Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references (leaves 165-177). / by Cathryn Ann Shaw-Reid. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006. / Includes bibliographical references (p. 210-219). / A methodology is presented for assessing the current and future utilization of agricultural crops as feedstocks for the production of transportation fuels, specifically, the use of corn grain and stover for ethanol production. The generic methodology integrates chemical process design and decision analysis tools. Four primary concepts are incorporated to address the performance of technologies and policies: 1) expansion of the system boundaries to include the entire process life cycle, 2) incorporation of both economic and environmental metrics for multi-objective optimization with tradeoff analysis using Pareto curves, 3) explicit incorporation of uncertainty analysis using Bayesian updating, and 4) integration of multiple feedstocks, processes, and products, in a network optimization framework, with subsequent decomposition to more refined models, for an improvement assessment of specific research and development goals. The first step is an assessment of the emerging corn grain ethanol industry in the U.S. Using life cycle assessment with Bayesian uncertainty propagation, the net energy balance of corn grain ethanol production is calculated and shown to be slightly positive. / (cont.) The variability in the system suggests that this variance is dependent primarily on corn production location, distribution requirements, and ethanol conversion and purification efficiency lead to the significant variance. From an economic performance, an optimized facility can produce ethanol competitively with gasoline at $55/barrel, on an unsubsidized and energy equivalent basis. The life cycle greenhouse gas emissions decrease of - 5% - 30% between gasoline and ethanol on a miles driven basis. A potential modification to the process is the use of an alternative feedstock, such as lignocellulosic waste and residues, which have larger resource availability and lower economic cost. Compared to the original case, cellulosic ethanol would have a higher net energy ratio with lower greenhouse gas emissions, but the current projected economic costs are prohibitive. An improvement analysis of potential technology advancements using multiple object network optimization across the entire supply chain suggests that research and development should focus on feedstock logistics and the pretreatment stage. / by Jeremy C. Johnson. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 111-117). / Self-assembled nanoscale structures are the basis for various technological advancements in functional materials, sensors, and molecular circuits and factories. With significant progress in self-assembly of periodic nanostructures (such as monolayers), the focus is now shifting towards non-periodic structures. Control of various interaction force fields (electrostatic, Van der Waals, etc.) between the nanoparticles and external controls can result in the formation of nanostructures with desired geometry. The aim is to design the nanoparticles and the external actuators such that the desired structure can be self-assembled rapidly with high reliability and avoiding any kinetic trapping that an ill-designed energy landscape might cause. Deterministic dynamic modeling of such self-assembled nanostructures, directed by external fields, through a Master Equation approach, leads to a set of differential equations of such large size that even the most efficient solution algorithms are overwhelmed. Thus, model reduction is a key necessity. This thesis presents a methodological approach and specific algorithms, which generate time-varying, reduced-order models for the description of directed self-assembly of nanoparticles by external fields. The approach is based on Finite State Projection and is adaptive, i.e., it generates reduced-order models that vary over time. The algorithm uses event-detection concepts to determine automatically, during simulation, suitable time points at which the projection space and thus the structure of the reduced-order model change, in such a way that the computational load remains low while the upper bound on the simulation error, resulting from model reduction, is lower than a prescribed maximum limit. The thesis also presents an optimal control strategy that can guide any initial random configuration of nanoparticles to a final structure of desired geometry, in minimum time. It employs a multi-resolution view of the dynamically evolving configurations of nanoparticles, which are described through the simulation methodology described before. External charges, attracting or repelling the nanoparticles, are the controls, whose location and intensity are determined by the optimality conditions of the optimal control strategy. To ensure analytic consistency of the parametric sensitivities, during the computation of the optimal controls, and thus guarantee the optimality of the resulting control policy, a priori determination of enlarged constant projection spaces is shown to be essential. The thesis also presents a series of case studies, which illustrate how the proposed methods can be used to simulate effectively directed self-assembly of an appreciable number of nanoparticles, and reach the desired geometry. These case studies also illuminate several of its features, such as: superiority over a static optimal solution; evasion of kinetic traps; and effective handling of combinatorial complications arising for systems with large-size domains and many particles. / by Sivaraman Ramaswamy. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references. / (cont.) micromasking. Porous films seem especially prone, perhaps due to polymer diffusion into the pore structure. Control of polymerization during the etch through the use of lower-polymerizing fluorocarbons or the addition of oxygen was shown to effectively control excessive roughening on solid films, while porous dielectrics remain challenging. Finally, an inductively-coupled plasma beam source was used to conduct a preliminary investigation into roughening of polysilicon in an HBr plasma beam. The initial polysilicon topography was shown to seed striation formation at glancing ion incident angles due to scattering and ion shadowing. These results indicate that, in a pure etching process (no deposition) the surface topography can be an important source of roughness and striation formation on sidewalls. / For the patterning of sub 100 nm features, a clear understanding of the origin and control of line edge roughness (LER) is extremely desirable, both from a fundamental as well as a manufacturing perspective. Until recently, LER studies have focused on the analysis of top-down SEM micrographs of post-developed photoresist lines. However, the effect of plasma etch on sidewall roughness has not received sufficient attention. Plasma etching processes often roughen the feature sidewalls, leading to the formation of anisotropic striations. It is this post-etch sidewall roughness which will ultimately affect device performance. Sidewall roughness transfer through all layers of a process stack (photoresist, ARC/hardmask, and oxide) was observed by cleaving dense line/space patterns parallel to the lines, and directly scanning the exposed sidewall with an atomic force microscope. This technique vividly highlighted the structural nature of the post-etch sidewall, and allowed the extraction of quantitative roughness data as a function of depth. Sidewall roughness transfer can be improved through a variety of processing and material solutions. Maintaining a smooth sidewall immediately prior to the substrate etch (for example, through modulation of the ARC/hardmask open chemistry) leads to smoother sidewalls after oxide or polysilicon etch. However, smoothing must typically be balanced against critical dimension control. Additionally, the resist platform can add to roughness transfer. Thin and/or fluorinated photoresist can enhance roughness due to the poorer etch resistance of these materials. Low-k (OSG) and porous low-k (MSQ) dielectrics can suffer from enhanced roughening during etching in fluorocarbon plasmas due to / by Stacy A. Rasgon. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references (p. 232-239). / by Alexander F. Diaz. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 117-121). / Traditional cancer treatment strategies include systemic chemotherapy, external beam radiation, and surgical excision. Chemotherapy is nonspecific, and targets all rapidly dividing cells. External beam radiation and surgery only target known cancer sites. However, targeted therapeutics, such as antibodies, will bind to all cancer cells that express the targeted antigen, including small metastases that are invisible by current imaging technology. In the past decade, nine antibodies have been approved for the treatment of cancer and are demonstrating moderate success in the clinic. Some of these antibodies have intrinsic toxic effects and block the interaction of growth factors or induce cell death. Other antibodies are conjugated to drugs, toxins, or radioactive isotopes. Unfortunately, antibodies exhibit slow clearance from the body and exposure of healthy tissues to toxins or radiation can result in undesirable side effects that limit the doses that can be safety administered to the patient. We have used rational engineering design and mathematical modeling to develop a novel pretargeted radioimmunotherapy (PRIT) approach for the treatment of cancer. In PRIT, a bifunctional antibody is administered and allowed to bind to a cancer antigen. After sufficient tumor uptake of the antibody, a small molecule carrying a radionuclide is administered and captured by the pretargeted antibody while unbound molecules clear rapidly from the body. PRIT combines the high binding specificity of antibodies with the rapid clearance properties of small molecules. We have identified a small molecule metal chelate, DOTA, which exhibits rapid whole-body clearance and that has demonstrated safety in humans. / (cont.) We engineered a high-affinity antibody fragment specific to DOTA and subsequently engineered a novel bispecific antibody (bsAb) construct with specificity for both DOTA and carcinoembryonic antigen (CEA). The bsAb exhibits retention of parental affinities, in vivo stability, and tumor targeting. The engineered PRIT approach was tested in a mouse tumor model and demonstrates excellent DOTA capture at the site of the tumor with the best 48 hour tumor to blood and tumor to kidney ratios reported to date for CEA targeting. The PRIT approach developed here can be easily applied to other disease targets and has the potential to impact clinical cancer radioimmunotherapy. / by Kelly Davis Orcutt. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1923. / Includes bibliographical references (leaf 41). / submitted by Bernard Lewis. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. / Includes bibliographical references. / by Stephanie Simmons. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references. / Poly(methyl methacrylate)s (PMMA) containing polyhedral oligomeric silsesquioxane (POSS) nanoparticles (d [approx.] 