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A B S T R A C T S
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Complex Materials for Telecommunication and Nanotechnology
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Nanotechnology for Networks: Merging bottom-up self-assembly with top-down engineering design
Professor Ted Sargent
Electrical and Computer Engineering, University of Toronto
The optical Internet of the future will demand enhanced optical-domain agility combined with assured stability; new functions such as processing of signals in the optical domain; and new levels of integration, especially at the optical-electronic and optical-wireless interfaces.
I will present our latest research into the architectures that will enable such a network, and on the physical origins and implementations of the materials and devices that will answer its functional requirements. I will show how we have been harnessing the vast potential of novel materials chemistry and self-organization to produce new materials and structures which address anticipated network needs. I will describe our recent demonstration of quantum dots embedded in spin-processible semiconducting polymers which produce light across the entire spectrum used in optical communications. I will discuss how we are combining these materials with micron-lengthscale photonic crystals to control electronic wavefunctions and electromagnetic waves in tandem.
Surpassing the Diffraction Limit with a Planar Left-Handed Transmission-Line Lens
Anthony Grbic and George V. Eleftheriades
Electrical & Computer Engineering, University of Toronto
We report experimental results around 1.0 GHz that demonstrate the ability of a planar “left-handed” isotropic lens, with a relative refractive index of n=-1, to form images that surpass the diffraction limit. The left-handed lens is a planar slab consisting of a grid of printed metallic strips over a ground plane, loaded with series capacitors (C) and shunt inductors (L). This left-handed slab is embedded between two unloaded printed grids that act as homogeneous media with a positive index of refraction. This work opens up the potential for applications in high-resolution microwave and eventually optical imaging and photolithography.
Furthermore, these artificial left-handed media (metamaterials) are being utilized for creating a new range of RF/microwave devices that would enable next generations of wireless communication and radar hardware. This new class of metamaterial devices offers reduced size, increased operating bandwidth and new or enhanced functionality compared to their traditional counterparts.
Electrophoretic deposited nano-structured thin films for ceramic integration
Ms. Juan Li
University of Tokyo
Electron-beam irradiation of Ge-doped silica for the fabrication of optical devices
Dr. Sonia Garcia-Blanco
Electrical and Computer Engineering, University of Toronto
Integrated optical circuits based on silica-on-silicon have found a wide range of applications in telecommunications and more recently as a platform for optical bio-sensors. The traditional fabrication methods, based on photolithography followed by dry etching, present some drawbacks for certain applications, for example where a surface waveguide with easily accessible core is required. Therefore recent attention has focused on the use of direct exposure methods for imprinting waveguides into silica.
In this work, different kinds of irradiation have been successfully used to direct-write optical waveguides in Ge-doped FHD silica. However, understanding the micro-structural modifications induced in the silica by the different irradiations is necessary in order to efficiently use the method for useful applications. I will describe in this talk our understanding of the micro-structural modifications induced in Ge-doped silica by an energetic electron beam, leading to densification of the material and subsequent refractive index change. Different applications for such components will also be outlined.
Dynamic deformation behavior of sp2 -bonded boron nitride nano-array on an atomic scale
Dr. Chihiro Iwamoto
Materials Engineering, University of Tokyo
Nanostructures sometimes show interesting mechanical properties that are completely different from those of bulk materials. In this study, we produced a new nanostructure, the sp2-bonded boron nitride nano-array (BNNA) which have flat graphitic BN layers, and examined its mechanical properties by real-time observation with a high-resolution electron microscope.
In order to produce the BNNA, BN was deposited on the narrow edge of the Si flake, by inductively coupled plasma chemical vapor deposition (ICP-CVD) using a time-dependent biasing technique. The sample was observed its dynamic deformation behavior using a high-resolution transmission electron microscopy with piezo-ceramic tube for three-axis positioning of an indenter. The variation of the lattice image was recorded on videotape using a fiber-optics-coupled TV system with a time resolution of 1/30 s.
High-resolution observation of the BN showed that the orderly BNNA structure produced on a narrow edge of the Si flake under the present experimental condition. Thus, to confirm the mechanical behavior, the BNNA was bended perpendicular to the layers. The deformation behavior suggests that the BNNA is remarkably flexible and resilient to the stress perpendicular to its BN sheets. Moreover, we attempted to bend the layer to the maximum. It was found that the minimum radius of curvature is less than 0.3 nm, which is almost correspond to the spacing between adjacent BN layers. In spite of such large strain, the BN layer did not break.
Size-tunable electroluminescence from nanocomposite material at telecommunication wavelength
Frederick Chang
Electrical and Computer Engineering, University of Toronto
When conjugated polymer and colloidal PbS nanocrystal are mixed together, we have a conveniently processible and size-tunable nanocomposite material which emits at telecommunication wavelength. I will present results on photoluminescence and electroluminescence from the nanocomposite material in the range of 1000 to 1600 nm tunable through quantum-size effect. The impact of using different capping ligands on electroluminescence will also be discussed.
