Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (leaves 164-172). / by Tani Chen. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1996. / Includes bibliographical references (p. 114-118). / by Chinlim Ong. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1989. / Science hard copy bound in 2 v. / Includes bibliographical references (leaves 300-307). / by Francis Eric Finch. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004. / Includes bibliographical references. / Microchemical systems or microreactors refer to a new class of continuous reactors that have feature sizes in the submillimeter range. In particular, microfabricated chemical reactors are built using silicon-based photolithographic fabrication techniques that were originally developed to create integrated microelectronic circuits. Because silicon microfabrication allows precise control over the geometry of the reactor features down to the micron scale, as well as the integration of a variety of sensors into the fluidic path, microfabricated reactors are promising as versatile chemical synthesis tools that present capabilities exceeding those of their macroscale counterparts. In addition, small reactor volumes enhance the control of fast exothermic reactions and allow new reaction chemistries deemed too difficult to control in conventional reactors to be carried out safely. One example of such chemistry is the direct fluorination of organic molecules. This thesis addresses the design, fabrication, and application of a gas-liquid microreactor as a discovery tool for the synthesis of fluorinated compounds by direct fluorination. A microfabrication methodology was developed to create microfluidic channels chemically compatible with the highly corrosive direct fluorination environment. Electron-beam evaporated nickel in combination with thermally grown silicon oxide coatings were employed as corrosion barriers for microchannels formed in a silicon substrate. The direct fluorination of toluene was safely demonstrated at room temperature and on preparative yields for substrate concentrations ranging between 0.1 and 1.0 M. The product distribution was studied as a function of the number of fluorine equivalents and solvent type. / (cont.) Extensive gas-liquid flow visualization studies were conducted in single and dual-channel devices with triangular cross section (channel hydraulic diameter of [approx.]224 [mu]m) using pulsed-laser fluorescence and continuous-wave microscopy. A gas-liquid flow regime map containing slug and annular-dry flows was obtained at flow conditions relevant for gas-liquid microchemical systems, i.e., liquid superficial velocities below 0.01 m/s. These flow visualization studies served as the design basis of a scaled-out gas-liquid reactor with a multilayer, multichannel architecture and a liquid volumetric throughput of 80 mL/h. A nonintrusive optical gas-liquid flow velocimetry technique was developed to verify uniform flow distribution across the microchannels of this reactor. / by Nuria De Mas Valls. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1953. / Vita. / Includes bibliographical references (leaves A85-A87). / by Murrary Wilford Rosenthal. / Sc.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1958. / Includes bibliographical references (leaves 147-151). / by Robert G. Shaver. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007. / Includes bibliographical references (p. 241-257). / Transplantation of isolated islets of Langerhans has promising potential to cure type 1 diabetes by inducing long-term normoglycemia and insulin independence. The feasibility of clinical islet transplantations has been established according to the Edmonton Protocol. However, results are variable, and it is not yet possible to predict transplantation outcome from in vitro measurements with islet preparations. Currently, islet enumeration is based on microscopic visualization after staining with a zinc-specific binding dye (dithizone, DTZ) and manual counting with normalization on the basis of an islet equivalent (IE), an islet with volume equivalent to that of a sphere with a 150 Pm diameter. Islet viability is based on a live/dead staining test with two fluorescent dyes, fluorescein diacetate (FDA) and propidium iodide (PI). These methods are operator- dependent and prone to error due to the variability in islet size and shape and are not predictive of transplantation outcome. We developed quantitative assays that allowed reproducible evaluation of meaningful properties that affect the clinical outcome in impure human islet preparations. For purity estimation, we examined light microscopic (LM) morphological analysis of 1-jm sections to estimate the islet volume fraction and compared the results with those of electron microscopy (EM) ultrastructural analysis on the same preparations. / (cont.) For quantifying the total number of cells in a preparation, we developed an assay based on nuclei counting and compared three different counting methods: (1) visual counting in a hemacytometer and automatic counting by (2) aperture resistance measurements (Coulter Multisizer II) and (3) flow cytometer measurements (Guava PCA). The methods differed in