Theses and Dissertations at Montana State University (MSU)
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Item Design and fabrication of membrane-based pressure sensor for capillary pressure measurement in micromodels(Montana State University - Bozeman, College of Engineering, 2021) Raventhiran, Nishagar; Chairperson, Graduate Committee: Yaofa LiPressure is a fundamental quantity in virtually all problems in fluid dynamics from macro-scale to micro/nano scale flows. Although technologies are well developed for its measurement at the macro-scale, pressure quantification at the microscale is still not trivial. Yet, precise pressure mapping at microscale such as in microfluidics is imperative in a variety of applications, including porous media flows and biomedical engineering. In particular, pore-scale capillary pressure is a defining variable in multiphase flow in porous media and has rarely been directly measured. To that end, this study aims to design and fabricate an on-chip sensor that enables quantification of capillary pressure in microfluidic porous media, called micromodels. The micromodel is fabricated in polydimethylsiloxane (PDMS) using soft lithography with a thin membrane incorporated that deflects with pressure variations in the fluid flow. Employing a microscope coupled with a high-speed camera and the astigmatism particle tracking principle, precise pressure measurement is achieved with an accuracy of ~ 60Pa. This sensor is then applied to characterize the viscous pressure drop in single phase flows, and the capillary pressure in a water-air multiphase in microchannels, and good agreement is obtained between the sensor measurement, theoretical values and measurements employing a commercial pressure transducer. This thesis provides a novel method for in-situ quantification of local pressure and potentially 2D pressure field in microfluidics and thus opens the door to a renewed understanding of pore-scale physics of multiphase flow in porous media.Item Analysis of water transport phenomena in thin porous media of a polymer electrolyte membrane fuel cell(Montana State University - Bozeman, College of Engineering, 2018) Battrell, Logan Robb; Chairperson, Graduate Committee: Ryan Anderson; Aubree Trunkle, Erica Eggleton, Lifeng Zhang and Ryan Anderson were co-authors of the article, 'Quantifying cathode water transport via anode humidity measurements in a polymer electrolyte membrane fuel cell' in the journal 'Energies' which is contained within this thesis.; Ning Zhu, Lifeng Zhang and Ryan Anderson were co-authors of the article, 'Transient, spatially resolved desaturation of gas diffusion layers measured via synchrotron visualization' in the journal 'International journal of hydrogen energy' which is contained within this thesis.; Virat Patel, Ning Zhu, Lifeng Zhang and Ryan Anderson were co-authors of the article, '4-D imaging of the desaturation of gas diffusion layers by synchrotron radiography' submitted to the journal 'Journal of power sources' which is contained within this thesis.This thesis explores and quantifies water transport related to the desaturation of the thin porous layer known as the Gas Diffusion Layer (GDL) associated with Polymer Electrolyte Membrane (PEM) fuel cells. The proper management of water within this layer is critical to optimal fuel cell performance. If there is not enough water, the membrane can become dehydrated, which leads to poor cell performance, but if too much water accumulates or becomes flooded, gas transport is restricted, which also lowers performance and can potentially lead to total cell failure. Understanding the desaturation of this layer is thus key to obtaining and maintaining optimal fuel cell performance. This behavior is explored both at the macroscale, through the quantification of the removal of excess water from an active fuel cell, as well as at the micro-scale, through the use of synchrotron X-ray computed tomography (X-ray CT) to visualize and quantify the desaturation of an initially flooded GDL. The macro-scale investigation extends the previously developed qualitative Anode Water Removal (AWR) test, which functions to identify when poor PEM fuel cell performance is due to excess water, to a diagnostic protocol that quantifies the amount of water being removed by the test through an analysis of the anode pressure drop. Results show that the protocol can be applied to a variety of fuel cell setups and can be used to quickly quantify water management capabilities of novel GDL materials. The microscale investigations show that while both convection and evaporation play a role in the desaturation, evaporation is required to fully desaturate the GDL. Additionally, the microscale investigation allows for the spatial segmentation of the GDL to identify local desaturation rates and temporal saturation profiles, which show that the overall desaturation of the GDL is a heterogeneous process that depends on initial conditions, flow field geometry and the natural anisotropy of the material. Results show that future control strategies and modeling studies will need to expand their investigated domains in order to accurately capture the fully heterogeneous nature of this process.Item Temperature dependent solvation in phospholipid membranes(Montana State University - Bozeman, College of Letters & Science, 2017) Gobrogge, Christine Ann; Chairperson, Graduate Committee: Robert Walker; Victoria A. Kong and Robert A. Walker were co-authors of the article, 'Temperature dependent solvation and partitioning of coumarin 152 in phospholipid membranes' in the journal 'Journal of physical chemistry B' which is contained within this thesis.; Heather S. Blanchard and Robert A. Walker were co-authors of the article, 'Temperature dependent partitioning of C152 in phosphatidylcholine lipid bilayers' in the journal 'Journal of physical chemistry B' which is contained within this thesis.; Robert A. Walker was a co-author of the article, 'Quantifying solute partitioning in phosphatidylcholine membranes' submitted to the journal 'The journal of analytical chemistry' which is contained within this thesis.Experiments described in this dissertation were designed to systematically investigate solute partitioning in phospholipid bilayers as a function of phospholipid identity, solute identity, membrane phase, and membrane composition. Experiments use time-resolved fluorescence, steady-state fluorescence, dynamic light scattering, and differential scanning calorimetry to experimentally quantify solute partitioning in three specific regions of a model membrane, as well as track how solutes