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Georgia Tech
1.
Essenmacher, Scott D.
Particle affinity for oil-water interfaces and selective adsorption.
Degree: MS, Chemical and Biomolecular Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/60242 
► Many applications require the selective removal of particulate contaminants from aqueous solutions. Standard froth flotation is a very efficient process that is commonly used in…
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▼ Many applications require the selective removal of particulate contaminants from aqueous solutions. Standard froth flotation is a very efficient process that is commonly used in these applications to indiscriminately remove very hydrophobic micron-sized particulate contaminants. It is desirable to have a method that can take advantage of the efficiency of such a process and be selective with regards to what particles are removed from the solution. One such method would be to coat the air bubbles in froth flotation with a thin layer of oil. This allows for the possibility of selecting oils that have strong attractive intermolecular interactions with a targeted particle and weak attractive interactions with other particles in the solution, which could cause only the targeted particle to strongly adsorb to the oil-water interface and rise to the top of the suspension with the bubble, while the other particles remain in the suspension. Demonstrating this concept of using oil-coated air bubbles to selectively remove particulate contaminants from process effluents, called “affinity flotation,” would be novel. This study focuses on the first step required to prove affinity flotation, which is examining potential oil and particle combinations that could be used to demonstrate the idea of affinity flotation. The main goals of this study are to (1) find three oils that can selectively remove only one particle from an aqueous suspension via one of the following attractive intermolecular interactions: hydrophobic, π-π, and acid-base; and (2) quantify the strength of the affinity the particles have for each of the possible oil-water interfaces. Potential oil and particle combinations were chosen based off the propensity of their molecular structures to have one of the aforementioned intermolecular interactions between them. These potential combinations were then screened using simple foaming ability and foam stability tests. Confocal microscopy was used to verify that capillary foams could be made for the chosen oil and particle combinations. The strength of the affinity a particle has for an oil-water interface was determined by using data collected through measuring the oil-water interfacial tension, the three phase contact angle of a particle at the interface, and the particle size. Results suggest that all of the oils were selective to one type of particle (i.e. only one particle had a high affinity for the oil-water interface, while the other particles had a low affinity); however, only two of the oils (DINCH and heptane) were selective towards the particles that were originally chosen because they have primarily one type of attractive intermolecular interaction with the oil (PVC via acid-base with DINCH and HMDS modified silica via hydrophobic with heptane). The other oil, toluene, was selective for PVC, but not for PS. The attractive intermolecular interactions between toluene and PS were too strong, resulting in the undesirable result of PS having a low affinity for the toluene-water interface. The calculated strength of…
Advisors/Committee Members: Behrens, Sven H. (advisor), Meredith, James C. (advisor), Brettmann, Blair (advisor).
Subjects/Keywords: Selective particle adsorption; Oil-water interfaces; Detachment energy
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APA (6th Edition):
Essenmacher, S. D. (2018). Particle affinity for oil-water interfaces and selective adsorption. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60242
Chicago Manual of Style (16th Edition):
Essenmacher, Scott D. “Particle affinity for oil-water interfaces and selective adsorption.” 2018. Masters Thesis, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/60242.
MLA Handbook (7th Edition):
Essenmacher, Scott D. “Particle affinity for oil-water interfaces and selective adsorption.” 2018. Web. 15 Apr 2021.
Vancouver:
Essenmacher SD. Particle affinity for oil-water interfaces and selective adsorption. [Internet] [Masters thesis]. Georgia Tech; 2018. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/60242.
Council of Science Editors:
Essenmacher SD. Particle affinity for oil-water interfaces and selective adsorption. [Masters Thesis]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/60242
2.
Tsao, Joanna W.
Influence of nanoscale roughness on wetting behavior in liquid/liquid systems.
Degree: MS, Chemical and Biomolecular Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53045
► Wetting behavior of fluid/fluid/solid systems, largely influenced by surface properties and interactions between the three phases, plays a big role in nature and in industrial…
(more)
▼ Wetting behavior of fluid/fluid/solid systems, largely influenced by surface properties and interactions between the three phases, plays a big role in nature and in industrial applications
Traditionally, wetting studies have focused on liquid/vapor systems, especially the study of a sessile liquid droplet in air. Liquid/vapor systems can only probe the effects of surface properties and interactions between the solid and the wetting liquid. This type of characterization is inadequate for liquid/liquid systems, where surface wettability is additionally influenced by interactions between the two wetting liquids.
The present study is the first to examine the effects of nanoscale roughness on wetting behavior in liquid/liquid systems and the modulation of roughness effects by fluid properties and the wetting order. This study examines both equilibrium and dynamic wetting behavior in liquid/liquid systems using well characterized substrates.
Rough substrates were fabricated by coating glass substrates with nanometer sized polymer particles. Partial dissolution of the particles and molecular de-deposition of the polymer allowed for tuning of substrate roughness while retaining the original surface chemistry. The effectiveness of this fabrication technique was verified using electron microscopy and electrokinetic analysis. We examined the wetting behavior in three fluid/fluid systems: an air/water system, a decane/water system, and an octanol/water system. The oils were chosen based on their different polarities.
Equilibrium wetting behavior was determined using contact angle measurements. Results indicate that for all systems where the primary wetting fluid was a liquid, an increase of the surface roughness resulted in Cassie-Baxter wetting. How hydrophilic a surface appears with regard to a water/fluid interface depended on the polarity of that fluid. The octanol/water system provided the strongest evidence regarding the effect of wetting order: a transition from Wenzel to Cassie-Baxter wetting was only observed when water was the primary wetting liquid. The observed transition was confirmed using a modified Wenzel/Cassie-Baxter model.
The kinetics of droplet spreading was measured using high speed optical microscopy. After a droplet was placed on a solid surface, the motion of the contact line was imaged at a rate of 1000 fps. The wetted area was then extracted using custom Matlab® scripts. The spreading kinetics underwent a transition between two regimes: a visco-inertial regime and a slower spreading regime. Results indicated that surface roughness influenced spreading kinetics in both regimes. The overall spreading rate was always slower for rough surfaces than for smoother surfaces. In liquid/liquid systems, the duration of visco-inertial regime was dependent on the surface roughness as well; in general, it was shorter for smooth substrates compared to rough substrates. Increasing the viscosity of the non-aqueous fluid significantly increased the duration of the visco-inertial regime and decreased the overall…
Advisors/Committee Members: Behrens, Sven H. (advisor), Hess, Dennis (committee member), Meredith, James C. (committee member).
