dosages can be screened simultaneously on the same surface. This work will advance future studies in developing a portable assay capable of screening lipophilic cancer and neurotropic compounds for topographically-driven cell outgrowth and migration. / A Dissertation submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2018. / April 5, 2018. / cell migration, drug screening, evaporative edge lithography, lipid multilayers, lipid patterning, neurite outgrowth / Includes bibliographical references. / Steven Lenhert, Professor Directing Dissertation; Jingjiao Guan, University Representative; Kathryn Jones, Committee Member; Thomas Keller, Committee Member; Jonathan Dennis, Committee Member.

<p> Much scientific knowledge already exists on the Cretaceous-Paleogene (K/Pg) Boundary Deposit from outcrop and shallow core near to outcrop. The significance of this study is to learn from the only deep-well core on land, from the northern Gulf of Mexico (GoM) known to preserve this deposit. This core was chosen because of its pristine (unweathered) condition. The aim was to characterize the portion of this core which was influenced by the Chicxulub Impact event 65.5 Ma to enhance the scientific knowledge of the K/Pg boundary. I hypothesized that this core represents three lithofacies: 1) pre-impact chalk, 2) mass wasting deposit and fall back material, 3) Midway Shale; and that the mass wasting deposit and fall back material were deposited as a direct result of the impact event. I tested these hypotheses by employing: 1) Macroscopic descriptions, 2) Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) of selected portions, 3) 10% HCl treatment and microscopic descriptions of the resulting insoluble portions. The findings show that the core can be divided into three main sections in ascending order: 1) a lighter carbonate, 2) a darker carbonate, and 3) a black shale. From optical and SEM analysis, I find that the microfossils and ubiquitous coccoliths found throughout the carbonate sections of this core do not exist in the core above section 2. Section 2 is mostly a Chicxulub Impact induced mass wasting deposit. In order to investigate better the non-carbonate components of the core, representative portions were treated with 10% HCl, an investigative technique not commonly applied to cores of the K/Pg boundary. Under an optical microscope ,10% HCl insoluble portions from the K/Pg boundary reveal no regularly shaped impact spherules. I find no Si-rich spherules and posit that the spherules in this core are almost entirely, Ca-rich.</p><p>

<p> At present modulators in communications industry utilize non-linear materials like indium tin oxide (ITO) and DLD-164 as a dielectric, which makes the fabrication process cumbersome and expensive. This thesis discusses the possibility of using only gold and air as conductor and dielectric to characterize a signal modulating device. Both electro-absorption modulation (EAM) and phase change driven modulation is possible with the design. For the change in phase a length of 2.992 &micro;<i>m</i> for the modulating arm of a Mach-Zehnder modulator (MZM) was achieved for operation at 525 <i>nm</i>. High absorptions of electromagnetic (EM) waves was seen at the 480 <i>nm</i> mark allowing a length of just 4.95 &micro;<i>m</i> for EAM. The results suggest that an all plasmonic noble metal modulator utilizing air as a dielectric is possible for operation in the visible 400 <i>nm</i> to 700 <i>nm</i> range. The concept is supported by proof-of-principle based simulations. </p><p> This thesis proposes a novel idea of an all plasmonic modulator driven by changes in free carrier concentration in gold and surface plasmon polariton (SPP) excitations under an applied potential. The prototype model is simulated using a commercial finite difference time domain solver. The simulation enviro<i> nm</i>ent allows Maxwell&rsquo;s equations to be solved in the time domain to investigate light propagation and absorption characteristics under an externally applied electric potential. The free carrier concentration dependent permittivity of gold is exploited to investigate possible applications in nano-photonics and optical communications.</p><p>