Organic IR Light Emitters
Xiaodong Feng
Materials Science and Engineering, University of Toronto
Nanometer-scale pattern transfer using ion implantion
Naomi Matsuura
Centre for Advanced Nanotechnology
Materials Science and Engineering, University of Toronto
Conventional, broad-area, ion implantation has been combined with unconventional masking to create 2-D geometrical patterns of amorphization in single crystals, with selectable motifs. The patterns are fully developed by use of selective etching. Two examples are
discussed. In the first example, a self-assembled array (with lattice spacing ~1 micron) of silica spheres is used as an implant mask over InP. The variation of the mask thickness created by the sphere geometry modulates the implantation depth in a periodic fashion, which is subsequently revealed after selective etching of the associated amorphized volumes. In the second example, nanochannel arrays in an alumina film are used as an implant mask to produce a hexagonal closed packed array of amorphized cylinders in InP and SrTiO3 substrates. The ion beam-amorphized regions of the substrate are then removed by
selective chemical etching to achieve the full 3-D patterning of 55 nm diameter holes on a 100 nm lattice spacing.
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Complex Materials for Manufacturing and Biotechnology
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Hydroxyl capacity, Basicity and electronic band structure of acceptor-doped proton conducting oxides
Prof. Shu Yamaguchi
University of Tokyo
Issues in Thermal Spray: Effect of Density Variation during phase Change on Splat Shapes
Mehdi Raessi
Mechanical and Industrial Engineering, University of Toronto
During thermal spray coating process, droplets of molten (or semi-molten)
coating material impact the substrate, spread, solidify, and build up the
coating. Therefore, studying the droplet impact and solidification problem
is vital in enhancing our knowledge about the coating characteristic. In
this study, a three-dimensional model of droplet impact and solidification
has been modified to include the effects of density variation during phase
change. The governing equations for conservation of mass, momentum, and
energy, and a volume of fluid (VOF) equation are derived by assuming
different but constant solid and liquid densities. A fixed-grid control
volume discretization of the momentum and energy equations, combined with a
volume-tracking algorithm to track free surfaces, has been developed.
The numerical model was validated against the Stefan problem and a planar
solidification problem, for which analytical solutions are available. The
numerical and analytical solutions were in good agreement. The numerical
model was then applied to simulate solidification shrinkage of molten tin in
a rectangular mold. Finally, the effects of density variation during phase
change were studied during the impact and solidification of a tin droplet
impinging onto a stainless steel substrate.
Thermodynamic study of solidification
refining of silicon with Si-Al melts
Takeshi Yoshikawa
University of Tokyo
Effect of thermal exposure on stress
distribution in TGO layer of EB-PVD TBC
Toru Tomimatsu
Materials Engineering, University of Tokyo
Thermal barrier coatings (TBCs) become a hot topic of research and development recently although they have been used for thermal protection of hot section components in gas turbines for propulsion and power generation for a long time. The failure of TBC systems is typically associated with buckling and spalling of ceramic top coat from the thermally grown oxide (TGO) or at TGO/bond-coat interface. Therefore, the adherence and stress in the TGO layer is important to understand damage mechanism of TBCs. Luminescence spectroscopy is a powerful tool to measure the stress in TGO layer. Although the average value of stress in the TGO in some kind of TBCs has been evaluated by this technique, in order to correlate stresses with places in various degradation states, the local stress distribution should be evaluated. The purpose of this paper is to measure the stress distribution in the TGO layers after heat exposure with high spatial resolution by micro-luminescence spectroscopy.
The thickness of the TGO increases with an increase in heat exposure time and the growth of the TGO nearly follows the parabolic rule of oxidation. The typical example of stress distribution on the polished cross section after thermal exposure for 100 h shows compressive stresses exist in almost all the area in TGO. The stress in the TGO layer is not uniform and the stress near the top coat is smaller than that close to the bond coat. This is in agreement with a larger thermal strain mismatch between the TGO and the bond coat. It should be noted that the stress at the position of concave downward imperfections exhibits similar value near the top coat to that close to the bond coat. The experimental results are discussed based micro-mechanics analysis.
Protein-Based Supramolecular Architectures: Controlling Self-Assembly at Molecular Interfaces
Professor Christopher M. Yip
Departments of Chemical Engineering and Applied Chemistry / Biochemistry
Institute of Biomaterials and Biomedical Engineering, University of Toronto
The rational design of protein-based supramolecular architectures requires careful consideration of not only intramolecular structure but also the intermolecular interactions that control their self-association into higher order structures. We are particularly interested in the role of interfacial structure and chemistry in defining the nucleation and growth of these systems and specifically the synthesis of extended two-dimensional protein arrays. Our recent research efforts have focused on the development and application of new integrated imaging tools that combine the power of scanning probe microscopy (SPM) with the functional aspects of high-resolution optical imaging and spectroscopy to address questions related to the interplay between molecules, cells, and surfaces.
