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University of Colorado
1.
Zhang, Qiaoxuan.
Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids.
Degree: MS, 2015, University of Colorado
URL: https://scholar.colorado.edu/mats_gradetds/2 
► We experimentally realize polydomain and monodomain chiral ferromagnetic liquid crystal colloids that exhibit solitonic and knotted vector field configurations. Formed by dispersions of ferromagnetic…
(more)
▼ We experimentally realize polydomain and monodomain chiral ferromagnetic liquid crystal colloids that exhibit solitonic and knotted vector field configurations. Formed by dispersions of ferromagnetic nanoplatelets in chiral nematic liquid crystals, these soft colloidal ferro-magnets exhibit spontaneous long-range alignment of magnetic dipole moments of individual platelets, giving rise to a continuum of magnetization field M(r). Competing effects of surface confinement and chirality prompt spontaneous formation and enable optical generation of localized twisted solitonic structures with double twist tubes and torus knots of M(r), which exhibit a strong sensitivity to direction and magnitude of weak magnetic fields of ~10 G. Numerical modeling, implemented through free energy minimization to arrive at field-dependent three-dimensional structures of M(r), shows a good agreement with experiments and provides insights into the corresponding physical underpinnings.
Advisors/Committee Members: Ivan I. Smalyukh, Noal A. Clark, Andrew P. Goodwin.
Subjects/Keywords: Colloids; Ferromagnetic switching; Liquid crystal; Solitons; Topology; Applied Mathematics; Engineering Physics; Materials Science and Engineering
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APA (6th Edition):
Zhang, Q. (2015). Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/mats_gradetds/2
Chicago Manual of Style (16th Edition):
Zhang, Qiaoxuan. “Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids.” 2015. Masters Thesis, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/mats_gradetds/2.
MLA Handbook (7th Edition):
Zhang, Qiaoxuan. “Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids.” 2015. Web. 08 Mar 2021.
Vancouver:
Zhang Q. Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids. [Internet] [Masters thesis]. University of Colorado; 2015. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/mats_gradetds/2.
Council of Science Editors:
Zhang Q. Ferromagnetic Switching of Knotted Vector Fields in Chiral Liquid Crystal Colloids. [Masters Thesis]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/mats_gradetds/2
University of Colorado
2.
Ackerman, Paul Jeffrey.
Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals.
Degree: PhD, 2016, University of Colorado
URL: https://scholar.colorado.edu/ecen_gradetds/140
► As a result of their intrinsic orientational order, soft elasticity, and facile response to external stimuli, liquid crystals (LCs) provide a rich environment for…
(more)
▼ As a result of their intrinsic orientational order, soft elasticity, and facile response to external stimuli, liquid crystals (LCs) provide a rich environment for both fundamental science and viable technological applications. In this thesis
I explore the emergent properties of confinement-frustrated chiral nematic LCs and nanoparticle-LC composites. Due to a complex free energy landscape, con- fined LCs exhibit a large number of local and global energy minima and can facilitate self-assembly of many types of topological solitons. These localized configurations of molecular orientation field are useful for technological applications, have properties that are enhanced by colloidal inclusions and enable the fundamental studies of nanoparticle interactions. Experimental and numerical ex- ploration of these topologically nontrivial solitons may influence the experimental realization of their analogs in physical systems ranging from elementary particles to cosmology.
The delicate interplay of topology, chirality and confinement of LCs can enable spontaneous or optical vortex initiated self-assembly of solitons. In turn, the optical generation and patterning of reconfigurable LC solitons can enable the production of optical vortices in laser beams, demon- strating hierarchical control of defects in matter and light with potential technological applications. The elasticity and facile response of LCs to applied fields facilitates the self-assembly of crystals and chains of solitons, giant electrostriction, as well as electrically driven nonequilibrium dynamics in the form of reversible directional motion of stable defect pairs. Concepts of chirality and topo- logical invariants, such as Hopf index and Skyrmion number, are invoked to examine and classify a variety of spatial solitons, including Skyrmions, Hopfions, and torons, as well as to analyze the role of chirality and the unexpected observation of twist handedness reversal that enables soliton stability.
By introducing colloidal particles to the confined chiral LCs, we probe how new composite material properties can emerge spontaneously or be pre-designed and then probed by combining the facile response of the LC host and the unique properties of nanoparticles. This allows us to achieve polar ferromagnetic response in chiral ferromagnetic LC colloids as well as to probe plasmon- exciton interactions through controlling metal and semiconductor quantum dot nanoparticles within topological defects.
