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JAIN, ALOKA BIOPARTICLE SEPARATION TECHNIQUE THROUGH MICROCHANNELS USING SEQUENTIAL PRESSURE PULSES
MS, University of Cincinnati, 2004, Engineering : Electrical Engineering
In this work, an on-chip magnetic bead separator in an aqueous solution has been implemented on a plastic substrate. The technique has been successfully characterized in separating magnetic microspheres of 4.1 µm diameter from a suspension solution in DI water. µTAS (Micro Total Analysis System) frequently need to deal with bioparticle suspensions in solution. Separation of certain bioparticles is often desirable. Traditionally, methods like physical filtration have been used to separate biomolecules from suspension solutions. These methods, though well-established are not suited for integration on to mass-fabricated plastic lab-on-a-chip devices. The method developed in this work relies on the differential force exerted by application of high amplitude, short duration pressure pulses on a suspension solution, resulting in separation of suspended particles. From a dispensed volume of 500 nl of the suspension solution, up to 300 nl, or 60 % of volume has been cleared of particles.

Committee:

Dr. Chong Ahn (Advisor)

Keywords:

Bioparticle separation; magnetic bead separation; blood separation; pressure pulses; biomems

Shinbrough, KaiInfrared and Thermal-Desorption Spectroscopy of H2 and D2 in Metal Organic Frameworks
BA, Oberlin College, 2017, Physics and Astronomy
In this thesis we provide an introduction to the use of Metal-Organic Frameworks (MOFs) for hydrogen storage and for the separation of hydrogen isotopologues, H2 and D2. MOFs are a class of materials comprised of `building-block’ metal-oxide clusters connected by organic ligands, which have the capacity to adsorb molecules such as hydrogen through weak, physisorptive mechanisms. We provide some background on the quantum mechanical structure of hydrogen isotopologues, the structure of a few state-of-the-art MOFs, the quantum mechanics of infrared spectroscopy, and the desorption dynamics of adsorbates generally. We provide a description of the experimental apparatus and procedure used in this work to acquire thermal desorption (TD) and simultaneous, in situ infrared (IR) spectra. Notably, this apparatus makes use of a pressure gauge to record TD spectra—to the best of the author’s knowledge, this is the first time such an apparatus has been created and shown to produce reproducible, physically-informative TD spectra. We demonstrate the potential of this novel spectroscopic technique on three MOFs, as we report their respective TDS and IR signatures. The agreement between our TDS and IR techniques is remarkable, as is the amount of information apparent in the TD spectra, and the agreement of our TD spectra with those in the literature. With our simple technique we are able to clearly distinguish the TD spectra of H2 and D2, allowing for the evaluation of MOFs with respect to their isotopologue separating ability. In addition to a proof of concept as to the proficiency of the experimental apparatus, this work presents two main findings: that the desorption of hydrogen isotopologues from MOFs does not follow the coverage-independent Polanyi-Wigner equation, and that stronger binding MOFs exhibit diminishing returns with respect to their ability to separate hydrogen isotopologues via temperature programming. As we argue on several occasions in this thesis, the TD spectra of hydrogen desorbing from the MOFs examined with our technique do not obey the coverage-independent Polanyi-Wigner equation. This is foremost demonstrated by the poor ab initio fits of our spectra to the equation. This result is also corroborated by the coverage dependence of the TD spectra of Co-MOF-74 (dobdc), however, and further by the ramp rate dependence of these spectra. In demonstrating this result, we advise against the use of the coverage-independent Polanyi-Wigner equation—and analysis techniques based off of it—when considering the desorption of hydrogen from MOFs. As these techniques have begun to feature prominently in the literature, this result proves exceedingly pertinent. We arrive at the latter conclusion by examining the MOFs reported on as a group, and examining the separation of H2 and D2 TD peaks as a function of MOF binding energy. We conclude through experimental as well as through computational techniques that the prospect of temperature-programmed separation through total desorption of H2 and total adsorption of D2 is exceedingly bleak. This surprising result rules out the most straightforward use of MOFs for hydrogen isotopologue separation, what we name Zero Point Energy Separation (ZPES) at a single site. As the field surrounding MOFs tacitly assumes this as a promising possibility, again this result proves exceedingly pertinent. The prospect of more imaginative uses of MOFs for temperature-programmed isotopologue separation remains open, as does the possibility of isotopologue separation through other mechanisms involving MOFs.

Committee:

Stephen FitzGerald (Advisor)

Subjects:

Materials Science; Physical Chemistry; Physics; Quantum Physics

Keywords:

MOFs; Metal-Organic Frameworks; Porous materials; H2-D2 separation; hydrogen separation; deuterium separation; temperature-programmed desorption; thermal desorption spectroscopy; infrared spectroscopy; trapped hydrogen; quantum sieving

Hu, KeSpeech Segregation in Background Noise and Competing Speech
Doctor of Philosophy, The Ohio State University, 2012, Computer Science and Engineering

In real-world listening environments, speech reaching our ear is often accompanied by acoustic interference such as environmental sounds, music or another voice. Noise distorts speech and poses a substantial difficulty to many applications including hearing aid design and automatic speech recognition. Monaural speech segregation refers to the problem of separating speech based on only one recording and is a widely regarded challenge. In the last decades, significant progress has been made on this problem but the challenge remains.

This dissertation addresses monaural speech segregation from different interference. First, we research the problem of unvoiced speech segregation which is less studied compared to voiced speech segregation probably due to its difficulty. We propose to utilize segregated voiced speech to assist unvoiced speech segregation. Specifically, we remove all periodic signals including voiced speech from the noisy input and then estimate noise energy in unvoiced intervals using noise-dominant time-frequency units in neighboring voiced intervals. The estimated interference is used by a subtraction stage to extract unvoiced segments, which are then grouped by either simple thresholding or classification. We demonstrate that the proposed system performs substantially better than speech enhancement methods.

Interference can be nonspeech signals or other voices. Cochannel speech refers to a mixture of two speech signals. Cochannel speech separation is often addressed by model-based methods, which assume speaker identities and pretrained speaker models. To address this speaker-dependency limitation, we propose an unsupervised approach to cochannel speech separation. We employ a tandem algorithm to perform simultaneous grouping of speech and develop an unsupervised clustering method to group simultaneous streams across time. The proposed objective function for clustering measures the speaker difference of each hypothesized grouping and incorporates pitch constraints. For unvoiced speech segregation, we employ an onset/offset based analysis for segmentation, and then divide the segments into unvoiced-voiced and unvoiced-unvoiced portions for separation. We show that this method achieves considerable SNR gains over a range of input SNR conditions, and despite its unsupervised nature produces competitive performance to model-based and speaker independent methods.

In cochannel speech separation, speaker identities are sometimes known and clean utterances of each speaker are readily available. We can thus describe speakers using models to assist separation. One issue in model-based cochannel speech separation is generalization to different signal levels. We propose an iterative algorithm to separate speech signals and estimate the input SNR jointly. We employ hidden Markov models to describe speaker acoustic characteristics and temporal dynamics. Initially, we use unadapted speaker models to segregate two speech signals and then use them to estimate the input SNR. The input SNR is then utilized to adapt speaker models for re-estimating the speech signals. The two steps iterate until convergence. Systematic evaluations show that our iterative method improves segregation performance significantly and also converges relatively fast. In comparison with related model-based methods, it is computationally simpler and performs better in a number of input SNR conditions, in terms of both SNR gains and hit minus false-alarm rates.

