Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989. / GRSN 410199 / Includes bibliographical references (leaves 75-76). / by Robert S. Betros. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 115-127). / Conducting polymers such as polypyrrole, polythiophene and polyaniline are currently studied as novel biologically inspired actuators. The actuation mechanism of these materials depends upon the motion of ions in and out of the polymer film during electrochemical cycling. The diffusion of ions into the bulk of the film causes the dynamic mechanical and electrical properties of the material to change during oxidation and reduction. The mechanism of this change is not fully understood, as it can depend on many different factors such as oxidation state, solvation of the film and the level of counter ion swelling. In-situ measurement of the dynamic mechanical compliance and electrical impedance of polypyrrole as a function of charge is difficult, since the compliance depends upon the excitation frequency as well as the electrochemical stimulus. Here, we have developed novel experimental techniques that use stochastic input waveforms to dynamically measure the compliance and impedance response of conducting polymers as a function of frequency and an electrochemical stimulus. A stochastic stress input signal with a bandwidth of 30 Hz is used, which allows us to compute the mechanical compliance transfer function of polypyrrole as function of the electrochemistry. The low frequency compliance changes between 50-80%, as charge is injected into polypyrrole in neat 1-butyl-3-methylimidazolium hexafluorophosphate. The compliance changes reversibly as ions diffuse in and out of the film, which indicates that the compliance depends upon the level of counter ion swelling. The effect of cationic and anionic charging on the polypyrrole compliance is demonstrated in multiple ionic/solvent combinations. The stochastic signals are also used to the characterize the isometric and isotonic responses of conducting polymer actuators. This technique is used to demonstrate the effect of temperature and solution conductivity on actuation and to develop methods that can be used to improve polymer actuator performance. Efficient techniques to incorporate functionalized carbon nanotubes into conducting polymers using layer by layer deposition and drop casting methods have been explored. These new composite materials and techniques significantly reduce creep, improve conductivity and increase stiffness of the polymer actuators. / by Priam Vasudevan Pillai. / Ph.D.

Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1974. Ph.D. / Vita. / Bibliography: leaves 114-118. / Ph.D.

Thesis (M. Eng. in Manufacturing)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 52). / Data recently collected from an industrial thin film manufacturer indicate that almost 8% of devices are rejected due to excess metal, or unwanted metal on the device surface. Experimentation and analysis suggest that almost half of these defects are caused by incomplete removal of nickel oxides that form on top of the conductive nickel surface throughout the heated environment of the upstream process. This study classified and identified the composition of these excess metal defects, evaluated recommended wet etch methods to remove nickel oxide, and finally proposes a wet etch process that will rapidly remove defects while continuing to maintain the desired semi-anisotropic etch profile, uncharacteristic of most wet immersion etch processes. Results attested that rapid exposure to dilute (40%) nitric acid followed by immediate immersion into a cleaning agent, proprietary nickel etchant, and titanium tungsten etchant removed all nickel oxide defects. Upon implementation, this method has the potential to reduce scrap due to excess metal by 3% and reduce overall etch process time by 25%. In addition, a process was developed to completely etch patterned substrates with high defect density mid process and rework them from raw substrates. / by Neha H. Dave. / M.Eng.in Manufacturing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 378-382). / by James Frederic Bredt. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (leaf 51). / A meter-scale model of the fibrous 1CGD molecule, a synthetic collagen-like peptide, was modeled and manufactured for educational use. We chose to model and manufacture the 1CGD molecule because collagen is of biological importance, the molecular coordinates are well-established, and because the molecular structure and geometry of 1 CGD are representative of many general concepts important to the study of proteins. The 1CGD molecule consists of three polypeptide chains. Our model is three separately manufactured chains intertwined with one another after manufacture. The A chain of the 1 CGD molecule was first modeled using the SolidWorks computer aided drawing (CAD) software. The CAD model was then converted to a file that enabled us to manufacture a master part via a three-dimensional printing (3DP) process available from Z Corporation. The 3DP master part was used to manufacture a room temperature vulcanized (RTV) brush-on blanket mold and rigid plaster mother mold. The mold, created by artist Bob Shure at Skylight Studios, was then used to cast parts using a two component liquid plastic that cures to a solid material. The parting lines of the final parts were cleaned up and the final parts painted to complete the model. This thesis details the specifics of the manufacturing requirements, constraints, attempts, and ultimate process used to make a functional 1 CGD model. / by Emily E. Cofer. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references. / This thesis documents the design process for magnetic induction systems to harvest energy from mechanical vibrations. Two styles of magnetic induction systems - magnet-through-coil and magnet-across-coils - were analyzed. MATLAB models were created to serve as a design aid and optimization tool for both styles of magnetic induction systems. Prototypes were built to test the predictions of the MATLAB models. The experimental data was found to be in good agreement with the model predictions. / by Aparna S. Jonnalagadda. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical 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. 114-119). / Gallium nitride (GaN)-based microelectronics are one of the most exciting semiconductor technologies for high power density and high frequency electronics. The excellent electrical properties of GaN and its related alloys (high critical electric field, carrier concentration, and carrier mobility) have enabled record-breaking performance of GaN-based high electron mobility transistors (HEMTs) for radio-frequency (RF) applications. However, the very high power density in the active region of GaN HEMTs leads to significant degradation in performance as the device temperature increases. Thus, effective thermal management of GaN-based electronics is a key to enabling the technology to reach its full potential. Despite the vast amount of research into thermal issues in GaN-based electronics, including both modeling and experimental studies, there are a number of poorly understood issues. For instance, the heat source distribution in GaN HEMTs for RF applications has not been quantified nor have metrics been published for the heat flux in the near-junction region. Often, device engineers neglect the importance of thermal boundary conditions, which play a major role in shaping the temperature distribution in the device. Temperature rise in GaN HEMTs is typically modeled using computationally expensive numerical methods; analytical methods that are more computationally efficient are often quite limited. In this thesis, a literature review is given that discusses previous research in thermal issues in GaN-based electronics and that provides a perspective on the important factors to consider for thermal management. Electro-thermal modeling tools validated with test devices were used to derive quantitative information about the heat source distribution in GaN HEMTs. Both numerical and analytical thermal models were developed that provide helpful insight into the dominant factors in the formation of highly localized hotspots in the near-junction region. The Kirchhoff transformation, a technique for solving the heat conduction equation for situations in which the thermal conductivity of a material depends on temperature, was extended and applied to GaN HEMTs. The research described in this thesis provides critical information in understanding thermal issues in GaN-based electronics required to develop next generation near-junction thermal management technologies. / by Kevin Robert Bagnall. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical 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 (pages 125-128). / This thesis describes a new class of programmable-aperture light field cameras based on an all-digital, grayscale aperture. A number of prototypes utilizing this arbitrarily-controllable programmable aperture (ACPA) light field technology are presented. This new method of capturing light field data lends itself to an improved deconvolution technique dubbed "Programmable Deconvolution," as well as to 3D scanning and super-resolution imaging. The use & performance of ACPA cameras in these applications is explored both in theory and with experimental results. Additionally, a framework for ACPA camera design for optimal 3D scanning is described. / by Thomas Bradford Milnes. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaves 24-26). / by Murthy V.R.K.N. Nukala. / M.S.