Thesis (M.S.)--Rochester Institute of Technology, 1994. / Typescript. Includes bibliographical references (leaves 98-99).

Des efforts de miniaturisation sont nécessaires dans le domaine des dispositifs actifs implantables afin de limiter l’invasivité et de réduire les risques de complications suite aux opérations chirurgicales. Les marges de progression pour la réduction des dimensions tendent à se réduire pour les systèmes actuels tels que les stimulateurs cardiaques, les neurostimulateurs ou les capteurs autonomes in vivo. Une rupture technologique est nécessaire pour permettre de repousser les limites des systèmes actuels. Le titane est un matériau possédant des propriétés de biocompatibilité. Il est stable et inerte en contact avec les tissus humains. De plus, ses caractéristiques mécaniques en font un matériau prometteur pour le développement de microsystèmes implantables. Dans le cadre du projet R&D MISTIC (Micro-Structuration du Titane pour Innovations Cardiologiques), l’objectif principal de cette thèse est de développer une brique technologique sur la gravure profonde du titane pour l’intégration de microsystèmes dans des dispositifs actifs implantables. Des études concernant la gravure profonde du titane en plasma de Cl₂ ont été menées afin de déterminer les mécanismes mis en jeu. L’ajout d’espèces fluorées permet, par la création d’un nouveau chemin réactionnel, d’accroître la vitesse de gravure du titane et d’augmenter la sélectivité par rapport au masque de Nickel. Un procédé de gravure du titane sur une profondeur de 300 μm a été mis au point sur des plaquettes de 100 mm de diamètre. L’application des résultats de ces études et le transfert du procédé vers la gravure pleine plaque ont permis de réaliser des démonstrateurs de traversées électriques en titane. / Miniaturization efforts are required in the field of implantable active devices in order to limit invasiveness and reduce the risks of complications following surgical operations. Progression margins for the reduction of dimensions tend to be reduced for current systems such as cardiac pacemakers, neurostimulators or in vivo autonomous sensors. A technological break is needed to push the limits of current systems. Titanium is a material with biocompatibility properties. It is stable and inert in contact with the human tissues.Moreover, its mechanical characteristics make it a promising material for the development of implantable microsystems. As a part of the MISTIC R&D project (Micro-Structuring of Titanium for Innovations in Cardiology), the main objective of this PhD thesis is to develop a technological brick on the deep etching of titanium for the integration of microsystems in active implantable devices. Studies on the deep etching of titanium into Cl₂ plasma have been carried out in order to determine the mechanisms involved. Further, by adding fluorinated species in the process through the creation of a new reaction pathway, an increase in the titanium etch rate and an improvement of the selectivity with the nickel hard mask were achieved. A process for titanium etching over a depth of 300 μm has been developed on 100 mm diameter wafers. The application of the results of these studies and the transfer of the process to the full wafer etching made it possible to produce the demonstrators with titanium-based electrical feedthrough.

Silicon is an essential element in today’s modern world. Nanostructured Si is a more recently studied variant, which has currently garnered much attention. When its spatial dimensions are confined below a certain limit, its optical properties change dramatically. It transforms from an indirect bandgap material that does not absorb or emit light efficiently into one which can emit visible light at room temperatures. Although much work has been conducted in understanding the properties of nanostructured Si, in particular porous Si surfaces, a clear understanding of the origin of photoluminescence has not yet been produced. Typical synthesis approaches used to produce nanostructured Si, in particular porous Si and nanocrystalline Si have involved complex preparations used at high temperatures, pressures, or currents. The purpose of this thesis is to develop an easier synthesis approach to produce nanostructured Si as well as arrive at a clearer understanding of the origin of photoluminescence in these systems. We used a simple chemical etching technique followed by sonication to produce nanostructured Si suspensions. The etching process involved producing pores on the surface of a Si substrate in a solution containing hydrofluoric acid and an oxidant. Nanocrystalline Si as well as nanoscale amorphous porous Si suspensions were successfully synthesized using this process. We probed into the phase, composition, and origin of photoluminescence in these materials, through the use of several characterization techniques. TEM and SEM were used to determine morphology and phase. FT-IR and XPS were employed to study chemical compositions, and steady state and time resolved optical spectroscopy techniques were applied to resolve their photoluminescent properties. Our work has revealed that the type of oxidant utilized during etching had a significant impact on the final product. When using nitric acid as the oxidant, we formed nanocrystalline Si suspensions composed of particles with a crystal structure different than the common polymorph of Si. These particles emitted UV to blue wavelengths. Iron(III) chloride was also employed as an oxidant, and it created amorphous Si nanostructures from a bulk crystalline Si source. These suspensions showed ultra-bright visible photoluminescence, which could be tuned through engineering the surface.

