Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / In title on t.p., double-underscored "p" appears as subscript. / Includes bibliographical references (p. 17). / An amorphous Ni-W alloy matrix was incorporated with W particulate through two types of electrodeposition. The plating bath for the electrodeposition contained nickel sulfate, sodium tungstate, sodium citrate, ammonium chloride, and a variable amount of 1 gm tungsten particulate ranging in concentration from about 5g/L to 15g/L.The first method was electrodeposition with only moderate stirring of the plating bath. The second method had a forced flow of solution on the substrate via a pump. The results showed incorporation in both methods, but the flowed method resulted in more incorporation. The amount of incorporation increased with the amount of particulate in solution until a limit that lies somewhere between 10g/L and 15g/L of particle concentration. At this point, the incorporation became hindered by the excess amount of particulate in solution. It was also shown that an increase of particulate concentration caused more voids in the material, and the flowed method caused less voids than the normal method. A tapering in the amount of incorporation between the substrate side and the surface side of the deposit was observed; the area close to the substrate had a higher incorporation than the area near the surface. Hardness testing showed mechanical property differences through the thickness of the deposit with the area near the substrate being softer than the area near the surface. Compression testing showed an increase in the strain and a decrease in the stress before failure, suggesting an improvement in ductility. / by Donald R. Jenket, II. / S.B.

Thesis: Ph. D. in Electronic Materials, Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016. / Cataloged from PDF version of thesis. "June 2016." / Includes bibliographical references (pages 163-189). / Germanium and silicon are ideal candidate materials for use as anodes in microbatteries since both are well established in microelectronics and reversibly store large amounts of lithium. However, implementation of either material has been limited by poor cyclability due to the large volumetric changes occurring during cycling. To better understand the mechanical stresses associated with these changes, in situ stress curvature measurements on thin film electrodes were conducted. The effect of the initial electrode structure on electrochemistry and mechanics was investigated by post-deposition annealing of hydrogenated silicon thin films. Compared to as-deposited films, annealed electrodes lithiated at lower potentials during the first cycle and could form Li₁₅Si₄ . Moreover, annealed electrodes underwent large structural changes in the first two cycles compared to as-deposited films, with polycrystalline silicon films showing the largest change. The changes in electrochemistry and mechanical behavior were attributed to the loss of hydrogen and densification of the film. In addition to silicon, stress evolution in lithium-germanium films was also investigated and stresses were found to be roughly one-third those of silicon. Rate testing revealed that germanium electrodes exhibit a smaller loss in capacity at high cycling rates than silicon. Cycling below 100mV resulted in crystalline Li₁₅Ge₄ formation which appeared as a tensile peak in the stress-capacity plots. Extended cycling of uncoated electrodes resulted in an irreversible reduction of stress but no loss in capacity, an outcome associated with the thin film fracturing while remaining adherent to the substrate. The reduced plastic flow stresses observed in lithium-germanium and their weak dependence on cycling rate may explain why germanium offers improved cyclability and reduced rate sensitivity compared to silicon. In addition to uncoated electrodes, lithium phosphorous oxynitride (LiPON) coated electrodes were also examined. By coating silicon and germanium thin films with LiPON, mechanical degradation (i.e. crack and island formation) and chemical degradation (i.e. reduction in solid electrolyte interphase formation) processes were strongly suppressed. The improvement in mechanical and electrochemical stability enabled more detailed studies of lithium-silicon and lithium-germanium alloying, including the kinetics of phase formation and dissolution (e.g. of Li₁₅Si₄ and Li₁₅Ge₄). / by Ahmed Al-Obeidi. / Ph. D. in Electronic Materials

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (leaves 86-88). / by Rita Gupta. / M.S.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, June 2010. / "May 2009." Page 47 blank. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 28-29). / The present study investigates the naturally occurring interface between bone and tendon using scanning electron microscopy. The micrographs revealed a cartilaginous layer, 100 to 400 [mu]m thick apposing bone, that contained cells varying in size and shape as a function of their location in this cartilaginous layer. Further investigation is required to conclude whether these cells are undergoing further differentiation during development of this graded layer. This study found the interface between bone and the cartilaginous layer to be interdigitated, which may explain why injuries at the bone-tendon interface are comparatively rare. Also, the cartilaginous layer was revealed to be substantially mineralized. A somewhat higher concentration of calcium and phosphorus was observed near the interface with the apposing bone that gradually diminished into the cartilaginous layer. These findings support the four zone description of the bone-tendon interface established by others using histological methods. However, further research is suggested to resolve other questions about the observed sub-micrometer morphologies of the bone-tendon interface. / by Willie Mae Reese. / S.B.