Subjects/Keywords: Surface roughness; Equilibrium wetting behavior; Dynamic wetting behavior; Contact angles; Surface characterization
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APA (6th Edition):
Tsao, J. W. (2014). Influence of nanoscale roughness on wetting behavior in liquid/liquid systems. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53045
Chicago Manual of Style (16th Edition):
Tsao, Joanna W. “Influence of nanoscale roughness on wetting behavior in liquid/liquid systems.” 2014. Masters Thesis, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/53045.
MLA Handbook (7th Edition):
Tsao, Joanna W. “Influence of nanoscale roughness on wetting behavior in liquid/liquid systems.” 2014. Web. 15 Apr 2021.
Vancouver:
Tsao JW. Influence of nanoscale roughness on wetting behavior in liquid/liquid systems. [Internet] [Masters thesis]. Georgia Tech; 2014. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/53045.
Council of Science Editors:
Tsao JW. Influence of nanoscale roughness on wetting behavior in liquid/liquid systems. [Masters Thesis]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53045
3.
Ravi Sankar, Ashwin.
Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility.
Degree: MS, Chemical and Biomolecular Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/50414
► Organic π-conjugated Donor-Acceptor copolymers are emerging as potential candidate materials for organic field effect transistor (OFET) and organic photovoltaic (OPV) applications. The electron-deficient benzothiadiazole group…
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▼ Organic π-conjugated Donor-Acceptor copolymers are emerging as potential candidate materials for organic field effect transistor (OFET) and organic photovoltaic (OPV) applications. The electron-deficient benzothiadiazole group coupled with an electron-rich oligothiophene to form donor-acceptor copolymers has attracted significant attention. These low optical band gap materials absorb photons in the range of 400-800 nm and exhibit good thermal stability. In particular, poly(benzothiadiazole-sexithiophene) (PBT6) exhibits excellent performance in optoelectronic devices and high thermal stability. Here, we present the chemical synthesis and characterization of the polymer, PBT6. Three samples of PBT-6 with differing molecular weights in the range of Mn 18000-45000 Da were synthesized. Each polymer was characterized with respect to its photophysical, thermal properties and field-effected mobility was determined. Devices were prepared by drop-casting polymer solutions in 1,2-dichlorobenzene (DCB) onto an OFET (bottom gate/bottom contact) substrate and the devices were used to examine the charge transport properties of each polymer system. The optimal solvent to be used for processing technique was determined and surface techniques using OTS-8 and OTS-18 were compared through contact angle measurements. The measured charge carrier mobilities were in the range of 0.45-0.6 cm² / V.s. Polymer films prepared via drop-casting and which were thermal annealed exhibit mobilities as high as 0.825 cm² / V.s. This work examines the effect of molecular weight on the charge carrier transport properties and demonstrates the correlation of performance with molecular ordering. Drop-casted films of PBT-6 exhibit highly ordered crystalline lamellar structure with high degree of π- π stacking with edge-on orientation on the substrate. The longer conjugation lengths promote intrachain charge transfer. This high degree of molecular ordering in high MW samples of PBT6 improves the interchain and intrachain charge transfer leading to enhanced mobilities. The increased molecular weight (MW) facilitates in forming more uniform thin films which is vital in processing and application of polymer thin film technologies. These results and observations clearly demonstrate the potential of PBT-6 as a semiconducting material for Optoelectronic devices.
Advisors/Committee Members: Reichmanis, Elsa (committee member), Hess, Dennis W. (committee member), Behrens, Sven H. (committee member).
Subjects/Keywords: Polymeric semiconductor; Organic electronics; Molecular weights; Semiconductors; Copolymers; Organic field-effect transistors; Photoconductivity
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APA (6th Edition):
Ravi Sankar, A. (2013). Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50414
Chicago Manual of Style (16th Edition):
Ravi Sankar, Ashwin. “Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility.” 2013. Masters Thesis, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/50414.
MLA Handbook (7th Edition):
Ravi Sankar, Ashwin. “Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility.” 2013. Web. 15 Apr 2021.
Vancouver:
Ravi Sankar A. Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/50414.
Council of Science Editors:
Ravi Sankar A. Molecular weight effects of PBT-6 polymeric semiconductor on charge carrier mobility. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50414
Georgia Tech
4.
Wang, Songcheng.
Oil-coated bubbles in complex colloidal systems: Fundamentals and applications.
Degree: PhD, Chemical and Biomolecular Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/62239
► Froth flotation is an efficient method to selectively separate particulate species from aqueous dispersions or slurries. It has been widely utilized in many industries, such…
(more)
▼ Froth flotation is an efficient method to selectively separate particulate species from aqueous dispersions or slurries. It has been widely utilized in many industries, such as mineral operation, oil recovery, waste paper recycling and waste water treatment, to name but a few. It relies on the principle that hydrophobic particles can attach to gas bubbles while hydrophilic ones cannot. In many cases, however, the particles that we want to separate are too hydrophilic to attach to gas bubbles. To overcome this limitation, our strategy is to coat the gas bubbles with a thin layer of oil, making the bubble surface more polar compared to uncoated bubbles; as a result, less hydrophobic or even mildly hydrophilic particles can attach as well. In this study, we have systematically examined the fundamental aspects of oil-coated bubble flotation and have shown that it has thermodynamic, kinetic and hydrodynamic advantages over the traditional method. Inspired by our previous studies on capillary foams, we also developed a simple and convenient assay: a foaming test to evaluate the ability of particles to be collected and separated by gas bubbles. Finally, we focused on an industrially-relevant separation system (de-inking) to examine the performance of oil-coated bubble flotation. We found that oil-coated bubble flotation often dramatically outperforms the standard technique with uncoated bubbles; the highest ink removal efficiency was observed in systems containing multivalent salts at low pH when using bubbles coated with 1-octanol. This work sheds light on the mechanism of oil-coated bubble flotation in the separation of less hydrophobic or even mildly hydrophilic particles, and is expected to trigger broader interests in many other separation systems.
Advisors/Committee Members: Behrens, Sven H. (advisor), Meredith, Carson (advisor), Deng, Yulin (committee member), Luettgen, Christopher (committee member), Burton, Justin (committee member).
Subjects/Keywords: Froth flotation; Oil-coated bubble; De-inking; Bubble rise dynamics; Fluid-particle separation
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APA (6th Edition):
Wang, S. (2018). Oil-coated bubbles in complex colloidal systems: Fundamentals and applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62239
Chicago Manual of Style (16th Edition):
Wang, Songcheng. “Oil-coated bubbles in complex colloidal systems: Fundamentals and applications.” 2018. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/62239.
MLA Handbook (7th Edition):
Wang, Songcheng. “Oil-coated bubbles in complex colloidal systems: Fundamentals and applications.” 2018. Web. 15 Apr 2021.