Committee:

DeLiang Wang (Committee Chair); Eric Fosler-Lussier (Committee Member); Mikhail Belkin (Committee Member)

Subjects:

Computer Science

Keywords:

Monaural Speech Separation; CASA; Unvoiced Speech; Nonspeech Interference; Cochannel Speech Separation; Unsupervised Clustering; Model-based Method; Iterative Estimation

Xu, JieLabeled and Label-less Magnetic Cell Separation and Analysis using Cell Tracking Velocimetry
Doctor of Philosophy, The Ohio State University, 2012, Chemical and Biomolecular Engineering

Magnetic cell separation and related analysis technology continues its maturation with practioners demanding higher system performance using cells with either magnetically labeled or based on the intrinsic magnetic properties of cells. Typical performance metrics include a very high purity and recovery of the targeted cells or a high level of removal of undesired cells while still recovering the majority of desired cells. While this technology is widely used in biological or clinical research laboratories for diagnostic or therapeutic applications, there still exist many engineering challenges. These challenges include unique system designs or cells with various magnetic susceptibilities, and a more fundamental understanding of the magnetic cell separation process.

In this dissertation, an instrument referred to as cell tracking velocimetry was used and further perfected as a powerful analytical tool to assist in this continued improvement of magnetic cell separation technology and approaches. For the first time, side by side comparison of two versions of the CTV magnets: permanent verses electromagnet version, on the same targets were compared. The accuracy and sensitivity of the two versions of CTV system was evaluated, and suggestions were made for choice of version for experimental targets with different magnetic susceptibilities. Also, single particle magnetization measurement of micron sized magnetic particles was made possible by the CTV. Three types of commercially available magnetic particles were studied as examples in this study. The average magnetization values from cell tracking velocimetry were found to have good agreements with the reported values from commercially used instruments which usually output only a bulk value.

With respect to magnetic cell separation systems, immuno-labeled magnetic cell separation was carried out for the application of T cell depletion for the purpose of a mismatched, bone marrow transplantation. Flow simulations using FLUENT were carried out to explore flow rate and shear stress effect on separation results. A number of parameters in the particle labeling and magnetic separation part were optimized for two new types of immuno magnetic particles used in the study. Also, separation results analyzed by CTV were compared to results obtained from flow cytometry; advantages and limitations for this method were also discussed. Additionally, this study theoretically and experimentally explored the relationship between magnetic pressure and shear stress in terms of separation system performance. Shear stress, often neglected in the process of magnetic cell separation, plays an important role in breaking antibody antigen bond, non-specific binding of particles and cells, and direct affecting separation results.

Magnetic cell separation utilize the intrinsic magnetic properties of cells were carried out in the practice of red blood cell separation and algae separation for biofuel production. For red blood cell, with the need of continuous separation of weakly paramagnetic red blood cells with relatively high separation efficiency, the new continuous magnetic separation system was designed to replace the previously tested catch and release batch mode system. Continuous in-line deoxygenation was also made possible with a hollow fiber liquid gas contactor, and new design of deoxygenator was pursued to solve the cell loss problem. The separation efficiency of the continuous system was tested and confirmed to be comparable to the high gradient batch mode system. Large scale red blood cell separation was made possible with continuously running a multiple, 2 by 2 systems. For algae, a preliminary study on the intrinsic magnetophoresis of some algae stains was carried out, and improvement on their magnetic susceptibilities used either genetic modifying stains or media optimization techniques. CTV results and further separation test confirmed the feasibility of magnetic separation of algae cultures from large volume of solutions.

Committee:

Jeffrey Chalmers (Advisor)

Subjects:

Chemical Engineering

Keywords:

Magnetic cell separation; Cell tracking velocimetry; T cell depletion; Red blood cell separation; Magnetic algae culture

Clark, AdamPredicting the Crosswind Performance of High Bypass Ratio Turbofan Engine Inlets
Doctor of Philosophy, The Ohio State University, 2016, Aero/Astro Engineering
Takeoffs in crosswind conditions are a common occurrence in flight operations around the world, and flow separation from the inlet of a jet engine at this condition can lead to fan stall, surge, or aeromechanical excitation. The ability to predict flow separation and reattachment is critical to the design of a performance-optimized inlet and to reduce the risk of crosswind performance shortfalls during engine certification. This dissertation shows the derivation of an aerodynamic loading coefficient referred to as the Reattachment Parameter (RP). Analysis of wind tunnel test data for five different inlet designs at five different crosswind speeds show that inlet reattachment occurs when a single, critical value of RP is reached. A process for predicting flow reattachment is developed that relies solely on static pressure distributions from inviscid CFD and the RP coefficient. Validation of predictions from this process were accomplished with wind tunnel testing of two new ultra-high bypass ratio (UHBR) inlets and full-scale testing of a new conventional-length inlet on a modern turbofan engine. The average error in the reattachment predictions of the two UHBR inlets was 1.4% of peak flow and 4.3% of peak flow for the full-scale engine test. Reattachment predictions with the RP process were consistently found to be more accurate than those from RANS CFD. A second key advantage of the RP process is that, by leveraging inviscid CFD, a reattachment prediction can be made with about 1/100,000th the computational cost of a RANS prediction, which provides a tremendous advantage during inlet design work. Results from the RP process suggested that spinner size and shape may affect the crosswind performance of an inlet, so the effect of replacing a standard wind tunnel spinner with one that is larger and more representative of flight hardware was examined. Analysis with the RP process predicted reattachment with the larger spinner would occur 10.6% of peak flow earlier than the smaller spinner. Wind tunnel testing of both spinners showed a 9.5% of peak flow earlier reattachment for the larger spinner. Finally, the ability of the RP coefficient to quantify the circumferential distribution of aerodynamic loading is used to develop a novel design strategy referred to as `load balancing'. Knowledge of the circumferential locations which experience the highest aerodynamic loading allows a designer to alter the inlet geometry in order to achieve a more uniform load distribution. This process provides inlet designers with a unique ability to improve the crosswind performance of an inlet without negatively affecting other important performance characteristics.

Committee:

Jen-Ping Chen (Advisor); Jeffrey Bons (Committee Member); Michael Dunn (Committee Member); Richard Freuler (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

CFD; jet engine; inlet; crosswind; separation; reattachment; distortion; IDC; RANS; Euler; inviscid; loading parameter; pressure gradient; aerodynamics; nacelle; angle of attack; separation bubble; aerodynamic loading; pressure coefficient; hysteresis

Bhagat, Ali Asgar SaleemInertial microfluidics for particle separation and filtration
PhD, University of Cincinnati, 2009, Engineering : Electrical Engineering
Filtration and separation of particles has numerous industrial and research applications in biology and medicine. In this work, inertial microfluidics is used to develop devices for continuous and passive separation and filtration of particles. Although particles are generally expected to follow laminar flow streamlines in the absence of external forces, inertial forces can cause particles to migrate across microchannels in an accurate and predictable manner. Thus, this work demonstrates how a simple spiral microfluidic channel can be used for high-throughput separation and filtration of particulate mixtures by exploiting these inertial forces and taking advantage of Dean forces present in curved channels. The developed technique was used to demonstrate a complete separation between 1.9 µm and 7.32 µm diameter polystyrene particles and filtration of red blood cells. The inertial forces can also be modulated by controlling fluidic shear in microchannels with rectangular, high aspect ratio cross-section in order to cause preferential particle migration. This approach was used successfully to demonstrate a complete filtration of 1.9 µm and 780 nm diameter particles in straight rectangular microchannels. The ability to continuously and passively focus particles based on size at high flow rates in microchannels is expected to have numerous applications in high-throughput bioparticle separation and filtration systems. The simple planar nature of the devices should permit easy integration with the existing lab-on-a-chip (LOC) systems.

