Abstract Book

The Manitoba Materials Conference poster competition brings together students and postdoctoral fellows from 36 research groups across the university from the departments of Chemistry, Civil Engineering, Electrical & Computer Engineering, Geological Sciences, Mechanical & Manufacturing Engineering, Physics & Astronomy, Food Science and Textile Science.

This competition is sponsored by the Manitoba Institute for Materials.

Conference Chair: Dr. Johan van Lierop, Physics & Astronomy

MIM Director: Dr. Michael Freund, Chemistry

 

Complex Crystalline Materials and Nanostructures

 

[1]           RAMAN SPECTROSCOPY OF THE CARBONACEOUS MATERIAL FROM THE KAPOETA METEORITE: EVIDENCE FOR THE EXISTENCE OF MICRO/NANODIAMONDS

Abdu, Yassir, Postdoctoral Fellow

Geological Sciences

Advisor: Dr. F.C. Hawthorne

 

Nanometer-sized (1-3 nm) diamonds that pre-date the formation of our solar system (presolar nanodiamonds) were first discovered in meteorites [1]. They were named presolar or interstellar nanodiamonds because they contain isotopically anomalous noble gases, particularly Xe-HL, which is enriched both in the heavy (H) and the light (L) isotopes of Xe. The origin and the process by which these presolar nanodiamonds have formed is still debated, however many authors favor the formation from a process similar to the chemical-vapor-deposition (CVD), which is used in the laboratory for the production of nanodiamonds. Raman spectroscopy is a powerful technique that is commonly used in the analysis of carbon-based materials, and it has recently been applied to study diamonds in meteorites [2]. Here we report on preliminary results from micro-Raman spectroscopy measurements on a carbonaceous material from the Kapoeta meteorite. The Raman spectra indicate the presence of micro/nanodiamonds coexisting with a graphite-like amorphous carbon phase. The results will be discussed in relation to Raman studies of diamond from other types of meteorites and synthetic CVD nanodiamonds.  

 

[1] Lewis, R.S. et al. 1978, Nature, 326, 160.

[2] Karczemska, A. et al. 2007, Diamond and Related Materials, 16, 781.

 

[2]           SUPPRESSION OF BLOCKING BEHAVIOR IN A MACROSCOPIC FCC NANOPARTICLE CRYSTAL   

Desautels, Ryan, Ph.D. Candidate

Physics and Astronomy

Advisor: Dr. J. van Lierop

 

An increased awareness of our dependence on non-renewable resources is driving the need for more energy efficient technologies. New functional magnetic materials are essential components for the development of these technologies. Nanoscale physics, physics at sizes comparable to a DNA helix or a virus, is a rapidly growing area of research which strives to understand and develop these new magnetic materials. It is well known that synthetic materials (metamaterials) exhibit interesting magnetic properties. These properties are generally different than those of the isolated components or the bulk material. We present a novel protein crystallization technique which allows us to fabricate bulk three-dimensional ordered arrays (nanocrystals) of magnetoferritin nanoparticles. These perfectly faceted crystals of magnetoferritin nanoparticles of sizes up to a few hundred micrometers mitigate the effects of structural disorder revealing long range magnetic ordering effects. A comparison of the magnetic properties between uncrystallized amorphous magnetoferritin nanoparticles and three-dimensional crystals of magnetoferritin nanoparticles reveal the differences caused by interparticle interactions. For example, interparticle interactions alter the temperature dependence of the low field magnetization and susceptibility. Surprisingly, no superparamagnetism was detected in the nanocrystal up to 400 K, significantly above room temperature, whereas the uncrystallized magnetoferritin nanoparticles exhibit superparamagnetism above 50 K.

 

[3]           CHARACTERISING LONE-PAIR ACTIVITY OF BIREFRINGENT LEAD(II) COORDINATION POLYMERS BY ²⁰⁷PB SOLID-STATE NMR

Greer, Brandon, M.Sc. Candidate

Chemistry

Advisor: Dr. S. Kroeker

 

Lead(II) coordination polymers composed of metal-organic fragments are often valued in optical applications for their birefringence, owing to the wide range of structural and electronic attributes that can be accessed through polymer design and tuning. The stereochemical activity of the lone-pair electrons on the lead(II) atom has a decisive impact on the local geometry, and correspondingly, on the extended crystalline structure. We use solid-state ²⁰⁷Pb NMR and density functional theory calculations to investigate the relationship between lone-pair activity and structure for a series of lead(II) coordination polymers containing [N(CN)₂]- or [Au(CN)₂]- bridging ligands and substituted terpyridine ancillary ligands.²⁰⁷Pb anisotropic shielding exhibits correlations with local structure and birefringent properties, while DFT calculations describe the effect of ligand basicity on lead(II) lone-pair activity. This work provides a compelling link between spectroscopic and optical properties, suggesting ²⁰⁷Pb NMR may have a role in materials design.

 

[4]           SPIN WAVE EVOLUTION IN FERROMAGNETIC MICROSTRUCTURES

Hayward, Lauren, Undergraduate Student

Physics and Astronomy

Advisor: Dr. B. Southern

 

Confined spin waves in single magnetic microstrips are investigated using a microwave photovoltage technique. Direct mapping of the spin wave evolution between surface, edge, and central modes is achieved by tuning the direction of the applied magnetic field. Both theoretical and numerical methods are used to study the evolution of the excitations and provide excellent agreement with the experimental results. The most prominent feature observed is a mode repulsing behavior which indicates mode hybridization in the dipole dominated part of the spin wave spectrum.

 

[5]           THEORETICAL MODEL FOR ELECTRON DENSITY WAVES HAVING THE GRAPHENE STRUCTURE

Hernandez-Melgar, Javier, B.Sc.(Hons.) Candidate

Physics and Astronomy

Advisors: Dr. J.M. Vail and Dr. Z. Wang

 

We have developed a theoretical model for the analysis of two dimensional electron density waves such that the minima of the self-consistent field (SCF) single-electron energy have the same pattern as the atomic sites in graphene. The many-electron system is described very simply in terms of tight binding with atomic-like basis functions from the Hartree approximation. We consider the case where the periodic potential due to the atomic cores of the host material is suppressed in favor of an effective electron mass. The only periodic potential in the model system is then due to the electron density wave. In order for electron density waves to constitute the stable ground state, the effective pairwise electron-electron interaction must include not only Coulomb, but other contributions. These additional contributions are commonly attributed to electron-phonon interaction. If the effective pairwise interaction leads to a stable ground state with periodic electron density having the graphene structure, then such systems may be investigated in terms of electron-phonon coupling strength. Variation of chemical composition and other static characteristics, are often considered when attempting to widen the range of systems possessing some or all of the electronic properties of graphene. The present work then adds dynamic host-system characteristics to static considerations for such studies. In the present work, the solution of the Hartree equation depends on satisfying the mathematical self-consistency condition between the parameters of the atomic-like basis functions and the effective pairwise coupling. For systems that can satisfy the SCF condition, the question of stability must be addressed: Is there a many-electron configuration having lower energy than the density wave? It can easily be seen that a uniform electronic density is a solution of the Hartree equations when the effective mass approximation is used. Thus the density wave state will only be stable if its total energy is less than that of the uniform density state. We have determined the analytical form of the SCF condition, using cylindrically symmetric harmonic oscillator wave functions for the atomic-like basis. Further work in progress addresses the SCF and total-energy stability conditions, to be analysed quantitatively.

 

[6]           UNDERSTANDING AND CONTROLLING TOPOTACTIC REDUCTIONS OF N=1 RUDDLESDEN-POPPER MANGANATES

Hernden, Brad, M.Sc. Candidate

Chemistry

Advisor: Dr. M. Bieringer

 

Over the last decade metal hydride solid state reductions have led to the synthesis of many novel oxygen defect transition metal oxides. This technique provides insight into solid state reaction mechanisms which are under kinetic control. Progress towards step-wise mechanistic reactions in solid state chemistry is becoming viable using this technique. Limitations in current literature include the absence of well characterized metal hydride reactivity as reductants and rationalization for the choice of metal hydride reductant used.

Low temperature metal hydride reductions of the Sr_2-xCaxMnO₄ (0<x<2) system has been explored. Using a variety of group I and II metal hydrides as solid state reductants allowed for evaluation of reaction trends for the reduction of manganate Ruddlesden-Popper phases. These trends emphasize the differences in reactivity among group I and II metal hydrides and the impact of metal hydride choice on the topotactic reduction. The targeted synthesis of Sr₂MnO_4-x (0<x<0.37) phases will be presented including the use of novel hydride reductants.

In addition the potential insertion of small cations into the Ruddlesden-Popper phases during solid state reduction will be presented.

 

[7]           INVESTIGATION OF TWO STEP FORMATION PATHWAY OF A POTENTIAL SOLID OXIDE ION ELECTROLYTE IN-DOPED CeO₂

Shafi, Shahid, Ph.D. Candidate

Chemistry

Advisor: Dr. M. Bieringer

 

Commercial oxide-ion electrolytes have the fluorite structure with anion vacancies. CeO₂ crystallizes in the fluorite type structure, doping with divalent and trivalent cations creates oxide ion vacancies in the structure making them potential candidates for solid oxide-ion electrolytes. In particular lanthanum doped CeO₂ (Ce_(1-x)Ln_xO₂-d) have drawn significant attention due to very high oxide ion conductivity compared to that of Y₂O₃-doped ZrO₂ (YSZ). The objective of this work is to explore the formation of In-doped CeO₂ via a two-step synthesis using in-situ powder X-ray diffraction. In-depth analysis of reaction pathways via in-situ techniques is important as it allows identification of metastable phases. Often, ex-situ investigation would not provide as much information and noteworthy intermediates would stay unnoticed. The ex-situ attempts for the direct synthesis of In-doped CeO₂ from stoichiometric amounts of CeO₂ and In₂O₃ has not been successful despite similar ionic radii for In³⁺ and Ce⁴⁺, this reaction was followed in-situ and confirmed that the direct synthesis is not possible. The alternate two-step synthesis route involves formation of In-doped perovskite BaCe_(1-x)In_xO₃-d and subsequent decomposition using CO₂. The entire phase diagram of BaCO₃-CeO₂-In₂O₃ and CeO₂-In₂O₃ systems belonging to this synthesis will be presented. The Ce_(1-x)In_xO₂-d phases are metastable and can only be prepared at low temperatures through CO₂ capture reaction. The competition between CO₂ capture reaction and In-doped CeO₂ decomposition was investigated and the maximum In-doping that can be achieved with BaCe_(1-x)In_xO₃-d as an intermediate was identified. The CO₂ capture reaction is an excellent route for the synthesis of doped CeO₂ and the research methodologies developed in this study can be extended to other promising materials. 

