Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, June 2015. / Cataloged from PDF version of thesis. "May 2015." / Includes bibliographical references (pages 44-46). / Developmental research and characterization was conducted on novel biomaterials for a larger project of product and architectural scale digital fabrication using natural bioplastics and hierarchical computational design carried out by the Mediated Matter team, led by Laia Mogas-Soldevila and Jorge Duro-Royo. Chitosan and alginate (among other natural polymers) are processed from shellfish waste and algae, respectively, and highly viscous solutions are extruded as a layer-by-layer printing material which dries into a solid, single material product with spatially variable functionality. Additional solid materials are added including cellulose microfibers and kaolinite platelets as volumetric aggregates, strengthening or stiffening aggregates, and as modes for directional properties. All materials used for aggregates, like that of the hydrogel matrices, were naturally sourced and recyclable. These composite materials were analyzed through microscopy and mechanical testing to begin to determine their agency in the aforementioned purposes. The most promising materials were selected and then discussed at length in an attempt to understand the factors behind ease of production, scalability, and potential for optimization, and as the research continues, they will be tested in the digital fabrication platform at the installation scale. / by Daniel Lizardo. / S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (p. 180-188). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Monolithic optoelectronic integration on silicon-based integrated circuits has to date been limited to date by the large material differences between silicon (Si) and the direct-bandgap GaAs compounds from which optoelectronic components are fabricated. Graded Ge/GeSi buffer layers grown on standard Si substrates have been shown to produce near-lattice matched virtual substrates for GaAs integration on Si. This study investigated the crystal growth conditions and device fabrication techniques necessary for successful GaAs-based laser integration on Ge/GeSi buffer layers on Si substrates. The nucleation conditions for GaAs on Ge/GeSi/Si substrates have been comprehensively examined. High-temperature ( 2 700⁰ C) initiation with properly chosen V/III gas flow ratio yields high-quality, stacking fault-free GaAs films on Ge/GeSi/Si substrates, but also encourages the vapor-phase transport of Ge from the substrate into the active regions of integrated GaAs devices. A new two-step GaAs nucleation process was developed that enabled the first demonstration of high-quality Ge-free GaAs light-emitting diodes on Ge/GeSi/Si substrates. The large thermal expansion mismatch between Si, Ge, and GaAs introduces additional strain to integrated device layers on Ge/GeSi/Si substrates grown at high temperatures. This study conclusively demonstrated the link between thermal mismatch strain and increased misfit dislocation formation in InxGa(lx)As/GaAs quantum well structures integrated on Ge/GeSi/Si substrates. / (cont.) The thermal mismatch strain was successfully countered by the introduction of compressive InGaAs graded buffer layers above the Ge/GeSi/Si substrate surface, and strain-free GaAs layers at growth temperatures suitable for laser integration have been demonstrated. The integration of edge-emitting heterostructure lasers on Ge/GeSi/Si substrates introduces additional waveguide design issues addressed by this study. Low-index Alo.6Gao.4As cladding layers, along with a graded-index separate confinement heterostructure, were introduced to reduce photon losses. Interfacial roughness transmitted from the Ge/GeSi/Si substrate was reduced with a pre-growth chemical-mechanical polishing step, and smooth mirror facets on integrated devices were fabricated by cleaving thinned lasers parallel to the substrate offcut direction. Continuously operating edge-emitting GaAs/AlGaAs quantum well lasers on Ge/GeSi/Si substrates were demonstrated at room temperature with an operating wavelength of 858 nm. Series resistance heating in early devices was reduced by the introduction of a top-contact geometry and optimized cladding layer structure, and improved laser diodes had a differential quantum efficiency of 40%, a threshold current density of 269 A/cm2, and a characteristic temperature of 129 K. Identical devices fabricated on GaAs substrates had similar performance characteristics. Lasers on Ge/GeSi/Si substrates fell below threshold after 4 hours of continuous operation-a dramatic improvement over early measured lifetimes of less than 20 minutes ... / by Michael Edward Groenert. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (leaves 97-114). / This thesis applies the theory of lattice dynamics towards two applications: vibrational entropy in alloys and dielectric absorption in oxides. Vibrational entropies between ordered-L12 and disordered phases in the Au3Cu, Cu3Au, Cu3Pd, Pd3Cu, Cu3Pt, Au3Pd, and Pd3Au systems are calculated. This study was done using first-principles energy calculations and the supercell method. Calculated values of ASʻrder-disorder ranged between -0.05 - 0.07 kB. Length-dependent transferable force constants are used to predict vibrational entropies in the Au-Cu, Au-Pd, and Cu-Pd systems. The stiffness of these force constants is obtained from a function that depends on bond length; this function is determined by fitting polynomials to a small set of calculated force constants. Once a function that describes force constant stiffness vs. bond length is determined for a particular pair type, the function can be transferred between different configurations and chemical systems to construct force constants for an arbitrary structure. These transferable force constants are shown to accurately predict vibrational entropies of L12-ordered and disordered phases in Cu3Au, Au3Pd, Pd3Au, Cu3Pd, and Pd3Au. The dielectric absorption at microwave frequencies in binary oxides is calculated within an empirical Buckingham energy model. For MgO, the calculated dielectric losses at room temperature agrees relatively well with experiments, and the temperature dependence is in qualitative agreement. We also model systems to gain insight into the effects of different cation sizes and masses. We explain our results in terms of anharmonic forces, atomic masses, and phonon dispersion curves. / by Eric John Wu. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 43-46). / The skin is an ideal organ for the safe and convenient delivery of vaccines, small molecules, and other biologics. Members of the Irvine and Hammond groups have developed a polyelectrolyte multilayer thin film-coated microneedle platform that can achieve simultaneous DNA and nanoparticle delivery. This delivery platform has the advantage of direct delivery of DNA or polymer nanoparticles to immune-active cells at the interface between the dermis and epidermis, enhancing uptake of the delivered cargo by resident immune cells. Ideal for the delivery of DNA vaccines, this platform aims to bridge the gap in the lack of efficient delivery platforms hampering the effectiveness of DNA vaccines. The ability to co-deliver polymer nanoparticles can serve as a conduit for delivering immune stimulating adjuvants or other drugs for therapeutic applications. An overview of current vaccine and delivery system research is presented. Market factors for the commercialization of the polyelectrolyte multilayer thin film-coated microneedle delivery platform are considered along with the risk factors in bringing this invention to market. An assessment of the intellectual property surrounding the platform is performed and a preliminary market entry strategy is developed for minimizing the risks commercialization. / by Peter W. Fung. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaves 88-89). / Indium is a minor but very valuable metal. Decreasing supplies of indium from refining and increasing demands from LCD, low-temperature soldering and compound semiconductors have stimulated the indium price increase dramatically. Traditionally, indium is refined as a by-product of zinc refining. However, this type of indium extraction method is expected to last for the next 10-20 years and this opens a window to extract indium from other ores, especially from tin ore. Interestingly, extraction of indium from tin circuit can be considered as the major business and the pure tin metal is just considered as a by-product due to high indium price and low tin price. Relatively high estimated concentration levels of indium in Malaysian tin ore means that Malaysian tin refiners can withstand high degree of fluctuation of price in the free market due to hedge buying and speculation. Note that the business model for global indium market is duopoly or oligopoly but obviously not monopoly. Between duopoly and oligopoly, the most probable model is oligopoly. Thus, the potential competitors and partnership are also discussed here. Besides, LCD and low-temperature soldering and compound semiconductor are three main applications of indium which affect the indium price. / (cont.) The unique properties of indium for three major applications will be discussed from the material engineering prospective. A cost modeling spreadsheet has been built to estimate the cost of production of indium from tin and zinc ores under different conditions. Hence, the decision tree has been drawn based on the conditions of different indium concentration level and price. From the discussions on the sources, market, applications of indium, the future prospects for indium can be concluded. The outcomes of this work can be extended to cases outside of the geographical boundary of Malaysia by gathering some relevant information. / by Foo Nun Yong. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. / Includes bibliographical references (p. 87-93). / Controlled-release drug delivery systems are capable of treating debilitating diseases, including cancer. Brain cancer, in particular glioblastoma multiforme (GBM), is an extremely invasive cancer with a dismal prognosis. The use of drugs capable of crossing the blood-brain barrier has shown modest prolongation in patient survival, but not without unsatisfactory systemic, dose-limiting toxicity. Localized delivery of potent chemotherapeutics aims to lower systemic toxicity while increasing drug concentrations directly to the tumor site. I have developed implantable drug delivery microcapsule devices for the localized delivery of temozolomide and for treatment of glioblastoma multiforme in this work. I have been able to modulate the drug release profiles from these microcapsules based on the physical chemistry of the drug and the dimensions of the release orifices in these devices. Experimental in vitro studies were performed in order to test the function, reliability, and drug release kinetics of the devices. The experimental release curves showed mass flow rates of 36 ug/hr for single-orifice devices and an 88 ug/hr mass flow rate for multiple-orifice devices loaded with temozolomide. Intracranial temozolomide-filled microcapsules were tested in a rodent 9L glioma model. Outcomes were animal survival and immunohistochemical analysis of tissue for evidence of DNA strand breaks via terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Results showed that localized delivery of chemotherapeutics from microcapsule devices is capable of prolonging animal survival and may offer an alternative to the harsh side-effects and low response rates inherent to systemic drug administration in GBM patients. / by Alexander Wesley Scott. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / 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 (pages 181-198). / Chalcogenide glasses (ChGs) are amorphous compounds containing the chalcogen elements (S, Se, Te) and exhibit wide infrared transparency windows. They are easy to synthesize in bulk and thin film forms and their compositional flexibility allows tuning of optical properties such as refractive index making them ideal for infrared photonics. We have studied the material attenuation in ChGs that arises due to the presence of impurities in the raw materials and established UV photolithography-based process flows that enable fabrication of chalcogenide glass waveguides and microresonators for near- and mid-IR wavelength ranges. Waveguides and optical resonators are key microphotonic elements for many on-chip applications such as telecommunications and chemical sensing. In this thesis, we show that scattering losses dominate in our ChG microphotonic devices while material attenuation from impurities is low. We demonstrate resonators coated with nanoporous polymers to improve their selectivity against target analytes for sensing applications. We exploit the photosensitivity of As2S3 glass to build silicon-based tunable photonic devices that offer post-fabrication tuning to optimize performance. Resonators also serve as a test platform for studying the effects of radiation on silicon and chalcogenide materials systems. Further, we propose new mid-IR microphotonic device designs using ChG materials and the challenges associated with measuring mid-IR devices along with solutions to address them. We employ input-to-output offsets, standard tapered waveguides, and a fiber collimator to improve mid-IR measurements and demonstrate transparent ChG waveguides with losses as low as 2.5 dB/cm. Finally, we propose a novel design that integrates PbTe detectors with ChG waveguides for on-chip mid-IR detection. Our simulations show that the use of a low-index spacer layer leads to a well-distributed field along the width of the detector due to a reduction in the effective index of the structure. We develop a fabrication process for waveguide-integrated detector designs and fabricate prototype structures that exhibit attenuation at telecom and mid-IR wavelengths. Such an integrated sensor design will enable the creation and deployment of low-cost remote sensor arrays with small footprints, and ultimately lead to "lab-on-a-chip" structures. / by Vivek Singh. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1993. / Includes bibliographical references (leaves 186-196). / by Syun-Ming Jang. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references (leaf 41). / In a world where the miniaturization and the portability of electronic devices is king, batteries play an ever-increasingly important role. They are vital components in many consumer electronics such as cell phones and PDAs, in medical devices, and in novel applications, such as unmanned vehicles and hybrids. As the power demands of these devices increases, battery performance must improve accordingly. This thesis is an introductory investigation into the electrochemical properties of a promising new battery cathode material: lithium vanadium phosphate (Li3V2(PO4)3) (LVP). Studies of other members of the phospho-olivine family, which LVP is a part of, indicate that the olivines have high lithium diffusivity but low electronic conductivity. LVP is part of the phosphor- olivine family, which traditionally has been shown to have high lithium diffusivity but low electronic conductivity. LVP was synthesized via a solid-state reaction and cast into composite cathodes. (90/5/5 ratio of LVP, Super P Carbon, and PVDF.) These composite cathodes were used in lithium anode, LiPF6 liquid electrolyte, Swage-type cells that were galvanostatically cycled from 3.OV to 4.2V and from 3.4V to 4.8V at C/20 rates. Electrochemical impedance spectroscopy was carried out on an LVP / liquid electrolyte / LVP cells from 0.01Hz to 1MHz. Finally, temperature conductivity measurements were taken from a die-pressed LVP bar. The results of the experimentation indicate that LVP has much promise as a new battery cathode material, but there are still a number of concerns to address. / (cont.) LVP has a higher operating voltage (4.78V) than the current Li-ion battery standard (3.6V), but there are issues with becoming amorphous, cycleability, and active material accessibility. From the EIS data, passivating films on the surface of the LVP cathode do not seem to be a factor in limiting performance. The conductivity data gives a higher than expected conductivity (4.62* 10-4 S/cm). / by Chwan Hai H. Hsiung. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Block coopolymers(BCP) have become of interest in the pursuit novel methods of nanolithography. Their ability to self-assembly into periodic geometries with nanoscale feature sizes makes them attractive as etching masks and templating materials for microelectronics and nanodevices. BCP provide a scalable and low-cost method that is compatible with existing semiconductor fabrication technologies. Though various studies have looked at several combinations of block copolymers we focus on the use of solvent annealing as a method to tune the morphology of PS-b-PFS and PS-b- PFS-b-PS block copolymers. These polymers have shown promise as precursors to a variety of materials and in particular this combination of block copolymers is attractive because we have at our dispossible etching methods with a high selectivity between these two polymers. / by Juanml Carlos Ybarra. / S.B.