Vancouver:
Wang S. Oil-coated bubbles in complex colloidal systems: Fundamentals and applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/62239.
Council of Science Editors:
Wang S. Oil-coated bubbles in complex colloidal systems: Fundamentals and applications. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/62239
Georgia Tech
5.
Mulyadi, Arie Tri Nugroho.
Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications.
Degree: PhD, Chemical and Biomolecular Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/59135
► Modification strategies for cellulose nanofibrils to generate hydrophobic fiber surface and carbon-based fiber were proposed. The enhanced functionality for the obtained nanofiber was utilized for…
(more)
▼ Modification strategies for cellulose nanofibrils to generate hydrophobic fiber surface and carbon-based fiber were proposed. The enhanced functionality for the obtained nanofiber was utilized for diverse engineering applications, such as reinforcing filler for hydrophobic thermoplastic, oil absorbent, and carbon-based electrocatalyst. As the neat cellulose nanofibrils are amphiphilic nanoparticles with relatively high surface energy, surface hydrophobization is an important approach to lower the surface energy and induce hydrophobic-oleophilic surface characteristics. In the case of utilizing cellulose nanofibrils as filler materials, surface compatibility with hydrophobic polymers is a problem that causes an ineffective stress transfer between the filler and polymer matrix. Surface hydrophobization of cellulose nanofibrils was found necessary to improve the tensile strength of the nanocomposite, especially at higher filler loading. Furthermore, the hydrophobic cellulose nanofibrils were found useful to prepare a 3D porous material such as aerogel. The flexible, high porosity, and low density properties of the hydrophobic aerogel allowed the material to have high absorption capacity toward oil/organic solvent and to be compressible. In the case of carbon nanofibers prepared from cellulose nanofibrils precursor, functionalization methods such as heteroatoms-doping and recombination were included to enhance the electrochemical and catalytic activity of the carbon material. The results show that the obtained carbon nanofibers can compete with the graphene-based carbon material as electrocatalysts.
Advisors/Committee Members: Deng, Yulin (advisor), Schork, Francis J. (advisor), Behrens, Sven H. (advisor), Grover, Martha (advisor), Singh, Preet (advisor).
Subjects/Keywords: Cellulose nanofibrils; Composites; Aerogels; Bio-carbons; Electrocatalysts
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APA (6th Edition):
Mulyadi, A. T. N. (2016). Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59135
Chicago Manual of Style (16th Edition):
Mulyadi, Arie Tri Nugroho. “Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications.” 2016. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/59135.
MLA Handbook (7th Edition):
Mulyadi, Arie Tri Nugroho. “Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications.” 2016. Web. 15 Apr 2021.
Vancouver:
Mulyadi ATN. Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/59135.
Council of Science Editors:
Mulyadi ATN. Functionalization and carbonization of cellulose nanofibrils as high-performance fiber materials and their applications. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/59135
Georgia Tech
6.
Tsao, Joanna.
Role of surface roughness for colloidal interactions in aqueous media.
Degree: PhD, Chemical and Biomolecular Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/59136
► The stability of colloidal dispersions is important for many industrial applications, but there are often discrepancies between theoretical descriptions and experimental observations of surface roughness…
(more)
▼ The stability of colloidal dispersions is important for many industrial applications, but there are often discrepancies between theoretical descriptions and experimental observations of surface roughness effects, in part because experimental methods used to vary surface topography simultaneously vary surface chemistry. This work sought to experimentally isolate surface roughness effects on colloidal interactions and to specifically examine how surface roughness modulates the electrostatic, van der Waals, and depletion interactions. Roughness effects on these interactions were determined by measuring particle-plate interactions using total internal reflection microscopy with colloidal probe particles of varied surface topography but similar surface chemistry. Results indicate a systematic weakening of the van der Waals attraction as well as an enhancement of the electrostatic repulsion with increasing particle surface roughness. Increasing surface roughness was also shown to suppress the depletion interaction, a phenomenon that has been predicted theoretically but has never been shown for particles that differed only in surface topography. This experimental work demonstrates the influence of surface topography on the DLVO and depletion interactions and can hopefully be used as a benchmark for future, improved models for surface roughness effects on colloidal interactions.
Advisors/Committee Members: Behrens, Sven H. (advisor), Breedveld, Victor (committee member), Champion, Julie (committee member), Meredith, Carson (committee member), Yiacoumi, Sotira (committee member).
Subjects/Keywords: Surface roughness; Total internal reflection microscopy; Electrostatic repulsion; Van der Waals attraction; Depletion interactions
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APA (6th Edition):
Tsao, J. (2016). Role of surface roughness for colloidal interactions in aqueous media. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59136
Chicago Manual of Style (16th Edition):
Tsao, Joanna. “Role of surface roughness for colloidal interactions in aqueous media.” 2016. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/59136.
MLA Handbook (7th Edition):
Tsao, Joanna. “Role of surface roughness for colloidal interactions in aqueous media.” 2016. Web. 15 Apr 2021.
Vancouver:
Tsao J. Role of surface roughness for colloidal interactions in aqueous media. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/59136.
Council of Science Editors:
Tsao J. Role of surface roughness for colloidal interactions in aqueous media. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/59136
Georgia Tech
7.
Du, Xiaotang.
Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods.
Degree: PhD, Chemical and Biomolecular Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/60169
► The recent progress and increasing popularity in digital printing technology created new challenges in recycled paper quality and recycling process runnability due to the sub-micron…
(more)
▼ The recent progress and increasing popularity in digital printing technology created new challenges in recycled paper quality and recycling process runnability due to the sub-micron size, strongly negative charge, and hydrophilic nature of ink particles. As a result, hydrophilic inks are not compatible with state of art flotation deinking that relies on surface hydrophobicity. The new hydrophilic ink would stay in the recirculating water, redeposit into the fiber lumen and decrease the fiber brightness. Adsorption deinking by chitosan and advanced flotation methods were studied for removal of hydrophilic inks from cellulose fiber and water. The ink behavior during pulping was investigated and it was shown that 53% of total ink stays in water phase, 31% redeposits into fiber lumen during pulping and 16% remains attached with cellulose fiber. Thus, redeposited ink is a major concern to control cellulose fiber quality and chitosan can adsorb ink particles during pulping which results in 5 points increase in ISO Brightness besides 90% water saving and 20% energy saving. For free inks in water, two different advanced flotation techniques were studied, including electroflotation and oily-bubble flotation. Firstly, electric treatment agglomerates ink particle from 60nm to 700nm and removes 25% ink through electroflotation mechanism. Secondly, the adsorption of ink particles on silicone oil/water interface was proved by dynamic interfacial tension, and the silicone oil coated bubble flotation shows advantages in both thermodynamics and kinetics. The usefulness of an oil layer outside air bubbles in reducing adsorption energy barrier was demonstrated by a model system and the root cause for the decrease in energy barrier is van der Waals interactions.
