Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Vita. / Bibliography: leaves 183-185. / by Lee Arnold Silverman. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 89-92. / by Yukio Kuroda. / M.S.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 37-38). / A three-dimensional finite element model was created to analyze the mechanical interactions between the various substructures within the human eye. During certain activities, mechanical interactions may lead to a resultant distribution of stresses within the eye that may in turn produce various retinal diseases. The entire eye was modeled using dynamic finite element analysis to incorporate the mechanical effects of all of the substructures on the retina. A set of mechanical properties for each substructure was determined from previously published studies. Saccadic motion was modeled in the normal human eye to determine the location and magnitude of peak stresses in the retina and optic nerve head during initial loading. After 0.6125 ms, stresses as high as 5.4 x 10⁷ Pa were reached. The peak stresses occurred in the portions of the retina and the optic nerve head close to the boundary between these two substructures. / by Venetia Chan. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 97-98. / by Se-Yong Oh. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 71-75. / by Peter Gerard Schunemann. / M.S.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / M.I.T. copy lacks leaf 40. Vita. / Bibliography: leaves 202-206. / by Timothy Van Johnson. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographies. / by G. William Tasker. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 114-116. / by Yongun Lee. / M.S.

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 142-149). / III-V semiconducting nanostructures present a promising platform for the realization of advanced optoelectronic devices due to their superior intrinsic materials properties including direct band gap energies that span the visible light spectrum and high carrier mobilities. Additionally, the inherently high surface-to-volume ratio of nanostructures allows for the efficient relaxation of stress enabling the realization of defect free heterostructures between highly mismatched materials. As a result, nanostructures are being investigated as a route towards the direct integration of III-V materials on silicon substrates and as platforms for the fabrication of novel heterostructures not achievable in a thin film geometry. Due to their small size, however, many of the methods used to calculate stress and strain in 2D bulk systems are no longer valid as free surface effects allow for relaxation creating more complicated stress and strain fields. These inhomogeneous strain fields could have significant impacts on both device fabrication and operation. Therefore, it will be vital to develop techniques that can accurately predict and measure the stress and strain in individual nanostructures. In this thesis, we demonstrate how the combination of advanced transmission electron microscopy (TEM) and continuum modeling techniques can provide a quantitative understanding of the complex strain fields in nanostructures with high spatial resolutions. Using techniques such as convergent beam electron diffraction, nanobeam electron diffraction, and geometric phase analysis we quantify and map the strain fields in top-down fabricated InAlN/GaN high electron mobility transistor structures and GaAs/GaAsP core-shell nanowires grown by a particle-mediated vapor-liquid-solid mechanism. By comparing our experimental results to strain fields calculated by finite element analysis, we show that these techniques can provide quantitative strain information with spatial resolutions on the order of 1 nm. Our results highlight the importance of nanoscale characterization of strain in nanostructures and point to future opportunities for strain engineering to precisely tune the behavior and operation of these highly relevant structures. / by Eric James Jones. / Ph. D.

Carbon nanotubes (CNTs) are known to exhibit outstanding mechanical, electrical, thermal, and coupled electromechanical properties. CNTs can be employed towards the design of an innovative strain sensor with enhanced multifunctionality due to their load carrying capability, sensing properties, high thermal stability, and outstanding electrical conductivity. All these features indicate the prospect to use CNTs in a very wide range of applications, for instance, highly sensitive resistance-type strain/force sensors, wearable electronics, flexible microelectronic devices, robotic skins, and in-situ structural health monitoring. CNT-based strain sensors can be divided into two different types, the individual CNT- based strain sensors and the ensemble CNT-based strain sensors e.g. CNT/polymer nanocomposites and CNT thin films. In contrast, to individual CNT-based strain sensors with very high gauge factor (GF) e.g. ~3000, the ensemble CNT-based strain sensors exhibit very low GFs e.g. for a SWCNT thin film strain sensor, GF is ~1. This research discusses the mechanisms and the optimizing principles of a SWCNT thin film piezoresistive sensor, and provide an experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like alignment, network density, bundle diameter (effective tunneling area), and SWCNT length is studied. The tunneling effect is significant in SWCNT thin films showing higher degrees of alignment, due to greater inter-tube distances between the SWCNTs as compared to random oriented SWCNT thin films. It can be concluded that SWCNT thin films featuring higher alignment would have a higher GF. On the other hand, the use of sparse network density which comprises of aligned SWCNTs can as well intensify the tunneling effect which can result to a further increase in the GF. In addition, it is well-known that percolation is greatly influenced by the geometry of the nanotubes e.g. bundle diameter and length. A study on the influence of bundle diameter of SWCNTs on the piezoresistivity behavior of mechanically drawn SWCNT thin films showed the best performance with an improved GF of ~10 when compared to the randomly oriented SWCNT thin films with GF of ~1. The non-linear piezoresistivity of the mechanically drawn SWCNT thin films is considered to be the main mechanism behind the high strain sensitivity. Furthermore, information about the average length and length distribution is very essential when examining the influence of individual nanotube length on the strain sensitivity. With that in mind, we use our previously developed preparative ultracentrifuge method (PUM), and our newly developed gel electrophoresis and simultaneous Raman and photolumiscence spectroscopy (GEP-SRSPL) to characterize the average length and length distribution of SWCNTs respectively. / A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / September 28, 2015. / Alignment, Gauge Fcator, Network density, Piezoresistivity, Single Walled Carbon nanotubes, Strain sensor / Includes bibliographical references. / Tao Liu, Professor Directing Dissertation; Sachin Shanbhag, University Representative; Mei Zhang, Committee Member; Okenwa Okoli, Committee Member; William Oates, Committee Member.