 

[8]           SURFACE SPIN STABILITY IN γ-Fe₂O₃ NANOPARTICLES WITH A Cu SHELL

Skoropata, Elizabeth, M.Sc. Candidate

Physics and Astronomy

Advisor: Dr. J. van Lierop

 

The small size and high surface area of nanoparticles make them attractive candidates for use in a wide variety of applications such as drug delivery, data storage and contrast enhancement for magnetic resonance imaging. However, the suitability of nanoparticles for use in such applications relies on how well their response to an externally applied magnetic field can be understood and controlled. Finite size and surface effects tend to suppress the magnetic response of nanoparticle, and a current challenge facing materials researchers is to optimize the magnetic properties of nanoparticles and create nanoparticles with magnetic properties well suited to applications. In order to study the effect that the surface environment of a nanoparticle has on the magnetic properties we have synthesized bare γ-Fe₂O₃ and novel γ-Fe₂O₃ core/Cu shell nanoparticles and examined the changes in the magnetic properties between the two systems. The structure and composition of each sample was characterized using transmission electron microscopy, x-ray powder diffraction and x-ray photoelectron spectroscopy. Results indicated that for all Cu shell thicknesses a monolayer of CuO had formed at the core/shell interface. While bulk CuO has no net magnetization, x-ray magnetic circular dichroism results indicated that the interfacial CuO layer was magnetized. The magnetic CuO interacted with Fe ions at the surface of the γ-Fe₂O₃ nanoparticles which resulted in an increase of the magnetization of the nanoparticle that indicated a recovery of the γ-Fe₂O₃ surface magnetism.

 

[9]           NONLINEAR MICROMAGNETIC SIMULATIONS OF PERMALLOY STRIPS

Wismayer, Matthew, Postdoctoral Fellow

Physics and Astronomy

Advisor: Dr. B. Southern

 

Confined nonlinear spin-wave modes in a permalloy (Py) rectangular strip are investigated using the micromagnetic method to solve the Landau-Lifshitz-Gilbert equation for damped precessional motion. The study involves accurately modeling the relaxed and dynamic states for a normally magnetised microstrip. The relaxed state is determined by applying a large static magnetic field perpendicular to the strip plane thereby saturating the total magnetisation. The dynamic state is modeled by applying a time dependent sinusoidal field of constant amplitude and frequency along the length of the strip. A Fourier analysis of the dynamic magnetisation is used to map out the spin-wave mode spectrum as a function of the applied static field. The spin-wave spectrum in the nonlinear regime shows good qualitative agreement with measurements obtained from the photo-voltage technique. These micromagnetic simulations expand the current understanding on how nonlinear spin-wave modes interact via the magnetostatic force.

 

[10]           A GENERAL, ONE-POT, GREEN METHOD FOR THE SYNTHESIS AND FUNCTIONALIZATION OF METAL OXIDE NANOPARTICLES

Worden, Matthew, M.Sc. Candidate

Chemistry

Advisor: Dr. T. Hegmann

 

The rise of nanotechnology along with increasing interest in developing simpler, environmentally friendly synthetic methods points to a need to apply to ‘green’ techniques to nano fabrication. This was accomplished as shown in a recent publication from our group, which detailed a one-pot, aqueous, room temperature synthesis of magnetite (Fe₃O₄) nanoparticles through the reduction of an organometallic precursor with sodium borohydride. Research focusing on our efforts to expand this procedure to a more general synthesis of a wide variety of metal oxide nanoparticles (e.g., Mn₃O₄, Co₃O₄, as well as mixed metal oxides) will be presented. Analytical data - such as XRD, XPS, and IR spectroscopy - characterizing the particles will be included. Furthermore, this procedure allows for a variety of hydrophilic and hydrophobic coatings to be applied onto the particles, a necessary step towards specific applications. Our ongoing investigations into the techniques involved in obtaining certain coatings and the effects thereof will also be presented.

 

[11]           CHARACTERIZATION AND BIO-COMPATIBILITY OF IRON OXIDE NANOPARTICLES SYNTHESIZED USING A NOVEL ONE STEP, LOW TEMPERATURE REDUCTION METHOD

Yathindranath, Vinith, Ph.D. Candidate

Chemistry

Advisor: Dr. T. Hegmann

 

Iron oxide nanoparticles (IONPs) have a number of emerging applications in clinical medicine and hence there is a greater demand for better ways of preparing IONPs that are biocompatible. Here we report a versatile one-pot room temperature synthesis of IONPs from iron(III)acetyl acetonate following a new hydrolysis/reduction method. Using this method, we have made ‘bare’, hydrophilic poly(ethylene glycol), L-arginine and L-glutamic and hydrophobic oleic acid coated IONPs.  Physicochemical characterization of the resulting IONPs were performed using powder x-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and Mossbauer spectroscopy. The average particle size determined using TEM for the IONPs synthesized at room temperature were around 5 nm with narrow size distribution. To determine bio-compatibility of the IONPs, cell viability assays were performed in Caco2 and HepG2 cell lines using MTT cytotoxicity assay. Permeability of hydrophobic oleic acid coated IONPs were carried out on confluent monolayers of human brain micro endothelial cells grown on Transwell membrane inserts. In the permeability studies, IONPs were found in all cases in the receiver compartment after 24 hours as determined by the Prussian blue absorbance with respect to the control (which didn't receive any IONPs). Oleic acid coated IONPs exhibited poor dispersibility in DMEM, but still permeated the cell membrane in all cases. Applied magnetic field clearly produced an enhancement in the permeability of IONPs over 24 hours.

 

Complex Natural Systems

 

[12]           DETECTING THE ELECTRO-DEFORMATION OF BIOLOGICAL CELLS IN MICROFLUIDIC CHANNELS - A MECHANISM FOR BIOPHYSICAL FLOW CYTOMETRY

Ferrier, Graham, Ph.D. Candidate

Electrical and Computer Engineering

Advisor: Dr. D. Thomson

 

The electrical properties of a biological cell are linked to its surface morphology and mechanical properties, which provide insight into its physiological state. In this work, biological cells flowing in a fluid-filled channel generate position-dependent electrical signatures while passing over a pair of interdigitated coplanar electrodes. Low- (< 3 MHz) and high-frequency (1.5 GHz) electrical signals are coupled to the electrodes to actuate and detect cells, respectively. In conductive cell buffers such as phosphate buffered saline (PBS), the low-frequency signal forces cells away from the electrodes toward the top surface (ceiling) of the channel. At sufficiently large signal strengths, these cells are pressed into the ceiling, and may subsequently become deformed. High-frequency signals provide the sensitivity required to dynamically detect the cell-to-wall interaction. Distinct electrical signatures are observed when cells are driven into contact with the ceiling, as compared with the equivalent signatures from "rigid" polystyrene spheres. Simulations of the equation of motion are used to estimate the experimental trajectories of both un-actuated and actuated cells as they pass over the electrodes. Since distinctive cell phenotypes exhibit unique surface and mechanical properties, their respective wall interactions may form a basis for their differentiation.

 

[13]           FINGERPRINTING TURQUOISE DEPOSITS IN THE AMERICAN SOUTHWEST

Hull, Sharon, Ph.D. Candidate

Geological Sciences/Anthropology

Advisor: Dr. M. Fayek

 

Archaeologists have used a number of geochemical techniques to obtain provenance information to develop and refine models for human migration, local exchange networks, and large-scale trade structures. Techniques have been developed to analyze a variety of archaeological material such as obsidian, turquoise, quartz, marble, chert, and ceramics. New instrumentation is less destructive, more precise, and requires less material for analysis. Regardless of instrumentation and new techniques, to begin reconstruction or model the transport of mineral resources it is necessary to have accurate knowledge of the mineral of interest and the provenance regions. For example, we developed a technique to geochemically fingerprint turquoise provenance regions using the isotopic compositions of hydrogen (D/H) and copper (⁶⁵Cu/⁶³Cu) measured by an ion microprobe. The use of isotopic ratios overcomes many of the limitations experienced in earlier studies using trace element composition patterns. Turquoise is a complex mineral and the use of a microanalytical technique for analyzing solid samples allows us to avoid inclusions and matrix that may be present in samples prepared for bulk analyses and the artifacts can be returned to their original collections. As turquoise artifacts are geochemically characterized, their signatures are added and compared to a data base that also contains the geochemical fingerprints of turquoise provenance regions. This database is an on-going project that will continually expand as more turquoise provenance regions and artifacts are analyzed allowing examination of turquoise procurement strategies and exchange through time and space.

 

[14]           CHARACTERISTICS OF FEMTOSECOND LASER ABLATION ON BIOMINERALS

Yang, Panseok, M.Sc. Candidate

Geological Sciences

 

Suppressed particle-size-related-fractionation (PSRF) and improved particle size distribution, makes femtosecond (fs) laser ablation the preferred solid sampling method over nanosecond (ns) laser ablation, especially for volatile elements and elements with high first ionization potentials. In this study, volatile elements such as Zn, Hg, and Pb in biominerals (fish otoliths and fin-rays) were analyzed by Ti:sapphire fs (~46 fs) near-infrared ( = 785 nm) laser ablation inductively coupled plasma mass spectrometry (NIR-fs-LA-ICP-MS) and were compared with the results of Nd:YAG ns (~6 ns) ultra-violet ( = 213 nm) laser ablation. In addition to the volatile elements, Sr, Ba, Cu, and Cd were also analyzed for comparison between the two laser ablation techniques. Concentrations of the elements were determined by using MACS-3, a pelleted calcium carbonate reference material obtained from US Geological Survey. The signal of ⁴³Ca⁺ was used as an internal reference, correcting for variations in the laser ablation yield and transport efficiencies and sensitivity of the instrument. For NIR-fs-LA-ICP-MS, the influence of various laser parameters - beam diameters, focus positions relative to sample surface, repetition rates, laser fluences, and scan speed - on the ablation of biominerals is evaluated. Femtosecond laser ablation provided improved accuracy, superior to that obtained using ns LA-ICP-MS. Furthermore, fs laser pulses significantly reduce the frequency and amplitude of spikes in sample signals commonly observed from ns laser ablation, and thus reduce fractionation at the laser beam sites. These reduced noise levels from fs laser ablation can contribute to more precise isotope ratio determination.

 

[15]           WIRELESS HYGROTHERMAL TRANSDUCER FOR BUILDING STRUCTURE HEALTH MONITORING

Zhao, Jun Hui, Postdoctoral Fellow

Electrical and Computer Engineering/ISIS Canada

Advisor: Dr. D. Thomson

 

Hygrothermal behavior has a great impact on the strength and integrity of the building components. For monitoring moisture induced structural deterioration and performance degradation such as frost damage and mold growth, a wireless, passive inductor-capacitor (LC) resonant circuit technique is explored for measurement of the moisture level. The working mechanism is based on capacitance change induced by variation of effective dielectric constant due to the presence of water within the building materials such as stones and the corresponding change of the resonant frequency of the LC circuit. The moisture level can be determined by detecting the resonant frequency shift. In this study, the LC resonant circuit moisture sensor consists of an inductive sensing coil and a capacitor formed by two stainless steel bars. Another inductive interrogator coil was built as a signal transmitter and receiver. The coupling signal between the sensing coil and interrogator coil was measured using Impedance Analyzer. A relative humidity (RH) sensor was imbedded inside the hole beside the two bars so that the moisture level inside the stone can also be evaluated based on the RH value. With the water moisture continually penetrating into the region between the electrodes of the two bars, accumulation of the moisture increases the effective dielectric constant, leading to the increase of the capacitance and the corresponding shift of the resonant frequency. The resonant frequency changed from 5.96 MHz to 4.80 MHz while the moisture sensor indicated the relative humidity inside the stone changed from about 10% to 100% at room temperature. The results for drying cycles were also investigated. Since electrical signal can be inductively transmitted between two spiral inductors which can be separately positioned in the different locations, thus, wireless monitoring of the structural health becomes possible using a simply configured two bars capacitive component and an induction coil. In addition, these sensors can work wirelessly without requiring batteries.