1.5 nm) were subjected to heological, mechanical, and morphological tests to determine the effects that POSS has on the melt-state and solid-state properties of this commercially important amorphous polymer. The effect of POSS on the rheological properties varied depending on the type of POSS cage and whether the POSS was covalently tethered to the PMMA backbone. A highly miscible acrylic-POSS species plasticizes PMMA, decreasing the glass transition temperature by approximately 10⁰C at a loading of 10 vol%. An essentially immiscible POSS species (cyclohexyl-POSS) does not alter the ... of PMMA but is able to decrease slightly the zero shear-rate viscosity at low loadings. Incorporating a POSS filler (isobutyl-POSS) into an isobutyl-POSS-PMMA copolymer causes a significant increase in viscosity at all loadings. The addition of POSS fillers to PMMA leads to an enhancement in the toughness in both slow-speed tension (strain rate = ... ) and high rate split-Hopkinson pressure bar tests (strain rate = ... ). In particular, the combined addition of two distinct POSS species - one miscible, one immiscible - led to the greatest enhancement in toughness and excellent reproducibility. A four-fold increase in tensile toughness was observed through the use of these two disparate POSS species. / (cont.) Polyhedral oligomeric silsesquioxane macromers were copolymerized separately with a glassy polymer [PMMA, ... = 104⁰C] and a rubbery polymer [Poly(n-butyl acrylate), ... = -52⁰C] to determine the effect of the polymer glass transition temperature on the ultimate properties of an acrylic copolymer. Copolymers of POSS and PMMA show a significant decrease in ... . Conversely, copolymers of POSS and poly(n-butyl acrylate) have significantly higher glass transition temperatures than the pure PBA. These also exhibit a more than two order of magnitude increase in the room temperature modulus measured in DMA and tensile tests. The increase in modulus was due to nanocrystallites of POSS within the butyl acrylate matrix. / by Edward Thomas Kopesky. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007. / Includes bibliographical references (p. [119]-128). / The synthesis of micron-sized polymeric particles with precise control over shape, monodispersity and chemistry is a technologically important objective. Varied applications including medical diagnostics. designer fabrics and optical devices could benefit from the availability of geometrically complex and chemically inhomogeneous particles. Microfluidics has recently emerged as an important alternative route to the synthesis of such complex particles. This thesis presents three new approaches to complex particle and structure synthesis in microfluidic devices. In the first approach. droplets formed by shearing a curable photopolymer. using a continuous water phase at a T-junction, were constrained to adopt non-spherical shapes by confining them using appropriate microchannel geometries. The non-spherical shapes formed were permanently preserved by photopolymerizing the constrained droplets in situ using focused ultraviolet (UV) light from an inverted microscope. The second and more general method called Continuous Flow Lithography (CFL) is a one-phase, projection photolithography based process to continuously synthesize polymeric microparticles in any 2-D extruded shape down to the colloidal length scale. / (cont.) Polymerization was also performed across laminar. co-flowing streams to generate Janus particles containing different chemistries, whose relative proportions could be tuned easily. CFL was also used to synthesize 'particle surfactants' that assembled at the interface of oil-water emulsions or formed micelle-like structures in water. While CFL was able to synthesize particles in non-spherical shapes with chemical anisotropy, particle throughput and resolution was a concern. To mitigate these problems, a new setup called Stop Flow Lithography (SFL) was devised. In SFL, a flowing stream of oligomner is stopped before polymerizing an array of particles into it, providing for much improved resolution over particles synthesized in flow. The formed particles are then flushed out at high flow rates before the cycle of stop-polymerize-flow is repeated. The high flow rates enable orders-of-magnitude improvements in particle throughput over CFL. However, the deformation of the PDMS elastomer due to the imposed pressure restricts how quickly the flow can be stopped before each polymerization event. We have developed a simple model that captures the dependence of the time required to stop the flow on geometric parameters such as the height, length and width of the microchannel, as well as on the externally imposed pressure. / (cont.) A third approach to synthesizing particles uses elastomeric phase masks to build all-PDMS devices. Coherent laser light passing through a phase mask generates a complex 3D distribution of intensity that selectively exposes certain regions while leaving out others. This results in the formation of 3-D structures whose features can be tuned at the micron scale and below. We have attempted the formation of 3-D structures in hydrogel polymers which could have important implications in the field of tissue engineering. Finally, we have developed a simple model of the oxygen inhibited polymerization that occurs in flow lithography. This model is able to qualitatively predict the presence of a thin, uncrosslinked layer of oligomer close to the walls of the PDMS device. This layer is critical to our ability to flow out particles in flow lithography. This thesis demonstrates that microfluidics is indeed a viable and promising route to the synthesis of complex polymeric particles and structures. / by Dhananjay Dendukuri. / Ph.D.