Committee:

Ian Papautsky, PhD (Committee Chair); Chong Ahn, PhD (Committee Member); Jason Heikenfeld, PhD (Committee Member); Rupak Banerjee, PhD (Committee Member); Dionysios Dionysiou, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

inertial microfluidics; lab-on-a-chip; passive microfluidics; particle separation; particle filtration; continuous high-throughput separation

Yang, RuidongStudies on Molecular and Ion Transport in Silicalite Membranes and Applications as Ion Separator for Redox Flow Battery
PhD, University of Cincinnati, 2014, Engineering and Applied Science: Chemical Engineering
Microporous zeolite membranes have been widely studied for molecular separations based on size exclusion or preferential adsorption-diffusion mechanisms. The MFI-type zeolite membranes were also demonstrated for brine water desalination by molecular sieving effect. In this research, the pure silica MFI-type zeolite (i.e. silicalite) membrane has been for the first time demonstrated for selective permeation of hydrated proton (i.e. H3O+) in acidic electrolyte solutions. The silicalite membrane allows for permeation of H3O+ ions, but is inaccessible to the large hydrated multivalent vanadium ions due to steric effect. The silicalite membrane has been further demonstrated as an effective ion separator in the all-vanadium redox flow battery (RFB).The silicalite is nonionic and its proton conductivity relies on the electric field-driven H3O+ transport through the sub nanometer-sized pores under the RFB operation conditions. The silicalite membrane displayed a significantly reduced self-discharge rate because of its high proton-to-vanadium ion transport selectivity. However, the nonionic nature of the silicalite membrane and very small diffusion channel size render low proton conductivity and is therefore inefficient as ion exchange membranes (IEMs) for practical applications. The proton transport efficiency may be improved by reducing the membrane thickness. However, the zeolite thin films are extremely fragile and must be supported on mechanically strong and rigid porous substrates. In this work, silicalite-Nafion composite membranes were synthesized to achieve a colloidal silicalite skin on the Nafion thin film base. The “colloidal zeolite-ionic polymer” layered composite membrane combines the advantages of high proton-selectivity of the zeolite layer and the mechanical flexibility and low proton transport resistance of the ionic polymer membrane. The composite membrane exhibited higher proton/vanadium ion separation selectivity and lower electrical resistance than the commercial Nafion 117 membrane. The high proton transport selectivity is a result of the molecular sieving effect between the H3O+ and multivalent vanadium ions by the zeolitic pores; thus the zeolite particles significantly reduced the effective membrane surface area for vanadium ion permeation. The low resistance of the composite membrane can be attributed to the reduced thickness of the Nafion base film and the thinness of the colloidal silicalite top layer. The composite membrane outperformed the Nafion 117 membrane in the vanadium RFB operation in terms of the overall charge-discharge energy efficiency. Efforts have been made in further investigation of ion and molecular transport diffusivity in the polycrystalline silicalite film using zeolite-coated optical fiber interferometers. A physical model has been established for analyzing the molecular diffusivity in the zeolite layer based on the temporal responses of the optical interferometric signals during the transient process of molecular sorption. Experiments were first carried out to study the diffusivity of isobutane to evaluate the effectiveness of the proposed optical method. The isobutane diffusivities in silicalite measured by this method were in good agreement with the values reported in literature. The zeolite coated fiber optic interferometer was however ineffective in monitoring ion sorption or ion exchange in the silicalite films. It is suggested that more sensitive fiber optic devices are needed for studying the ion diffusion.

Committee:

Junhang Dong, Ph.D. (Committee Chair); Anastasios Angelopoulos, Ph.D. (Committee Member); Vikram Kuppa, Ph.D. (Committee Member); Joo Youp Lee, Ph.D. (Committee Member); Dale Schaefer, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Zeolite;Redox flow battery;Ion separation;Membrane separation;Composite membrane;Optical interferometer

Chatterjee, ArpitaSize-Dependant Separation of Multiple Particles in Spiral Microchannels
MS, University of Cincinnati, 2011, Engineering and Applied Science: Electrical Engineering
This work describes continuous separation of a multi-particle mixture in a simple spiral microchannel. The approach uses the concept of inertial microfluidics and takes advantage of the inertial lift forces coupled with rotational Dean drag to cause neutrally-buoyant particles to focus in a single equilibrium position near the inner channel wall. This position is strongly dependent on particle diameter. A 5-loop low-aspect-ratio Archimedean spiral microchannel with dimensions of 500 µmx100 µm (WxH) and 1 cm initial radius of curvature was used to demonstrate for the first time simultaneously focusing and separation of four particles. The polystyrene particles (7.32 µm, 10 µm, 15 µm, 20 µm in diameter) were selected for this work since they are compatible to the size of blood cells. The device exhibited a 80~90% separation efficiency, which is comparable to that of other microfluidic separation systems. The primary advantage of this passive technique is that it uses simple planar geometry and provides higher sample throughput. As a result of these advantages, it can be implemented on a lab-on-a-chip device for hematology and clinical application.

Committee:

Ian Papautsky, PhD (Committee Chair); Chong Ahn, PhD (Committee Member); Joseph Nevin, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Dean Drag flows;Inertial Microfluidics;passive separation;Inertial lift flows;Spiral Microchannel;continuous separation

Yen, ChiSynthesis and Surface Modification of Nanoporous Poly(ε-caprolactone) Membrane for Biomedical Applications
Doctor of Philosophy, The Ohio State University, 2010, Chemical and Biomolecular Engineering

The nanoporous PCL membranes were prepared via the combination of thermally- and nonsolvent-induced phase separations. For the phase separation process, nonsolvent has significant effect on pore formation and drug release rate. In nonsolvent-induced phase separation, a large amount of nonsolvent was added to casting solutions in order to improve pore connectivity within the membrane. The use of a Teflon plate for membrane casting can result in uniform nanoporous membranes and consistent lysozyme diffusion. Pore connectivity was improved significantly when coagulation bath temperature was lowered. By using a 5°C water coagulation bath in the wet-process precipitation, the average pore size reduced from 90 nm to 55 nm while increasing the casting solution concentration from 15 wt% to 25 wt% PCL. Thus, by varying the polymer concentration of the casting solution, the lysozyme release rate can be manipulated with precise control. The potential application of nanoporous PCL membranes to achieve the preferable zero-order release rate is demonstrated in this dissertation.