Advisors/Committee Members: Hsieh, Jeffery S. (advisor), Behrens, Sven H. (advisor), Meredith, Carson (committee member), Hess, Dennis W. (committee member), Singh, Preet (committee member).
Subjects/Keywords: Hydrophilic ink; Deinking; Flotation; Colloids; Microstickies; Electric treatment
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APA (6th Edition):
Du, X. (2017). Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60169
Chicago Manual of Style (16th Edition):
Du, Xiaotang. “Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/60169.
MLA Handbook (7th Edition):
Du, Xiaotang. “Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods.” 2017. Web. 15 Apr 2021.
Vancouver:
Du X. Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/60169.
Council of Science Editors:
Du X. Enhanced contaminants removal for paper recycling by adsorption deinking and new flotation methods. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60169
Georgia Tech
8.
Liu, Wenying.
Electrospun nanofibers for regenerative medicine.
Degree: PhD, Chemical and Biomolecular Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/54305
► Electrospun nanofibers represent a class of versatile scaffolds for tissue engineering applications owing to their ability to mimic the nanoscale features of the native extracellular…
(more)
▼ Electrospun nanofibers represent a class of versatile scaffolds for tissue engineering applications owing to their ability to mimic the nanoscale features of the native extracellular matrix (ECM). In addition, nanofibers produced by electrospinning can be readily collected as uniaxially aligned assemblies to recapitulate the architecture of the ECM in tissues with anisotropic characteristics, such as tendon-to-bone insertions, tendons, and nerves. This dissertation focuses on the design, fabrication, functionalization, and assessment of various types of scaffolds consisting of aligned nanofibers, which can be used to augment regeneration in tissues with anisotropic structures.
Briefly, for tendon-to-bone insertion repair, I assessed the capability of aligned nanofibers with a gradient in mineral content to induce spatially graded osteogenesis of adipose-derived mesenchymal stem cells (ASCs). I also developed an alternative approach to the production of a gradient in the density of osteoblasts. The graded pattern of osteoblasts generated using both approaches could mimic their distribution in the native tendon-to-bone insertion. To further enhance the stiffness of the scaffolds, a new solution was developed to coat the scaffold with a thicker mineral layer. In a third project, a novel method of generating crimp in aligned nanofibers was developed. A solvent plasticizer was employed to release the residual stress retained in the nanofibers during electrospinning, which led to the generation of crimp. Finally, the outgrowth of neurites derived from embryoid bodies (EBs) was studied using aligned nanofibers as the substrates. Depending on the strength of adhesion between nanofibers and neurites, two patterns of outgrowth – parallel and perpendicular (to the alignment) – were observed. Maturation of neurons derived from dissociated EBs was also investigated, as characterized by their extracellular action potential and the ability to form neuromuscular junctions with co-cultured muscle cells.
Advisors/Committee Members: Xia, Younan (advisor), Behrens, Sven H. (committee member), Champion, Julie A. (committee member), García, Andrés J. (committee member), Taite, Lakeshia J. (committee member).
Subjects/Keywords: Electrospinning; Nanofibers
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APA (6th Edition):
Liu, W. (2014). Electrospun nanofibers for regenerative medicine. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54305
Chicago Manual of Style (16th Edition):
Liu, Wenying. “Electrospun nanofibers for regenerative medicine.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/54305.
MLA Handbook (7th Edition):
Liu, Wenying. “Electrospun nanofibers for regenerative medicine.” 2014. Web. 15 Apr 2021.
Vancouver:
Liu W. Electrospun nanofibers for regenerative medicine. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/54305.
Council of Science Editors:
Liu W. Electrospun nanofibers for regenerative medicine. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54305
Georgia Tech
9.
Shitta, Abiola.
Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules.
Degree: PhD, Chemical and Biomolecular Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/56202
► This thesis investigates new uses and benefits of colloidal particles adsorbing to the liquid-liquid interface of emulsion droplets. The first part of this thesis investigates…
(more)
▼ This thesis investigates new uses and benefits of colloidal particles adsorbing to the liquid-liquid interface of emulsion droplets. The first part of this thesis investigates morphology control of double emulsions of the water-in-oil-in-water (W/O/W) variety due to the use of interfacially adsorbing particles. W/O/W emulsions typically yield oil droplets containing a multitude of internal water droplets when scalable emulsification procedures are used. W/O/W emulsions containing a single internal aqueous core are preferred for some applications; but single core double emulsions usually require small-scale continuous processes that have low yields. As a result of the investigation into double emulsion morphology control, a readily scalable batch procedure for the production of single core droplets was developed that requires particulate emulsifiers of appropriate concentration and wettability as well as osmotically induced coalescence of the internal droplets. The second part of this thesis describes a different method of morphology control applied to pairs of immiscible droplets brought into contact in a liquid medium. It was found that colloidal particles adsorbing selectively to the different liquid interfaces can change the balance of interfacial tensions responsible for the wetting morphology of the two droplets. Therefore, particles can be used as “wetting modifiers” that allow for control of the equilibrium droplet configuration in a way that was previously considered achievable only with the help of surfactants. The third and final part of this thesis explores the use of particle stabilized emulsion droplets in a new strategy for microencapsulation. In collaboration with an industrial research sponsor, double walled microcapsules with polymer-particle composite shells were developed. The composite shells were formed by interfacial polymerization at the particle covered liquid interfaces. The developed microcapsules were characterized with regard to their potential benefits for the storage and sustained release of aqueous cargoes.
Advisors/Committee Members: Behrens, Sven H (advisor), Deng, Yulin (advisor), Fernandez-Nieves, Alberto (advisor), Meredith, Carson (advisor), Breedveld, Victor (advisor).
Subjects/Keywords: Microcapsules; Microencapsulation; Encapsulation; Polymerization; Interfacial polymerization; Colloids; Particles; Pickering particles; Surfactants; Droplets; Interfacial tension; Double emulsions; Osmotic gradient; Coalescence
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APA (6th Edition):
Shitta, A. (2015). Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56202
Chicago Manual of Style (16th Edition):
Shitta, Abiola. “Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/56202.
MLA Handbook (7th Edition):
Shitta, Abiola. “Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules.” 2015. Web. 15 Apr 2021.
Vancouver:
Shitta A. Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/56202.