the way nuclei were distinguished from fragments, accuracy, time required and range of linearity. Total amount of tissue was also quantified by DNA measurements. A theoretical framework was developed in order to combine volume fraction data from the LM analysis with the total number of cells in the tissue from nuclei measurements in order to estimate the total number of islets present in impure preparations. To evaluate tissue viability, we used oxygen consumption rate measurements (OCR), an assay of mitochondrial function. We developed a very small stirred chamber system (Micro Oxygen Uptake System, Model FO/SYS210T, Instech Laboratories, Plymouth Meeting, PA) specifically designed for measurements with islets. OCR measurements combined with an assay of total amount of tissue quantification (nuclei counting or DNA analysis) provide a measure of the tissue fractional viability. / (cont.) We used the methods we developed to characterize a large number of islet preparations of different species prior to and following culture. We also studied the transient response of cells and islets to various stresses, as reflected by assays of different type. We found that membrane integrity tests are poor indicators of the fractional viability of a cell sample, while mitochondrial function assays identify cell death at its earlier stages. We examined the predictive capability of the assays we developed through in vivo studies. Ttransplantation experiments were performed with rat islets implanted into mice and high purity fraction of human islets transplanted into mice. We found that OCR measurements combined with a measure of total amount of tissue (nuclei or DNA) are good predictors of the transplantation outcome. / by Anna Pisania. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1993. / Includes bibliographical references (leaves 262-268). / by William Roy Haulbook. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (leaves 136-143). / The effects of reaction and deposition conditions on the properties of the conjugated electroluminescent polymer poly(p-phenylene vinylene) (PPV) prepared by parylene-based chemical vapor deposition (CVD) are explored in this thesis. A reactor for CVD of PPV is designed and constructed, and both a,a'-dibromo p-xylene and a,a.'-dichloro p-xylene are tested as source monomers. By sufficiently baking out the CVD system, reproducible fabrication of unoxidized CVD PPV is achieved for the first time. The optical characteristics of the CVD PPV are in good agreement with solution-processed material, but the polymer does exhibit enhanced aliphatic hydrocarbon incorporation, which can influence the polymer bandgap and therefore emission color. For the same deposition conditions, these hydrocarbon defects are more prominent in polymer prepared from the bromine monomer. By correlating changes in polymer composition with the CVD reaction and deposition conditions, the source of the aliphatk hydrocarbon incorporation is determined to be fragmentation of the starting monomer during the pyrolysis step. Tuning the peak emission color of the CVD polymer through copolymerization is also addressed. Fabrication of device-quality CVD PPV films is achieved for the first time through a greater understanding of how the deposition conditions influence the polymer film structure. Several different growth morphologies are observed below the critical surface polymerization temperature, such as island, transitional, and coalesced or 'layered' growth. By re-designing the reactor configuration to allow film deposition at room temperature, single-layered CVD PPV devices with reasonable tum-on voltages and light output easily seen with the naked eye in a well-lit room are realized. A highly novel, parallel method for selective deposition of CVD PPV is also developed through use of chemical surface modification, achieving one-step patterned growth of the deposited material. Treatment of the substrate with evaporated iron, iron salts, or organo-iron complexes is found to inhibit polymer growth. Spatial control of the inhibitor through microcontact printing of carboxylic-acid terminated alkanethiols used in conjunction with metal salts, or photolithographic patterning of evaporated metal films, allows fabrication of selectively grown features as small as 5 μm and films as thick as 3500 A. This is more than sufficient for use as the active element in LEDs, and the selectively grown PPV is successfully incorporated into a functional device. Iron treatment also inhibits the deposition of other parylene-based CVD polymers such as parylene-N and parylene-C, resulting in selectively grown structures on the order of several microns in thickness. For the parylene systems, a wide range of transition metal elements, salts, and organometallic complexes are found to produce the same growth inhibition effect, which suggests that the chemical surface modification approach presented here may be a general technique for controlling the growth of vapor-processed parylene-based polymers. / by Kathleen Michelle Vaeth. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995. / Includes bibliographical references (leaves 318-324). / by John Christopher Arnold. / Ph.D.