Recrystallisation annealing, a repeated heat treatment between different stages of cold rolling of martensitic chromium steel strip, is successful when neither high rolling forces nor wear of the working rolls occur during the subsequent cold rolling. Mechanical properties as tensile strength, yield, elongation or hardness have been, by tradition, the criteria that described the quality of the annealing process. In recent years, the development of the measurement equipment in the rolling mills and of the instruments for material investigations has accentuated more and more the role played by the microstructural properties in the evaluation of the heat treatment. Two microstructural characteristics of the degree of annealing are, firstly and most important, the recrystallisation degree, and, secondly, the secondary carbide density. The sample manufacturing and heat treatment, modelling and microstructure investigations by light optical- (LOM) and scanning electron microscopy (SEM) described in this article were carried out at Sandvik Materials Technology’s R&D Department and Bell Furnace Line in Sandviken, Sweden, while microstructure investigations and evaluation by scanning electron microscopy with field emission gun (FEG-SEM) and electron back scatter diffraction (EBSD) were done at the Corrosion and Metals Research Institute (KIMAB) in Stockholm, Sweden. The first part of this work shows that, in contrast to the traditional methods LOM and SEM, that use chemical etching for the preparation of the samples, EBSD can successfully characterise recrystallised structures in annealed martensitic chromium steels. Unlike conventional microscopy with LOM and SEM, EBSD is able to reveal the grain geometry, as well as to separate and identify the different phases in this kind of steels (ferrite, M23-, M6-carbides). Important parameters such as grain size, particle size and recrystallised fraction can be measured with high accuracy. This information can be used to understand, evaluate, control and even predict the recrystallisation annealing of martensitic chromium steel. The second part of this work presents how the results from microstructure description by EBSD can be directly used in relatively simple empirical models for determination of recrystallisation degree as function of the annealing parameters and the deformation history. EBSD was applied to evaluate the degree of recrystallisation in a series of annealing tests, with the purpose to model recrystallisation temperature in two types of martensitic chromium steel strip, a traditional one and one alloyed with molybdenum, cold rolled with different amounts of reduction and annealed with different temperatures, soaking times and heating rates. The empirical quadratic models were built with Umetrics’ software for experimental design, MODDEÒ 8.0 and they defined the recrystallisation degree (limits for LAGB and HAGB were set to 1.5° and 7.5° for the first grade and 2.5° and 10° for second one) and the secondary carbides density as functions of annealing temperature, soaking time and cold reduction (the factor heating rate was removed as nonsignificant). To be observed that these empirical models were fit much better for the recrystallisation degree than for the secondary carbides density. The modelling work described above, together with the implementation of online physical temperature models in the bell annealers may lead to an increased productivity in the production plant by shortening the annealing cycle and minimising scrap and thus to an economical gain of ca 1,5 MSEK per year at Sandvik Materials Technology.

Polyetheretherketone (PEEK) is a Federal and Drug Administration (FDA) approved biomaterial that has been used as an orthopedic implant material due to its inherent properties. Laser etching has become a popular means to create identication markers on the individual implants as required by the FDA. The interaction of laser energy with polymeric materials could potentially cause changes in the material's biocompatibility and mechanical properties. The objective of this study was to determine the effect of laser energy on the biocompatibility and mechanical properties of implantable PEEK by measuring contact angle, micro-tensile testing, nite-element modeling (FEM), and biocompatibility testing according to International Organization for Standardization (ISO) 10993 for cytotoxicity. The results of the study showed that the etching characteristics were mostly in by the laser power and the laser pulse spacing. The mechanical properties were degraded by the laser and the tensile strength of the material was decreased by 50% is some cases. The laser, however, did not affect the biocompatibility. The biocompatibility testing of the material showed no cytotoxic effect using an agar overlay method. The contact angle measurements demonstrated that the laser etching produced a hydrophobic effect to the surface. The FEM model demonstrated a good correlation between the laser power and the vaporization of the PEEK material. The results of the study showed the effect of laser energy on biocompatibility and mechanical properties.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this laboratory study was to determine whether etching of flat bovine enamel surfaces with a 50 per cent aqueous solution of phosphoric acid for 60 seconds increases the bonding of a conventional restorative acrylic resin and a new polycarboxylate cement. The test specimens were subjected to 24 hours, 30 days and six months storage in water and then subjected• to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strength of both materials. The results of the Newman-Keul's test showed that pretreating the enamel surface with 50 per cent phosphoric acid significantly increased the bonding of the restorative resin, and that the cavity sealer supplied by the manufacturer further improved the resin attachment to enamel surfaces previously etched with phosphoric acid. The bonding of the resin to acid-etched enamel surfaces pretreated with or without the cavity sealer was unaffected by prolonged storage in water, temperature stress cycling, and intermittent tensile stress cycling. However, a significant reduction in the adhesion of the acrylic resin to polished-enamel surfaces pretreated with or without the cavity sealer was observed when the test specimens were subjected to the same testing conditions. The data obtained for the polycarboxylate cement test specimens showed that etching of the enamel surface with phosphoric acid also provided slightly higher adhesive values than the control specimens. Results obtained revealed that prolonged storage in water, and temperature and mechanical stress cycling did not affect the adhesion of the polycarboxylate cement to acid-etched enamel surfaces. However, thermal and mechanical stress cycling after prolonged storage in water appeared to decrease the adhesion of the cement to polished enamel surfaces. When Ca45 was used to assess the marginal seal of resin restorations placed into acid-etched Class V cavity preparations in extracted human teeth, the autoradiographs showed that etching of the cavity preparations with 50 per cent phosphoric acid improved the marginal seal of the restorative resin after one-week storage in water. When both the acid-etched and control restorations were thermal stress cycled 2500 times at a 40°C temperature differential, a slight improvement in the marginal seal of the acid-etched restorations was observed.