Advisors/Committee Members: Ivan I. Smalyukh, Jao van de Lagemaat, Noel A. Clark, Rafael Piestun, Wounjhang Park.
Subjects/Keywords: chirality; liquid crystals; nanoparticles; self-assembly; solitons; topology; Engineering; Physics
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APA (6th Edition):
Ackerman, P. J. (2016). Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/ecen_gradetds/140
Chicago Manual of Style (16th Edition):
Ackerman, Paul Jeffrey. “Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/ecen_gradetds/140.
MLA Handbook (7th Edition):
Ackerman, Paul Jeffrey. “Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals.” 2016. Web. 08 Mar 2021.
Vancouver:
Ackerman PJ. Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/ecen_gradetds/140.
Council of Science Editors:
Ackerman PJ. Self-Assembly of Topological Solitons and Functional Nanoparticles in Liquid Crystals. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/ecen_gradetds/140
University of Colorado
3.
Conkey, Donald Benjamin.
Light Control through Highly Scattering Media.
Degree: PhD, Electrical, Computer & Energy Engineering, 2013, University of Colorado
URL: https://scholar.colorado.edu/ecen_gradetds/75
► Imaging through opaque, highly scattering walls is a long sought after capability with potential applications in a variety of fields, such as biomedical imaging.…
(more)
▼ Imaging through opaque, highly scattering walls is a long sought after capability with potential applications in a variety of fields, such as biomedical imaging. The use of wavefront shaping to compensate for scattering has recently brought a renewed interest as a potential solution to this problem. This method relies on the ability to shape an incident wavefront to pre-compensate for scattering, thus providing light control through a scattering layer. In order for these techniques to begin to extend the imaging depth inside of living biological tissue several constraints must be overcome. As living biological tissue is dynamic these techniques must be able to optimize fast enough to overcome the dynamic nature of the tissue. Also key to the practicality of overcoming scattering is focusing light without direct access behind the scattering wall. This thesis presents means of overcoming these limitations through novel optimization algorithms, wavefront shaping for high-speed modulation, and photoacoustic feedback and imaging behind a scattering layer.
A genetic algorithm (GA) is applied for wavefront optimization as a means of enabling parallel mode optimization to increase the speed of the optimization procedure. The results presented show that not only does the GA optimize more quickly, it is more robust in low signal-to-noise (SNR) environments than other optimization algorithms. The low SNR performance is critical to high speed performance, because SNR decreases with the integration time. The GA wavefront optimization is extended towards more complex light control problems, specifically multi-color image projection through scattering layers.
Advisors/Committee Members: Rafael Piestun, Todd W. Murray, Kevin H. Wagner, Ivan I. Smalyukh, Youzhi Li.
Subjects/Keywords: Adaptive Optics; Holography; Imaging; Photoacoustics; Scattering; Turbid Media; Electrical and Computer Engineering; Optics; Physics
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APA (6th Edition):
Conkey, D. B. (2013). Light Control through Highly Scattering Media. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/ecen_gradetds/75
Chicago Manual of Style (16th Edition):
Conkey, Donald Benjamin. “Light Control through Highly Scattering Media.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/ecen_gradetds/75.
MLA Handbook (7th Edition):
Conkey, Donald Benjamin. “Light Control through Highly Scattering Media.” 2013. Web. 08 Mar 2021.
Vancouver:
Conkey DB. Light Control through Highly Scattering Media. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/ecen_gradetds/75.
Council of Science Editors:
Conkey DB. Light Control through Highly Scattering Media. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/ecen_gradetds/75
University of Colorado
4.
Trivedi, Rahuk P.
Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals.
Degree: PhD, Electrical, Computer & Energy Engineering, 2012, University of Colorado
URL: https://scholar.colorado.edu/ecen_gradetds/50
► Liquid Crystals (LCs) have proven to be important for electro-optic device applications such as displays, spatial light modulators, non-mechanical beam-steerers, etc. Owing to their…
(more)
▼ Liquid Crystals (LCs) have proven to be important for electro-optic device applications such as displays, spatial light modulators, non-mechanical beam-steerers, etc. Owing to their unique mechanical, electrical, and optical properties, they are also being explored for wide array of advanced technological applications such as biosensors, tunable lenses, distributed feedback lasers, muscle-like actuators, etc. The thesis explores LC media from the standpoint of controlling their elastic and optical properties by generating and manipulating assemblies of defects and colloidal particles. To achieve the goal of optically manipulating these configurations comprising defects and particles at microscale with an unprecedented control, and then to visualize the resultant molecular director patterns, requires development of powerful optical system. The thesis discusses design and implementation of such an integrated system capable of 3D holographic optical manipulation and multi-modal 3D imaging (in nonlinear optical modes like multiphoton fluorescence, coherent anti-Stokes Raman scattering, etc.) and how they are used to extensively study a vast number of LC based systems.