 

Composite Material Systems

 

[16]           DEVELOPMENT OF COMPOSITE METEOROLOGICAL TOWERS

Alshurafa, Sami, Ph.D. Candidate

Civil Engineering

Advisor: Dr. D. Polyzois       

 

A new generation of towers is being developed at the University of Manitoba to support meteorological and wind monitoring instruments that address issues of icing, durability and survivability in cold climates using composite materials. The research project involves: analysis, design and fabrication of full scale composite towers; testing; monitoring the structural and serviceability performance under severe weather conditions; and, icing mitigation to ensure the continuous operation of the towers.

 

[17]           MODEL FOR TIME-DEPENDENT DAMAGE EVOLUTION AND ITS INFLUENCE ON CREEP OF MULTIDIRECTIONAL POLYMER COMPOSITE LAMINATES

Asadi, Amir, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. R. Jayaraman

 

Various damage modes that evolve with time in polymer composite laminates, such as transverse cracking, vertical cracking, delamination, and fiber fracture, as well as the interaction among them, influence the time-dependent degradation in modulus (creep) and strength (creep rupture) of polymer composite laminates. This study is focused on modeling simultaneous time-dependent evolution of transverse cracking in multiple plies of a multidirectional polymer composite laminate (e.g. [θm/90n]s, [0/ θm/90n]s), their influence on each other's evolution and their effect on creep of polymer composite laminates. The developed model is based on variational analysis and modified lamination theory. The variational analysis module in the model is used to determine the stress state at any given creep time. Then, the stored elastic energy, determined using this stress state, is compared with a critical energy for fracture to determine the crack evolution with creep time. The creep strain is calculated using the modified lamination theory module of the model. Model predictions are compared with experimental results to validate the model. 

 

[18]           BIO-COMPOSITES FROM HEMP FIBERS

Fahimian, Mahi, Ph.D. Candidate  & O'Connor, Brian, Undergraduate Student

Mechanical and Manufacturing Engineering

Advisor: Dr. R. Jayaraman

 

Natural fiber bio-composite, consisting of unsaturated polyester and needle - punched non-woven hemp fiber mats,  has been developed to replace glass fiber composites in transportation applications.  The composites have been manufactured using vacuum assisted resin transfer molding (VARTM) and hemp fiber mats.  The properties of the composite have been tailored by controlling the mat manufacturing parameters  such as punch density and punch depth. Biocomposites with 20% fiber volume fraction show a  modulus similar to that of glass fiber composite with 30%  fiber volume fraction.  Various fiber surface treatments have been studied to improve the hemp fiber-matrix interfacial bonding. Acrylonitrile treated fibers have been found to provide optimal bonding and composite properties. Demonstrative bus parts have been manufactured using this hemp fiber biocomposite.

 

[19]           POLYMER NANO-COMPOSITE

Khorsand, Amirreza, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. R. Jayaraman

 

Polymer composites are important commercial materials with applications that include filled elastomers for damping, electrical insulators, thermal conductors, and high-performance composites for use in aircraft. During the past four decades, the properties of polymer composites have been tailored at two - three size scales, millimeter (laminate level), micrometer (lamina level), and sub-micron (fibre level). Discovery of carbon nano-tubes (with diameters in the range 10  - 50 nm (1 nm = 10^-9m), length of few microns, modulus and strength 1000 times and 100 times that of the currently used carbon fibers, has ignited the current interest in tailoring the structure of composites in a fourth size scale, namely the nano-scale. Current efforts, in the realm of structural composites, are exclusively focused on nano carbon fibers/tubes and nano-clay. Depending on the reinforcement, both structural and functional properties can be tailored into a composite. For example, using carbon nano-tubes, both mechanical and electrical properties can be improved significantly. Current research is focused on tailoring the composite properties by controlling the structure at all four size scales. As a first step, structure at the nano-scale is focused. Composite micro fibers with nano reinforcement are manufactured by melt spinning and its properties are characterized as a function of reinforcement geometry, orientation, and volume fraction.

 

[20]           NOVEL CONDUCTING POLYMER-HETEROPOLY ACID HYBRID MATERIAL FOR ARTIFICIAL PHOTOSYNTHETIC MEMBRANES

McDonald, Michael, Ph.D. Candidate

Chemistry

Advisor: Dr. M. Freund

 

Artificial photosynthetic (AP) approaches to convert and store solar energy will require membranes capable of conducting both ions and electrons while remaining relatively transparent and chemically stable. A new approach is applied herein involving previously described in situ chemical polymerization of electronically conducting poly(3,4-ethylenedioxythiophene) (PEDOT) in the presence of proton conducting heteropoly acid (HPA) phosphomolybdic acid (PMA). The electrochemical behaviour of the PEDOT/PMA hybrid material was investigated and it was found that the conducting polymer (CP) is susceptible to irreversible oxidative processes at potentials where water is oxidized. This will be problematic in AP devices should the process occur in very close proximity to a conducting polymer-based membrane. It was found that PEDOT grants the system good electrical performance in terms of conductivity and stability over a large pH window; however, the presence of PMA was not found to provide sufficient proton conductivity. This was addressed in an additional study by tuning the ionic (and in turn, electronic) conductivity in creating composites with the proton-permselective polymer Nafion. It was found that a material of this nature with near-equal conductivity for optimal chemical conversion efficiency will consist of roughly three parts Nafion and one part PEDOT/PMA.

 

[21]           ELECTRICAL CHARACTERIZATION OF SEMICONDUCTING MICROWIRES AND THEIR JUNCTION WITH IONIC AND ELECTRONIC CONDUCTING POLYMER COMPOSITES

McEleney, Kevin, Postdoctoral Fellow

Chemistry

Advisor: Dr. M. Freund

 

The ever-growing demand for energy and the pressure to reduce reliance on the fossil fuel-based economies has encouraged considerable motivation to develop clean and renewable energy sources. Solar energy is perhaps the most abundant energy source we have available thus a potent resource. As the solar flux is not constant at all times of the day we need to develop a way to harvest the light energy and store for later use. Utilizing light to drive redox reactions we can store solar energy as chemical bonds. In order to achieve this a working device would require a light harvesting component (semiconducting microwires), redox catalysts and some method for separating the oxidation and reduction reactions (membrane).As part of a global effort to develop new solar energy collectors we have been exploring the role of the membrane in managing ionic and electronic conductivity in the system as well as the junction between the semiconducting microwires and the membrane. This work will focus on the development of new contact forming methods for semiconducting microwires as well as the characterization of the microwire-conducting membrane junction.

 

[22]           DESIGN AND FABRICATION OF ELECTRONIC/IONIC CONDUCTING MEMBRANES FOR ARTIFICIAL PHOTOSYNTHESIS

McFarlane, Shaune, Postdoctoral Fellow

Chemistry

Advisor: Dr. M. Freund

 

Artificial photosynthetic systems will require multifunctional membranes. In contrast to fuel cells, such a system will require the membrane to conduct both ions associated with redox processes and electrons/holes associated with light absorption. An approach to designing and fabricating an artificial photosynthetic membrane, involving a composite material fashioned from state-of-the-art electronically and ionically conducting polymers will be presented. It will be shown that while artificial photosynthetic systems that use these polymers as a membrane material have attractive electronic, ionic, physical, and optical properties, there are important tradeoffs, which in turn present opportunities for the design and synthesis of new materials for artificial photosynthetic systems.

 

[23]           STIFFNESS OF EXTRACELLULAR MATRIX CONTROL CELL FATE -3D BIOMIMETIC NANO-COMPOSITE SCAFFOLD FOR BONE REGENERATION

Mohamed, Azeden, Postdoctoral Fellow

Mechanical and Manufacturing Engineering/Biochemistry and Molecular Genetics

Advisor: Dr. M. Xing

 

Introduction: Recent discoveries in novel biodegradable materials, nanotechnology and stem cell research have led tissue engineered bone graft to become a promising alternative therapy to repair and re-construct bone defects caused by trauma, tumors and congenital diseases. Typical bone tissue engineering strategies utilize biocompatible and biodegradable synthetic scaffolds within which progenitor cells reside. Upon implantation, the scaffold provides a structural support as well as a microenvironment (niche) to regulate progenitor stem cell differentiation and promote bone regeneration by utilizing localized physical and biochemical cues. One of these physical cues, elasticity of the extracellular matrix (ECM), has been clearly demonstrated to influence the fate of cell differentiation. It has also been found that solely changing the stiffness of the ECM dictates the commitment of mesenchymal stem cells (MSCs) to various lineages such as neurons, myoblasts and osteoblasts. However, the mechanism of how the physical cues of ECM stiffness is sensed and processed by progenitor cells to regulate differentiation is elusive.

 

Methods: To investigate how elasticity of the ECM regulates progenitor cell fates, we designed three-dimensional (3D) scaffolds with controllable stiffness created by various percentages of hydroxyapatite (HA) and collagen (Col) composition, which are the major natural components of bone. Pre-osteoblasts were seeded into scaffolds. The impact on osteogenesis induced by various stiffnesses of the ECM has been verified by immunohistology, gene expression and protein analyses. Bioinformatics was employed to aid in the identification of the signaling pathway of mechanotansduction between ECM and cells.

 

Results: It has been confirmed that matrix stiffness influences osteogenesis in the biomimetic scaffolds based on the data from reverse transcription real-time PCR (RT qPCR).

 

[24]           XPS CHARACTERIZATION OF PROTON AND ELECTRON CONDUCTING COMPOSITES

Tan, Damaris, M.Sc. Candidate

Chemistry

Advisor: Dr. M. Freund

 

Membrane composites consisting of electron and proton conducting composites will be required for artificial photosynthetic applications. In order to function in an artificial photosynthetic device, they need to be conductive, homogeneous and transparent. Previous studies have shown that 12% PEDOT-PSS in Nafion has sufficient electrical conductivity to handle the expected charge generated in an artificial photosynthetic device. However, at this concentration of conducting polymer the transparency of this membrane is quite low. We can improve the transparency by bleaching the membrane. The two conducting polymers in aqueous dispersion were drop cast to form a freestanding membrane. To bleach the membrane, it was soaked in hydrogen peroxide and irradiated with UV light. The surface of the membranes were characterized by X-ray photoelectron spectroscopy (XPS). The bleached and as prepared composites were compared for their homogeneity and differences in the chemical composition.