The fabrication of new and novel materials contributes to qualitative enhancement of human life. Among the various branches of fabrication, nanolithography is an emerging neoteric fabrication technology. Even though nanofabrication procedures and the techniques can be precisely controlled through various error prevention techniques and algorithms, there is always a probability of human or instrumental error in a fabrication process. Minimization or rectification of errors during the fabrication process would increase the productivity and reduce cost per unit of the fabricated devices. Therefore there is a compelling need for an error rectification system. Compared to the number of techniques available for fabrication using nanolithography, the techniques available for error rectification are very limited. Successful implementation of more error rectification techniques may have a huge impact in device fabrication and manufacturing processes. The main focus our work is the development of a lithographic error rectification system that we named as Polymeric Submicron Editor (POSE). This system is made of submicron "pens" and "erasers" made from flexible polymers. The pens and erasers were made of polydiemethylsiloxane (PDMS) and agarose hydrogel respectively. They are fabricated by template synthesis from anisotropically track etched conical micropores in glass. The polymeric pens mounted to piezoelectric motors were used to deposit and remove submicron patterns driven by diffusion. This entire deposition system is housed on an inverted microscope to optically track and register the area of deposition so that if required it can be erased and rectified by agarose hydrogel erasers and PDMS pens. POSE can deposit, erase and rectify patterns with submicron resolution. Apart from the development of POSE, this process also led to the development of techniques for, (i) two dimensional gradient etching in tracked glass, (ii) mask less photolithography and with tracks etched glass and (iii) polymeric microfabrication which will also be covered in detail in this dissertation

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this laboratory study was to determine if the bond strengths of composite resins and unfilled resins was affected similarly when applied to enamel surfaces which had been previously etched with 50 per cent phosphoric acid. The test specimens were subjected to 24 hours, 30 days, and 6 months storage in water and then subjected to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strengths of the composite resins (Adaptic and HL-72) and the unfilled resin (Sevriton). The following results were obtained: (1) Pretreating the enamel surface with 50 per cent phosphoric acid for 60 seconds significantly increased the bond strength of composite resins; (2) when placed on acid etched enamel, there was no significant difference in initial bond strengths obtained for the Adaptic and unfilled Sevriton resins; (3) with prolonged water storage, the Adaptic composite resins developed significant loss of bond strength when compared to the unfilled Sevriton resins and the composite HL-72 resins; (4) when Adaptic resins and the HL-72 resin specimens were compared, there was no significant difference in initial bond strengths but the HL-72 specimens were less affected by storage time. Ca45 was used to assess the marginal seal of Adaptic, HL-72, and Sevriton in acid etched and non-etched Class V restorations. One-half of the specimens were thermal cycled 2500 times and stored in water for one week. Control specimens were tested at the end of one week without the thermal cycle. On the basis of these results, it was concluded that acid etching enhances the marginal seal of both composite and unfilled resins. Both composite and unfilled resins experienced increased marginal leakage when the acid etch preparations were thermal cycled, but there were no observable difference in the marginal seal of unfilled resins and composite resins when placed in acid etched restorations.

No description available.

No description available.