Understanding of LCs and topological defects go hand in hand. Appreciation of defects leads to their precise control, which in turn can lead to applications. The thesis describes discovery of optically generated stable, quasiparticle-like, localized defect structures in a LC cell, that we call "Torons". Torons enable twist of molecules in three dimensions and resemble both Skyrmion-like and Hopf fibration features. Under different conditions of generation, we optically realize an intriguing variety of novel solitonic defect structures comprising rather complicated configurations of point and line topological defects.
Introducing colloidal particles to LC systems imparts to these hybrid material system a fascinating degree of richness of properties on account of colloidal assemblies supported by networks of LC defects as well as variety of localized defects supported by colloidal particles. To fully understand and exploit the resultant interactions involving colloids and defects in LC systems to achieve the full potential of their practical applications, it is required that these be explored on the level of individual particles and defects. We explore a multitude of interactions mediated by defects over different length scales and demonstrate for the first time, creation of several types of colloidal assemblies such as sparse colloidal structures and three-dimensional defect-bound colloidal structures.
Advisors/Committee Members: Ivan I Smalyukh, Noel A. Clark, Rafael Piestun, David M. Walba, Wounjhang Park.
Subjects/Keywords: Colloids; Liquid Crystals; Optical Microscopy; Topological Defects; Condensed Matter Physics; Materials Science and Engineering; Optics
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APA (6th Edition):
Trivedi, R. P. (2012). Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/ecen_gradetds/50
Chicago Manual of Style (16th Edition):
Trivedi, Rahuk P. “Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals.” 2012. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/ecen_gradetds/50.
MLA Handbook (7th Edition):
Trivedi, Rahuk P. “Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals.” 2012. Web. 08 Mar 2021.
Vancouver:
Trivedi RP. Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/ecen_gradetds/50.
Council of Science Editors:
Trivedi RP. Optical manipulation and imaging of assemblies of topological defects and colloids in liquid crystals. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/ecen_gradetds/50
University of Colorado
5.
Sheetah, Ghadah Hadi Saud.
Self-Assembly of Liquid Crystalline and Colloidal Nanostructures.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/mats_gradetds/8
► Nanostructure liquid crystal composites are perfect for designing novel materials with predefined properties that can be of substantial interest in many fields including materials…
(more)
▼ Nanostructure liquid crystal composites are perfect for designing novel materials with predefined properties that can be of substantial interest in many fields including materials science, electronics, optics, and energy storage. Liquid Crystals (LCs) are a good candidate to work as a host medium for nanoparticles with different properties given their low cost and facile responsive characteristic to external stimuli such as voltages as low as one volt. Concentrated dispersions of anisotropic gold, silver, and metal alloy nanoparticles in nematic hosts have been achieved and successfully controlled using low-voltage fields. However, to enable versatile designs of material behavior of these composites, simultaneous dispersion of anisotropic particles with different shapes, alignment properties, and compositions is often needed. For example, integrated plasmonic gold nanoparticles in the up-convergent nanoparticles (UCNPs) or quantum dots (QDs) semiconductor matrices serves as nano antennae that can harvest the light energy to the nanostructured matrix giving rise to potential applications. In this work, spectral characteristics of dispersions of multiple types of anisotropic nanoparticles in a common nematic host LC provide an unprecedented variety of electrically- and optically-tunable material behavior. Different composites of inclusions of plasmonic gold nanorods, quantum dots, dyes will be explored and implementing such composites in an inexpensive, energy-efficient, large-area, fast-switching smart windows applications, along with exploring different self-assembled systems by entropically driven forces will be discussed. Overall, utilizing LCs as a guest medium to these nanoparticles allows for unique features as well as promising properties through the design of novel self-assembly based hybrid nanostructures. This can give rise to potential and practical applications for the fabrication of optical or electro-optical devices such as climate dependent optimal solar gain smart windows, switchable plasmonic polarizers, and may expand to further satisfy renewable energy needs.