 

High Performance Computing

 

[25]           BENCHMARKING OF DENSITY FUNCTIONAL THEORY METHODS FOR THE OLEFIN POLYMERIZATION CATALYSIS: A SEARCH FOR RELIABLE REFERENCE METHODS

Shamov, Grigory A., Postdoctoral Fellow

Chemistry

Advisor: Dr. G. Schreckenbach

 

Rational design of the olefin polymerization catalysts requires realistic, that is, large enough, models systems, and a computational method able to provide balanced description of all aspects of these systems (activation barriers, non-bonded interactions, etc.) The commonly used DFT methods were shown to have problems with some or all of these aspects, and no universal DFT recipe has been created to date. Thus there is the need of benchmarking of DFT methods in order to achieve accurate predictions. However, for transition metal catalysis, experimental kinetic and thermodynamic data are scarce. Standard high-level coupled cluster theory methods such as CCSD(T) cannot yet be applied to the larger systems due to their very unfavorable scaling and high basis set requirements. In this work we have tested the two following alternatives to CCSD(T): the semiempirical variants of spin-scaled MP2 theory (SCS-MP2), and the Diffusion Monte Carlo (DMC) method. We compare results of these methods against CCSD(T) for the smallest Ti(IV) model catalyst of olefin polymerization, considering chain transfer and chain propagation steps that determine the polymer molecular weight. Then, for the larger, more realistic models we benchmark a variety of pure GGA, global and range-separated hybrids, with and without dispersion corrections, against SCS-MP2 and DMC. This work is part of the Research Programme of the Dutch Polymer Institute (DPI), Eindhoven, The Netherlands, Project #641

 

[26]           ACCELARATING OPTICAL FLOW WITH HIGH PERFORMANCE COMPUTING

Sharma, Bhanu; Mijares Chan, Jose Juan, Ph.D. Candidate

Electrical and Computer Engineering

Advisors: Dr. R. Thulasiraman and Dr. G. Thomas

 

This work addresses a fundamental problem from image processing, the computation of optical flow and its computational constraints. The Optical flow, being form from a sequence of images, is used to describe the motion approximations of an object within an image plane. Multiple methods had been developed since 1940s. Within this work, the correlation-based comparison method is selected due to its better performance against the lack of frames or a poor signal-to-noise ratio. Even though, the correlation-based method is robust, the computational cost becomes a constraint for its implementation. For this matter, a high performance computing solution is presented including the use of graphic processing units and its algorithmic optimization.

 

High Temperature Aerospace Materials

 

[27]           FAILURE MECHANISM OF REPAIRED POLYCRYSTALINE IN738 AND DS R80 SUPERALLOYS.

Abrokwah, Emmanuel, M.Sc. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. N.L.  Richards

 

Superalloys have been used quite extensively in the past decades in high temperature applications in the Aerospace and Power generation industries due to their high resistance to the creep, fatigue and oxidation damaging mechanism. Its strength is mainly derived from precipitating gamma prime phase and solid solution alloying. The cost of these Superalloys are very expensive making repair options to damaged component parts more attractive as opposed to buying new equipment when they are damaged. Replacement cost for a modern HTP stage 1 blade is $500,000 USD per engine. Repair cost of up to 60% replacement cost is feasible making the drive towards repairing damage component more attractive. Various repair techniques such as Electron beam, Laser, Cold spray, Low heat input, Diffusion bonding, Wide gap brazing, Plasma spray and Gas Tungsten Arc Welding are being used. Amongst these methods the widely understood and more familiar technique which is more cost effective to repair industries is Gas Tungsten Arc Welding.  However, after repair, there is varying fatigue data for these repaired components. Some of the repaired components have comparatively good mechanical properties as the base line material whiles as others have inferior mechanical properties compared to the base line material. These disparities have been identified as lack of repair process optimization that causes defects in the repaired component. This implies that extra failure mechanisms are present in the repaired component which accounts for the inferior fatigue properties witnessed in some of the repaired components. It is therefore imperative to identify what these failure mechanism are, how they occur and in which areas of the repaired components they are noted. This knowledge will better equip the engineer to be able to select the best repair techniques and process parameters to minimize the effect of these failure mechanisms in the repaired components.  The main objective of this research is to identify the failure mechanism present in the repaired components in both Polycrystalline IN738 and DS R80.

 

[28]           MICROCONSTITUENTS CAUSING WELD HEAT AFFECTED ZONE MICROFISSURING IN INCONEL 738 SUPERALLOY

Amegadzie, Mark Yao, M.Sc. Candidate

Mechanical and Manufacturing Engineering

Advisors: Dr. M.C. Chaturvedi and Dr. O.A. Ojo

 

Inconel 738 is one of the most widely used heat resistant alloys for the hot section components of aero and industrial gas turbines. The alloy, however, is extremely difficult to fabricate and repair by fusion welding due to its high susceptibility to heat affected zone (HAZ) intergranular microfissuring. In the present work, the HAZ microstructure in tungsten inert gas welded IN 738 superalloy was carefully studied by electron microcopy techniques to identify the microconstituents that are responsible for the high susceptibility of the material to microfissuring. The HAZ cracking was observed to be closely associated with eutectic-type liquation reaction of solidification products present in the cast alloy, including MC - type carbides, M2SC sulpho-carbides and M3B2borides. In addition, non-equilibrium liquid phase dissolution of the main strengthening of the superalloy, γ' precipitates, was found to be another vital factor contributing to the low resistance of the material to cracking under thermally induced welding stresses. The results of the investigation will be presented.

 

[29]           FATIGUE BEHAVIOR OF A NEWLY DEVELOPED AEROSPACE SUPERALLOY HAYNES 282        

Buckson, Richard, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. O.A. Ojo

 

Strain-controlled Low Cycle Fatigue (LCF) and Fatigue Crack Propagation (FCG) tests were carried out on a newly developed Aerospace superalloy, Haynes 282, in its standard heat treatment condition. LCF test results demonstrated that Haynes 282 exhibited a relatively short period of initial cyclic hardening followed by a regime of cyclic softening to specimen failure at all the strain amplitudes employed in the work.  An increase in the stress ratio lead to an increased crack propagation rate. However, in contrast to common assumptions, the loading frequency was observed to have an influence on the crack growth behaviour. The cyclic deformation parameters determined in the work indicate strong fatigue deformation resistance of the newly developed superalloy.

 

[30]           IMPROVING THE OXIDATION BEHAVIOUR OF A NICKEL BASED SUPERALLOY PRODUCED BY POWDER METALLURGY

Murray, D. Clark, M.Sc. Candidate

Mechanical and Manufacturing Engineering

Advisors: Dr. N.L. Richards and Dr. W.F. Caley

 

Nickel based Superalloys are often used in applications that require both high temperature strength and excellent oxidation resistance. The high temperature strength of these materials is often found through a γ' phase (Ni₃Al) in these alloys and oxidation resistance is said to dramatically improve through minor additions of reactive elements. In the present research a Ni-12Cr-9Fe (w/o) master powder has been blended with a lubricant and combinations of aluminum, silicon and yttrium in an effort to qualify and quantify the oxidation resistance of the various compositions. The transverse rupture strength (TRS) bars have been produced through the methods of cold uni-axial die compaction, an intermediate temperature lubricant removal stage and followed by a sintering profile previously developed (1300°C w/ 2h hold). The density of the majority of compacts post sinter was approximately 80%. In an effort to increase the density of these compacts prior to oxidation, Gleeble thermo-mechanical deformation has been performed. This deformation has yielded densities in the compacts of approximately 90% although the ¥' strengthening phase found in many Ni-based Superalloys was no longer noted through microscopy. Various heat treatment procedures will be performed on the densified compacts in an effort to restore the γ' phase to the microstructure. Subsequently the compacts they will be sectioned into coupons and oxidized at 900°C through static oxidation for times up to 1000h. The roles of the elemental powders added to the ternary system in providing optimum oxidation resistance may then be assessed.

 

[31]           PROCESSING OF AEROSPACE SUPERALLOYS THROUGH LINEAR FRICTION TECHNIQUE

Ola, Oyedele, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisors: Dr. M.C. Chaturvedi and Dr. O.A. Ojo

 

Linear friction welding (LFW) is a relatively new and state-of-the-art process for joining aerospace materials that are very difficult to weld. These materials include polycrystalline, directionally solidified and single crystal nickel-base superalloys used in manufacturing hot section components of aerospace gas turbine engines. LFW is especially attractive for joining these materials due to its effectiveness in eliminating a major limitation of conventional fusion welding processes, which is grain boundary liquation cracking. However, LFW produces some microstructural anomalies that have been difficult to explain. The goal of this work was to study, and understand, the development of these microstructural anomalies, which is critical to improving the joining procedure and mechanical properties of linear friction welded joints in nickel-base superalloys. The results of this work will be presented.

 

[32]           ELECTRON MICROSCOPY IDENTIFICATION OF M5B3 BORIDE AND ITS EFFECT ON MECHANICAL PROPERTY IN HY 282 SUPERALLOY

Osoba, Lawrence, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. O.A. Ojo

 

Haynes 282 is a new γ' strengthened nickel-base superalloy designed for high temperature applications in aerospace and power generation turbine engines. The properties and performance of materials depend on their initial microstructure or those developed in service. Therefore, the microstructure of the newly developed HY 282 superalloy in the fully heat treated condition was carefully studied using electron microscopy techniques. In addition to M23C6 and MC-type carbide particles previously reported to be present in the alloy, precipitates based on a new phase, M5B3boride, which has not been reported in the new alloy were identified along the intergranular region. Formation of the grain boundary M5B3 borides was found to significantly reduce the ductility of the new alloy at high temperatures. In contrast to what is expected based on solid-state reaction, the present study showed that a possible way of mitigating against the ductility damage caused by the borides is by increasing the grain boundary surface area in the alloy through thermo-mechanically induced grain refinement. The results of the study will be presented.

 

Liquid and Solid Crystals

 

[33]           ALIGNMENT AND SELF-ASSEMBLY OF SURFACE-FUCTIONALIZED GOLD NANORODS IN LIQUID CRYSTALS

Feng, Xiang, Ph.D. Candidate

Chemistry

Advisor: Dr. T. Hegmann

 

The significant interest in anisometric nanomaterials arises from their unique optical and electronic properties that can easily be tuned through small changes in size, structure and shape. However, the fabrication of orientational ordered arrays of anisotropic nanoparticles from the bottom up remains a challenging quest. To address this problem, we dispersed hydrophobic gold nanorods coated with organosilanes in liquid crystals phases (nematic and columnar) and utilized different types of surface-modified substrates to obtain planar (homogeneous) or homeotropic alignment of liquid crystals and the dispersed gold nanorods. The quality of liquid crystal and nanorod alignment were characterized by polarized optical microscopy and polarized visible spectrophotometry, respectively. Here, surface-functionalized gold nanorods produced via a coating exchange from CTAB (cetyltrimethyl ammonium bromide) to functionalized liquid crystalline moieties are thought to facilitate the self-assembly and large-scale alignment of the nanorods.

 

[34]           MAGIC-SIZED CdSe NANOCRYSTALS IN A NEMATIC LIQUID CRYSTAL

Mirzaei, Javad         , Ph.D. Candidate

Chemistry

Advisor: Dr. T. Hegmann

 

Dispersions of metallic and semiconductor nanoparticles in nematic liquid crystals (NLCs) can have unique effects on the electro-optic properties of the NLC host [1]. Such particles also impact the optical characteristics including thin film texture, molecular alignment and defect formation.[2] Herein, we report on the effects of three types of quantum dots (QDs), from a family of magic-sized CdSe semiconductor nanocrystals exhibiting a bright bandgap photoluminescence with the maximum intensity at 463 nm, on the optical, alignment and electro-optic properties of a NLC and comparing the results with existing data[3-4] from other types of particles. Several mixtures of the NLC doped with small quantities of such QDs have been prepared, and the optical as well as electro-optic properties have been studied. Here, fluorescence confocal polarized microscopy has proven to be an indispensable tool to elucidate the effects of these luminescent particles.

1)H. Qi and T. Hegmann, J. Mater. Chem., 2006, 16, 4197-4205.

2) T. Hegmann, H. Qi and V. M. Marx, J. Inorg. Organomet. P., 2007, 17, 483-508.

3) B. Kinkead and T. Hegmann, J. Mater. Chem., 2010, 20, 448-458.

4) M. Urbanski, B. Kinkead, T. Hegmann and H.-S. Kitzerow, Liquid Crystals, 2010, 37, 1151 - 1156.