Council of Science Editors:
Shitta A. Morphology Control for Particle Stabilized Droplets and Droplet Templated Microcapsules. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/56202
Georgia Tech
10.
Park, Won Min.
Self-assembly of protein-based suprastructures.
Degree: PhD, Chemical and Biomolecular Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/58135
► Strategies for self-assembly of protein-based suprastructures were developed. Recombinant protein building blocks were designed, produced, and self-assembled into various suprastructures, which include spheres, vesicles, nanosheets…
(more)
▼ Strategies for self-assembly of protein-based suprastructures were developed. Recombinant protein building blocks were designed, produced, and self-assembled into various suprastructures, which include spheres, vesicles, nanosheets and porous particles. Morphology was manipulated by engineering protein building blocks, controlling self-assembly processes, and combining inorganic nanocrystals into hybrid materials. Self-assembly of spherical protein coacervates was achieved in the extracellular matrix, mediated by spontaneous diffusion-coacervation and high-affinity binding of building blocks. Vesicles and two-dimensional nanosheets were self-assembled from recombinant protein complexes, whose molecular geometry dictated the morphologies of self-assembled structures. Self-clustering hybrid flower-shaped nanoparticles were prepared and further assembled into hierarchically structured porous supraparticles. All the suprastructures were created as modular systems which enabled incorporation folded functional proteins. Enzymes incorporated in the porous supraparticles showed enhanced inactivation of a pro-inflammatory cytokine, tumor necrosis factor-α. The modular design approach, combined with manipulation of morphology, offer opportunities for practical applications.
Advisors/Committee Members: Champion, Julie A. (advisor), Babensee, Julia E. (committee member), Behrens, Sven H. (committee member), Bommarius, Andreas S. (committee member), Sambanis, Athanassios (committee member).
Subjects/Keywords: Protein; Self-assembly
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APA (6th Edition):
Park, W. M. (2015). Self-assembly of protein-based suprastructures. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58135
Chicago Manual of Style (16th Edition):
Park, Won Min. “Self-assembly of protein-based suprastructures.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/58135.
MLA Handbook (7th Edition):
Park, Won Min. “Self-assembly of protein-based suprastructures.” 2015. Web. 15 Apr 2021.
Vancouver:
Park WM. Self-assembly of protein-based suprastructures. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/58135.
Council of Science Editors:
Park WM. Self-assembly of protein-based suprastructures. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/58135
11.
Zhang, Yi.
Particles as stabilizers and wetting modifiers in colloidal multiphase systems.
Degree: PhD, Chemical and Biomolecular Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55586
► Common colloidal systems such as particle suspensions, foams, and emulsions are simply fine dispersions of one phase in another. More complex systems containing multiple dispersed…
(more)
▼ Common colloidal systems such as particle suspensions, foams, and emulsions are simply fine dispersions of one phase in another. More complex systems containing multiple dispersed fluids (gas bubbles and liquid droplets or droplets of different immiscible liquids) also occur naturally and even play increasingly important roles in industrial applications such as cosmetics, pharmaceutical formulations, water purification, or food processing. Their various applications depend both on their stability and on their intrinsic wetting morphology. Surfactants traditionally serve as stabilizers and wetting modifiers, but solid particles can sometimes achieve the same goal; moreover, they can have the advantage of providing better resistance to harsh application conditions, posing fewer environmental concerns, and allowing for easier recovery. As part of my doctoral research on particles as stabilizers in a colloidal multiphase system, I discovered a new class of foam material, capillary foam, which is obtained by frothing a particle suspension in the presence of a small amount of oil. I studied the stabilization mechanism, formation stages, effects of process parameters, and various applications of capillary foams. In addition to serving as co-stabilizers, it has been discovered that colloidal particles can be used as efficient wetting modifiers. In the final part of my thesis, the interfacial activity of isotropic silica nanoparticles is analyzed. It is demonstrated that isotropic particles can change interfacial tensions as long as they are delivered to and have strong affinity for the interface. A thermodynamic model is developed to estimate the effective interfacial tensions and packing density of particles in fluid-fluid interfaces, which matches the experimentally measured results.
Advisors/Committee Members: Behrens, Sven H. (advisor), Meredith, Carson (advisor), Reichmanis, Elsa (committee member), Deng, Yulin (committee member), Fernandez-Nieves, Alberto (committee member).
Subjects/Keywords: Colloids; Interfacial science; Foams; Wetting
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APA (6th Edition):
Zhang, Y. (2016). Particles as stabilizers and wetting modifiers in colloidal multiphase systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55586
Chicago Manual of Style (16th Edition):
Zhang, Yi. “Particles as stabilizers and wetting modifiers in colloidal multiphase systems.” 2016. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/55586.
MLA Handbook (7th Edition):
Zhang, Yi. “Particles as stabilizers and wetting modifiers in colloidal multiphase systems.” 2016. Web. 15 Apr 2021.
Vancouver:
Zhang Y. Particles as stabilizers and wetting modifiers in colloidal multiphase systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/55586.
Council of Science Editors:
Zhang Y. Particles as stabilizers and wetting modifiers in colloidal multiphase systems. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55586
12.
Peng, Chunqing.
Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles.
Degree: PhD, Materials Science and Engineering, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/43684
► Polymer/inorganic nanoparticle hybrid thin films, primarily composed of functional inorganic nanoparticles, are of great interest to researchers because of their interesting electronic, photonic, and optical…
(more)
▼ Polymer/inorganic nanoparticle hybrid thin films, primarily composed of functional inorganic nanoparticles, are of great interest to researchers because of their interesting electronic, photonic, and optical properties. In the past two decades, layer-by-layer (LbL) assembly has become one of the most powerful techniques to fabricate such hybrid thin films. This method offers an easy, inexpensive, versatile, and robust fabrication technique for multilayer formation, with precisely controllable nanostructure and tunable properties. In this thesis, various ways to control the structure of hybrid thin films, primarily composed of polyelectrolytes and indium tin oxide (ITO), are the main topics of study. ITO is one of the most widely used conductive transparent oxides (TCOs) for applications such as flat panel displays, photovoltaic cells, and functional windows. In this work, polyethyleneimine (PEI) was used to stabilize the ITO suspensions and improve the film buildup rate during the LbL assembly of poly(sodium 4-styrenesulfonate) (PSS) and ITO. The growth rate was doubled due to the stronger interaction forces between the PSS and PEI-modified ITO layer. The assembly of hybrid films was often initiated by a polyelectrolyte precursor layer, and the characteristics of the precursor layer were found to significantly affect the assembly of the hybrid thin films. The LbL assembly of ITO nanoparticles was realized on several substrates, including cellulose fibers, write-on transparencies, silicon wafers, quartz crystals, and glasses. By coating the cellulose fibers with ITO nanoparticles, a new type of conductive paper was manufactured. By LbL assembly of ITO on write-on transparencies, transparent conductive thin films with conductivity of 10⁻⁴ S/cm and transparency of over 80 % in the visible range were also prepared. As a result of this work on the mechanisms and applications of LbL grown films, the understanding of the LbL assembly of polyelectrolytes and inorganic nanoparticles was significantly extended. In addition to working with ITO nanoparticles, this thesis also demonstrated the ability to grow bicomponent [PEI/SiO₂]n thin films. It was further demonstrated that under the right pH conditions, these films can be grown exponentially (e-LbL), resulting in much thicker films, consisting of mostly the inorganic nanoparticles, in much fewer assembly steps than traditional linearly grown films (l-LbL). These results open the door to new research opportunities for achieving structured nanoparticle thin films, whose functionality depends primarily on the properties of the nanoparticles.
