Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (leaves 58-59). / Consumer demand is hard to predict in any industry, let alone the automotive industry. Vehicle manufacturers try to produce according to what their customers want, but if these wants change, the company is faced with lots of unsold cars and a huge changeover cost. In order to help fight the problems of demand variability, automotive manufacturers have begun the move towards plant flexibility. This includes designing vehicles comprised of similar subassemblies and the development of flexible tooling. The hope is that multiple vehicles can be produced on the same line so if demand starts to fluctuate, they can change the production levels of their styles with minimal lead time. There are a number of different approaches to flexible tooling. One approach using programmable robotic repositionable tools (PRRT) is particularly promising because it can handle a large number of styles and requires low style specific reinvestment costs. This thesis examines the PRRT technology as well as other forms of flexible tooling to understand the conditions under which these approaches make the most economic sense. / (cont.) For this project an algorithm was developed to choose assembly tools based on subassembly characteristics, production levels, style counts, and flexibility approaches. The algorithm was connected to an already existing vehicle assembly model and two forms of economic analysis were performed. The first looked at the costs of using PRRT versus other forms of tooling for various product mixes. The second analyzed the potential cost savings when considering product changeover. The results indicated that the initial outlays for PRRTs cannot be justified even for a large number of styles unless multi-generational product changeover is also considered. However, PRRTs provide a cost effective flexible tooling option for plants producing multiple styles when considering product changeovers. / by Jeffrey C. Povelaites. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 112-115). / Optical technologies are now ubiquitous in data communication, telecommunication, and computing networks for transmission distances beyond a few meters. The use of optical to transmit voice communication has changed the nature of the industry and been driving photonic component innovation for the past 30 years. Never before has the world demanded more data to run its collective everyday lives. Technological lifecycles have shortened and to keep pace with the rapidly increasing quantities and demands of data needs, firms are placing a stronger emphasis on the development of new technologies to replace old ones. The use of electrical interconnects has been the workhorse for data transmission for over a century and a new technology is poised to succeed it. Due to the limitation of current transmission medium, an adoption of new technology is inevitable and the question is when and what are the drivers? In this thesis, an analysis will be conducted to examine the adoption of optical interconnect cables in different lengths using different costs of new technology. These results will be used to understand how each driver affects the overall adoption of optical interconnect cables, the limitation of adoption, and a potential timeline of adoption for each length examined. / by Louisa Chiao. / M.Eng.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Ashok Murthy. / Sc.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / Cataloged from PDF version of thesis. Pages 160 and 161 are blank. / Includes bibliographical references. / The conformations of conjugated polymers can be altered by nearby environments. The intrapolymer conformation and interpolymer assemblies have a crucial impact on a variety of properties such as absorption, energy migration, and fluorescence. In this dissertation, the conformational changes and their effects on photophysics in different environments will be discussed. In Chapter 1, the basic principles to understand this thesis will be reviewed, including the processes of absorption and emission, exciton migration, the Langmuir-Blodgett technique, and interfacial phenomena. In Chapter 2, the conformational control and alignment of conjugated polymers at the air-water interface and how this alignment of polymers can lead to new emissive aggregates will be presented. The emission has the characteristics of excimers with the improved fluorescence quantum yields. The transfer of the aligned aggregates to glass substrates is attempted and these excimer films undergo reorganization upon exposure to solvent vapors, which triggers the fluorescence color change from yellow to cyan, leading to fluorescence-based chemical sensors. In Chapter 3, exciton migration to low-energy emissive traps at amphiphilic interfaces will be discussed. This chapter will deliver the design of interfaces and how the exciton migration can occur at the air-water interface and the hydrocarbon-water interface in lyotropic liquid crystals. To expand this interfacial exciton migration to more generalizable interfaces, Chapter 4 will show the fabrication of oil-in-water emulsions and how exciton migration in oil-in-water emulsion can produce distinct fluorescences between solution and interfaces. Chapter 