 

Microelectricalmechanical Systems (MEMS)

 

[35]           ESTIMATING THE SAMPLE INTERACTION VOLUME IN DYNAMIC HETERODYNED ELECTROSTATIC FORCE MICROSCOPY        

Anema, Everet, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. D. Oliver

 

The electric force microscope (EFM) is a unique tool that spatially maps electrical properties such as surface charge. This technique also allows for the inspection of local variations in the permittivity of material, a variation that is not restricted to the surface of the material. The primary objective of this project was to determine the volume of material that the EFM tip was interacting with. This objective was accomplished using field theory to predict the electric field inside the chamber of the EFM and with the predicted fields calculate the portion of the material that is responsible for the majority of the force. To validate the mathematical models it was necessary to compare the results with the actual experiment that was modelled. The experiments were conducted in vacuum using dynamic heterodyned EFM approach. This technique applies an amplitude modulated signal to the tip and observes the variation in resonant amplitude to determine the force acting on the tip, and from this the electrical properties of the material. The sample used was the calibration grating TGZ-01/02/03 manufactured by Mikro Masch. These samples consist of an Si substrate with a series of SiO₂ steps of varying heights. These samples were used to change the ratio of Si to SiO₂ in the material directly below the tip. Two models were created, one analytical and the second using COMSOL, a finite element package. The two models have fairly good agreement with each other based on the force acting on the tip; they differ by about 8%.  An estimate of this force based on experimental data is within an order of magnitude of the values obtained using the models.

 

[36]           POLYMER-BASED MEMS CHEMICAPACITOR SENSOR

Emadi, Arezoo, Ph.D. Candidate

Electrical and Computer Engineering

Advisor: Dr. C. Shafai

 

Promising gas detectors are polymer-based sensors, which benefit from a vast range of organic polymers that react differently to a desired volatile. Traditionally polymer-based sensors utilize a composite film of an insulating polymer together with conductive filler, and resistance measurements are performed to study the sensor response to a desired analyte. However, it is observed that any temperature variation alters sensor sensitivity and causes an error in the sensor response. To overcome this disadvantage, another sensor structure is proposed and fabricated. The proposed design employs a micro-resistive heater that maintains a constant temperature throughout device. The resistive heater along with interdigitated electrodes is fabricated on a thin silicon platform and capacitive measurements can be performed to investigate the presence of volatile, therefore, there is no need for conductive filler in the sensing film. A very low cost and high accurate capacitance-to-digital convertor can be utilized to convert the measured capacitance to a digital signal. The micro-heater can be biased to effectively achieve and maintain the desired temperature above ambient temperature. Different geometries are considered to design an efficient structure with optimum required input power and minimum temperature variation across sensing area. Different micro-heater location and shapes are investigated as the heating element. 3D COMSOL heat transfer simulations indicate cantilever structure with heater at one side and located toward end on cantilever as the optimum structure.

 

[37]           ANALYZING DIRECTIONAL LEUKOCYTE MIGRATION USING MICROFLUIDIC DEVICES

Li, Jing, M.Sc. Candidate

Physics and Astronomy

Advisor: Dr. F. Lin

 

Immune cell migration is a fundamental process that enables immunosurveillance and immune responses. Understanding the mechanism of immune cell migration is not only of importance to the biology of cells, but also has high relevance to cell trafficking mediated physiological problems and diseases such as embryogenesis, wound healing, autoimmune diseases and cancers. Immune cell migration can be directed by different environmental factors such as chemical concentration gradients through a process called chemotaxis. In addition to chemical gradient directed cell migration, direct current (DC) electric fields can be generated in vivo and in vitro, and such electric fields can also guide the migration of immune cells (i.e. electrotaxis). Conventional cell migration assays are generally lack of control for configuring extracellular environments and consume large amount of reagents. Recent development of microfluidic devices offers a novel approach for studying cell migration under miniaturized and well-controlled experimental conditions. The focus of the present study is on applying microfluidic systems to quantitative measurement and analysis of immune cell chemotaxis and electrotaxis. Using a simple microfluidic device that can produce defined and stable chemoattractant gradients, we demonstrated chemotaxis of human neutrophils and T lymphocytes to different chemokine gradients. Furthermore, we showed that neutrophil chemotaxis to a chemokine gradient with physiologically relevant profiles can be measured at the single cell level in the microfluidic device by directly loading just a drop of blood to the device. In addition to chemotaxis, we developed microfluidic devices that can generate uniform direct current electric fields. Using these devices, we in the first time demonstrated electrotaxis of activated human T lymphocytes. This finding is consistent with previous electrotaxis studies on other leukocyte subsets suggesting electrotaxis is a novel guiding mechanisms for immune cell migration. In summary, our study provides novel microfluidic tools for analyzing immune cell migration directed by chemical and electrical cues.

 

[38]           A MEMS ELECTRIC FIELD SENSOR OPTIMIZATION BY MULTI-OBJECTIVE NICHED PARETO GENETIC ALGORITHM

Roy, Mark, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. C. Shafai

 

Micro-electro-mechanical systems (MEMS) have traditionally been optimized manually based on the solutions to dynamic equations and intuition. This paper presents the application of a multi-objective niched Pareto genetic algorithm to optimize a synthesized design of a MEMS electric field sensor. The geometry of the sensor design is varied in order to meet the objectives of maximal displacement, minimal stress, minimal temperature and a resonant frequency near 2kHz. The algorithm gradually evolves a set of solutions towards a Pareto set in which no solution is better in all objectives than any other solution. When the algorithm has finished the designer may choose one or more solutions from the set which best meets their objectives allowing them to see the available trade-offs. The results show comparable or better performance in simulation than devices optimized manually or by other means.

 

[39]           MICROWAVE SENSOR FOR THE DETECTION OF SINGLE SUPERPARAMAGNETIC MICROBEADS IN A MICROFLUIDIC DEVICE FOR USE IN BIOPARTICLE SEPARATION AND COUNTING

Rzeszowski, Szymon, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. G. Bridges

 

Appropriately coated magnetic microbeads are a reliable and gentle way of isolating specific bioparticles from a sample and have been widely used in laboratories for decades. This is typically performed on large volume samples involving millions of particles. Microfluidics enables the manipulation and control of fluids at the nanolitre volume scale, and in combination with appropriate microelectronics, enables the integration and automation of various laboratory processes onto a single device, including single bioparticle detection and manipulation. The detection of a single magnetic microbead is critical for detecting single bioparticles. We present a high frequency inductance sensor that is capable of detecting single 4.5 µm superparamagnetic beads as they flow inside a 25 µm deep channel. The sensor is based on a microwave interferometer and a resonator terminated by a loop-shaped electrode at the bottom of the microfluidic channel. The sensor can detect inductance changes as a magnetic bead passes over loop electrode. The superparamagnetic beads we employ are composed of single-domain nanoparticles of iron-oxide embedded in a polymer matrix. The high-frequency magnetic properties of these beads are largely untested and this sensor provides insight into their magnetic permeability at a frequency of 1.5 GHz. Although various other magnetic sensors have been developed, our approach does not require an additional dc biasing magnetic field, which is advantageous for microelectronic fabrication.

 

[40]           A TUNABLE MEMS-ENABLED FREQUENCY SELECTIVE SURFACE

Safari Hassan Abadi, Mojtaba, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. C. Shafai

 

A frequency selective surface (FSS) based on switchable slots on the ground plane is presented. The switching is done using an actuating MEMS bridge over the slot. The intent is to demonstrate the control of the resonance frequency of the FSS by deflecting the bridge. It is shown that by applying a voltage between the bridge and the ground plane, the bridge displaces and changes the capacitance of the system which in turn changes the resonance frequency. Two analyses are presented, (1) Electromechanical analysis to show how the bridge deflects by the voltage, (2) EM analysis to show how the resonance frequency changes by the bridge deflection. The measurement results for two up and down positions of the MEMS bridge are given, which show a good agreement with simulation results.

 

[41]           QUASI-STATIC OPTIMIZATION OF A MICROMACHINED ELECTRIC FIELD MILL

Zhou, Yu, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. C. Shafai

 

A micromachined Electric Field Mill (MEFM) has been developed and has shown capable of measuring both dc and ac electric fields. The sensor operates by using thermal actuators to oscillate a perforated grounded shutter over underlying electrodes. In this presentation, a new generation of sensor is investigated, were the dimensions of the perforations in the shutter are optimized to maximize sensor resolution. Quasi-static electric field charging of sense electrodes has been explored to maximize the charging signal. Simulations have shown that the induced charge on the electrodes, therefore the current signal, is dependent on the inverse of the gap between the shutter and electrodes, and dependent on the size of perforations in the shutter as well as the spacing between perforations. The current sensor design also suffers from charging effect, which reduces sensor sensitivity over time. Shielding of the electrodes, by means of a grounded guarding ring is investigated. Presented simulations demonstrate that the guarding ring can greatly reduce the fringing field at the edge of the shutter. This will have the benefits of reduced charging, as well as reduced electric field interference from thermal actuators which will increase sensor resolution.

 

Photonic and Phononic Interactions

 

[42]           USING A SPINTRONIC MICROWAVE SENSOR TO SEE THE INVISIBLE

Cao, Zhong Xing, Ph.D. Candidate

Physics and Astronomy

Advisor: Dr. C.-M. Hu

 

Microwave propagation in a dielectric medium underlies all responses of microwave energy interaction with the dielectric system. Therefore, it is generally accepted that the dielectric properties can be accurately reconstructed by characterizing the spatial distribution of absorbed microwave energy.  For this purpose, both the amplitude and the phase of microwave fields are essential in order to deduce the complex dielectric constant of materials due to energy loss. The advantage of microwaves is that they can penetrate into the object and enable the detections of ‘hiding’ objects, which is important for health care and security applications. However, the microwave wavelength is comparable or even larger than the size of objects under test, therefore, such sub-wavelength features are restricted to the near-field. The development of spintronic techniques shines light on the detection of the interaction between microwave and dielectric materials, especially due to its phase-resolved capability. In contrast to the amplitude which is easily measured by a conventional static or time-average approach such as a power meter, conventional phase meters have an upper frequency limit of a few 100 kHz imposed by the ability of electronic circuits under high-speed operation. Very recently, a novel sensor has been invented in our group, which has both amplitude- and phase-resolved capabilities for probing microwave fields. Furthermore, due to the sub-mm size of such a spintronic sensor, it can be situated very close to the sample for near-field imaging. The interaction in the sub-wavelength scale between microwaves and dielectric materials can therefore be detected. In this poster, we demonstrate both the phase and amplitude-resolved capabilities of this sensor, the sub-wavelength feature of objects invisible to the eye, as well as the dielectric dependence of the imaging.