Advisors/Committee Members: Ivan I. Smalyukh, Noel A. Clark, Patrica Rankin, David M. Walba, Yifu Ding.
Subjects/Keywords: colloidal nanostructures; liquid crystals; nanoparticles; renewable energy; plasmonic gold nanorods; Materials Science and Engineering; Nanotechnology; Physics
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APA (6th Edition):
Sheetah, G. H. S. (2018). Self-Assembly of Liquid Crystalline and Colloidal Nanostructures. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/mats_gradetds/8
Chicago Manual of Style (16th Edition):
Sheetah, Ghadah Hadi Saud. “Self-Assembly of Liquid Crystalline and Colloidal Nanostructures.” 2018. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/mats_gradetds/8.
MLA Handbook (7th Edition):
Sheetah, Ghadah Hadi Saud. “Self-Assembly of Liquid Crystalline and Colloidal Nanostructures.” 2018. Web. 08 Mar 2021.
Vancouver:
Sheetah GHS. Self-Assembly of Liquid Crystalline and Colloidal Nanostructures. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/mats_gradetds/8.
Council of Science Editors:
Sheetah GHS. Self-Assembly of Liquid Crystalline and Colloidal Nanostructures. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/mats_gradetds/8
University of Colorado
6.
Seifpour, Arezou.
Molecular simulations of assembly of functionalized spherical nanoparticles.
Degree: PhD, Chemical & Biochemical Engineering, 2013, University of Colorado
URL: https://scholar.colorado.edu/chbe_gradetds/34
► Precise assembly of nanoparticles is crucial for creating spatially engineered materials that can be used for photonics, photovoltaic, and metamaterials applications. One way to…
(more)
▼ Precise assembly of nanoparticles is crucial for creating spatially engineered materials that can be used for photonics, photovoltaic, and metamaterials applications. One way to control nanoparticle assembly is by functionalizing the nanoparticle with ligands, such as polymers, DNA, and proteins, that can manipulate the interactions between the nanoparticles in the medium the particles are placed in. This thesis research aims to design ligands to provide a new route to the programmable assembly of nanoparticles.
We first investigate using Monte Carlo simulation the effect of copolymer ligands on nanoparticle assembly. We first study a single nanoparticle grafted with many copolymer chains to understand how monomer sequence (e.g. alternating ABAB, or diblock A
xB
x) and chemistry of the copolymers affect the grafted chain conformation at various particle diameters, grafting densities, copolymer chain lengths, and monomer-monomer interactions in an implicit small molecule solvent. We find that the size of the grafted chain varies non-monotonically with increasing blockiness of the monomer sequence for a small particle diameter. From this first study, we selected the two sequences with the most different chain conformations – alternating and diblock – and studied the effect of the sequence and a range of monomer chemistries of the copolymer on the characteristics of assembly of multiple copolymer-functionalized nanoparticles. We find that the alternating sequence produces nanoclusters that are relatively isotropic, whereas diblock sequence tends to form anisotropic structures that are smaller and more compact when the block closer to the surface is attractive and larger loosely held together clusters when the outer block is attractive.
Next, we conduct molecular dynamics simulations to study the effect of DNA ligands on nanoparticle assembly. Specifically we investigate the effect of grafted DNA strand composition (e.g. G/C content, placement and sequence) and bidispersity in DNA strand lengths on the thermodynamics and structure of assembly of functionalized nanoparticles. We find that higher G/C content increases cluster dissociation temperature for smaller particles. Placement of G/C block inward along the strand decreases number of neighbors within the assembled cluster. Finally, increased bidispersity in DNA strand lengths leads a distribution of inter-particle distances in the assembled cluster.
Advisors/Committee Members: Arthi Jayaraman, Wounjhang Park, Christine M. Hrenya, Ivan I. Smalyukh, Mark P. Stoykovich.
Subjects/Keywords: nanoparticle; assembly; grafted chain; DNA ligands; bidispersity; Chemical Engineering; Nanoscience and Nanotechnology
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APA (6th Edition):
Seifpour, A. (2013). Molecular simulations of assembly of functionalized spherical nanoparticles. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chbe_gradetds/34
Chicago Manual of Style (16th Edition):
Seifpour, Arezou. “Molecular simulations of assembly of functionalized spherical nanoparticles.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/chbe_gradetds/34.
