Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 39-40). / Micro-scale optical components capable of on-demand reconfiguration of their internal morphology and composition would enable unprecedented control of light propogation on the microscale. Double emulsions formed from immiscible hydrocarbons and fluorocarbons offer a promising platform as reconfigurable micro-optical lenses. These droplet-based lenses can be reconfigured to strongly focusing, nearly transparent, or strongly scattering geometries. The dynamic variation of the lenses' optical interfaces can greatly enhance the lenses' ability to manipulate light. Finite Difference Time Domain and Raytracing techniques were used to characterize the optical properties of the drops and the simulations were verified experimentally immersing the lenses in an aqueous fluorescent medium in order to visualize their light manipulation capabilities. The lenses show a rapid response to external light stimuli or heat gradients and are susceptible to chemical triggers. / by Sara Nagelberg. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 165-168). / Micromechanical circuits such as MEMS switches, tunable capacitors (varactors) or resonators in general have lower loss and consume less power than their CMOS counterparts and have seen an increase of applications in high-value communication systems as well as low-cost commercial communication networks. Significant advances have been made in the areas of MEMS switches. However, MEMS resonators that operate in GHz range, have high quality factor and are highly tunable are still under active pursue. In this thesis, we study the design of a tunable capacitor that can be integrated with a resonant cavity to form a tunable electromagnetic cavity resonator. The design, fabrication, modeling and testing of a proof-of-concept MEMS tunable capacitor are presented. The tunable capacitor consists of a circular fulcrum that acts as a pivot for a thin silicon plate. The outer plate is an electrostatic, circular zipping actuator that bends the center plate through the fulcrum. By doing so, it opens the gap of the capacitor, which is formed by two smooth surfaces, one being the center plate, that are initially separated by a dielectric layer. The design is enabled mainly by the deep reactive ion etching and anodic bonding microfabrication techniques. / (cont.) The structure of the device is modeled using both numerical methods with Matlab boundary value problem (BVP) and finite element analysis with ANSYS. The Matlab results match well with the ANSYS results for the before pull-in and the zip-in actuation stages. The Matlab model is used to perform parametric design studies. Two types of assembly methods are used to construct the final devices: wafer-level and die-level. Depending on how they are assembled, the devices operate in different actuation stages. A laser interferometer system is used to measure the center displacement of the plate and an impedance analyzer is used to measure the capacitance change. Testing results are comparable with the ANSYS simulations. Based on the lessons learned from the proof-of-concept tunable capacitor, a design of the electromagnetic cavity resonator with an integrated tunable capacitor is proposed. / by Xue'en Yang. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / 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. 36). / Advanced automotive technology such as adaptive cruise control and navigation systems are becoming ever more popular. With all of the technology to aid the driver, it is difficult to recognize when the technology used to inform the driver is more of a distraction than a benefit. Specifically, the user interaction associated with navigation systems has not been perfected. In response, the Computer Science and Artificial Intelligence Laboratory at MIT has created City Browser, an in-vehicle naturalistic navigation system that allows the user to search an online database for points on interest and to find directions. To gain feedback on the operation of the system in order to improve it for consumer use, a user study was conducted with over 90 participants. Each subject was also separated into different demographic groups as to quantify the difference of age and gender on system interaction. During the course of the experiment, three different forms of data collection were obtained: self report questionnaires, audio recordings, and physiology measurements such as heart rate, breathing rate, and skin conductance. The results indicate that users' feel the system is enjoyable, useful, and easy to learn. At the same time, users were also displeased with the voice of the system and felt that operating the system required a high level of concentration. The system had a response accuracy of 54.7% and had tendency to recognize the voice of 25-34 and 45-54 year old males better than other demographic group. The physiological measurements taken from the study were deemed to be inconclusive for determining the task difficulty and hence, more testing and analysis is needed. Overall, the City Browser system has proven to be practical in allowing users access to real time directions and points of interest in the greater Boston area. The results from this user study will allow the system to continually develop into a product for consumer use. / by Shannon Colette Roberts. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 42). / This thesis explores the use of binary actuators to adjust the shape of an array of mirrors. To explore this concept, an experimental system was refurbished and recalibrated. This experimental system was used to explore the range of possible configurations that could be reached by a simple binary actuated system. System models are required for accurate control of these binary actuated structures. This thesis develops and tests the accuracy of two different modeling approaches, linear and iterative. The linear model assumes that each actuator contributes a constant value to the angle of the center mirror, and that this value is not dependent on the other actuator positions. The actuator contributions are summed to find the angle of the center mirror. These contributions are found two ways: by taking a relevant single data point for each actuator, and by using a least squares fitting of a large subset of data. The iterative model assumes that each actuator adds some constant value, similar to the previous model, and that it also adds some portion of the current angle. A multiplication and shift are therefore found for each actuator, and these multiplications and shifts successively applied, starting with the initial angles, to find the final angular position. While the linear model with measured values for the actuator contributions predicted the data poorly, the linear model with the least squares fitted values performed much better. The iterative model initially produced large errors, but these errors were found to be readily correctable and once removed, the iterative model predicted the data better than the linear model. / by Teresa M. Gomez. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 53-55). / The medical application of injection of monoclonal antibodies using a controllable auto-loading needle-free jet injector has been evaluated for two potentially limiting factors: viscosity of the formulation and shearing of the antibody during ejection. We used the Hepatitis B monoclonal antibody C86322M for its easy access and widespread usage. We used repeatability studies of glycerol at up to 200 m/s and 200 [mu]L delivery volume to demonstrate precision at viscosities up to 21.6x10-³ Pa-s. We determined that viscosity alone would not limit the jet injector's performance. Additionally, we evaluated the integrity of the antibody post-ejection using the enzyme-linked immunosorbent assay (ELISA) and gel electrophoresis methods. Using the ELISA method, we compared the ability of the antibody to bind to its specific antigen, HBsAg, both before and after ejection at multiple speeds. Changes in molecular size and charge of the monoclonal antibodies were evaluated by gel electrophoresis, more specifically with SDS polyacrylamide gels in reducing and non-reducing situations, native gel electrophoresis, and IEF gel electrophoresis. Most of these techniques revealed little to no change between pre-ejectate and ejectate migration, indicative of an unchanging molecular size and overall charge. However, with IEF gel electrophoresis, we observed two extra residues around a pI of 6.8. A change in charge due to alterations of protein side-chains may affect the stability of the molecule, and so this result is worth further pursuing on a quantitative basis. Despite this possibility, overall we have demonstrated that at 1 g/L, no significant aggregation or degradation results from jet ejection. / by Tiffany Jin. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 50-51). / The aim of this collaborative project between Massachusetts Institute of Technology (MIT) and Cyprus Institute was to develop an experimental procedure for identifying fresh submarine groundwater discharge (SGD) in Cyprus. SGD is a flow of water from coastal aquifers into the ocean driven by a hydraulic gradient and other forces. Understanding SGD is crucial for informed groundwater management. In some cases, SGD creates submarine springs which can be tapped to provide supplementary freshwater. This is particularly enticing for countries such as Cyprus, where energy- and cost-intensive desalination plants are necessary to meet freshwater demand. A preliminary protocol for locating SGD was developed based on a review of literature and interviews with experts. The protocol was tailored to suit resources available in Cyprus. Because groundwater temperature typically deviates from ocean water, an infrared camera mounted on a manned aircraft was used to obtain an ocean surface temperature map. Areas exhibiting temperature anomalies were revisited by boat to measure salinity in situ using a conductivity, temperature and depth sensor (CTD). This protocol was tested in Chrysochou Bay, selected based on relatively high estimates of SGD from published water mass balances as well as recommendations from local fishermen. The designed method proved effective; areas of anomalous salinities and temperatures were found. However the protocol can be improved based on experience gained through this study. Manned aircrafts are unfit for a large-scale study due to high costs, flight restrictions, and lack of appropriate navigational equipment on accessible vehicles. Unmanned aerial vehicles are more suitable for a full-scale study. Additionally, obtaining a salinity profile by a series of point measurements, as with the CTD, is time-consuming. A towed resistivity array would provide similar salinity profiles in a fraction of the time. A thorough investigation of SGD is planned in Cyprus in the spring, when SGD is highest. This paper presents a recommended procedure for the spring investigation based on the results of this study. / by Kathryn M. Olesnavage. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 86-88). / The gastrointestinal system plays a vital role in the functioning of the human body, processing food into useable energy, controlling homeostasis, and serving as the front line of the immune system. The intestines are aided in their many functions by the gut microbiome, a collection of 100 trillion anaerobic bacteria cells that live inside the GI tract. Although they play an essential part in the organ system, they remain little-represented in in vitro gastrointestinal models because of the difficulty of replicating the anaerobic conditions of the intestines. We constructed an in vitro model capable of growing aerobic epithelial intestinal cells along with anaerobic microbes in the same bioreactor. A device called the apical flow module seals a 12-well transwell and provides an inlet and outlet port into the apical chamber. Media is deoxygenated using nitrogen bubbles before it is pumped using a nitrogen-actuated pneumatic pump block. Microbes are injected into the anaerobic fluid through a rubber septum injection port before the fluid flows into the sealed transwell. Effluent is collected in sterile tubes at a controlled height so as to regulate the apical side pressure. Oxygen is provided to the basolateral human epithelial cells through basolateral circulation achieved using a pneumatic circulation plate. Preliminary testing confirms our ability to control the oxygen in all parts of the system and to grow cocultures of human and bacteria cells. Epithelial cells grown in our bioreactor show signs of behaving more similarly to cells in vivo when exposed to the conditions present in our system, providing researchers with an oxygen-controlled gastrointestinal in vitro model. / by Steven John Holcomb. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2002. / Includes bibliographical references (leaves 32-33). / An experimental study was performed to record and model the stress-strain behavior of a novel bioelastomer (PSG) during five one-week intervals of in vivo degradation. Also of interest were the changes in compressive Young's modulus of due to the degradation. Samples of PSG were implanted in Sprague-Dawley rats, extracted after each interval, and tested on a compression testing machine. The stress-strain behavior of the PSG was recorded and compared to two theoretical models: a Gaussian model and an 8-chain (non-Gaussian) model. The 8-chain model yielded the better predictions for the highly nonlinear PSG stress-strain behavior. The compressive Young's modulus for PSG decreased significantly after the first week of degradation, but remained relatively stable for the final four weeks. The proportional change in volume due to in vivo degradation of PSG was less than that of PLGA, a widely-used bioelastomer. Additionally, the PSG maintained its physical shape much better than PLGA. / by Robert A. Aronstam. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / 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. 107-115). / Hybrid systems, describing interactions between analog and discrete dynamics, are pervasive in engineered systems and pose unique, challenging performance verification and control synthesis problems. Existing approaches either lead to computationally intensive and sometimes undecidable problems, or make use of highly specialized discrete abstractions with questionable robustness properties. The thesis addresses some of these challenges by developing a systematic, computationally tractable approach for design and certification of systems with discrete, finite-valued actuation and sensing. This approach is inspired by classical robust control, and is based on the use of finite state machines as nominal models of the hybrid systems. The development does not assume a particular algebraic or topological structure on the signal sets. The thesis adopts an input/output view of systems, proposes specific classes of inequality constraints to describe performance objectives, and presents corresponding 'small gain' type arguments for robust performance verification. A notion of approximation that is compatible with the goal of controller synthesis is defined. An approximation architecture that is capable of handling unstable systems is also proposed. / (cont.) Constructive algorithms for generating finite state machine approximations of the hybrid systems of interest, and for efficiently computing a-posteriori bounds on the approximation error are presented. Analysis of finite state machine models, which reduces to searching for an appropriate storage function, is also shown to be related to the problem of checking for the existence of negative cost cycles in a network, thus allowing for a verification algorithm with polynomial worst-case complexity. Synthesis of robust control laws is shown to reduce to solving a discrete, infinite horizon min-max problem. The resulting controllers consist of a finite state machine state observer for the hybrid system and a memoryless full state feedback switching control law. The use of this framework is demonstrated through a simple benchmark example, the problem of stabilizing a double integrator using switched gain feedback and binary sensing. Finally, some extensions to incremental performance objectives and robustness measures are presented. / by Danielle C. Tarraf. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (p. 66). / by Indrani Chakraborty. / M.S.