 

[43]           SERS IMAGING OF FUNGI WITH GOLD NANOPARTICLES SYNTHESIZED IN VIVO

Farazkhorasani, Fatemeh, Ph.D. Candidate

Chemistry

Advisor: Dr. K.M. Gough

 

Metal nanoparticles are of great interest both fundamentally and technologically due to their unique chemical and physical properties compared to their bulk counterparts. Fungi are able to reduce metals and produce various intracellular and extracellular metal colloids without the need for external reducing reagents. Fungi have pervasive and essential roles in plant survival that include symbiotic relationships wherein fungi trade services for food. They also include some of the more deadly pathogens that threaten crops and human health; others participate in symbiotic relationships with plants, helping them acquire nutrients from soils. These substantial positive and negative impacts of fungi on human and ecosystem activities necessitate better understanding of fungal diversity, biology, and ecology. Incubation of Aspergillus nidulans hyphae with aqueous chloroaurate results in rapid in vivo synthesis of gold nanoparticles (AuNPs) within and on the hyphal surface. Composition as AuNP is confirmed by scanning transmission x-ray microscopy. Transmission electron microscopy images of cells after incubation vividly show the formation of AuNPs, ranging in size from a few nm to several microns. Larger particles are triangles or irregular hexagons, while smaller particles appear to be globular, and ~10-50 nm in diameter, hence suitable for SERS. Most of the AuNPs were associated with hyphal walls, both in the cytoplasm and on the outer wall surface. SERS spectra are readily generated from these samples and analysis is ongoing. We now seek to restrict NP formation to cell wall, in a series of Aspergillus mutants with significant variations in wall morphology. Our latest studies on pH, temperature, metal concentration, exposure time and starting biomass illustrate the importance of these parameters for the control of NP formation (size and location) while maintaining adequate cell viability.

 

[44]           OBSERVATION OF BRAGG AND HYBRIDIZATION GAPS IN 2D PHONONIC CRYSTALS

Lee, Eric Jin Ser, Ph.D. Candidate

Physics and Astronomy

Advisor: Dr. J.H. Page

 

There is growing interest in the properties of phononic crystals [1-4], which may exhibit band gaps due to Bragg scattering [1,2] and/or a hybridization mechanism [5-7].  Recently, the coexistence of a hybridization gap and a Bragg gap at different frequencies in a 3D phononic crystal has been reported [7].  Here, we focus on 2D crystals, where the lattice constant a can be tuned by changing the separation between the scatterers.  Since the bandgap frequencies for these two types of gap depend differently on a, their different physical origins can be distinguished experimentally.  We observe both types of gaps separately, and also the competition between the hybridization and Bragg mechanisms when they occur at similar frequencies in the same crystals.  Here, transmission experiments to investigate the band structure were conducted in a water tank using pairs of identical transducers spanning the frequency range from 0.5 to 4.0 MHz.  Further confirmation of the different character of the hybridization gaps in our crystals was revealed by comparison with random samples.  The hybridization gaps are robust in that they occur in all samples at similar frequencies, while Bragg gaps are destroyed by disorder and shift in frequency as the lattice constant is varied.  In the hybridization gaps, the group velocity was found to be negative, with this effect being especially pronounced in the phononic crystals compared with the random samples.

 

References:  [1]  A. Sukhovich, L. Jing, and J. H. Page: Phys. Rev. B 77 (2008) 014301.  [2]  S. Yang, J. H. Page, Z. Liu, et al.: Phys. Rev. Lett. 88 (2002) 104301.  [3]  S. Yang, J. H. Page, Z. Liu, et al.: Phys. Rev. Lett. 93 (2004) 024301.  [4]  A. Sukhovich, B. Merheb, K. Muralidharan, et al.: Phys. Rev. Lett. 102 (2009) 154301.  [5]  X. D. Jing, P. Sheng, and M. Y. Zhou: Phys. Rev. A 46 (1992) 6513.  [6]  X. Zhang, Z. Y. Liu, F. G. Wu, et al.: Phys. Rev. E 73 (2006) 066604.  [7] T. Still, W. Cheng, M. Retsch, et al.: Phys. Rev. Lett. 100 (2008) 194301.

 

Soft and Disordered Materials

 

[45]           DRUG CONTAINING, ANTIMICROBIAL MICRO- AND SUBMICRO- POLYUREA CAPSULES BASED ON INTERFACIAL CROSSLINKING OF POLYETHYLENIMINE

He, Wei, M.Sc. Candidate

Textile Science

Advisor: Dr. S. Liu

 

Narrowly-dispersed polyurea capsules in the diameter range of 0.2µm - 5µm can be synthesized from polyethylenimine and diisocyanate via interfacial crosslinking with oil-in-oil emulsion carried out under room temperature for a short period of time (10 min). Different solvents such as water, ethanol, DMF can be adopted as disperse phase. The mild reaction conditions and the flexibility in solvent selection allow a wide selection of antimicrobial drugs, nutrients, and growth factors for encapsulation. In case of cortisone, a model hydrophobic drug , loading capacity and efficiency are 26wt% and 57% respectively. The encapsulated drug can be released at 37 degree Celsius for over 7days. The process can be regulated to leave specific amounts of isocyante groups on the microcapsule after synthesis so an antimicrobial moiety such as quaternary ammonium compound (QAC) can be conveniently attached to the surface of the capsules in a short period of time avoiding leaching of the encapsulated bioactive agents. The grafted QAC can endow the capsule of surface antimicrobial activity as positively charged of QAC can attract negatively charged bacteria and cause disruption of cell membranes.  The QAC grafted capsules demonstrated 61% reduction of E.coli after 30 minutes contact with the bacterial suspension at room temperature.

 

[46]           TRANSVERSE CONFINEMENT OF ELASTIC WAVES NEAR THE EXPECTED LOCALIZATION TRANSITION IN A HIGHLY POROUS GLASS NETWORK

Strybulevych, Anatoliy, Postdoctoral Fellow

Physics and Astronomy

Advisor: Dr. J.H. Page

 

Given the recent successful experimental observation of the Anderson localization of elastic waves in a three-dimensional network of aluminum beads [1], the investigation of wave transport in similar systems is of considerable interest.  In this poster, we use ultrasonic techniques to study departures from normal diffusive behavior in a highly porous network, with a solid volume fraction of only 0.33, formed from sintered glass beads.  At intermediate frequencies, where the wavelength is comparable with the pore sizes in the medium, very strong scattering is observed, with values of kl for longitudinal waves close to 1.  Previous measurements in this system revealed a plateau in the diffusion coefficient, determined by fitting the predictions of the diffusion approximation to the time dependence of the transmitted intensity, over a wide range of frequencies [2].  To look for possible deviations from normal diffusive transport in this system, the transverse spreading of a tightly focused input beam was measured on the opposite face of the sample.  The mean square width of the transverse profile is found to increase with propagation time more slowly than expected for diffuse waves, a signature of renormalization of the diffusion coefficient due to interference effects that can lead to Anderson localization.  As the frequency is increased from the lower edge of the intermediate frequency regime, the long-time transverse width decreases but remains larger than the sample thickness, indicating that, over the range of frequencies studied, a transition to localized modes is being approached but not yet reached in these measurements. 

 

[1] H. Hu, A. Strybulevych, J.H. Page, S.E. Skipetrov, and B.A. van Tiggelen, Nature Physics, 4, 945-948 (2008).

[2] J.H. Page, W.K. Hildebrand, J. Back, R. Holmes, and J. Bobowski, Phys. Stat. Sol. (c), 11, 2925-2928 (2004).

 

[47]           THEORETICAL STUDY OF THE FLOW BEHAVIOR INSIDE A CYLINDRICAL TUBE WITH GRAFTED POLYMERS

Suo, Tongchuan, Postdoctoral Fellow

Physics and Astronomy

Advisor: Dr. M. Whitmore

 

A self-consistent mean-field theory of flow through a cylindrical tube with grafted polymers is presented. The polymer density profile can be calculated in the presence of any fluid flow profile and, conversely, the fluid flow profile can be determined from any polymer profile. Consequently, they can both be calculated in a self-consistent manner. The numerical results indicate that, although the grafted polymer chains are always stretched by the flow field, the overall concentration profile may or may not changed compared with the case without flow. The conditions under which each occurs are discussed.

 

[48]           SINGLE- AND DOUBLE-RESONANCE NMR STUDIES OF PHASE SEPARATION AND CRYSTALLIZATION IN MODEL NUCLEAR WASTE GLASSES

Wren, John, Ph.D. Candidate

Chemistry

Advisor: Dr. S. Kroeker

 

Borosilicate glasses are commonly used in the immobilization of radioactive waste. However the poor solubility of certain fission products restricts waste loading in commercial glasses. To better understand the nature of phase separation and crystallization phenomena, we have investigated a series of molybdenum-bearing borosilicate glasses modeled on typical industrial waste compositions. Double-resonance NMR methods were implemented to probe the proximity of network-forming (¹¹B, ²⁹Si) and network-modifying (¹³³Cs, ²³Na) cations, correlating positively with phase-separated and homogeneous glasses. Moreover, single-resonance NMR experiments (⁹⁵Mo, ¹³³Cs, ²³Na) are found to be particularly valuable for detecting the presence of crystallization products precipitated from the glass, especially where diffraction-based techniques may be limited by cation-cation substitution, small crystal size and low levels of crystallinity. In the model glasses under investigation, previously unknown mixed-alkali molybdates were identified by NMR in the complex phase assemblage quenched from the melt. The results can be interpreted in terms of the degree of glass homogeneity, a key parameter in long-term chemical durability.

 

Surfaces and Interfaces

 

[49]           RAMAN STUDY OF SPUTTERED HFO2 THIN FILMS

Belo, Gustavo, Ph.D. Candidate

Electrical and Computer Engineering

Advisor: Dr. D.A. Buchanan

 

The crystalline phase of Hafnium dioxide (HfO₂) thin films deposited by magnetron sputtering using different conditions and pots-deposition annealing are investigated using Linear Raman Spectroscopy. The 250 nm thin films were deposited using Hf metal and HfO targets with Ar:O₂ ratios 1:4 and 7:0 sccm respectively and power density 3.7 W/cm². A post-deposition rapid thermal annealing (RTA) was performed in all samples for 90 s at 600, 400 and 800°C. Room temperature Raman spectra features in the 100 - 750 cm^-1 spectral range are assigned to vibrational modes associated to the crystalline structure. The observed data were fitted to a sum of appropriate number of Lorentzians and the Raman bands were identified considering the active symmetry modes expected from a monoclinic or tetragonal phase. The as-deposited Hf target film exhibit a tetragonal phase while the as-deposited HfO target film is amorphous. As the annealing temperature increases both films become amorphous and at 600°C starts to crystallize in a monoclinic phase.

 

[50]           CONTROLLED RELEASE OF DOXORUBICIN FROM PH AND REDOX DUAL RESPONSIVE PEG-REDUCIBLE POLY(BETA-AMINO ESTER)S COPOLYMERIC MICELLES

Chen, Jun, Postdoctoral Fellow

Mechanical and Manufacturing Engineering/Textile Sciences

Advisors: Dr. M. Xing and Dr. W. Zhong

 

The goal of this study is to develop and characterize a novel pH and redox dual responsive micelles. These micelles will preserve their core-shell structure under physiological conditions but will sharply respond to acidic, and/or reductive environment to rapidly release their incorporated drug. The novel copolymer containing disulfide bonds in each repeat unit of poly(beta-amino ester)s was synthesized via Michael addition polymerization from 2, 2'-dithiodiethanol diacrylate and 4, 4'-trimethylene dipiperidine and methoxy-PEG-NH₂. Results of NMR and GPC characterizations suggested that the copolymer may have 2-3 PEG chains as graft to form the structure of Reducible Poly(beta-amino ester)s-g-Poly(ethylene glycol). PH and redox sensitivities of the copolymeric micelles were evaluated using a fluorescence spectrometry and dynamic light scattering. An anti-cancer drug, doxorubicin (DOX), was trapped into the micelles. The experiments of in vitro drug release from the DOX-loaded micelles confirmed that DOX released faster from micelles in a weakly acidic environment (pH 6.5) than at pH 7.4, or in the presence of higher concentration (5 mM) of reducing agent (DTT). Particularly, DOX was found to release faster from the DOX-loaded micelles in an environment with both stimuli (pH 6.5 and 5 mM DTT), than in conditions with only one stimulus (pH 6.5 or 5mM DTT). MTT assay showed that the DOX-loaded micelles had a comparative cytotocixity to the HepG2 tumor cells compared to DOX, while blank micelles showed a very low cytotocixity to the tumor cells. The confocal images in different time points confirmed the efficient intracellular doxorubicin release from the DOX-loaded micelles.

