Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 121-129). / This thesis describes the development of a novel in vitro model of monocytes transmigration under flow and use in the study of early molecular events of atherogenesis. In this work, we focused on how endothelial dysfunction, specifically mediated by disturbed flow from atherosusceptible regions of the vasculature, is both communicated to recruited monocytes as they reside in the subendothelial matrix, and how reciprocally, monocytes may exacerbate the endothelial dysfunctional state. We built and integrated our in vitro model to a unique flow apparatus that can precisely replicate atheroprone and atheroprotective shear stress waveforms. We carefully characterized the model that relies on a fibronectin-coated collagenous matrix seeded with a confluent monolayer of endothelial cells co-cultured with THP- 1 monocytes under flow. We used the model to draw biological insight from endothelial:monocyte co-cultures under flow. We found that monocytes preferentially accumulate on endothelial monolayers exposed to atheroprone flow. We also observed the upregulation of IL-1[beta] in endothelial cells exposed to atheroprone flow when co-cultured with monocytes but not in endothelial cells alone, in each of three independent experiments; yet the aggregated results are not statistically relevant due to variability. Flow-driven dysfunctional endothelium recruits and interacts with monocytes that soon after transmigration become dysfunctional foam cells. Our novel in vitro model that congregates endothelial cells, monocytes and flow responds to the pressing need to understand the interplay between these protagonist cells during atherogenesis, and allowed us to define further monocyte- and flow-mediated transition of endothelium from normal to dysfunctional to diseased states. Harnessing the power of a versatile platform of transmigration under flow may foster the discovery of novel targets for atherogenesis and the development of original therapeutic strategies. / by Alexis S. Turjman. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references. / Biological systems inherently posses the ability to synthesize and assemble nanomaterials with remarkable precision, as evident in biomineralization. These unique abilities of nature continue to inspire us to develop new approaches of nanobiotechnology to integrate advanced materials into medicine and electronics. Particularly, peptides are believed to play an important role in biotemplating and biological self-assembly. In order to understand the interface between inorganic materials and peptides and realize biological self-assembly, this work adopted M13 virus as a model system. The genetic engineering of M13 viruses enables us to grow various nanomaterials and achieve virus monolayer assembly on charged polyelectrolyte multilayers. The fundamental understanding and new discoveries obtained by this work can mature into an engineering discipline demonstrating that biological approaches may represent a new paradigm to provide novel technological advantages. The use of a biological template for a nanostructured battery electrode ramps up the device's performance and scales down its overall size. This work presents a new way of exploiting biological entities for the bottom-up assembly of battery devices by utilizing biological self-assembly and biotemplating. Viruses are genetically engineered such that they function as a toolkit for constructing the battery. / by Ki Tae Nam. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Mark Gregory Steckel. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaf 22). / This work builds on the initial design of a polymer microchip for controlled-release drug delivery. Currently, the microchip employs a nonbiodegradable sealant layer, and the new design aims to fabricate it only of biodegradable parts. Experiments were conducted to evaluate two potential designs that are fabricated via lamination, and a final design was proposed based on the results. Design 1 sought to replace the sealant directly with a PLA backing layer, but the laminated backing layer was found to leak in 14C-dextran release experiments. Design 2 used a laminated film instead of the original injected membrane. The laminated film was optimized to a 200- [mu]m thick poly(D,L-lactic-co-glycolic acid) 2A membrane, and the film-laminated microchip was shown to release 14C-dextran within a 40-day period. The final proposed design was based on Design 2, which demonstrated more potential as a future means of drug delivery. / by Jina Kim. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (v. 2, p. 343-355). / Previous experimental research into ancient pottery production has proven that potters can produce vessels with varying materials properties, such as thermal shock resistance and permeability. These properties are differentially useful for certain tasks, such as cooking or water-cooling. In certain cases, such as the use of shell temper in North America, an improvement in thermal shock resistance seems to provide an explanation for why the new temper was adopted along with the introduction of a new food type -- maize. It remains an unanswered question, however, whether potters in a large variety of situations were choosing to alter their production techniques or materials to produce pots intended for different functions that exhibit different materials properties. I investigated this question by applying techniques and concepts from materials science, anthropology, and archaeology. This combination of materials science and social science was pioneered by Heather Lechtman and Dorothy Hosler, and is called the "materials approach." My research focuses specifically on pottery production in the Middle Balsas Region of Guerrero, Mexico, from approximately 300 BC to AD 1300. I investigated whether potters in the Middle Balsas were using different production techniques or raw materials for vessels that were