Along with achieving the zero-order release rate, the nanoporous PCL membranes also provide immunoprotection for cell-based therapies/devices. Immunoisolation can be achieved by preventing Immunoglobulin G (IgG) from diffusing through the nanoporous PCL membranes. With appropriate pore size, the nanoporous PCL membranes can allow the diffusion of therapeutic agents (lysozyme) and block the diffusion of immune molecules (IgG). The application of the nanoporous PCL membranes to cell-based therapies/devices is also demonstrated in this dissertation.

Extensive fibrosis induced by the healing process can be detrimental to the long-term performance of implantable applications. The prevention of fibroblast adhesion to the nanoporous PCL membrane surface is crucial for constant and well controlled drug release. This study shows a novel method to modify the nanoporous PCL membrane surface with poly(ethylene glycol) (PEG) . To achieve this goal, oxygen plasma and PEG(400) monoacrylate were used to graft the PEG onto the membrane surface through covalent bonding. Initially, various plasma treatment conditions were investigated to optimize the PEG-grafting quality and to achieve minimum fibroblast adhesion. After the treatment, water contact angle measurements and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra confirmed that PEG was successfully grafted onto the PCL membrane. X-ray photoelectron spectroscopy (XPS) revealed that different plasma powers and treatment times can change the surface composition of membranes. Cell adhesion and morphology studies indicate that either lower plasma power or shorter treatment time is able to significantly improve resistance to cell adhesion. With the use of appropriate plasma treatment conditions, the effects of grafting density and PEG chain length on reducing fibroblast adhesion were also investigated in this study. PEG-diacrylates were also investigated for their influence on fibroblast adhesion. For PEG-diacrylates, increasing molecular weight can lead to a higher resistance against cell adhesion. However, PEG-diacrylates were not as effective as PEG(400)-monoacrylate for providing the resistance to cell adhesion.

Committee:

W.S. Winston Ho (Advisor); Boyaka Prosper N. (Committee Member); Koelling Kurt W. (Committee Member); Lee L. James (Committee Member)

Subjects:

Biomedical Research; Chemical Engineering; Engineering; Polymers

Keywords:

Polycaprolactone (PCL); Thermally-induced phase separation (TIPS); Nonsolvent-induced phase separation (NIPS); Nanoporous; Drug delivery; Controlled release; Lysozyme; Poly(ethylene glycol) (PEG); Oxygen plasma; Surface modification; biofouling

Kuntaegowdanahalli, Sathyakumar S.Inertial microfluidics for continuous particle separation in spiral microchannels
MS, University of Cincinnati, 2009, Engineering : Electrical Engineering
This work describes the use of inertial microfluidics for continuous multi-particle separation in simple spiral microchannels. The dominant inertial forces coupled with the Dean rotational force due to the spiral microchannel geometry cause particles to occupy a single equilibrium position near the inner microchannel wall. The position at which particles equilibrate is dependent on the ratio of the inertial lift to the Dean drag. Using this concept, a spiral lab-on-a-chip (LOC) design was demonstrated for the first time for focusing particles at distinct equilibrium positions in the microchannel cross-section based on size. The individual streams can be collected with an appropriately designed outlet system. To demonstrate this principle experimentally, a 5-loop Archimedean spiral microchannel with a fixed width of 500 µm and a height of 130 µm was used to simultaneously and continuously separate 10 µm, 15 µm, and 20 µm diameter polystyrene particles. The device exhibited a 85% separation efficiency. The approach was applied to separating SH-SY5Y neuroblastoma cells and C6 glioma cells with 80% efficiency and high relative viability (>90%). The simple planar structure and high sample throughput (> 1 million cells/min) offered by this passive microfluidic approach makes it attractive for many LOC devices for biomedical and environmental applications.

Committee:

Ian Papautsky, PhD (Committee Chair); Jason Heikenfeld, PhD (Committee Member); Fred Beyette, PhD (Committee Member)

Subjects:

Biomedical Research; Electrical Engineering

Keywords:

Passive separation; Dean flows; Inertial microfluidics; Cell separation

Paik, Kristopher DoojinInhibition of pro-inflammatory processes reduces sensitization of the behavioral response to maternal separation
Master of Science (MS), Wright State University, 2009, Anatomy
The current study examined the behavioral sensitization of guinea pig pups in response to consecutive days of maternal separation. In the first experiment, guinea pigs that received centrally administered artificial cerebrospinal fluid or IL-10 exhibited sensitization of passive behaviors from Day 1 to Day 2. IL-10 decreased the levels of passive behaviors on Day 1, as well as the increase on Day 2. The second experiment used unoperated pups, which also showed sensitization of the passive response from Day 1 to Day 2, though the effect appeared reduced relative to control pups of Experiment 1. Collectively, this investigation confirms previous evidence that passive behaviors are due in part to pro-inflammatory cytokines. It also provides evidence that the increase in passive measures from the first separation to the second may be caused by a sensitization of pro-inflammatory mechanisms.

Committee:

Michael Hennessy (Advisor); Patricia Schiml-Webb (Committee Member); John Pearson (Committee Member)

Subjects:

Psychology

Keywords:

pro-inflammatory cytokines; maternal separation; sensitization; depression; guinea pigs

Patel, Ankit ArvindNovel P-(SBMA) Grafted Glass Fiber Filters and Glass Slides for Oil-Water Separation and Underwater Self-Cleaning Applications
Master of Science in Engineering, University of Akron, 2012, Chemical Engineering
Oil-water separation is a major problem in industries such as oil-production and waste-water treatment where millions of gallons of oil-contaminated water are produced. Therefore a nontoxic, quick, effortless, cost-efficient, and ready-to-go technique is required. Superhydrophilic and underwater superoleophobic sulfobetaine methacrylate (SBMA) surfaces were successfully prepared using surface-initiated atom transfer radical polymerization (SI-ATRP) and were characterized by contact angle measurements and ellipsometry. The contact angles obtained for the p-(SBMA) grafted glass slides in-air (8-13º) and underwater (162-169º) allow them to be classified as superhydrophilic and superoleophobic respectively. The p-(SBMA) grafted glass fiber filters showed exceptional results at separating water from oil without even allowing miniscule amounts of visible oil to permeate through. The p-(SBMA) grafted glass fiber filters can be used for oil-water separation purposes, while the p-(SBMA) grafted glass slides can be used for self-cleaning, while both can be used for antifouling applications.