5 will discuss the structural variations of novel functional conjugated polymers and how substituents can change the conformation of the polymer backbones. Additionally, how this conformational change affects the electronic and optical properties of polymers will be examined. / by Byungjin Koo. / Ph. D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (p. 71-74). / A business model was created in order to explore the commercial application of a bi-layer bone-ligament scaffold to the treatment of torn anterior cruciate ligaments (ACL) requiring replacement. The two main keys in producing the bone scaffold are triple co-precipitation of type-I collagen, chodroitin-6-sulphate, and calcium phosphate minerals and the use of lyophilization to create a network where all the materials are homogeneously dispersed and present in significant amounts. This process allows the creation of a porous network whose physical characteristics, mechanical properties, and material content can all be changed to create a scaffold that closely mimics natural bone. A collagen and chondroitin-6-sulphate scaffold is used for ligament regeneration. The ACL replacement market was chosen because it is one of the most commonly surgically repaired ligaments in the body and because all of the current treatments have drawbacks. / (cont.) The exercise of creating a business model made it clear that the commercial potential of starting a company that focused on marketing a direct ACL replacement scaffold would most likely not be successful mainly because surgeons would hesitate to use this product over current methods that are satisfactory and it would be difficult to separate our product from other newer methods which all boast similar advantages over current treatment options. However, the commercial potential of using the technology to create a scaffold for graft site morbidity in certain ACL replacement surgeries is large because there is no competition, and the implantation procedure for the surgeon would be simple. / by Jessica C. Li. / M.Eng.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (p. 49). / This paper explores a possible design for a CMOS compatible, athermal, optical waveguide. The design explored is a slot waveguide with light guided in the low index material. A design paradigm is proposed which shows the relationship between cross-sectional parameters and their impact on both the effective index of refraction and the thermo-optic coefficient of the device. Two materials choices were explored to serve as the low index material, poly(ether imide) (PI) and poly(methyl methacrylate) (PMMA). The slot waveguide with PI as the low index material had a simulated, device thermo-optic coefficient of -8.5 x 10-4K-1, and the slot waveguide with PMMA as the low index material had a simulated, device thermo-optic coefficient of 1.7 x 10-5K-1. / by Luis Enrique Fernandez. / S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 80-86). / The development of materials with biomimetic mechanical and biological properties is of great interest for regenerative medicine applications. Hydrogels are a promising class of biomaterials due to several advantages, however, the mechanical weakness remains a critical challenge for applications as tissue scaffolds. Particularly, scaffolds for load-bearing tissues such as cartilage and bone need to have great strength to keep their integrity after implantation. This thesis focused on the development of cell-laden hydrogels that have high mechanical strength and good biological properties. The first work of the thesis was to synthesize a biodegradable hydrogel, poly(glucose malate)methacrylate (PGMma), from two natural monomers glucose and malic acid. The PGMma hydrogels were cell-adhesive, and mechanically tunable by altering the formulation. In the second work, double-network (DN) hydrogels were prepared from two biomacromolecules, gellan gum and gelatin. The DN hydrogels prepared exhibited much higher strength than traditional hydrogels, the maximal strength being 6.9MPa. By using a cell-compatible two-step photocrosslinking process, it was also possible to encapsulate cells with high viability. Further research into the materials as tissue scaffolds showed that the DN hydrogels weakened when they were prepared at cell-compatible conditions, and stronger cell-hydrogel interaction is needed to improve the function of the encapsulated cells. Therefore in the last work, microgel-reinforced (MR) hydrogels that have better mechanical strength and biological properties in comparison to DN hydrogels were prepared by embedding stiff GG microgels into soft and ductile gelatin hydrogels. The MR hydrogels exhibited higher strength than the DN hydrogels and the gelatin hydrogels. The cells encapsulated in MR hydrogels showed high metabolic activity and high level of osteogenic behaviors similar to the cells encapsulated in gelatin hydrogels, which was not the case for DN hydrogels. The MR hydrogels, the final product of all these works could be potentially useful for load-bearing tissue scaffolds. / by Hyeongho Shin. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 117-133). / Grain boundaries in polycrystals form a complex interconnected network of intercrystalline interfaces. The crystallographic character of individual grain boundaries and the network structure of the grain boundary ensemble have been experimentally observed to have a strong influence on many materials properties. This observation suggests that if we could control the types of grain boundaries present in a polycrystal and their spatial arrangement then it would be possible to dramatically improve the properties of polycrystalline materials and tailor them to specific engineering applications. However, there are a number of major obstacles that have, until now, precluded the realization of this opportunity: (1) methods capable of simultaneously quantifying the crystallographic and topological structure of grain boundary networks do not exist; (2) theoretical models relating grain boundary network structure to physical properties have not yet been developed; and, consequently, (3) there are no techniques to quantitatively identify grain boundary network structures that would be beneficial for a given property. In this thesis I address these obstacles by first developing a new statistical description of grain boundary network structure called the triple junction distribution function (TJDF), which encodes both crystallographic and topological information. I establish new results regarding the physical symmetries of triple junctions and find a relationship between crystallographic texture and grain boundary network structure. I then use the TJDF to develop a model for the effective diffusivity of a grain boundary network. Finally, using the relationship between texture and grain boundary network structure that I develop, I describe a method for texture-mediated grain boundary network design. This process permits the theoretical design of grain boundary networks with properties tailored to a given engineering application and is applicable to any polycrystalline material. I demonstrate the potential of this technique by application to a specific design problem involving competing design objectives for mechanical and kinetic materials properties. The result is a designed microstructure that is predicted to outperform an isotropic polycrystal by seven orders of magnitude. / by Oliver Kent Johnson. / Ph. D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / "September 2006." / Includes bibliographical references (leaves 66-70). / In order to overcome the superparamagnetism in thin film magnetic recording media, a novel magnetic medium, called patterned medium, is studied here as a potential candidate for the future hard disk storage application. Within the patterned medium, one bit is stored in one magnetic unit, which has to be prepared "to-precision" along the track at uniform periodicity. A variety of magnetic recording media will be introduced and compared first. Detailed discussion will be focused on the potential techniques for patterned media fabrication. IP environment, market competition and business models will be given at the end. / by Guhua Yao. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (leaves 119-131). / Nanocrystalline materials have been studied extensively over the past two decades because of their useful and interesting physical properties. In most cases, these properties derive from the fine characteristic length scale of nanocrystalline structures and are superior to those realized in traditional coarse-grained materials. A fundamental challenge, however, involves the synthesis of high-quality specimens, which represent a classical far-from-equilibrium state due to the large presence of high-energy interfaces. Alloying presents a possibility to reduce this energy penalty through solute segregation and thermodynamic stabilization of the grain boundaries. The present work exploits this concept in the nanocrystalline Ni-W system. Atomistic computer simulations are used to evaluate the potential for stabilization based on the equilibrium solute distribution and energetics of nanocrystalline structures. Following this, a synthesis technique based on electrodeposition is developed where precise control over the alloying addition correlates with precise control over grain size. / (cont.) Investigations of the microstructure involving techniques such as transmission electron microscopy, x-ray diffraction, and atom probe tomography provide a detailed view of the structure and solute distribution in these materials, and the results are compared with atomistic simulations and thermodynamic models of nanostructure stabilization. The elevated temperature behavior of experimental specimens is also evaluated and compared to analytical models of microstructural evolution, showing that grain boundary relaxation is an important mechanism for the finest nanocrystalline grain sizes, having a significant influence on properties. With a new degree of control over the nanostructure, Ni-W alloys are produced over a broad range of grain sizes to investigate hardness trends and the breakdown of a classical scaling law in the nanocrystalline regime. An extension of the synthesis technique is also demonstrated for the production of functionally graded and nano-scale composite materials. Potential benefits of the methods developed in this work are highlighted for both fundamental scientific investigations and practical applications. / by Andrew J. Detor. / Ph.D.