This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 147-151). / Spot defects are a leading source of failure in the fabrication of integrated circuits (ICs). Thus, the IC industry inspects for defects at multiple stages of IC fabrication, especially the fabrication of IC photomasks. However, existing non-invasive imaging methods cannot image a modern photomask in a reasonable time-frame. Electroquasistatic (EQS) sensors are arrays of electrode pairs that capacitively couple to targets they sweep over. Utilizing high measurement frequencies and a number of parallel scanning electrode pairs, EQS sensors have been suggested as a potential high speed alternative for defect detection in IC fabrication. This thesis continues the investigation into EQS sensors for high speed imaging by exploring EQS sensors driven with high excitation frequencies. We develop electrode arrays that can be driven with high excitation frequencies and construct high frequency EQS sensors by attaching them to high frequency drive electronics. We also fabricate a test fixture for positioning these sensors relative to and sweeping them across targets on a conductive base. As the sensors sweep across targets, their impedance is measured from 1 - 500 MHz using an impedance analyzer and is later converted into the capacitance between the sensor's electrode array and the target. Capacitance changes are produced by a variable air gap and by a dielectric step, confirming these sensors can detect changes in a target's geometric and material properties with high excitation frequencies. Finally, we present concepts for a high speed measurement system which utilizes these sensors. / by Tyler Thomas Hamer. / S.M. / S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987. / Bibliography: leaves 176-181. / by Harry West. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 52-55). / Skeletal muscle is well known for a rapid adaptation to mechanical environmental changes. Understanding the effects of the mechanical stimulation such as stretching to muscle tissues is important for understanding the nature of muscle development and muscle diseases. While there are many reports studying the effects of stretching on 2-D cultures in vitro, few research groups have investigated their effects in 3-D muscle strips with high volumetric density. Here, we used the muscle strips that have fascicle-like shape, high volumetric density, and optimal alignment in 3-D. We present that the fascicle-like muscle tissue will have stronger performance and more matured structure in response to particular stimulation. We applied the static and cyclic stretching, electrical stimulation and two different co-stimulation. Both the static and cyclic stretching induced stronger cell-ECM adhesions of 3-D cultured muscle cells. The static tension at day 9 caused striated actin of the muscles, but the cyclic tension at day 1 caused weakening of actin structure with less alignment. Similarly, the stretching could affect other proteins, related to muscle development. Therefore, the effect of the stretching to the muscle tissue is highly time-dependent, and it is important to find optimal timing for efficient training. We also show that muscle performance by the co-stimulation is higher than by the electrical stimulation alone. Although conditions of the each mechanical and electrical stimuli were identical, the performances were changed only by phase shift between the two stimuli. We still do not know the exact mechanism, but our results support the potential use of high-performance engineered muscle tissues for moving bio-robots or drug testing platforms. / by Hyeon Yu Kim. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / Bibliography: leaves 89-91. / by Pasquale Rezza, Jr. / Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Cataloged from PDF version of thesis. "February 2019." / Includes bibliographical references (pages 203-211). / Lightweight engineering requires the development of low-density materials featuring high mechanical properties with an emphasis on high-specific stiffness and strength. Besides improvement in the composition of bulk materials, high specific mechanical properties are obtained by carefully architecting materials through the controlled introduction of porosities. The recent rise of additive manufacturing allows for the manufacturing of complex structures at the material length scale, opening an unprecedented design space of metamaterials. Amongst this design space, this thesis is concerned with the conception of three-dimensional isotropic metamaterials, a particularly important class of mechanical metamaterials exhibiting direction-independent behavior at the macroscopic level. / The mechanical behavior of the anisotropic Face-Centered-Cubic (FCC) and Body-Centered-Cubic (BCC) lattices is investigated at small and large strains, through a combined analytical, numerical and experimental study including an extensive characterization of stainless steel micro-lattices. Based on this investigation, elastically-isotropic truss lattices are designed via topological constraints obtained from analytical homogenization. The precise composition of anisotropic lattices including the Simple Cubic (SC), BCC and FCC