 

[51]           CORROSION BEHAVIOUR AT THE HEAD/NECK INTERFACE OF ARTIFICIAL HIP JOINTS

Dyrkacz, Richard, Ph.D. Candidate

Mechanical and Manufacturing Engineering

Advisor: Dr. U. Wyss

 

Metal-on-metal (me-on-me) hip prostheses have been known to display better wear behaviour than metal-on-polyethylene (me-on-PE) hip prostheses. For instance, me-on-me implants exhibit more than 100 times less volumetric wearing in comparison to me-on-PE implants (non cross-linked PE), when subjected to the same loading and lubrication conditions. Me-on-me implants, however, have shown in some cases to lead to adverse tissue reactions to metal wear requiring revision surgery. Recently, it was found that metal wear can also originate from the head/neck interface, possibly leading to the same adverse tissue reactions as metal wear from the articulation. The long-term purpose of this investigation is to assess the corrosion and fretting behaviour at the head/neck Morse taper of me-on-me and me-on-PE modular hip prostheses, and to assess the influence of head size on the corrosion and fretting behaviour. For this study, 36 mm head me-on-me modular hip prostheses were collected from the Implant Retrieval Analysis Program (IRAP) database of the Concordia Hip and Knee Institute. The corrosion and fretting of the head/neck interface will be presented using a novel scoring method.

 

[52]           MULTIFUNCTIONAL ELECTROSPUN NANOFIBROUS SCAFFOLDS FOR TISSUE ENGINEERING

Gao, Haiyun, M.Sc. Candidate

Textile Science

Advisor: Dr. W. Zhong

 

By mimicking the native extracellular matrix (ECM), electrospun nanofibrous scaffolds (ENSs) can provide both chemical and physical cues to modulate cell adherence and differentiation and to promote tissue regeneration while retaining bioresorbable and biocompatible properties. ENSs can also be vehicles that carry bioactive molecules or therapeutic agents to enhance tissue healing by releasing them in a sustained and controlled way. From a developmental biology perspective, healing is a synergic process that involves multiple growth factors, and growth factor-laden scaffolds can be used to control stem cell fate and to promote vascularization. 

We developed ENSs to deliver multiple biomolecules by loading them in the core-sheath structure and/or by conjugating them to the nanofiber surfaces. In our work, poly(L-lactide)-poly(ethylene glycol)-NH₂ (PLLA-b-PEG-NH₂) and poly(L-lactide) (PLLA) were emulsion electrospun into nanofibers with a core-sheath structure. A model drug, tetracycline hydrochloride (TCH), was loaded within the nanofibers. Amino and carboxyl reactive groups were then activated on the fiber surfaces using saturated water vapor exposure and base hydrolysis, respectively. These reactive groups allowed the surface of the ENS to be functionalized with two other bioactive molecules, FITC- and rhodamine-labeled bovine serum albumins, which were used as model proteins. The ENSs were shown to retain their antimicrobial capacity after two functionalization reactions, indicating that multifunctional nanofibers can potentially be developed into functional wound dressings or periodontal membranes or used in more complicated tissue systems where multiple growth factors and anti-infection precautions are critical for the successful implantation and regeneration of tissues.

 

[53]           SURFACE-ENGINEERED PET VASCULAR GRAFTS WITH IMPROVED LONG-TERM BIOCOMPATIBILITY

Li, Jiang, M.Sc. Candidate

Textile Sciences

Advisor: Dr. S. Liu

 

Since there are many coronary artery bypass graft surgeries each year and the supply of native vessels is insufficient, synthetic grafts become necessary. When vascular grafts made of synthetic polymers such as PET come in contact with blood, they are easy to occlude which is especially true for small-diameter grafts. So the luminal surface of vascular grafts should inhibit platelet adhesion and thrombosis formation. Now, immobilizing heparin, an anticoagulating agent, onto the surface of biomaterials is a common method. To adapt the long-term use of vascular grafts, covalent linkage is an ideal immobilization method for heparin. However, chemical modification of PET is a challenging task due to the chemical inertness and high crystallinity of PET. Besides, a proper surface density of heparin is also required to guarantee the performance of the biomaterials. My project aims to develop PET vascular grafts with ideal long-term biocompatibility in the simplest operation. We have durably immobilized heparin on the inner surface of PET vascular grafts based on a modification method of forming a surface interpenetrating network(IPN). Firstly, N-(2-aminoethyl) acrylamide(AEAM) was co-polymerized with a divinyl crosslinker on the surface of PET to form the IPN. This type of IPN was defined as thermoplastic semi-IPN and the surface modification produced by this technique is durable except when the substrate polymer is dissolved or melted which will not happen in this application. Then, heparin was immobilized through stable amide bonds with AEAM.  The immobilization of heparin through AEAM has been confirmed by XPS and the amount of immobilized heparin quantified by the titration with a cationic dye---Toluidine Blue dye. For the next step, our work is to obtain an optimal density of heparin on the surface and use biological test to demonstrate the performance of PET vascular grafts modified in our lab.

 

[54]           HIGH RESOLUTION ULTRASOUND IMAGING

Mijares Chan, Jose Juan, Ph.D. Candidate

Electrical and Computer Engineering

Advisor: Dr. G. Thomas

 

Ultrasound flaw detection is one of the techniques used in industrial ultrasonic testing. Flaw detection, when inspection is done within thin-layered materials, can become a challenging and time-consuming problem since identifying the echo patterns of a failure may require either specialized training and/or perform some signal enhancement. In this work, the use of pulse-echo ultrasound testing with synthetic aperture focusing and signal processing techniques to create high-resolution images of the region of interest is discussed. To overcome an excessive computational time, the use of graphic processing units is introduced. The proposed method was developed with the intention of providing a more reliable solution to identifying faults within different depths of a specimen.

 

[55]           EFFECT OF LOW POWER DEPOSITION AND LOW OXIDATION TEMPERATURE ON THE QUALITY OF SPUTTERED HFO₂ GATE DIELECTRICS

Minko, Auxence, Postdoctoral Fellow

Electrical and Computer Engineering

Advisor: Dr. D.A. Buchanan

 

The scaling of silicon integrated circuit has pushed the conventional SiO₂ to its physical limits. High-k based gate dielectric is the promising structure for the future of VLSI devices. Recently, many candidates such as zirconium dioxide (ZrO₂), aluminum oxide (Al₂O₃), and lanthanum aluminates (LaAlO₃) have been extensively discussed. In fact, high dielectric constant films offer the potential to maintain the same capacitance value of a thin SiO₂ while reducing, by physically thicker films, the leakage current. HfO₂ is considered as one of the most promising high-k candidates. HfO₂ films have been deposited by sputtering, by chemical vapor deposition (CVD), and by atomic layer deposition. While CVD and ALD remain reliable but expensive ways to grow hafnium dioxide dielectric, sputtering is a low cost alternative deposition method. However, silica or silicate interfacial layers are inevitably formed during the HfO₂ film growth on silicon. In this work, a thin HfO₂ film prepared by DC magnetron sputtering using a low-power deposition followed by a low-temperature thermal oxidation show greatly improved interfacial and electrical properties of the gate stack. The measurements by Ellipsometry and X-ray photoelectron spectroscopy (XPS) show the great quality of the prepared HfO₂ film, with a refractive index of 1.9 and an oxygen /hafnium ratio of 2:1. The Transmission Electron Microscopy (TEM) investigation shows that the thickness of the non-desirable interface layer is dramatically reduced to approximately 1 nm. A dielectric constant of ~22 and a low leakage current density of ~10-6 A/cm² at 1.3 MV/cm have been measured by capacitance-voltage (C-V) and current-voltage (I-V) measurements respectively.

 

[56]           DRESSING SOLUTION TO BURN WOUNDS: ANTIMICROBIAL AND NON-ADHESIVE WOUND DRESSINGS

Pu, Tianyun, M.Sc. Candidate

Textile Sciences

Advisor: Dr. S. Liu

 

Burn wound infections is the main reason for the failure of burn treatment and may bring lethal problems. Among burn wound dressing, those impregnated with silver show good performance of infection control. The design of a new antibacterial and a traumatic dressing for the purpose of treating burn wound is quite necessary because an ideal burn wound dressing should not only avoid infection but also do not adhere with the wound or new forming epidermis. This project aims to develop a new universal method of depositing hydrogel and AgNPs(silver nanoparticles) onto wound dressings so to achieve new antibacterial and a traumatic dressings. Silver has long been used as a wide-spectrum antibacterial agent, hydrogel has the ability to absorb water and keep a moist environment, so that it can be used to prevent adhesiveness which is caused by the exudates from wound. PU(polyurethane) film is chosen as a representative of wound dressings since it allows physicians to check the healing of wounds without removing the dressing due to its transparency. Using acylamide (AM), N,N'-Methylene bisacrylamide (MBA, crosslinker) and benzophenone (BP, initiator) to carry out photo initiated surface modification, PAMIPN (polyacrylamide interpenetrating polymer network)will be grafted on PU pristine film called PAM-PU. With AM,MBA,KPS(potassium persulfate) and silver nitrate for a heat initiated crosslink reaction, silver ion containing PAM hydrogel can grow on PAM-PU, called PAM-gel-PU. After immersing in sodium borohydride solution for reducing, nanosilver-PAM-gel-PU was obtained. Compared with silver ion, silver nanoparticle is less toxic to human skin. Hydrogel can absorb 679% water in terms of its original weight which means it can well absorb exudates from wound. From antibacterial test, after 2h contact with 10^7 CFU/ml bacterial suspension, 99.99% MRSA 40065(Methicillin-resistant Staphylococcus aureus) were killed by silver nanoparticle that indicates the nanosilver-PAM-gel-PU can effectively control infection and kill bacteria. Based on those preliminary results, the next step for this project is to carry out a cell detachment test to prove that fibroblast cells do not adhere to hydrogel. Treatment of burn wounds is costly both for the patient in terms of reduced quality of life and financially. Successful development of antimicrobial and non-adhesive dressings will make a valuable contribution to improving healing rates and the patient's quality of life.

 

[57]           ELECTRICAL CHARACTERIZATION OF SEMICONDUCTING MICROWIRES AND THEIR JUNCTION WITH IONIC AND ELECTRONIC CONDUCTING POLYMER COMPOSITES

Yahyaie, Iman         , Ph.D. Candidate

Electrical and Computer Engineering

Advisors: Dr. D. Oliver and Dr. D. Thomson

 

A new approach for the electrical (DC) characterization of single silicon microwires is presented. The approach involves a soft contact formation procedure using tungsten probes. Basic electrical properties such as DC resistivity (conductivity) of the microwires and also the doping distribution along the length of the microwires may be investigated using this approach. Furthermore, the junction between microwires and conducting polymers for the use in a proposed artificial photosynthesis system are also studied.