migrate into and out of lipid bilayers as a function of temperature. Phosphatidylcholine vesicles were comprised of DLPC (12:0 PC), DMPC (14:0 PC), and DPPC (16:0 PC). In all three lipid systems, coumarin 152 (C152) showed partitioning behavior that was qualitatively similar but quantitatively different. Partitioning into a gel phase membrane was slightly exothermic and slightly entropically unfavorable. Partitioning of C152 near the lipid membrane melting temperature was entropically driven and endothermic. Well above the melting temperature, exsolvation of C152 from the membrane back into the aqueous buffer was enthalpically driven but entropically unfavorable. Regardless of solution temperature, relatively little (<20%) C152 partitioned into the hydrophobic core of the membrane. The magnitudes of the thermodynamic forces driving C152 partitioning systematically increased with alkyl chain length (DLPC < DMPC < DPPC). C152 and C461 differ solely in the 4-position where C152 has a trifluoro methyl group in place of C461's -CH3 group. Fluorescence amplitudes were used to calculate absolute partition coefficients and average number of solutes per DPPC vesicle. C152 shows a ~10-fold greater affinity than C461 for lipid bilayers, despite both solutes having similar log P values. Differential scanning calorimetry traces of vesicles composed of binary mixtures of lipids show moderate miscibility between DLPC and DMPC and low miscibility between DMPC and DMPE. Time-resolved fluorescence decays indicate C152 partitioning into mixed PC membranes is nearly ideal; that is, even if mixed PC vesicles do form single lipid domains, C152 partitioning behavior is largely unaffected. Time-resolved fluorescence decays show C152 partitioning behavior into PC/PE membranes is distinctly non-ideal, but the cause of this non-ideal behavior requires further studies.Item Adsorption capacity of SAPO-34 and ZSM-5 zeolites determined by breakthrough experiments(Montana State University - Bozeman, College of Engineering, 2016) Ilic, Boris; Chairperson, Graduate Committee: Stephanie WettsteinAlthough it has been known for over 50 years that zeolite frameworks are flexible, it has been only of recent that a systematic investigation into this phenomenon has begun. An area that has not been significantly explored is the affect that zeolite flexibility may have on adsorption capacities. In order to explore this, a flow system was built and assembled, and the system performance was verified by replicating literature ZSM-5/isobutane, ZSM-5/n-hexane, and SAPO-34/methanol adsorption isotherms. Different packing schemes (powders, mixtures, pellets) were studied and corresponding adsorption capacities were evaluated for accuracy and precision. It was found that zeolite powder pressed into pellets led to the lowest deviation from literature values and that larger crystal sizes may also lead to more accurate values. While further investigation into packing methods is recommended, the relatively accurate adsorption capacities that were acquired suggests that the established flow system has been built and calibrated correctly, and that further adsorption experiments probing the flexibility of the zeolite structure can begin.Item Non-destructive assessment of household reverse osmosis water treatment membrane biofouiling(Montana State University - Bozeman, College of Engineering, 2015) Markwardt, Stephen Donald; Chairperson, Graduate Committee: Anne CamperReverse osmosis (RO) membrane treatment is well known for its ability to desalinate sea and brackish waters on a massive scale in large treatment plants. Conversely, RO membranes are also used to treat freshwater from questionable sources at the point of use. Both types of systems suffer from the negative effects of membrane fouling. There are four basic types of fouling: inorganic, colloidal, organic, and biofouling. Traditional methods for assessing fouling either cannot differentiate between the fouling types or destroy the membrane in the process. Currently, many new and innovative methods to non-destructively assess the degree and type of fouling inside a membrane unit are being researched. Most of these methods require the use of expensive electrodes and equipment which is not economical for point of use systems. This research was aimed at determining economical non-destructive methods to assess biofouling in point of use RO membrane treatment systems. Experimentation was performed on three parallel household RO membrane units operated under controlled feed water conditions to promote biofouling, inorganic fouling and a combination of both. Operational and biological parameters were monitored throughout the systems' lifespan. Membrane autopsies were also done to assess the degree and type of fouling. Statistical models were performed on the operational data to determine statistically relevant parameters between the fouling types that were subsequently validated by the membrane autopsies. Several non-destructive methods to assess the presence of biofouling were determined. Permeate flow rates decreased in a significantly different way when biofouling was present compared to when it was not. Large increases in permeate conductivity were also noted in membranes suffering from biofouling while they were not observed in membranes that had been inorganically fouled. The concentration of cell clumps in the retentate also increased in membranes experiencing biofouling while they did not increase in membranes that were inorganically fouled. These methods were found to not be sensitive enough to provide early warning for the presence of biofouling. However, these methods could be used to conveniently and economically assess the types of fouling problems being experienced household RO systems.Item Selective permeation through modified vinylindene fluoride membranes(Montana State University - Bozeman, College of Engineering, 1975) Zavaleta, RonanthItem The separation of oxygen from air using commercial, plasticized, and nonplasticized polymeric membranes(Montana State University - Bozeman, College of Engineering, 1985) Mus, Mark DavidItem Biological pretreatment for membrane water treatment sytems(Montana State University - Bozeman, College of Engineering, 2000) Wend, Christopher FrancisItem Temperature effects on the separation of isomeric xylenes using the pervaporation process(Montana State University - Bozeman, College of Engineering, 1985) Downs, William BlaineItem Separation of Hâ‚‚ from Nâ‚‚ by selective permeation through polymeric membranes(Montana State University - Bozeman, College of Engineering, 1976) Heyd, Robert Leo