Committee:

Lingyun Liu, Dr. (Advisor); George Chase, Dr. (Committee Member); Michael Cheung, Dr. (Committee Member); Homero Castaneda-Lopez, Dr. (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Environmental Engineering; Molecular Chemistry; Petrology; Polymer Chemistry; Polymers; Technology

Keywords:

Oil;Water;Separation;Superhydrophilic;Superoleophobic; Hydrophilic;Oleophobic;Underwater;SBMA;Sulfobetaine Methacrylate;p-(SBMA);Zwitterionic;Glass Fiber Filter;Self-Cleaning;ATRP

Matkar, Rushikesh AshokPhase Diagrams and Kinetics of Solid-Liquid Phase Transitions in Crystalline Polymer Blends
Doctor of Philosophy, University of Akron, 2007, Polymer Engineering
A free energy functional has been formulated based on an order parameter approach to describe the competition between liquid-liquid phase separation and solid-liquid phase separation. In the free energy description, the assumption of complete solvent rejection from the crystalline phase that is inherent in the Flory diluent theory was removed as solvent has been found to reside in the crystalline phase in the form of intercalates. Using this approach,we have calculated various phase diagrams in binary blends of crystalline and amorphous polymers that show upper or lower critical solution temperature. Also, the discrepancy in the χ values obtained from different experimental methods reported in the literature for the polymer blend of poly(vinylidenefluoride) and poly(methylmethacrylate) has been discussed in the context of the present model. Experimental phase diagram for the polymer blend of poly(caprolactone) and polystyrene has also been calculated. Of particular importance is that the crystalline phase concentration as a function of temperature has been calculated using free energy minimization methods instead of assuming it to be pure. In the limit of complete immiscibility of the solvent in the crystalline phase, the Flory diluent theory is recovered. The model is extended to binary crystalline blends and the formation of eutectic, peritectic and azeotrope phase diagrams has been explained on the basis of departure from ideal solid solution behavior. Experimental eutectic phase diagram from literature of a binary blend of crystalline polymer poly(caprolactone) and trioxane were recalculated using the aforementioned approach. Furthermore, simulations on the spatio temporal dynamics of crystallization in blends of crystalline and amorphous polymers were carried out using the Ginzburg-Landau approach. These simulations have provided insight into the distribution of the amorphous polymer in the blends during the crystallization process. The simulated results are in close accordance with the experimentally observed concentration profiles of atactic polypropylene during the crystallization of isotactic polypropylene in a blend of these polymers. Finally described are the unique thermodynamics and kinetics that occur in thermoplastic elastomer blends of polypropylene and synthetic rubber, leading to the unique biphasic crystalline morphology imparting these blends with their characteristic high toughness and high impact strength. Phase diagrams in such blends exhibit a combined upper and lower critical solution temperature. These phase diagrams have been calculated based on the present model developed, and simulated results explain the structural development in these blends.

Committee:

Thein Kyu (Advisor)

Keywords:

polymer; blends; phase transitions; phase diagrams; crystallization; phase separation; phase field; thermodynamics; kinetics; thermoplastic; elastomer; concentration profiles; Flory diluent

Zou, JianCarbon dioxide-selective membranes and their applications in hydrogen processing
Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering
In this work, new CO2-selective membranes were synthesized and their applications for fuel cell fuel processing and synthesis gas purification were investigated. In order to enhance CO2transport across membranes, the synthesized membranes contained both mobile and fixed site carriers in crosslinked poly(vinyl alcohol). The effects of crosslinking, membrane composition, feed pressure, water content, and temperature on transport properties were investigated. The membranes have shown a high permeability and a good CO2/H2 selectivity and maintained their separation performance up to 170°C. One type of these membranes showed a permeability of 8000 Barrers and a CO2/H2selectivity of 290 at 110°C. The applications of the synthesized membranes were demonstrated in a CO2-removal experiment, in which the CO2 concentration in retentate was decreased from 17% to < 10 ppm. With such membranes, there are several options to reduce the CO concentration of synthesis gas. One option is to develop a water gas shift (WGS) membrane reactor, in which both WGS reaction and CO2-removal take place. Another option is to use a proposed process consisting of a CO2-removal membrane followed by a conventional WGS reactor. In the membrane reactor, a CO concentration of less than 10 ppm and a H 2concentration of greater than 50% (on dry basis) were achieved at various flow rates of a simulated autothermal reformate. In the proposed CO2-removal/WGS process, with more than 99.5% CO2 removed from the synthesis gas, the CO concentration was decreased from 1.2% to less than 10 ppm (dry), which is the requirement for fuel cells. The WGS reactor had a gas hourly space velocity of 7650 h-1 at 150°C and the H2 concentration in the outlet was more than 54.7% (dry). The applications of the synthesized CO2-selective membranes for high-pressure synthesis gas purification were also studied. We studied the synthesized membranes at feed pressures > 200 psia and temperatures ranging from 100-150 °C. The effects of feed pressure, microporous support, temperature, and permeate pressure were investigated using a simulated synthesis gas containing 20% carbon dioxide and 80% hydrogen.

Committee:

W.S. Winston Ho (Advisor)

Keywords:

Polymer Membrane; Gas Separation; Carbon Dioxide Removal; Membrane Reactor; Hydrogen Processing; Water Gas Shift Reaction

Marks, Christopher R.Surface Stress Sensors for Closed Loop Low Reynolds Number Separation Control
Doctor of Philosophy (PhD), Wright State University, 2011, Engineering PhD
Low Reynolds number boundary layer separation causes reduced aerodynamic performance in a variety of applications such as MAVs, UAVs, and turbomachinery. The inclusion of a boundary layer separation control system offers a way to improve efficiency in conditions that would otherwise result in poor performance. Many effective passive and active boundary layer control methods exist. Active methods offer the ability to turn on, off, or adjust parameters of the flow control system with either an open loop or closed loop control strategy using sensors. This research investigates the use of a unique sensor called Surface Stress Sensitive Film (S3F) in a closed loop, low Reynolds number separation control system. S3F is an elastic film that responds to flow pressure gradients and shear stress along its wetted surface, allowing optical measurement of wall pressure and skin friction. A new method for installing the S3F sensor to assure a smooth interface between the wall and wetted S3F surface was investigated using Particle Image Velocimetry techniques (PIV). A Dielectric Barrier Discharge (DBD) plasma actuator is used to control laminar boundary layer separation on an Eppler 387 airfoil over a range of low Reynolds numbers. Several different DBD plasma actuator electrode configurations were fabricated and characterized in an open loop configuration to verify separation control of the Eppler 387 boundary layer. The open loop study led to the choice of a spanwise array of steady linear vertical jets generated by DBD plasma as the control system flow effecter. Operation of the plasma actuator resulted in a 33% reduction in section drag coefficient and reattachment of an otherwise separated boundary layer. The dissertation culminates with an experimental demonstration of S3F technology integrated with a control system and flow effecter for closed loop, low Reynolds number separation control. A simple On/Off controller and Proportional Integral (PI) controller were used to close the control loop.

Committee:

Mitch Wolff, PhD (Advisor); Rolf Sondergaard, PhD (Committee Member); James Menart, PhD (Committee Member); Mark Reeder, PhD (Committee Member); Joseph Shang, PhD (Committee Member)

Subjects:

Aerospace Engineering; Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

low Reynolds number; fluid dynamics; surface stress sensitive film; flow control; separation control; S3F; plasma actuator; dielectric barrier discharge;

Cooper, Charlie AustinCVD Modification and Vapor/Gas Separation Properties of Alumina Membranes
MS, University of Cincinnati, 2001, Engineering : Chemical Engineering
Chemical vapor deposition was used to modify 3.6nm pore, sol-gel derived, alpha- alumina membranes supported on macroporous alpha-alumina. Aluminum oxide was deposited in the pores of the alpha-alumina membrane by alternating additions of trimethylaluminum and water. By reducing the pore size, the permeance of non-condensable gasses was reduced much more than the permeance of condensable gasses due to capillary condensation. The modified membrane that exhibited the best separation properties had a water permeance ranging from 1.5x10-6mol/m2 sPa to 3.0x10-7mol/m 2 sPa, an oxygen permeance ranging from 1.7x10-7mol/m2 sPa to 1.5x10-9mol/m2 sPa, and a separation factor as high as 140. The microstructure of the pores was found not to be atomic layer CVD derived as initially thought, but contained some irregularities attributed to homogeneous reactions. GIS p-type zeolite membranes were also made and found to have similar separation properties to the more heavily modified alpha-alumina membranes.