intended for specific functions. I chose the Middle Balsas Region as the geographical focus for my research because little systematic archaeological investigation has focused on that area, especially in the Late Preclassic and Classic periods (300 BC-AD 900). In order to gather appropriate data, I mapped, surface collected, and excavated at three Middle Balsas sites. I then categorized the pottery and analyzed a selected portion via thin section analysis/petrography. / (cont.) The combination of field work and laboratory analyses that I used provided me with data on the production techniques practiced by Middle Balsas potters and allowed me to identify what wares and vessel shapes were characteristic of various time periods. I determined that Middle Balsas potters produced a consistent set of wares and vessel shapes made from a variety of clay sources, and that the clays I identified in their vessels always contained a consistent volume fraction of non-plastic inclusions. The majority of the clays used in these vessels naturally contain the high levels of non-plastic inclusions identified. When the clays did not contain this volume fraction of inclusions, the potters added a sand temper to the clays to reach their "ideal" volume fraction. The consistency that I identified in the production of Middle Balsas pottery lasted over one thousand years, which is unusual in Mesoamerica. I suggest that this production pattern may have occurred because a small number of potters who used a specific, shared technique made the vessels for the entire community. / by Jennifer L. Meanwell. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 127-134). / Grain boundaries are known to play a role in many important material properties including creep resistance, ductility and cracking resistance. Although the structure and properties of individual boundaries are important, the overall behavior of the material is determined largely by the connectivity of grain boundaries in the microstructure. Grain boundary networks may be studied in the framework of percolation theory by classifying boundaries as special or general to the property of interest. In standard percolation theory, boundaries are randomly assigned as special or general; however, this approach is invalid in realistic grain boundary networks due to the requirement for crystallographic consistency around any closed circuit in the microstructure. The goal of this work is to understand the effects of these local constraints on the connectivity and percolation behavior of crystallographically consistent grain boundary networks. Using computer simulations and analytical models, the behavior of crystallographically consistent networks is compared to that of randomly-assembled networks at several different length scales. At the most local level, triple junctions and quadruple nodes are found to be preferentially coordinated by special and general boundaries, leading to nonrandom network topologies that are quantified using topological parameters. / (cont.) Although the properties of the simulated microstructures, including connectivity length and average cluster radius of gyration, are described by the same scaling exponents as in standard percolation theory, the amplitude prefactors in the scaling relationships are changed as a result of the crystallographic constraint. The percolation threshold, an important parameter in microstructural design, is also found to differ from that of standard percolation theory by as much as ±0.05. Although all of the simulated grain boundary networks studied here are distinctly nonrandom, no two cases have the same behavior, the details of which depend strongly on the specific microstructural model. Therefore, a unified approach for locally correlated percolation problems is developed that allows the effects of the requirement for crystallographic consistency to be compared directly from system to system. This new approach can be extended beyond the study of grain boundary networks to include other locally-correlated percolation problems. / by Megan E. Frary. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references (p. 175-179). / The dewetting of solid metal polycrystalline films to form metal nanoparticles occurs by the nucleation and growth of holes in the film. For typical films on flat substrates, this process is not well-controlled and results in nanoparticles with nonuniform spatial and size distributions. Topographic substrates consisting of di-periodic inverted pyramid arrays and mono -periodic v-groove gratings of oxidized silicon were used to modulate the surface curvature of as-deposited polycrystalline gold films and control the dewetting process. The morphology of films dewetted on topographic substrates was found to depend on the both the relative geometry of the substrate and film thickness. Relatively thick films dewetted out of the pits and grooves prior to breaking up into particles while thinner films pinched off to form particles in the pits and grooves. If the pits or grooves were far apart, the pinch off also resulted in particles forming on the mesas between the pits. If the pits or grooves are close together, all the material pinches off into the topography. In the case of the inverted pyramids, this resulted in spatially ordered arrays of nanoparticles with narrow size distributions. A model that explains and predicts the effect of the relative geometry was developed based on competition between curvaturedriven evolution of the film-atmosphere interface and the dewetting of the film-substrate interface. It was also found that particles in both types of topographic substrates are strongly crystallographically oriented both out of the plane of the substrate and in the plane of the substrate despite the lack of an epitaxial relationship with the amorphous template. / (cont.) During the solid-state dewetting process, the growth of holes in the film is accompanied by material accumulation along the edge of the hole. Investigation of the dewetting edge at early stages revealed that the accumulation occurs unevenly in individual grains. Electron backscatter diffraction revealed that the unevenness is not due to grain orientation. / by Amanda L. Giermann. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 206-217). / Lack of energy supply and non-uniform distribution of traditional energy sources, such as coal, oil, and natural gas, have brought up tremendous social issues. To solve these issues, highly efficient energy conversion devices including solar cells, water splitting cells, and lithium-ion batteries are required. In this thesis, by utilizing the biological scaffolds of M13 bacteriophage, nanocomposites with novel nanostructures and various functional nanomaterials have been synthesized, assembled, and fabricated into devices. Using excellent properties from each functional material in the nanocomposites, performance of the energy conversion devices has been improved. Specifically, in dye-sensitized solar cells, the electron collection efficiency is improved by the complex of the viruses and single-walled carbon nanotubes. The light harvesting efficiency is also improved by localized surface plasmon-enhanced photo-absorption of dye-molecules, with and without adding viruses into the titania photoanodes of dye-sensitized solar cells. In addition, virus-graphene complex is utilized to enhance the performance of lithium-ion batteries, by increasing the electron conductivity throughout the cathode active materials. Moreover, two types of virus-templated perovskite ternary metal oxide materials (strontium titanate and bismuth ferrite) are synthesized and demonstrated for photocatalytic and photovoltaic properties. / by Xiangnan Dang. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (leaves 163-174). / High quality relaxed silicon-germanium graded buffers are an important platform for monolithic integration of high speed heterostructure field-effect transistors and III-V-based optoelectronics onto silicon substrates. In this thesis, dislocation dynamics in compositionally graded SiGe layers are explored and mobility enhancements in strained Si/SiGe metal-oxide-semiconductor field-effect transistors (MOSFETs) are evaluated. These results demonstrate the dramatic increases in microelectronics performance and functionality that can be obtained through use of the relaxed SiGe integration platform. By extending and modifying a model for dislocation glide kinetics in graded buffers to SiGe/Si, a complete picture of strain relaxation in SiGe graded buffers emerges. To investigate dislocation glide kinetics in these structures, a series of identical samples graded to 30% Ge have been grown at temperatures between 650ʻC and 900ʻC on (001)-, (001) offcut 6ʻ towards an in-plane <110>-, and (001) offcut 6ʻ towards an in-plane <100>-oriented Si substrates. The evolution of field threading dislocation density (TDD) with growth temperature in the on-axis samples indicates that dislocation nucleation and glide kinetics together control dislocation density in graded buffers. The TDD of samples grown on offcut substrates exhibits a more complicated temperature dependence, due to their reduced tendency towards dislocation pile-up formation at low temperature and dislocation reduction reactions at high temperature. Finally, by evaluating field threading dislocation density and dislocation pile-up density in a wide variety of SiGe graded buffers, a correlation between dislocation pile-up formation and increases in field threading dislocation density emerges. / (cont.) Record mobility strained Si p-MOSFETs have been fabricated on relaxed 40% Ge virtual substrates. Hole mobility enhancements saturate at virtual substrate compositions of 40% Ge and above, with mobility enhancements over twice that of co-processed bulk Si devices. In contrast, hole mobility in strained Si p-MOSFETs displays no strong dependence on strained layer thickness. These results indicate that strain is the primary variable in determining hole mobility in strained Si p-MOSFETs and that symmetric electron and hole mobility enhancements in strained Si MOSFETs can be obtained for virtual substrate compositions beyond 35% Ge. The effect of alloy scattering on carrier mobility in tensile strained SiGe surface channel MOSFETs is measured directly for the first time. Electron mobility is degraded much more severely than hole mobility in these heterostructures, in agreement with theoretical predictions. Dual channel heterostructures, which consist of the combination of buried compressively strained SiilyGey buried channels and tensile strained Si surface channels, grown on relaxed SilxGex virtual substrates, are explored in detail for the first time. Hole mobilities exceeding 700 cm2/V-s have been achieved by combining tensile strained Si surface channels and compressively strained 80% Ge buried channels grown on relaxed 50% Ge virtual substrates. This layer sequence exhibits nearly symmetric electron and hole mobilities, both enhanced relative to bulk Si ... / by Christopher W. Leitz. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (p. 26-27). / A series of one-dimensional photonic bandgap devices were fabricated using SiO2 and TiO2 films deposited from solution by the sol-gel method. A dielectric mirror, or broadband interference filter, was fabricated by alternating quarter-wave optical thickness layers of the two films on a silicon substrate for a total of six layer pairs. This device exhibited an omnidirectional photonic bandgap of 450 nm in TE-polarization and 110 nm in TM-polarization. A microcavity, or narrowband filter, was fabricated with a TiO2 Fabry-Perot cavity sandwiched between two mirrors of three layer pairs each. The resonant cavity corresponded to a wavelength of roughly 1500 nm and shifted to shorter wavelengths with increasing incident angles. A maximum resonant quality factor of 11. 7 was achieved. / by Andrew William Sparks. / S.B.