Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (p. 253-258). / by John Jason Sprague. / Ph.D.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (p. 45-49). / The layer-by-layer assembly of polyelectrolytes into multilayered films is an attractive approach for fabricating novel biomaterials, as it offers tremendous control over the internal composition and surface properties of their layered architectures. In this work, polyelectrolyte multilayers (PEMs) were evaluated as a platform for applications in controlling the spatial adhesion of living cells. An overview is presented on current developments and competing technologies within research and industry with respect to cell patterning and cell-based devices. Interviewed individuals in research and industry suggested a variety of potential applications of PEMs in cell patterning technology. A patent search on the core technologies (i.e. PEMs and patterning methods) and on applications in cell patterning, cell-based screening, and cell-based biosensors revealed ample opportunity for starting a new venture with a platform based on the layer-by-layer assembly of PEMs. A brief business plan for starting a new venture with a platform based on the layer-by-layer assembly of PEMs is proposed to initially target the high throughput screening and cell-based biosensor markets. / by Aleksandr John White. / M.Eng.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (leaves 120-124). / This thesis focuses on the use of a new sequential adsorption technique to deposit thin polyelectrolyte multilayer films. This involves alternately dipping a substrate into dilute aqueous solutions of a positively charged polyelectrolyte followed by a negatively charged polyelectrolyte, with a rinsing step in between. By repeating this process an arbitrary number of times, a thin film can be built up due to the electrostatic interaction between the two oppositely charged polyelectrolytes. This technique was used to create thin film electroluminescent devices based on poly(p-phenylene vinylene) (PPV) using a water soluble precursor to PPV and poly(acrylic acid) (PAA). The structure of such films has been shown to be highly dependent on the conditions of the dipping solutions. The pH of the solutions controls the degree of ionization of the PAA which influences the deposition process by affecting both the conformation of the PAA in solution as well as the charge density of the PAA on the surface. These films exhibited a light output of greater than 1000 cd/m 2 (about 10 times the brightness of a computer monitor), significantly higher than that typically reported for films of pure PPV. A time dependent charging process together with a reduction in the turn-on voltage with charging, and a non-rectifying device behavior, suggest an electrochemical mode of operation. In such a case, ions present in the film play an active role by modifying the electrical injection characteristics. More fundamental studies on the impedance and dielectric characteristics of sequentially adsorbed films were performed on layers of poly(allylamine hydrochloride) (PAH) with PAA as well as PAH with sulfonated polystyrene (SPS). This provided some insight into the level of ionic conductivity present in these films. Typically ionic conductivities were observed that ranged from about 10-12 S/cm at room temperature up to about 10-8 to 10-9 S/cm at 1 100°C. The apparent dielectric constant also increased to relatively large values at low frequencies implying the buildup of ions at the interface. The PAH/SPS system required much higher temperatures than the PAHIPAA system before any significant change in the electrical characteristics were observed suggesting that ionic motion is much more hindered in PAH/SPS films. / by Michael Frederick Durstock. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references. / To fabricate living cell-based immunological sensors, we have examined two PEO-based biomaterials that can be patterned to generate cellular array templates: poly(allylamine)-g- poly(ethylene glycol) graft-copolymer and poly(ethylene glycol) dimethacrylate hydrogel. Poly(allylamine)-g-poly(ethylene glycol) polycation graft-copolymers were designed, synthesized, and characterized in order to combine bio-functionality with patternability on charged polyelectrolyte multilayer surfaces. Polymer-on-polymer stamping (POPS) techniques were used to create micron scale patterned regions on negatively charged multilayer surfaces via direct stamping of these graft copolymers. The long PEG side chains effectively resisted adsorption of antibodies or other proteins, and created a bio-inert area when patterned by POPS. On the other hand, desired proteins can be covalently attached to the graft copolymer by introducing proper coupling agents. Arrays of proteins were produced by either simple adsorption or coupling of proteins onto the graft copolymer patterned surfaces. The protein arrays were utilized as templates in fabricating cellular arrays of non-adherent B cells. / (cont.) Poly(ethylene glycol) dimethacrylate hydrogel precursors were photopolymerized into 3D rmicrowell array templates via micromolding. After the floors of microwells were decorated with antibodies, hydrogel microwell array templates were employed in fabrication of cellular arrays. The topology of microwells facilitates the positioning of cells inside microwells and improves the binding stability of cells