Advisors/Committee Members: Gerhardt, Rosario A. (Committee Chair), Thio, Yonathan S. (Committee Co-Chair), Behrens, Sven H. (Committee Member), Deng, Yulin (Committee Member), Tsukruk, Vladimir V. (Committee Member).
Subjects/Keywords: Quartz crystal microbalance; Electrochemical impedance spectroscopy; Surface charges; Exponential growth of thin films; Assembly of nanoparticles; Conductive paper; Transparent conductive thin films; Neutron reflectometry; Indium tin oxide (ITO) nanoparticles; Colloidal suspension stabilization; Zeta potential; Atomic force microscopy; Nanoparticles; Thin films; Electrostatics; Polyelectrolytes
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APA (6th Edition):
Peng, C. (2011). Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/43684
Chicago Manual of Style (16th Edition):
Peng, Chunqing. “Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles.” 2011. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/43684.
MLA Handbook (7th Edition):
Peng, Chunqing. “Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles.” 2011. Web. 15 Apr 2021.
Vancouver:
Peng C. Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/43684.
Council of Science Editors:
Peng C. Electrostatic layer-by-layer assembly of hybrid thin films using polyelectrolytes and inorganic nanoparticles. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/43684
13.
Chun, Byeongjae.
Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches.
Degree: PhD, Chemical and Biomolecular Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54416
► Computational methodologies were employed to study a supramolecular micellar structure and its application, nanoreactor. This task was done through rigorous scale-up procedure using both atomistic…
(more)
▼ Computational methodologies were employed to study a supramolecular micellar structure and its application, nanoreactor. This task was done through rigorous scale-up procedure using both atomistic and mesoscopic simulations. Primarily, density functional theory (DFT) calculation was used to characterize the smallest unit of complex molecules in the multicomponent mixture system. The following step involved transferring the information achieved by DFT calculation to larger scale simulation, such as molecular dynamics (MD) simulation. Lastly, based on the atomistic simulation results, we performed a series of dissipative particle dynamics (DPD) simulations to study a full body of polymeric multicompartment micelle. In the course of research, we built a systematic procedure to minimize the complexity of computation and efficiently characterize macromolecular structures and its application.
Advisors/Committee Members: Jang, Seung Soon (advisor), Sholl, David S. (advisor), Behrens, Sven H. (committee member), Meredith , James C. (committee member), Jones, Christopher W. (committee member).
Subjects/Keywords: Molecular dynamics simulation; Density functional theory; Force field fitting; Multicompartment micelle; Nanoreactor; Nanophase segregation; Flory-huggins theory
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APA (6th Edition):
Chun, B. (2015). Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54416
Chicago Manual of Style (16th Edition):
Chun, Byeongjae. “Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches.” 2015. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/54416.
MLA Handbook (7th Edition):
Chun, Byeongjae. “Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches.” 2015. Web. 15 Apr 2021.
Vancouver:
Chun B. Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/54416.
Council of Science Editors:
Chun B. Characterization of nano-phase segregation in multicompartment micelle and its applications: Computational approaches. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54416
14.
Krajniak, Jan.
Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution.
Degree: PhD, Chemical and Biomolecular Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/49115
► The nematode Caenorhabditis elegans has served as one of the primary model organisms in neuroscience. As C. elegans research became more specific, so have the…
(more)
▼ The nematode Caenorhabditis elegans has served as one of the primary model organisms in neuroscience. As C. elegans research became more specific, so have the biological tools for manipulating C. elegans improved and matured. Additionally, in some avenues of research, technologies have been developed to manipulate the animals in very efficient and quantitative ways. However, the field of dynamic studies has remained without significant technological support. Dynamic studies focus on processes occurring over time and span a range of time-scales of i) minutes to hours requiring continuous imaging for accurate observation, ii) hours to days requiring periodic imaging of the same animal, and iii) days to weeks requiring daily monitoring. Because of a lack of suitable tools and technologies to perform these studies, researchers have to either apply standard biological methods with limited ability to observe processes dynamically or simply cannot perform such studies with the desired set of experimental conditions.
To address this problem, a comprehensive microfluidic toolkit for dynamic studies has been created. The first element is a novel method for reversible and repeatable immobilization at benign conditions in tandem with a microfluidic system for isolated culture of C. elegans with integrated temperature control. The second element is a system for efficient handling of C. elegans embryos in a high-throughput and scalable fashion for chemical and thermal embryonic stimulation with subsequent study of development. The third component is a system capable of selective immobilization of animals’ bodies, while simultaneously facilitating feeding and normal physiological function for live imaging. The last component is capable of culturing animals over their life-span with efficient animal handling, environmental control (temperature and dietary conditions), and high data content experimentation.
As a whole, the work in this thesis enables dynamic studies over the whole range of time scales applicable to C. elegans research. These types of studies were previously very difficult or near impossible to perform practically. Now, instead of building population composites to understand the dynamics of a process, risking affecting physiology via the experiment itself, or dealing with extremely labor intensive physical handling of animals, a toolkit for efficient handling of C. elegans facilitating dynamic and direct observation of individual animals is available. The biological applications range from dynamically studying lipid droplet morphology or studying synaptic vesicle transport, through observing the dynamics of synaptic re-arrangement during development or the effect of cancer drugs on development, to performing high-content life-span experiments able to ascertain the relationship between aging and behavior. Additionally, many of the principles in these designs can be expanded to accommodate research on other model organisms, such as other nematode species, zebra fish embryos, or cells and embryoid bodies.
Advisors/Committee Members: Lu, Hang (advisor), Behrens, Sven H. (committee member), Breedveld, Victor (committee member), Goldman, Daniel (committee member), Taite, Lakeshia J. (committee member).