We will explore how in situ SPM studies have provided us with novel insights into the role of electrostatic and hydrophobic forces on the assembly of b-helix and b-sheet forming peptides at ordered interfaces, including the creation of oriented protein nanostructures. Our recent efforts to combine in situ fluorescence spectroscopy with SPM are helping us to resolve the kinetics and phenomenological basis for structural transitions in supported planar lipid bilayers. Such systems are ideal for investigating the transmembrane receptor association, ligand binding, and signaling. We will describe how molecular dynamics simulations coupled with the functional integration of high resolution optical imaging tools (confocal and TIRF microscopies) with in situ SPM has been applied to the study of cell and molecular dynamics at interfaces.
The Mechanism of Isothermal Expansion of the Simple DNA Repeats: Application to the Synthesis of the Various Biomaterials
Hiroyuki Kurihara
Chemistry and Biotechnology, University of Tokyo
Exciting new material for fixing fractured bones
SD Ramsay, L Yang, RM Pilliar, JP Santerre
Institute of Biomaterials and Biomedical Engineering / Materials Science and Engineering
Frequently, complicated fractures, whether clinically induced as in reconstructive surgery, or resulting from trauma are stabilized by means of implanted fixation devices such as plates, rods and screws. Traditionally, metals have been selected for these applications because of their high stiffness and ease of fabrication. However there are problems associated with the use of such metallic devices, foremost is the issue of toxic metal ion release resulting from corrosion. The issue of disuse atrophy when the high stiffness metallic device bears the majority of the loads on the bone-implant system (stress shielding) is another problem as is the need for a second surgical operation in order to remove the implant once the fracture has healed. A substantial amount of recent research has focussed on developing new biodegradable polymeric implants that would address these problems associated with metallic implants. However, these new polymeric materials do not generally have sufficient stiffness to permit their use in any major load bearing applications.
Our research is focussed on a novel biodegradable ceramic-polymer (calcium polyphosphate/polyvinyl acid-carbonate copolymer) composite material with strength and stiffness similar to those of cortical bone, suggesting their use as fixation devices in major load bearing applications. This material offers the possibility of being implanted in a single surgical operation with the material’s stiffness gradually decreasing as the fracture heals, thereby reducing the degree of stress shielding as well as eliminating the need for a second surgical operation. Also, in the process of developing this material an apparently novel method for dramatically increasing the mechanical properties of porous ceramics has been discovered and is being investigated.
Selection of an active enzyme using phage display on the basis of catalytic activity in vivo
Takashi Taki
Chemistry and Biotechnology, University of Tokyo
Natural enzymes catalyze a variety of chemical reactions in organisms, and their high specificity and reactivity make them attractive targets of engineering for pharmaceutical, industrial, and environmental applications. Recently, selection of enzymatic activity has been developed and can be used as a complement to conventional method, rational design of enzyme. Phage display is one of the potent method for selection of enzymatic activity in vitro, but there exist some difficulties including an expression of the functional enzyme on the surface of the phage and linkage of enzyme and substrate (or product).
To solve these difficulties and also to elucidate unknown cellular network of enzymatic reactions, which is important for post-genome research, we constructed novel system using phage display. In this method, enzyme is not displayed on the surface of the phage and selected on the basis of their catalytic activity in vivo. As a model, we used biotin protein ligase (BPL) from E. coli and tag peptide (B-tag) recognized and biotinylated by BPL. Secreted phage particles were subjected to selection agaist avidin resin. We found that capsid protein of secreted phage particle that was fused to B-tag peptide was biotinylated specifically in the case of being secreted from E. coli carrying phagemid encoding BPL. We could also show selective enrichment of BirA gene encoding BPL from mix library after selection. These indicate our novel selection strategy is useful for selection of catalytic activity in vivo and can be applicable for generating artificial enzymes and searching for unidentified enzymes.
Biomaterials for Guided Nerve Regeneration
Thomas Freier
Chemical Engineering, University of Toronto
Following nerve injury, minimal regeneration is possible in the peripheral nervous system, while no spontaneous regeneration occurs in the central nervous system at all, leading to severe functional deficits. The gold standard for the repair of peripheral nerve transection injuries is the use of autografts, which necessitate the creation of a secondary injury in order to repair the damaged nerve, and hence have obvious limitations and drawbacks. No similar treatment alternatives exist for spinal cord transection injuries. One tissue engineering approach to repairing this damage is to implant a synthetic guidance channel or tube in the gap between the severed ends of the nerve, in order to provide a path and a favourable enviroment for growing axons, thus promoting nerve regeneration across the site of injury.
Hydrogel nerve guidance channels made of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) have been fabricated using a centrifugal casting method that relies on phase-separation during the polymerization process. The guidance channels have been shown to induce and support axonal cable regeneration following nerve transaction injuries in in-vivo animal models. The centrifugal casting process can be further used to modify the channels by incorporating biodegradable microspheres into the tube walls to serve as drug delivery devices, which can supply bioactive growth factors to the inside lumen of the channels and enhance nerve regeneration. A modification of the same technique also allows the fabrication of fully biodegradable nerve guidance channels. Examples will be given in the presentation.
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Nortel Institute for Telecommunications
Bahen Centre for Information Technology
40 St. George St.
University of Toronto
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