with protection from mechanical agitations. T cell arrays fabricated on hydrogel microwell array templates were tested as living cell- based immunological sensors. B cells were settled uniformly on T cell arrays to establish contacts between B and T cells over a large area. A level of T cell activation by target peptides were quantified using calcium sensitive fura dyes. A large set of individual T cell response data was acquired from a single T cell array and utilized to obtain average dose-response behavior of T cells. Average T cell responses were suitable as quantitative signal of a living cell-based immunological sensor. In addition, a potential application of T cell arrays in high throughput assay of individual T cell responses was investigated. / (cont.) Analysis of calcium oscillation frequency of individual T cells revealed that there is no clear correlation of calcium oscillation frequency with target peptide dose in this experiment. / by Heejae Kim. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 108-112). / The behavior of alloy 617 at 650°C in low oxygen partial pressure environments has been studied under static loading. Of particular interest was the crack growth rate in these conditions. For that, tests were conducted at a constant stress intensity factor of 49.45 MPa'm (45 ksidinch) using a direct current potential drop measurement system to determine crack length. High purity argon gas allowed establishing an oxygen partial pressure as low as 10-22 atm and premixed oxygen/argon gases were used to vary the oxygen potential. To go dee er into the understanding of the phenomena involved, a creep test (constant load of 1.21x10 N in argon environment) and a corrosion experiment (50 ppm oxygen in argon for 500 hours without any load) were also added. The crack growth tests led to a particularly unexpected result: whatever the oxygen potential, the crack growth rate increased with time and the plot for the crack length versus time displayed a recurrent parabolic shape without any change in the environment. No unique crack growth rate could be defined in a given environment and the influence of the environment on the crack growth rate was not clearly visible. Multiple features were found to surround the main crack: secondary cracks parallel to the principal one, intergranular cracking ahead of the crack tip, wedge cracks at grain boundaries and aggregates of Cr-rich carbides near the lips of the crack. Moreover no extensive oxide scale was formed on the surface of the sample exposed to the corrosive environment (50 ppm oxygen in argon) for 500 hours. The non-constant crack growth rates, together with the observed cracking features, were attributed to the competition between creep deformation and mechanical fracture, likely environmentally enhanced. An exponential law was found to fit the data for the crack growth rate as a function of time for a K of 49.45 MPalm (45 ksi'inch). The effects of the environment were overcome by mechanical and thermal processes leading to damage accumulation and so, a reaction of alloy 617 to the external stress and temperature highly dependent on time. This behavior was compared with the one of alloys Haynes 230 and Incoloy 908 in the same conditions. / by Fanny Mas. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 337-39). / Aligned arrays of carbon nanotubes (A-CNTs), called CNT forests, are the precursor for controlled-morphology macroscopic nanocomposites and nanoengineered composites due to theirscale-dependent, tunable physicall properties. Applications include polymer and ceramic matrix nanocomposites (PNCs and CMNCs), nanostiching as laminate interply reinforcement, as well as in supercapacitors, MEMS devices and electrodes for ion actuators and sensors. A key component of manufacturing materials comprised of A-CNTs is controlling the morphology and geometry of the CNT forest. Current laboratory findings show significant variability in CNT forest growth characteristics, and an experimental study was conducted to better understand and control for the observd process variations. An exploratory investigation of growth parameters allowed for a local optimization of growth temperature and hydrocarbon flow rates, as well as an acceptable range of sample placement in the CVD furnace to achieve ~1mm tall CNT forests. Results from this investigation led to the conclusion that the significant inconsistencies between consecutive growths must be due to factors out of direct control, mainly humidity. A new system is being developed to better control for and monitor water in the furnace. A second investigation focused on post growth cool down effects, and the possible shortening (deforestation) of CNTs at high temperatures without a renewing source of the carbon precursor. Deforestation conditions did not lead to CNT shortening. / by Hanna Megumi Vincent. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 187-193). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Ionic colloidal crystals are here defined as multicomponent ordered colloidal structures stabilized by attractive electrostatic interactions. These crystals are colloidal analogues to ionic materials including zincblende, rocksalt, cesium chloride, and fluorite. A thermodynamic study revealed that the screening ratio, charge ratio, and monodispersity are critical parameters in ionic colloidal crystal (ICC) formation. Experimentally, small ordered regions were observed under ideal thermodynamic conditions. However, no larger crystalline regions were found in these samples. The kinetics of ICC formation was studied using a variety of computational techniques, including Brownian dynamics, Monte Carlo, and a Newton's method solver. These techniques have each elucidated properties and processing conditions that are important to crystallization. The Brownian dynamics and Monte Carlo simulations showed that the previous experiments were highly undercooled. Furthermore, a narrow crystallization window was found, demonstrating the need to create particle systems that meet the narrow parameter space where ICCs should be stable. Pair interaction potentials were evaluated for their accuracy using a Poisson-Boltzmann (PB) equation solver. The PB solver was also used to further refine crystalline formation energies so that systems can be more accurately tailored. A surprising result from the PB solver showed that the lowest formation energy occurs when the quantity of surface charges on both particles are equal. Although this result is not predicted by any colloidal pair potentials, it was verified experimentally. This further illustrates that thermal mobility in these systems can be sufficient to maintain a stable solution despite attractive electrostatic interactions. Tailoring particle systems to balance the thermal and electrostatic interactions should allow widespread crystallization. However, these conditions require highly monodisperse particles to be fabricated with controlled surface charge and sizes. Currently these particles are not widely available and further research in this area should aid in the full realization of the ICC concept. In conclusion, all results are integrated to predict which particle systems should be produced to allow the formation of large ordered structures. / by Garry R. Maskaly. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 59). / The platinum market is a material market of increasing interest, as platinum demand has grown faster than supply in recent years. As a result, the price of platinum has increased, causing end-user firms to experience material scarcity through the presence of these high prices. A significant driver of this demand growth for the last several decades is demand automotive sector, which is responsible for almost 60% of total primary platinum demand, due to the use of platinum in three way catalysts. Platinum is one of the materials utilized to catalyze reactions that prevent vehicle emissions from entering the atmosphere, which can have a severe impact on air quality. Two factors will likely contribute to the future growth of automotive platinum demand: the trend in increased use of platinum per vehicle, and expected growth in the number of automobiles produced and sold around the world. While the automotive market is relatively saturated in developed economies, automotive sales growth potential is particularly high in developing areas, such as BRIC countries. It follows that future growth in automotive platinum demand is likely to be significant. As such, the study aims to characterize the drivers of automotive platinum demand and to establish how this demand sector impacts the platinum market as a whole. This characterization is achieved through regression analysis and by utilizing a platinum market simulation model. / (cont.) The regression results indicate that the automotive platinum demand has historically been an inelastic one. Global automotive sales have indeed been a driver of platinum demand behavior. Regression on automotive sales in India, a BRIC country has high correlation with wealth as measured by GDP per capita. In the US and Japan, automotive sales show high autocorrelation and additional correlative relationships were not confirmed. Model results show that the automotive industry drives platinum price increases when there is a combination of low elasticity of platinum demand and large growth rates in the global automotive industry. Recent news about new technologies suggests that demand elasticity may increase, and the model suggests that higher elasticity would reduce the impact of automotive industry growth on the total demand for platinum. / by Christopher George Whitfield. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991. / Includes bibliographical references (leaves 231-235). / by David Christophe Dunand. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references. / It is well known that the use of high-brightness LEDs for illumination has the potential to substitute conventional lighting and revolutionize the lighting industry over the next 10 to 20 years. However, successful penetration of this extremely large lighting market would require vast improvements in power conversion efficiencies, color index, light output per device and drastic reduction in cost. Quantum Dot white LED (QD WLED) technology may be one of the best choices, due to its higher energy efficiency, larger color render in index, better versatility and more importantly lower cost, compared to conventional blue LED plus YAG: Ce yellow phosphor technology. Due to the fundamental difference of the material structure, QD LEDs will win a steady position among existing white LED patents and a hybrid fabless plus IP business model has the best position to promote this technology to maximize its benefits and potential for the entire LED industry. / by Xinyue Zhao. / M.Eng.