Committee:

Dr. Jerry Lin (Advisor)

Keywords:

CVD; separation; alumina; membrane; microporous

KIM, SANGILMODIFIED ORDERED MESOPOROUS SILICA MEMBRANES FOR CO 2 -N 2 SEPARATION
MS, University of Cincinnati, 2003, Engineering : Chemical Engineering
Reducing CO 2 emissions for addressing climate change concerns is becoming increasingly important since the CO 2 concentration in the atmosphere has increased rapidly since industrial revolution. Most currently investigated mitigation processes require CO 2 in a concentrated form. However, the CO 2 from coal-fired power plants is mixed with N 2 , water vapor, oxygen, and other impurities and present at a low ~15% concentration. Therefore, capturing CO 2 from dilute streams is an important step for many mitigation methods. Membrane separation methods are particularly promising due to potentially high CO 2 selectivities and fluxes. By a proper choice of the pore size and surface properties, the CO 2 separation and permeation across a membrane can be increased. However, current membranes for CO 2 separation suffer from a poor control over the pore size on the nanoscale and their surface properties. Mesoporous MCM-48 silica was functionalized using hindered and unhindered amine. The presence and surface concentration of the amino groups in the mesoporous MCM-48 silica upon attachment was studied by the IR, Si/CHN elemental analysis, and TGA, which confirmed that amino groups were successfully attached and their concentrations on the MCM-48 were 2.5 and 1.5 mmol/g, respectively. In addition, in-situ IR and CO 2 adsorption studies of amine-modified MCM-48 silica as potential membrane materials showed high CO 2 selectivities over N 2 . Mesoporous MCM-48 silica membranes synthesized on porous alumina supports obtained by the solution growth method and 3-aminopropylsilyl groups were attached to the surface of these silica membrane. The unsteady-state gas permeation studies using H 2 , He, N 2 , and CO 2 indicated the absence of large pinhole (>5.0 nm) in these mesoporous silica membranes. However, the aminopropyl-modified MCM-48 membrane showed no CO 2 separation in a binary gas permeation experiment due to low packing density of amino groups. In order to achieve high packing density of the amino groups on the surface of mesoporous silica membranes, surface hydration to increase silanol group concentration on MCM-48 and alternative amino functional groups was emplolyed. The polymerization of the amin-containing alkoxide and branched polyethyleneimine (PEI), which has chains with numerous CO 2 -capturing amino groups were introduced in MCM-48 membranes. The PEI-modified membranes showed high N 2 selectivity over CO 2 .

Committee:

Dr. Vadim Guliants (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Mesoporous silica; carbon dioxide separation; inorganic membrane

Bloxham, Matthew JonA Global Approach to Turbomachinery Flow Control: Loss Reduction using Endwall Suction and Midspan Vortex Generator Jet Blowing
Doctor of Philosophy, The Ohio State University, 2010, Aeronautical and Astronautical Engineering

A flow control scheme using endwall suction and vortex generator jet (VGJ) blowing was employed to reduce the turbine passage losses associated with the endwall flow field and midspan separation. Unsteady midspan control at low Re had a significant impact on the wake total pressure losses, decreasing the area-average losses by 54%. The addition of leading edge endwall suction resulted in an area-average total pressure loss reduction of 57%. The minimal additional gains achieved with leading edge endwall suction showed that the horseshoe vortex was a secondary contributor to endwall loss production (primary contributor- passage vortex).

A similar flow control strategy was employed with an emphasis on passage vortex (PV) control. During the design, a theoretical model was used that predicted the trajectory of the passage vortex. The model required inviscid results obtained from two-dimensional CFD. It was used in the design of two flow control approaches, the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control on the endwall below the passage vortex trajectory. The redirection approach attempted to alter the trajectory of the PV by removing boundary layer fluid through judiciously placed suction holes. Suction hole positions were chosen using a potential flow model that emphasized the alignment of the endwall flow field with inviscid streamlines. Model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade comprised of the highly-loaded L1A blade profile.

Detailed wake total pressure losses were measured, while matching the suction and VGJ massflow rates, for the removal and redirection approaches at ReCx=25000 and blowing ratio, B, of 2. When compared with the no control results, the addition of steady VGJs and endwall suction reduced the wake losses by 69% (removal approach) and 68% (redirection approach). The majority of the total pressure loss reduction resulted from the spanwise VGJs, while the suction schemes provided modest additional reductions (<2%). At ReCx=50000, the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-average total pressure loss reductions of up to 28% were measured in the wake at ReCx=50000, B=0, with applied endwall suction employed using the removal scheme (compared to no suction at ReCx=50000). At which point, the total pressure loss core was almost completely eliminated. PIV showed that the endwall suction changed the location of the PV eliminating its influence on the suction surface of the turbine blade. Suction with the removal approach removed the corner vortex (CV) increasing the available span by more than 10%. The redirection approach was less effective at higher suction rates due to the continual presence of the CV.

A system analysis was performed that compared the power needed to operate the flow control system to the power gained by the system. The power gains were assessed by comparing the change in lift and wake total pressure losses with and without flow control. The resultant power ratio showed that only 23% of the total power gained was needed to operate the flow control system for an L1A rotor at ReCx=50000, B=2.

Committee:

Jeffrey Bons, PhD (Advisor); James Gregory, PhD (Committee Member); Jen-Ping Chen, PhD (Committee Member); Mohammad Samimy, PhD (Committee Member)

Subjects:

Engineering

Keywords:

turbomachinery; vortex generator jet; flow control; turbine; gas turbine; horseshoe vortex; passage vortex; corner vortex; separation

Marote, Melissa A.Finding The Two-Way Street: Women from Mother-Present/Father-Absent Homes and Their Ability to Make Close Female Friendships
Doctor of Philosophy (PhD), Ohio University, 2011, Counselor Education (Education)

This heuristic study involving seven coresearchers, which included the author, explores the experiences of women from mother-present/father-absent homes and their ability to form and maintain close female friendships. The heuristic research model was chosen to provide the opportunity to conduct research in a very personalized, collaborative way with my coresearchers. From our first meeting through the creative synthesis, it was vital to use a research model that honored the exploration of feelings with all their associated meanings. Little was found in the literature that paired father absence and women's ability to form close female friendships. The author wanted to discover if other women from mother-present/father-absent homes had challenges forming and maintaining close female friendships.

Some of the coresearchers' experiences (our ability to form and maintain close female friendships, the effects from our fathers' absence, and the meaning we ascribed to these experiences) were substantiated by the literature, while others were not. Some information could not be examined because it could not be located in the literature. Six core essence themes (which contained 44 dominant themes) including: the satisfaction of close female friendships, obstacles faced in making close female friends, mother's influence also needs consideration, yearning for Daddy, and father behaving badly are explored in detail.