 

Additions - Liquid and Solid Crystals

 

WITHDRAWN [58]              DOPING SMECTIC-C LIQUID CRYSTALS WITH CHIRAL NANOPARTICLES: NANOPARTICLES DECORATED WITH STRONG CHIRAL INDUCERS

Sharma, Anshul, M.Sc. Candidate

Chemistry

Advisor: Dr. T. Hegmann

 

Liquid crystals (LCs) show large variations in properties when subjected to electric fields, polarised light, temperature, pH, and other stimuli. In the presence of an electric field, the chiral smectic-C phase (SmC*) sandwiched between two rubbed polyimide-coated glass slides (just a few microns thick) orients in a way that gives rise to a spontaneous ferroelectric polarization (PS) that can be switched between two surface-stabilized states with fast response times and bistability. Such surface-stabilized ferroelectric LCs are widely used in various microdisplay applications. Usually SmC* LCs are prepared by mixing a chiral dopant of high polarization power with an achiral smectic (SmC) liquid crystal mixture. The polarization power is a function of the effective transfer of chirality. A very potent class of chiral dopants with atropisomeric biphenyl central cores have been developed by Lemieux et al., and were shown to induce some of the highest values of the polarization power ever reported in phenylpyrimidine SmC hosts featuring an ideal structural match.[1] To exploit this structural motif as nanoparticle capping, we prepared gold nanoparticles decorated with such atropisomeric biphenyl chiral moieties to serve as dopants for LC hosts. Based on our past work on (S)-naproxen-capped gold nanoparticles

as dopants in nematic LCs,[2] we studied the effectiveness of these chiral nanoparticles capped with atropisomers as dopants for SmC hosts.

[1] Robert P. Lemieux , Acc. Chem. Res. 2001, 34, 845.

[2] Hao Qi, Joe O’Neil and Torsten Hegmann , J. Mater. Chem. 2008, 18, 374.

 

Additions - Photonic and Phononic Interactions

 

[59]              Near-Infrared Properties of PPKTP and Stoichiometric MgO:PPSLT Crystals for High Power Femtosecond Optical Parametric Oscillators

Zhao, Haitao, Ph.D. Candidate

Electrical and Computer Engineering

Advisor: Dr. A. Major

 

Nonlinear material is critical point in building a femtosecond optical parametric oscillators (OPOs) in near-infrared radiation, which are powerful and indispensable tools for many applications that require wavelength tunability, short pulse duration, high peak power and high repetition rate. Although periodically poled lithium niobate (PPLN) has been commonly used for generation of near-IR irradiation, the low photorefractive damage threshold and high coercive field largely limit its operating range and output power.

In this work two new promising materials, periodically poled KTiOPO₄ (PPKTP) and periodically poled stoichiometric MgO-doped LiTaO₃ (MgO:PPSLT) crystals, were studied theoretically to assess their potential for the design of widely tunable infrared femtosecond OPOs excited with Yb-ion solid state lasers. The optical properties as well as the phase matching and wavelength tuning characteristics were thoroughly investigated using the appropriate Sellmeier equations. Through the choice of suitable grating period and temperature tuning both the PPKTP and MgO:PPSLT crystals can be designed to provide radiation from ~1.3 µm to their upper limit of transparency range. Moreover, the dispersive properties including group velocity dispersion (GVD) and group velocity mismatch (GVM) were also calculated. To the best of our knowledge, this is the first detailed account of PPKTP and MgO:PPSLT crystal properties relevant to optical parametric interactions in the near-IR. The aim of the presented analysis is to provide a thorough reference for the design of practical PPKTP- or MgO:PPSLT-based OPOs pumped by high power ultrafast Yb-ion solid state lasers.

 

Additions - Complex Natural Systems

 

[60]              A NOVEL WAY OF LOOKING AT THE CRYSTAL STRUCTURE PREDICTION PROBLEM - A CASE STUDY OF THE MILARITE GROUP

Oliver Gagne, Ph.D. Candidate

Geological Sciences

Advisor: Dr. F. Hawthorne

 

The general failure to make reliable crystal structure predictions from chemical composition has long been identified as a continuing scandal in Crystallography. Almost a century has passed since the famous X-Ray diffraction experiment that resulted in the first crystal-structure solution, yet the factors constraining crystal-structure arrangements are still not understood. Probing the stability limits of mineral groups that show solid solution gives new insight into the crystallization process. Examination of over 350 chemical analyses and structure refinements of the milarite group has defined the compositional limits of substitution at the A,B,C and D sites of the structure. There are currently 21 minerals in the group, forming 12 root charge-arrangements, plus 14 synthesized compositions that lead to an additional one. The stability of the root charge-arrangements may be examined with the newly developed predictive bond-valence methodology. Equations derived from a bond network are solved in a system of equations in order to obtain ideal bond-valence values, where feasibility becomes a question of whether there is a specific combination of cations and anions that can satisfy them. This is determined from an absolute scan of the International Crystal Structure Database (ICSD), where a statistical survey for bondlengths by atom, oxidation state and coordination number enables us to assign a bond-valence ranges to the possible combinations. Therefore, from a preset bond topology, one can obtain ideal bond-valence values and assign potential elements to the sites.  Customary bond-valence theory then permits conversion of the bond-valence values to cation-anion distances, optimized with a 3-D distance-least-squares calculation to obtain possible unit-cells of ordered atoms.

 

Additions - Complex Crystalline Materials and Nanostructures

 

[61]           WORK FUNCTION TUNING OF  REACTIVELY SPUTTERED Hf-Si-N METAL GATE ELECTRODES FOR ADVANCED CMOS TECHNOLOGY

Rekha Chaudhari, M.Sc. Candidate

Electrical and Computer Engineering

Advisor: Dr. D. Buchanan

 

Due to aggressive reduction of transistor dimensions, the conventional poly-silicon gated complementary metal oxide semiconductor devices have revealed short channel effects. The conventional poly-silicon is known to suffer from short channel effects such as poly depletion, high gate resistance and dopant penetration . To replace the conventional poly-silicon gate, extensive research on work function engineering of potential metal gates is being carried out globally to keep up with the scaling requirements for future CMOS devices . The ability to tune the work function of a single metal gate technology, over desired range is highly preferable. The purpose of this research is to discover the tuning of the Hf-Si-N gate work function through the incorporation of nitrogen.

Metal oxide semiconductor (MOS) capacitors are fabricated using thermal SiO₂ as gate oxide on lightly doped p-type Si wafer. Hafnium and Silicon target are reactively co-sputtered at 12mTorr in presence of N₂ and Ar. The gas flow ratio RN=N₂/ (N₂+Ar), is adjusted to vary the nitrogen concentration in Hf-Si-N films.

Electrical characterization measurements will be performed on all Hf-Si-N/SiO₂/Si gate stacks to extract the Hf-Si-N work function and other MOS device parameters, including gate oxide thickness, the acceptor doping concentration and flatband voltage. Interfacial barrier heights will be measured using internal photo-emission (IPE) as an independent confirmation of the Hf-Si-N gate work function.

 

Additions - High Temperature Aerospace Materials

 

[62]           NUMERICAL SIMULATION OF SOLIDIFICATION MICROSTRUCTURE IN HYBRID LASER-ARC SUPERALLOY WELDS

Gao, Zhiguo, Postdoctoral Fellow

Mechanical and Manufacturing Engineering

Advisor: Dr. O.A. Ojo

 

Advanced processing techniques and alloy design have been utilized to produce directionally solidified and single crystal nickel-base superalloys with improved elevated temperature properties, for aircraft engine applications. Unfortunately, the new generation superalloys are extremely difficult to join by such conventional techniques as arc and laser beam welding processes, due to the susceptibility of the materials to cracking induced by formation of stray crystals during weld solidification. To address this problem, application of an evolving material joining technique, hybrid laser-arc welding, to single crystal superalloys is being developed. Howbeit, due to increased process variables and the complex laser-arc interaction involved, efficient and effective optimization of the technique necessitates numerical simulation modeling of the joining process. In the present work, a 3-D numerical model that incorporates heat transfer and liquid metal flow was developed to simulate the influence of various process parameters on solidification microstructural development during hybrid laser-arc welding of single crystal superalloy. The development, validation and predictions of the 3-D model will be presented.

 

Additions - Soft and Disordered Materials

 

[63]           CHARACTERIZING THE RHEOLOGY OF VEGETABLE SHORTENING USING INDENTATION AND FINITE ELEMENT ANALYSIS

Gonzalez-Gutierrez, Joamin, M.Sc. Candidate

Food Science

Advisor: Dr. M. Scanlon

 

Vegetable shortening is an important ingredient in the food industry.  Rheological properties are critical to shortening functionality, and these are usually measured by indentation (penetrometer) tests.  However, the rheological response of these intricately-structured three-phase particle gel materials is complex.  Our hypothesis was that by integrating measurements of the fundamental material properties of vegetable shortening with a mechanical model, the indentation response could be predicted using commercially available finite element analysis software.  Commercial vegetable shortening was subject to both lubricated uniaxial compression and indentation testing using a 45 degree conical indenter.  The finite element analysis software package, Abaqus was used to determine the governing parameters of an elasto-viscous-plastic mechanical model for the shortening based on the compression analyses.  The model was used to predict the load-displacement response in the indentation tests.  The rheological behavior of shortening could be characterized by: purely linear-elastic at small strains, strain hardening and softening at intermediate strains, and purely plastic at large strains. Rate-dependency effects were manifest as a change in the shape of the stress-strain curve rather than just an increase in stress values with increasing crosshead speed.  The elasto-viscous-plastic model calibrated from the uniaxial compression data successfully predicted the indentation response of the vegetable shortening, although not as well at high loading rates.  From such analyses, it is apparent that indentation can be used both as a simple mechanical quality assurance test, but also to derive fundamental mechanical parameters for better characterizing vegetable shortening rheology for particular applications.

 

[64]           MECHANISMS OF STABILIZING FIBRE-ENRICHED DAIRY PRODUCTS

Repin, Nikolay, M.Sc. Candidate

Food Science

Advisor: Dr. M. Scanlon and Dr. G. Fulcher

 

Acidified dairy products are one of the oldest types of food products. Unfortunately all of them are low in dietary fibre. Thus, fortification with dietary fibre seems an attractive means of improving the nutritional profile of products such as yogurt or yogurt drinks. However, dairy products enriched with Glucagel (a commercial product high in barley beta-glucan) were found to suffer from textural defects. When the Glucagel concentration exceeded a certain value (5 g/L), dramatic phase separation was observed in set yogurt and yogurt drink whose volume fraction of casein micelles exceeded 0.11. To investigate interactions of beta-glucan polymers and casein micelles in the milk prior to setting of yogurt, mixtures of yogurt milk and Glucagel were systematically studied. Depending on the volume fraction of casein micelles and the Glucagel concentration, a stable phase or a gel or a sedimented material could exist.  The driving force for phase separation was depletion flocculation of casein micelles in the presence of beta-glucan.  The phase separation responsible for textural defects in yogurt systems supplemented with high amounts of Glucagel can be avoided by the reduction of beta-glucan molecular weight, a process that limits the range of attraction between micelles. Incubation of Glucagel with lichenase for varying times shifted the phase separation lines to higher concentration.  Enzymatic manipulation of Glucagel is thus an effective means of assuaging product quality issues as the natural properties of the healthful fibre ingredient change.