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1989. / Includes bibliographical references (leaves 222-227). / by Brian William Sheldon. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / Organic optoelectronic devices are appealing for low-performance applications on very low cost and flexible substrates, due to their low-temperature processing. However, it still remains a challenge to develop suitable fabrication techniques to pattern organic thin films on low-cost, large-area substrates. The two techniques used commercially are inkjet printing of polymers, which limits the morphology and performance of devices, and shadow-masking of vacuum sublimation for small molecule materials, which is not scalable to large-area substrates. In this thesis, we investigate the use of MicroElectroMechanical Systems (MEMS) to provide new ways of patterning organic materials deposited by an evaporative process. We present the design, fabrication, modeling and characterization of two generations of micromachined printheads developed to expand the possibilities of printing of organic optoelectronics. The design and fabrication of a compact electrostatic actuator enabling the first generation of printhead is first presented. It is then used to actuate a microshutter, and modulate the flux of evaporated organic materials in a vacuum chamber. We prove the feasibility of evaporative printing of small molecular organic materials at resolutions of the order of 800 dpi with high-throughput on large areas. / (cont.) We demonstrate that MicroElectroMechanical Systems can be used to pattern organic thin films in a way that combines the advantages of ink-jet printing and thermal evaporation. We also present the design and fabrication of a microevaporator for molecular organics, and show its suitability for the ambient printing of devices on low-cost substrates, without the limitations of ink-jet printing due to the drying of solvent on the substrate. We demonstrate the feasibility of using an array of pores in a membrane to capture molecular organic materials delivered by a solvent and an integrated microheater to release them by evaporation onto a substrate. This second generation of printhead enables evaporative printing of organic materials at ambient pressure. This thesis also provides a study of the failure of thin film platinum heaters used in the second generation printheads. We study the effect of current level, temperature, presence of a membrane, anneal conditions, and adhesion layer thickness on the failure of the heaters. / by Valérie Leblanc. / Ph.D.

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 (p. 211-222). / Gastropod mollusk nacre tablets and Polypterus senegalus armored scales share common features such as a very complex and changing structure spanning several length scales. The smallest building blocks are single crystals, have dimensions of a from tens of nanometers to several microns and are intimately blended with an organic glue present within pores or between the crystallites. In particular, our results strongly suggest that nacre tablets possess nanoscale porosity in the form of elongated tubules that may contain the intratablet macromolecules. Their unique structure allows these materials deform in a ductile way at the nanoscale, with no cracks observed, and to confine deformation at the microscale so as to impede crack propagation. Gradient in the mechanical properties are ubiquitous at both the microscale (scales) and the nanoscale (nacre tablets), preventing stress concentration and enhancing strain distribution. The armored scales thus exhibit a unique spatial functional form of mechanical properties with regions of differing levels of gradation within and between material layers, as well as layer with an undetectable gradation. Though highly mineralized, these biomaterials also exhibit greater local heterogeneity in their mechanical properties compared to pure minerals. Materials layers have distinct morphology and mechanical properties depending on their role (resistance to abrasion for harder outer layers, resistance to fracture for tougher inner layers) and their interface are reinforced (by anchored organic fiber ligaments and corrugated interfaces that maximize contact surface., preventing propagation of cracks both through and along the interfaces. / (cont.) The heterogeneity in size and shape of the crystallites and the pores, as well as the variation in the composition (mineral / organic, crystalline amorphous) are likely responsible for the desirable variations of mechanical properties as observed in these biocomposites at the smallest length scales, resulting in more spatially distributed strains and greater energy dissipation. / Benjamin J.F. Bruet. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references. / We propose several methodologies to study and optimize the electromagnetic process for Electromagnetic Forming (EMF) and Welding (EMW), thereby lowering the necessary process energy up to a factor of three and lengthening the life-time of EMW compression coils. We present a new theoretical approach to calculate a so-called critical kinetic energy to achieve a proper EMW joint, which is related to the volume of the accelerated mass and the Vicker's Hardness of the material. Using this novel approach, welding windows for several materials are presented. Studying the circuit theory, the current discharge pulse can be optimized to the needs of the EMW process, when opting for a critically damped RLC circuit. We present MultiSIM and MATLAB models that prove the proposed optimization and reflect the experimental EMW setup and parameters. Using the models, unknown parameters, such as machine inductance and resistance can be extrapolated for EMF and EMW machinery. Furthermore, the MATLAB model can calculate the optimal gap between the outer and inner workpiece for the outer workpiece to reach the maximum velocity at impact. Good correlation was found with regards to the High-Speed Videography used to study the EMF process in further detail measuring velocities between 50 m/s and 100 m/s. Studying the mechanical properties of the outer workpiece we propose an EMF-EMW setup that would decrease the strength of the outer workpiece by introducing a controlled amount of wrinkles through an EMF step with a mandrel inside the outer workpiece, followed by a lower critical energy EMW step. / (cont.) Through a failure study, accompanied by a metallurgical analysis, of an Aluminum Bronze Bitter coil we present a materials selection of other possible coil materials, as well as a new method called Electromagnetic Fatigue (EMFA) Analysis to study the crack initiation and propagation in electromagnetic high-current applications. Finally, through two sets of EMW experiments tubular lap joints that were stronger than the base material could be produced and the EMW process parameters of increased cleanliness, gap, wall thickness and a lower taper angle, for the case of our setup, showed to increase the final joint strength. / by Daniel G. Pressl. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1988. / Vita. / Includes bibliographical references. / by Chune-Ching Young. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 111-131). / Degradable polymeric materials provide opportunities for the development of improved vaccines and immunotherapies by acting as platforms that facilitate the delivery of molecules to appropriate tissue and cellular locations to achieve therapeutic outcomes. To this end, we have designed and characterized nano-films and particles employing a hydrolytically degradable polymer for the delivery of vaccine antigens and immunotherapeutics. We first describe protein- and oligonucleotide-loaded layer-by-layer (LbL)-assembled multilayer thin films constructed based on electrostatic interactions between a cationic poly(p-amino ester) (PBAE, denoted Poly-1) with a model protein antigen, ovalbumin (OVA), and/or immunostimulatory CpG oligonucleotides for transcutaneous delivery. Linear growth of nanoscale Poly-1/OVA bilayers was observed. Dried OVA protein-loaded films rapidly deconstructed when rehydrated in saline solutions, releasing OVA as non-aggregated/non-degraded protein, suggesting that the structure of biomolecules integrated into these multilayer films are preserved during release. Using confocal fluorescence microscopy and an in vivo murine ear skin model, we demonstrated delivery of OVA from LbL films into barrier-disrupted skin, uptake of the protein by skin-resident antigen-presenting cells (Langerhans cells), and transport of the antigen to the skin-draining lymph nodes. Dual incorporation of OVA and CpG oligonucleotides into the nanolayers of LbL films enabled dual release of the antigen and adjuvant with distinct kinetics for each component; OVA was rapidly released while CpG was released in a relatively sustained manner. Applied as skin patches, these films delivered OVA and CpG to Langerhans Cells in the skin. To our knowledge, this is the first demonstration of LbL films applied for the delivery of biomolecules into skin. This approach provides a new route for storage of vaccines and other immunotherapeutics in a solid-state thin film for subsequent delivery into the immunologically-rich milieu of the skin. In parallel, we also developed biodegradable core-shell nanoparticles with a PBAE core enveloped by a phospholipid bilayer shell for cytosolic delivery, with a view towards delivery of messenger RNA (mRNA)-based vaccines. The pH-responsive PBAE component was chosen to promote endosome disruption, while the lipid surface layer was selected to minimize toxicity of the polycation core. mRNA was efficiently adsorbed via electrostatic interactions onto the surface of these net positively charged nanoparticles. In vitro, mRNA-loaded particle uptake by dendritic cells led to mRNA delivery into the cytosol with low cytotoxicity, followed by translation of the encoded protein in these difficult-to-transfect cells at a frequency of -30%. Particles also promoted cytosolic uptake of co-delivered anti-tumor toxins in tumor cells resulting in synergistic killing, demonstrating potential for cancer therapy. In vivo, particles loaded with mRNA administered intranasally or intratracheally in mice led to the enhanced expression of the reporter protein luciferase compared to naked mRNA. This system may thus be promising for noninvasive delivery of mRNA-based vaccines. / by Xingfang Su. / Ph.D.