lattices allows achieving elastic isotropy. The introduction of elastically-isotropic hollow-truss lattices eliminates the need of combining anisotropic lattices, as the anisotropy in hollow-truss lattices is dictated by the ratio of the inner to outer radii of each beams. Finally, a new class of plate-lattice is proposed which reaches optimal isotropic elastic properties. They are conceived by placing plates along the close-packed planes of crystal structures. / Based on theoretical analysis, a design map is developed for elastically isotropic plate-lattices of cubic symmetry. The newly-proposed designs are validated through extensive unit cell simulations and experiments carried on polymeric specimens. Furthermore, the initial yield surface of the elastically-isotropic lattices is investigated numerically and the direction-dependency of the initial strength is reported using pole figures. A plate-lattice is found to exhibit an almost isotropic initial yield with its strength close to theoretical upper bound for porous solids. The main outcomes of this thesis are (i) the design strategies used to create elastically-isotropic three-dimensional lattices based on truss, shell and plates assemblies and (ii) the discovery of an optimal elastically-isotropic lattice family with almost optimal initial yield response. / by Thomas Tancogne-Dejean. / Sc. D. / Sc.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (page 70). / In recent years, biomimetics has been used as a source of inspiration to improve the performance of engineered systems in several disciplines. In this thesis, we emulate the function of the retractable dorsal fins in tunas to improve the maneuvering performance of a typical autonomous underwater vehicle, the REMUS 100 AUV. We are introducing dorsal-like fins on the AUV that can be erected to alter its maneuvering hydrodynamic coefficients, and hence affect the transient and steady-state turning response. In order to study systematically the effect of adding dorsal fins, we built a six degrees of freedom simulation model of the REMUS AUV. The model included body and rudder lift forces and moments, added mass forces and moments, gyroscopic and centrifugal forces, drag forces and moments, and body forces and moments such as buoyancy and gravity terms. To target the horizontal plane maneuvering characteristics, we reduced the model to a 3 DOF simulation, allowing the dorsal fin to vary in area, location along the length of the AUV, as well as having a turning angle with respect to the REMUS x-axis. We find that the addition of the fin can improve the performance, as measured by the radius of turning and rate of turning, moderately only when placed ahead of the center of gravity. However, when the dorsal fin is also allowed to rotate in the opposite direction that the rudder, substantial improvement in maneuvering performance is noted, increasing the turning rate up to 25%. / by Yuri Trakht. / Nav. E. / S.M. / Nav.E. Massachusetts Institute of Technology, Department of Mechanical Engineering / S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references. / The optical resolution of microscopy is limited by the wave-like characteristic of the light. There are many recent advances in overcoming this diffraction limited resolution, but mostly focused on fluorescent imaging. Furthermore, there are few non-fluorescence wide-field super-resolution techniques that can fully utilize the applicable laser power to optimize imaging speed. Structured illumination microscopy is a super-resolution method that relies on patterned excitation. This thesis has presented novel applications of structured illumination microscopy to surface plasmon resonance fluorescence and pump-probe scattering imaging. First, structured illumination microscopy was introduced to surface plasmon resonance fluorescence imaging for high signal-to-noise and high resolution. Secondly, a theoretical framework for three-dimensional wide-field pump-probe structured illumination microscopy has been developed to increase the lateral resolution and enable depth sectioning. Further, structured illumination wide-field photothermal digital phase microscopy is proposed as a high throughput, high sensitivity super-resolution imaging tool to diagnose ovarian cancer. Finally, I have derived the exact analytical solution to the heat conduction problem in which a sphere absorbs temporally modulated laser beam for photothermal microscopy. The proposed method also has a great potential to be applied to other pump-probe modalities such as transient absorption and stimulated Raman scattering. / Funding sources and sponsors: National Institutes of Health (9P41EB015871-26A1, 5R01NS051320, 4R44EB012415, and 1R01HL121386-OlAl), National Science Foundation (CBET-09395 11), Hamamatsu Corporation, Singapore-Massachusetts Institute of Technology Alliance for Research and Technology (SMART) Center, BioSystems and Micromechanics (BioSyM), and Samsung Scholarship / by Yang-Hyo Kim. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 82-84). / Radio frequency (RF) systems such as cell phones and GPS can perform better and last longer if we can reduce electrical heat loss in the wires. This is typically done in power systems by twisting or weaving the wires, following one of several patterns. Though, at radio frequencies, wire dimensions must scale down by as much as 1000 times in order to achieve the same effects. This project decomposes the problem into two main categories; the manufacturing of micron scale wires and the manipulation of these wires in order to form a twisted bundle. This project aims to produce twisted bundles of wire that have an AC resistance value at GHz frequencies approaching a fundamental limit in which electrical resistance is independent of frequency. This thesis focuses specifically on the first major problem: producing micron scale wires of considerable length. In order to accomplish this, I have developed a bottom-up approach to the manufacturing of microwires. Rather than reducing the diameter of a wire by drawing through successive dies, I have instead formed a wire by metalizing a small nanofiber core to reach the target diameter. Initially, I designed a mechanical system to harvest Nomex nanofibers 200-400 nm in diameter that have been electrospun onto a spinning drum. Next, I designed a system to concentrically coat the harvested nanofibers with a conductive seed layer via sputter deposition. Finally, I have designed a reel to reel system in order to electroplate over a segment of seeded nanofiber in order to achieve the target diameter. This now allows for the creation of microwires of considerable length for use in high frequency applications. / by Alexander Michael Couch. / S.M. / S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 127-130). / Various aluminum-water reactions were thermodynamically analyzed across a wide range of temperatures and pressures to determine the most favorable reaction under each condition. Results show that under most achievable temperatures and pressures the reaction will produce AlOOH, however at low temperatures and high pressures, this will transition to a reaction producing Al(OH)₃. This model was then corroborated experimentally using XRD and FTIR to identify the aluminum-water reaction products created at varying temperatures and pressures. A new Ga In eutectic-limited surface coating method was developed to produce effective, consistent, aluminum fuel. This coating method also allowed for the study of the effects of increased eutectic concentration on aluminum reaction yield. These reaction yield results showed a minimum threshold concentration of 1.9% eutectic was needed to create reactive fuel, and that adding concentrations beyond that would increase the reaction yield with diminishing returns. Using this aluminum technology, the world's first aluminum fueled car was made. A 10 kW power system fueled by an aluminum-water reaction was successfully integrated into a BMW i3 to replace its range extender and to power the vehicle. With a vision towards creating simpler power systems in the future, a liquid aluminum fuel was also developed. This fuel works by suspending 65% aluminum particles by mass into a mixture of mineral oil and fumed silica. This newly developed liquid fuel can be pumped easily, stay in suspension for months, and retains full levels of reaction completion. Finally, a joint hydrogen-steam IC engine concept was presented and analyzed. This engine utilizes both the thermal and hydrogen energy created by an aluminum-water reaction and shows ideal system efficiencies of as high as 33% while still operating at practical system pressures. / by Jason Zachary Fischman. / S.M. / S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 127-129). / An automated software system has been developed to allow robots to learn a generalized motor skill from demonstrations given by a human operator. Data is captured using a teleoperation suit as a task is performed repeatedly on Leonardo, the Robotic Life group's anthropomorphic robot, in different parts of his workspace. Stereo vision and tactile feedback data are also captured. Joint and end effector motions are measured through time, and an improved Mean Squared Velocity [MSV] analysis is performed to segment motions into possible goal-directed streams. Further combinatorial selection of subsets of markers allows final episodic boundary selection and time alignment of tasks. The task trials are then analyzed spatially using radial basis functions [RBFs] to interpolate demonstrations to span his workspace, using the object position as the motion blending parameter. An analysis of the motions in the object coordinate space [with the origin defined at the object] and absolute world-coordinate space [with the origin defined at the base of the robot], and motion variances in both coordinate frames, leads to a measure [referred to here as objectivity] of how much any part of an action is absolutely oriented, and how much is object-based. A secondary RBF solution, using end effector paths in the object coordinate frame, provides precise end-effector positioning relative to the object. The objectivity measure is used to blend between these two solutions, using the initial RBF solution to preserve quality of motion, and the secondary end-effector objective RBF solution to increase the robot's capability to engage objects accurately and robustly. / by Jeff Lieberman. / S.M.