Subjects/Keywords: Microfluidics; C. elgans; Dynamic studies; Developmental observation; Continuous live imaging; Lifespan; Caenorhabditis elegans; Molecular biology Automation; Computer vision; High resolution imaging; Microorganisms Imaging
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APA (6th Edition):
Krajniak, J. (2013). Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/49115
Chicago Manual of Style (16th Edition):
Krajniak, Jan. “Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/49115.
MLA Handbook (7th Edition):
Krajniak, Jan. “Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution.” 2013. Web. 15 Apr 2021.
Vancouver:
Krajniak J. Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/49115.
Council of Science Editors:
Krajniak J. Microfluidic toolkit for scalable live imaging, developmental and lifespan dynamic studies of C. elegans with single animal resolution. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/49115
15.
Peterson, Emily Cassidy.
Shear-induced microstructure in hollow fiber membrane dopes.
Degree: PhD, Chemical and Biomolecular Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/50245
► Hollow fiber membranes offer the opportunity to dramatically reduce the energy required to perform gas separations in the chemical industry. The membranes are fabricated from…
(more)
▼ Hollow fiber membranes offer the opportunity to dramatically reduce the energy required to perform gas separations in the chemical industry. The membranes are fabricated from highly non-Newtonian precursor materials, including concentrated polymer solutions that sometimes also contain dispersed particles. These materials are susceptible to shear-induced microstructural changes during processing, which can affect the characteristics of the resulting membrane. This thesis explores several shear-related effects using materials and flow conditions that are relevant for fiber spinning. The findings are discussed as they relate to membrane processing, and also from the standpoint of enhancing our fundamental understanding of the underlying phenomena.
First, the effect of shear on polymeric dope solutions was investigated. Shear-induced demixing—a phenomenon not previously studied in membrane materials—was found to occur in membrane dopes. Phase separation experiments also showed that shear-induced demixing promotes macrovoid formation. The demixing process was found to depend not only on the instantaneous shear conditions, but also on the shear history of the solution. This suggests that low-shear flow processes that occur in the upstream tubing and channels used for fiber spinning can affect macrovoid formation.
The effect of viscoelastic media on dispersed particles was also explored. Shear-small-angle light scattering results showed that particles suspended in membrane dope solutions formed aggregated, vorticity-oriented structures when shear rates in the shear-thinning regime of the polymer solution were applied. Shear rates well below the shear-thinning regime did not produce any structure. In fact, the application of a Newtonian shear rate to a sample already containing the vorticity structure caused the sample to return to isotropy. Measurements using a highly elastic, constant-viscosity Boger fluid showed that strong normal forces alone are not sufficient to form the vorticity structures, but that shear thinning is also required.
Lastly, a study was conducted examining cross-stream migration of particles dispersed in viscoelastic media. Fluids exhibiting varying degrees of shear thinning and normal forces were found to have different effects on the particle distribution along the shear gradient axis in Poiseuille flow. Shear thinning was found to promote migration toward the channel center, while normal stresses tended to cause migration toward the channel walls.
In addition to hollow fiber spinning, many other industrially relevant applications involve polymer solutions and suspensions of particles in viscoelastic media. Often, the properties and performance of the material depend strongly on the internal microstructure. The results from the research described in this thesis can be used to guide the design of materials and processing conditions, so that the desired microstructural characteristics can be achieved.
Advisors/Committee Members: Breedveld, Victor (advisor), Koros, William J. (committee member), Behrens, Sven H. (committee member), Meredith, Carson (committee member), Bucknall, David (committee member).
Subjects/Keywords: Rheology; Non-Newtonian fluids; Membrane dopes; Shear-induced microstructure; Suspensions; Polymer solutions; Demixing; Migration; Membrane filters; Gas separation membranes; Shear (Mechanics); Microstructure
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APA (6th Edition):
Peterson, E. C. (2013). Shear-induced microstructure in hollow fiber membrane dopes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50245
Chicago Manual of Style (16th Edition):
Peterson, Emily Cassidy. “Shear-induced microstructure in hollow fiber membrane dopes.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/50245.
MLA Handbook (7th Edition):
Peterson, Emily Cassidy. “Shear-induced microstructure in hollow fiber membrane dopes.” 2013. Web. 15 Apr 2021.
Vancouver:
Peterson EC. Shear-induced microstructure in hollow fiber membrane dopes. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/50245.
Council of Science Editors:
Peterson EC. Shear-induced microstructure in hollow fiber membrane dopes. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50245
16.
Qu, Zihao.
Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal.
Degree: PhD, Chemical and Biomolecular Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/60707
► Micro- and nano-particle adhesion plays an important role in many industrial fields, for example, in microelectromechanical systems (MEMS, affecting fabrication yield and operation), in printing…
(more)
▼ Micro- and nano-particle adhesion plays an important role in many industrial fields, for example, in microelectromechanical systems (MEMS, affecting fabrication yield and operation), in printing (transfer toner particles onto substrates), in coating and paints applications (adhesion of powder paint), or in composite materials (reduce filler-filler adhesion and enhance filler-matrix adhesion). In all of these examples, the particle-particle and particle-substrate interactions govern many aspects of process and product design. These complex interactions are determined by material properties (for example, the Hamaker constant and elastic modulus), particle size and shape, surface properties (e.g., surface energy and roughness), external load, humidity and electrostatic charges. Particle-particle and particle-substrate adhesion have been the focus of intense study; however, they have not been fully understood. The purposes of this study are to 1) understand particle-particle adhesion mechanisms of complex structured microparticles, and 2) tailor particle-polymer matrix adhesion for enhanced mechanical performance of polymer composites. Two biomaterial particles, micro-sized pollen grains and nano-sized cellulose nanocrystals (CNCs), were used as model particles for these two purposes, respectively. In this work, the morphology effect of pollen exine on pollen-pollen interaction was characterized with atomic force microscopy to reveal the unique interaction mechanism. A hybrid interaction model was developed to capture the effect of the micro-structured morphology. Meanwhile, the elastic modulus of pollen exine was analyzed for the first time to understand the effect of mechanical properties on pollen-pollen interaction. In the second part of this work, cellulose nanocrystals (CNCs) were chemically modified and rendered acrylic functional groups on the surfaces. The particle-matrix interaction was tuned to utilize the reinforcing effect of the modified CNCs. Three different processing methods were developed to optimize the reinforcing benefits from the modified CNCs. Overall, this work presents new insights for effects of surface physical (morphology and mechanical property) and chemical properties on particle-particle and particle-matrix adhesion. Pollen grains were investigated as a model of complex structured microparticles, and a unique particle-particle interaction due to the complex morphology was revealed. The elastic moduli of pollen shells were firstly characterized with direct measurements. In the second part of this work, a chemical modification route was developed for cellulose nanocrystals to improve the particle-matrix adhesion and compatibility. The results of his work provided new considerations for material applications including paints, coatings, drug delivery, and composites, among others.