Committee:

Tracy Leinbaugh, PhD (Committee Chair); Peter Mather, PhD (Committee Member); Yegan Pillay, PhD (Committee Member); Gregory Janson, PhD (Committee Member)

Subjects:

Counseling Education

Keywords:

father; father absence; divorce; separation; female friendship;

Kelley, Christopher STHE UNITARY EXECUTIVE AND THE PRESIDENTIAL SIGNING STATEMENT
Doctor of Philosophy, Miami University, 2003, Political Science
The presidential bill signing statement has generated very little attention by political scientists interested in presidential power and the relationship between the Congress and the president. Despite its lack of interest by presidential scholars, it is a commonly used device by presidents dating all the way back to the Monroe administration. This dissertation offers the first systematic examination of what the signing statement is, how it is used, and why it has become important to the executive branch in the last thirty years.

Committee:

Ryan Barilleaux (Advisor)

Subjects:

Political Science, General

Keywords:

Signing statement; Unitary Executive; Separation of Powers; Presidential Power

Alawani, NadrahStructural Characterization of Synthetic Polymers and Copolymers Using Multidimensional Mass Spectrometry Interfaced with Thermal Degradation, Liquid Chromatography and/or Ion Mobility Separation
Doctor of Philosophy, University of Akron, 2013, Chemistry
This dissertation focuses on coupling mass spectrometry (MS) and tandem mass spectrometry (MS/MS) to thermal degradation, liquid chromatography (LC) and/or ion mobility (IM) spectrometry for the characterization of complex mixtures. In chapter II, an introduction of the history and the principles of MS and LC are discussed. Chapter III illustrates the materials and instrumentation used to complete this dissertation. Polyethers have been characterized utilizing MS/MS, as presented in Chapter IV and Chapter VI. Diblock copolymers of polyethylene oxide and polycaprolactone, PEO-b-PCL, have been characterized by matrix-assisted laser desorption/ionization quadrupole/time-of-flight mass spectrometry (MALDI-Q/ToF) and LC-MS/MS (Chapter V). Thermoplastic elastomers have been characterized by thermal degradation using an atmospheric solids analysis probe (ASAP) and ion mobility mass spectrometry (IM-MS), as discussed in Chapter VII. Interfacing separation techniques with mass spectrometry permitted the detection of species present with low concentration in complex materials and improved the sensitivity of MS. In chapter IV, the fragmentation mechanisms in MS/MS experiments of cyclic and linear poly(ethylene oxide) macroinitiators are discussed. This study aimed at determining the influence of end groups on the fragmentation pathways. In the study reported in Chapter V, ultra high performance liquid chromatography (UHPLC) was interfaced with MS and MS/MS to achieve the separation and in-depth characterization and separation of amphiphilic diblock copolymers (PEO-b-PCL) in which the architecture of the PEO block is linear or cyclic. Applying UPLC-MS and UPLC-MS/MS provides fast accurate information about the number and type of the blocks in the copolymers. Chapter VI reports MS/MS and IM-MS analyses which were performed to elucidate the influence of molecular size and collision energy on the fragmentation pathways of polyethers subjected to collisionally activated dissociation. Survival yields and collision cross-sections were derived for several oligomers of polyethers by MS/MS and IM-MS, in order to understand their fragmentation energetics and fully characterize their structures. In Chapter VII, application of ASAP and IM separation were coupled with MS and MS/MS to characterize commercially available thermoplastic elastomers. These compounds are mainly composed of thermoplastic copolymers, but also contain additional chemicals to enhance their properties or to protect them from degradation. Using ASAP-IM-MS enables fast analysis, involving mild degradation at ASAP and subsequent characterization of the desorbates and pyrolyzates by IM-MS and MS/MS. Such multidimensional dispersion considerably simplifies the resulting spectra, permitting the conclusive separation and characterization of the multicomponent materials examined. Chapter VIII summarizes the findings of this dissertation and is followed by appendices.

Committee:

Chrys Wesdemiotis, Dr. (Advisor); Michael J. Taschner, Dr. (Committee Member); Peter L. Rinaldi, Dr. (Committee Member); Matthew Espe, Dr. (Committee Member); Yu Zhu, Dr. (Committee Member)

Subjects:

Analytical Chemistry; Chemistry

Keywords:

Mass spectrometry, liquid chromatography, thermal degradation , ion mobility, tandem mass spectrometry, atmospheric solids analysis probe, interfacing, separation, collisionally cross sections, survival yields curves

Li, PeiSynthesis of Room Temperature Ionic Liquid Based Polyimides for Gas Separations
Doctor of Philosophy in Engineering, University of Toledo, 2010, Chemical Engineering

Two diamino room temperature ionic liquids, 1,3-di(3-aminopropyl)imidazolium bis[(trifluoromethyl)sulfonyl]imide (monocationic RTIL or mRTIL) and 1,12-di[3-(3- aminopropyl)imidazolium]dodecane bis[(trifluoromethyl)sulfonyl]imide (dicationic RTIL or diRTIL) were synthesized using a Boc protection method. The two RTILs were incorporated within the 6FDA-MDA backbones to tune the solubility properties and improve the separation of CO2 from CH4.

The mRTIL was reacted with 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA-RTIL oligomers. Two oligomers, one with 6.5 repeat units and another with 3.3 repeat units, were further reacted with 6FDA and m-phenylenediamine (MDA) where the compositions of RTIL ranged from 6.5 to 25.8 mol% to form block copolyimides.

The diRTIL was successfully reacted with 6FDA and MDA and formed 6FDA-(MDA/diRTIL) random copolyimides with a concentration of diRTIL up to 30 mol%. An 8 mol% diRTIL based block copolyimide with an oligomer size of 9 repeat units was also synthesized.

The separation performance of all RTIL based copolyimides followed a trade-off relationship and did not exhibit a significant improvement for CO2/CH4 gas pair. The incorporation of RTIL caused the change in the free volumes, free volume distributions of the copolyimides and did not increase the CO2 solubility of the polyimides.

The increase in the RTIL mol% resulted in a decrease in molecular weight, 5% weight loss temperature, glass transition temperatures (Tg) and an increase in density. The long block copolyimides exhibited a higher d-spacing, fractional free volume (FFV) and specific free volume (SFV) than those of the short block copolyimides. The diRTIL based copolyimides exhibited smaller d-spacings, FFVs and SFVs with the increase in mol% of diRTIL. In addition, the 8 mol% diRTIL based block copolyimide exhibited a lower density, higher d-spacing, FFV and SFV than those of the 10 mol% random copolyimide.

The RTIL monomers contain more alkyl groups than that of the MDA, which could increase the chain flexibility of the copolyimides. The incorporation of the RTILs in the 6FDA-MDA backbones caused denser packing that resulted in a lower permeability and higher selectivity compared with the pure 6FDA-MDA. For the mRTIL based block copolyimides, the gas permeability and diffusivity (H2, O2, N2, CH4 and CO2) decreased and the permeability and diffusivity selectivity for CO2/CH4 and O2/N2 gas pair increased with the increase in mol% of the mRTILs. The long block copolyimides have a lower permeability/diffusivity and higher permeability selectivity/ diffusivity selectivity than those of the short block copolyimides. The solubilities of varied gases of the long and short block copolyimides were similar. And the solubilities of O2, N2 and CH4 increased while that of CO2 decreased with the increase in mRTIL content.