Advisors/Committee Members: Meredith, J. Carson (advisor), Behrens, Sven H. (committee member), Reichmanis, Elsa (committee member), Ludovice, Peter J. (committee member), Zhou, Min (committee member).
Subjects/Keywords: Pollen exine; Cellulose nanocrystal
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APA (6th Edition):
Qu, Z. (2017). Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60707
Chicago Manual of Style (16th Edition):
Qu, Zihao. “Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/60707.
MLA Handbook (7th Edition):
Qu, Zihao. “Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal.” 2017. Web. 15 Apr 2021.
Vancouver:
Qu Z. Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/60707.
Council of Science Editors:
Qu Z. Physical and chemical adhesion of complex structured biomaterial particles: Pollen exine and cellulose nanocrystal. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60707
17.
Kang, Ji-Hwan.
Triplet fusion photon upconversion systems: Towards low threshold applications.
Degree: PhD, Chemical and Biomolecular Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/59766
► Photon upconversion (UC), a promising anti-Stokes process that can convert two or more photons with low energy to a single photon of higher energy, can…
(more)
▼ Photon upconversion (UC), a promising anti-Stokes process that can convert two or more photons with low energy to a single photon of higher energy, can be readily achieved via triplet fusion or triplet-triplet annihilation (TTA) using low incident power density. To facilitate energy migration required for TTA-based upconversion systems, triplet exciton diffusion of the chromophores within an inert medium is of paramount importance, especially for practical device integration. However, the majority of studies have been carried out where the conditions have limitations such as deoxygenated organic solvents and bulk polymer matrices. The research objective here, therefore, is to find effective ways to apply active UC materials into potential devices powered by sunlight. In this thesis, we will investigate how to improve the diffusion-limited energy transfer in TTA-UC processes and demonstrate diverse approaches to enhance their optical properties in terms of materials science and engineering perspectives. First, we will discuss two microfluidics-based approaches which allow for the controlled formation of uniform microcapsules that contain a chromophore-embedded solution core. One is photo-induced interfacial polymerization and the other is multiple emulsion encapsulation using coaxially focused glass capillaries. These core-shell structures provide high quantum yields due to the preservation of molecular mobility in the fluidic phase, as well as structural rigidity and photochemical stability. In addition, we will address alternative photon energy manipulating approaches using the tunable interference structure of cholesteric liquid crystals and surface plasmon resonance coupling of gold nanorods to increase TTA-UC emission intensities and tailor the resultant optical properties.
Advisors/Committee Members: Reichmanis, Elsa (advisor), Hess, Dennis W. (committee member), Koros, William J. (committee member), Behrens, Sven H. (committee member), Kippelen, Bernard J. (committee member).
Subjects/Keywords: Upconversion; Anti-stokes shift; Triplet-triplet annihilation; Energy transfer
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APA (6th Edition):
Kang, J. (2017). Triplet fusion photon upconversion systems: Towards low threshold applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59766
Chicago Manual of Style (16th Edition):
Kang, Ji-Hwan. “Triplet fusion photon upconversion systems: Towards low threshold applications.” 2017. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/59766.
MLA Handbook (7th Edition):
Kang, Ji-Hwan. “Triplet fusion photon upconversion systems: Towards low threshold applications.” 2017. Web. 15 Apr 2021.
Vancouver:
Kang J. Triplet fusion photon upconversion systems: Towards low threshold applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/59766.
Council of Science Editors:
Kang J. Triplet fusion photon upconversion systems: Towards low threshold applications. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/59766
18.
Sharma, Aditi.
Studies on amyloid aggregation and cross-species prion transmission.
Degree: PhD, Chemical and Biomolecular Engineering, 2018, Georgia Tech
URL: http://hdl.handle.net/1853/61123
► Ordered aggregation of proteins into amyloids (and their transmissible versions, prions) has been shown to result in several neurodegenerative diseases in humans and other mammals.…
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▼ Ordered aggregation of proteins into amyloids (and their transmissible versions, prions) has been shown to result in several neurodegenerative diseases in humans and other mammals. While the effect of ions has been extensively studied in the context of measuring the stability of protein formulations and formation of disordered aggregates, there is limited information available on the effect of ions on the formation of ordered amyloid aggregates. In this thesis, we have investigated in detail the effect of presence of ionic co-solutes on the aggregation of amyloids.
Here, we have studied the efficiency of cross-transmission of the NM fragment of Sup35 prion protein, between three closely related species of the Saccharomyces sensu stricto group. Using anions of the Hofmeister series, we discerned the relative effects of protein sequence, seed conformation, and environment on the cross-species transmission of this protein. Further, through investigation of the aggregation of Amyloid beta-42 (Aβ42) and Sup35NM in the presence of anions we have uncovered interesting differences in their aggregation behavior suggesting key differences in the aggregation mechanism of these proteins. Lastly, we developed a computational model for amyloid aggregation kinetics and used it for global fitting of Sup35NM amyloid aggregation data. In all, this thesis expands the current knowledge of ion-specific effects on aggregation of amyloid proteins as well as of the mechanisms of amyloid aggregation.
Advisors/Committee Members: Bommarius, Andreas S. (advisor), Chernoff, Yury O. (committee member), Behrens, Sven H. (committee member), Champion, Julie A. (committee member), Finn, M. G. (committee member).
Subjects/Keywords: Protein aggregation; Amyloid; Prion; Hofmeister; Species barrier
Record Details
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Record Details
Similar Records
Cite
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sharma, A. (2018). Studies on amyloid aggregation and cross-species prion transmission. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61123
Chicago Manual of Style (16th Edition):
Sharma, Aditi. “Studies on amyloid aggregation and cross-species prion transmission.” 2018. Doctoral Dissertation, Georgia Tech. Accessed April 15, 2021.
http://hdl.handle.net/1853/61123.
MLA Handbook (7th Edition):
Sharma, Aditi. “Studies on amyloid aggregation and cross-species prion transmission.” 2018. Web. 15 Apr 2021.
Vancouver:
Sharma A. Studies on amyloid aggregation and cross-species prion transmission. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Apr 15].
Available from: http://hdl.handle.net/1853/61123.
Council of Science Editors:
Sharma A. Studies on amyloid aggregation and cross-species prion transmission. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/61123
. 
Open Access Theses and Dissertations