For the diRTIL based random copolyimides, the permeability, solubility and diffusivity of varied gases decreased with the increase in mol% of the RTIL. The permeability and diffusivity selectivity of CO2/CH4 and O2/N2 slightly increased while that of N2/CH4 decreased. The solubility selectivity of CO2/CH4 decreased.

Committee:

Maria Coleman, Dr. (Committee Chair); Jared Anderson, Dr. (Committee Member); Sasidhar Varanasi, Dr. (Committee Member); Saleh Jabarin, Dr. (Committee Member); Isabel Escobar, Dr. (Committee Member)

Subjects:

Chemical Engineering; Chemistry

Keywords:

membrane; gas separation; room temperature ionic liquid; polyimide

Cao, ZishuColloidal Zeolite Supported Ionic Liquid Membranes for CO2/N2 Separation
MS, University of Cincinnati, 2014, Engineering and Applied Science: Chemical Engineering
Ionic liquids (ILs) are a relatively new class of solvents which has shown promises for CO2 separation because of their green chemistry nature, high thermal stability, extremely low vapor pressure. IL membranes have shown good potential to separate CO2 from combustion flue gas (mainly containing CO2 and N2). In this thesis, colloidal silicalite film supported IL membranes have been developed aiming to enhance the CO2 permeance while maintaining high CO2 selectivity. In the silicalite film supported IL membrane, the entire membrane area is active for CO2 permeation rather than just the open area (porosity) between dense particles in the conventional porous supports because the silicalite particles are highly permeable to CO2 as well. The porous substrate used in this research has a macroporous alumina base (pore size of 0.1 µm and 2 mm in thickness) with a thin (<5 µm thick) skin of colloidal zeolite on the top. The silicalite particles are largely spherical with an average diameter of 70 nm. A pinhole-free IL membrane was obtained on the colloidal silicalite coated support. This zeolite supported IL membrane was investigated by single gas permeation measurement for molecules relevant to CO2 capture and for separation of CO2/N2 mixtures. At 25°C and atmospheric pressure, the CO2 and N2 single gas permeance of the IL membrane were 6.3×10-9 mol/m2•s•Pa and 3.5×10-10 mol/m2•s•Pa, respectively, that gave a CO2/N2 ideal selectivity (or permselectivity) of 18. The effects of temperature, pressure, CO2 composition, water vapor, SO2, and downstream pressure were studied. Increasing the operating temperature increased CO2 permeance but decreased the CO2/N2 selectivity. When temperature increased from 25 to 118 °C, the CO2 permeance increased from 6.3×10-9 to 11.7×10-9 mol/m2•s•Pa whereas the CO2/N2 permselectivity decreased from 18 to 4.8. These indicate that the N2 permeability is more sensitive to temperature than the CO2 permeability. Increasing the CO2 concentration (i.e. CO2 partial pressure) in feed gas increased the CO2 flux because of greater resultant driving force. However, the CO2 permeance and CO2/N2 separation selectivity were found initially decreasing with CO2 feed concentration and eventually become independent of pressure. Pressure tolerance tests demonstrated that the IL membrane remained stable without rupturing under 5 bars (the highest test in this work) of differential pressure across the membrane even at elevated temperatures of >100 °C. The presence of water vapor in the feed stream was found to enhance both the CO2 permeance and CO2/N2 selectivity at low CO2 partial pressure due to increased CO2 solubility and diffusivity after water is incorporated into the IL; however, water vapor had no apparent influence on the separation under high CO2 feed pressure. The existence of SO2 impurity (500 ppmv in feed) caused slight decrease in CO2 and N2 permeance without significantly affecting the CO2/N2 separation selectivity. It was also demonstrated that both CO2 permeance and CO2/N2 selectivity were higher when the permeate side was vacuumed (to create the driving force) as compared to the condition of helium sweeping.

Committee:

Junhang Dong, Ph.D. (Committee Chair); Joo Youp Lee, Ph.D. (Committee Member); Stephen Thiel, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

ionic liquid;membrane;CO2 separation;zeolite

Amin, AbdullahHigh Throughput Particle Separation Using Differential Fermat Spiral Microchannel with Variable Channel Width
Master of Science in Engineering, University of Akron, 2014, Mechanical Engineering
Cell separation is one of the most required processes in the areas of clinical diagnostics, cellular analysis, biological and environmental microbiological processes. Continuous efficient separation of microparticles at relatively high throughput has been a challenge for Lab on Chip (LOC) devices used in biological and environmental applications. In this thesis, a differential area Fermat spiral microfluidic device that is capable of high throughout particle separation is investigated. The device employs a differential area by varying width along with a Fermat spiral microchannel to maintain force ratio close to unity at relatively higher flow rate that facilitates focusing and separation of microparticles at higher throughput. Numerical investigations were performed to validate the performance of the proposed device. Consequently, experiments are performed and it is shown that using the differential Fermat design with particle diameter to channel height ratio of 0.08~0.16; the device can continuously sort 4.6µm and 9.94µm spherical particle at a flow rate of 700µL. To demonstrate the capability of high throughput separation of differently sized microparticles, numerical simulation of particle trajectories was performed at a flow rate of ~1700µL/min.

Committee:

Jiang Zhe, Dr. (Advisor); Francis Loth, Dr. (Committee Member); Marnie Saunders, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Particle Separation, Microfluidics

Poudel, ChetanInverted Linear Halbach Array for Separation of Magnetic Nanoparticles
BA, Oberlin College, 2014, Physics and Astronomy
Magnetic nanoparticles have unique physical and chemical properties, making them appealing candidates for biomedical applications. These applications depend critically on size and magnetic uniformity of the nanoparticles. Unfortunately, very few purification methods exist to sort nanoparticles based on their magnetic properties. Here, we describe an unusual approach to this problem through our construction of a device containing a linear array of permanent magnets in a Halbach configuration, where successive magnet blocks have their magnetization orientation at right angles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient where sorting of nanoparticles based on their magnetic moment is possible. Using a flow channel for nanoparticle suspensions at an appropriate distance away from the array allows us to accumulate high moment nanoparticles against the channel wall, while low moment nanoparticles flow unaffected. We have demonstrated promising results on toluene-based iron oxide nanoparticles with diameters ~5 and 20nm, and water-based nanoparticles with diameters ~15nm and ~25nm, which we characterize using vibrating sample magnetometry and small- angle x-ray scattering. Future work includes a design that allows finer control of fields and gradients and testing with particles of same size but different magnetization.

Committee:

Yumi Ijiri (Advisor)

Subjects:

Analytical Chemistry; Biomedical Engineering; Electromagnetism; Engineering; Materials Science; Nanoscience; Nanotechnology; Physics; Technology

Keywords:

nanoparticles;Halbach array;superparamagnetism;magnetic separation;small angle x-ray scattering;vibrating sample magnetometry;x-ray diffraction;transmission electron microscopy;structural characterization;magnetic characterization

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