MLA Handbook (7th Edition):
Seifpour, Arezou. “Molecular simulations of assembly of functionalized spherical nanoparticles.” 2013. Web. 08 Mar 2021.
Vancouver:
Seifpour A. Molecular simulations of assembly of functionalized spherical nanoparticles. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/chbe_gradetds/34.
Council of Science Editors:
Seifpour A. Molecular simulations of assembly of functionalized spherical nanoparticles. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chbe_gradetds/34
University of Colorado
7.
Noonan, Patrick Scott.
Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation.
Degree: PhD, Chemical & Biochemical Engineering, 2013, University of Colorado
URL: https://scholar.colorado.edu/chbe_gradetds/53
► The prominence of molecular self-assembly in chemical and biochemical processes related to sensing, electro-optical applications, and cellular mechanisms motivates fundamental studies of self-assembly processes.…
(more)
▼ The prominence of molecular self-assembly in chemical and biochemical processes related to sensing, electro-optical applications, and cellular mechanisms motivates fundamental studies of self-assembly processes. Here, we study how biomolecules and organic compounds interact at interfaces to cooperatively self-assemble into organized structures. In particular we are interested in understanding how liquid crystals (LCs), capable of forming anisotropic phases, behave under varying interfacial conditions. First, we systematically decreased the monolayer coverage of long chain alkylsilanes to study the interplay between surface energy and hydrocarbon chain density. Next, we studied the molecular mechanisms of how nucleic acids influenced interfacial molecular orientation at surfactant laden aqueous/LC interfaces. These studies motivated subsequent exploration of how bio-molecular interactions involving aptamers might induce LC reorientations. Finally, we explored ways to use receptor-mediated liposome fusion to induce LC reorientations at the aqueous/LC interface.
The findings presented here elucidate the molecular mechanisms that dictate LC reorientations capable of signal transduction in molecular sensing. For example, studies at the solid/LC and aqueous/LC interface revealed that a relatively low sub-monolayer coverage (~11%) of long alkyl chains can induce homeotropic alignment of calamitic LCs. Furthermore, when hydrophobic polyanions adsorb to aqueous/LC interfaces with an alkyl chain coverage close to this threshold, a LC reorientation to a planar/tilted LC alignment occurred. Experiments revealed that the interaction between exposed hydrophobic moieties and the LC were of critical importance toward inducing this LC reorientation. Furthermore, when specific binding events (
i.e. DNA hybridization, aptamer-ligand binding) were used to modulate the hydrophobic exposure of biomolecules at LC interfaces, the LC alignment was correlated with the hydrophobic exposure. Finally, we designed and characterized aqueous/LC interfaces that inhibited the spontaneous fusion of liposomes and the non-specific adsorption of macromolecular proteins, enabling receptor-mediated (
i.e. DNA hybridization) liposome fusion. These studies advance the understanding of molecular mechanisms that dictate LC alignment and provide examples of how liquid crystal reorientations can be exploited for molecular bio-sensing. Thus we have used a range of organic and bio-molecular species to gain a better understanding of the self-assembly processes that dictate LC alignment at solid/LC and aqueous/LC interfaces.
Advisors/Committee Members: Daniel K. Schwartz, Andrew P. Goodwin, Joel L. Kaar, Bruce E. Eaton, Ivan I. Smalyukh.
Subjects/Keywords: aptamers; biosensors; interfacial phenomena; liquid crystals; nucleic acids; Biochemical and Biomolecular Engineering; Chemical Engineering
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APA (6th Edition):
Noonan, P. S. (2013). Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chbe_gradetds/53
Chicago Manual of Style (16th Edition):
Noonan, Patrick Scott. “Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/chbe_gradetds/53.
MLA Handbook (7th Edition):
Noonan, Patrick Scott. “Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation.” 2013. Web. 08 Mar 2021.
Vancouver:
Noonan PS. Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/chbe_gradetds/53.
Council of Science Editors:
Noonan PS. Cooperative Self-Assembly at Interfaces and its Impact on Long Range Molecular Orientation. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chbe_gradetds/53
University of Colorado
8.
Gardner, Dennis Floyd, Jr.
Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/194
► This thesis discusses methods for high-resolution static and stroboscopic microscopy using tabletop coherent extreme ultraviolet (EUV) radiation from tabletop high-harmonic generation (HHG) sources. These…
(more)
▼ This thesis discusses methods for high-resolution static and stroboscopic microscopy using tabletop coherent extreme ultraviolet (EUV) radiation from tabletop high-harmonic generation (HHG) sources. These coherent short wavelength light sources are combined with a lensless, computational, phase and amplitude-contrast technique called ptychographic Coherent Diffractive Imaging (CDI). While ptychographic CDI techniques are currently widespread for visible, EUV and X-ray microscopy, no previous work has been able to achieve at-wavelength resolution of extended samples, especially in a reflection geometry, nor has previous work been able to image periodic samples with high-fidelity. In this work, a combination of experimental methods for high-numerical aperture imaging and novel computational algorithms enabled the highest resolution-to-wavelength demonstrations using any CDI technique. These algorithms include tilted plane correction, which enables high-resolution imaging of surfaces in a reflection geometry, and a powerful technique termed ‘modulus enforced probe’, which enables both imaging of periodic objects and convergence of the ptychographic CDI algorithm in fewer iterations. Furthermore, the ultrafast pulse duration of the high-harmonic radiation is harnessed to demonstrate proof-of-principle pump-probe imaging of nanostructures, capturing thermal transport processes in nanostructures with an axial resolution of 3 angstroms. Stroboscopic imaging with nanoscale resolution is a critical tool for the investigation of nanoscale heat flow and magnetic switching for the advancement of next generation nano-electronics, data storage, and nano-engineered systems.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Daniel E. Adams, Ivan I. Smalyukh, Mark Hernandez.
Subjects/Keywords: coherent diffractive imaging; computational imaging; extreme ultraviolet EUV; high harmonic generation; high-resolution microscopy; ptychography; Nanotechnology; Optics; Physics
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APA (6th Edition):
Gardner, Dennis Floyd, J. (2017). Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/194
Chicago Manual of Style (16th Edition):
Gardner, Dennis Floyd, Jr. “Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/phys_gradetds/194.
MLA Handbook (7th Edition):
Gardner, Dennis Floyd, Jr. “Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.” 2017. Web. 08 Mar 2021.
Vancouver:
Gardner, Dennis Floyd J. Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/phys_gradetds/194.
Council of Science Editors:
Gardner, Dennis Floyd J. Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/194
University of Colorado
9.
Turgut, Emrah.
Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/108
► Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications will require a better understanding of magnetic multilayers and their interactions with optical-laser pulses. In this thesis,…
(more)
▼ Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications will require a better understanding of magnetic multilayers and their interactions with optical-laser pulses. In this thesis, by combining the advantages of ultrabroad-band extreme-ultraviolet light including ultrafast time resolution, element selectivity and tabletop easy access,
I report three findings in the study of ultrafast magnetization dynamics in itinerant ferromagnets. First,
I experimentally prove that the transverse magneto-optical Kerr response with extreme-ultraviolet light has a purely magnetic origin and that our experimental technique is an artifact-free ultrafast magnetic probe. Second,
I demonstrate the first ultrafast magnetization enhancement driven by ultrafast spin currents in Ni/Ru/Fe multilayers. Third,
I engineer the sample system by choosing either insulating or spin-scattering spacer layers between the Ni and Fe magnetic layers and by structural ordering. Then,
I control the competition between ultrafast spin-flip scattering and superdiffusive spin-current mechanisms; either of these processes may to be the dominant mechanism in ultrafast demagnetization.
Finally,
I report two continuing experiments that are promising for future ultrafast magnetization studies with extreme-ultraviolet sources. These experiments are resonant-magnetic small-angle-scattering and the generation of bright circularly polarized high harmonics accompanied by a demonstration of the first x-ray magnetic circular dichroism with a tabletop system.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Daniel S. Dessau, Ivan I. Smalyukh, Thomas J. Silva.
Subjects/Keywords: Femtomagnetism; Magnetic Multilayers; Magnetization; Spintronics; Ultrafast; X-ray; Condensed Matter Physics; Optics
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APA (6th Edition):
Turgut, E. (2014). Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/108
Chicago Manual of Style (16th Edition):
Turgut, Emrah. “Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/phys_gradetds/108.
MLA Handbook (7th Edition):
Turgut, Emrah. “Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.” 2014. Web. 08 Mar 2021.
Vancouver:
Turgut E. Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/phys_gradetds/108.
Council of Science Editors:
Turgut E. Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/108
University of Colorado
10.
Varney, Michael Christopher Mason.
Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/114
► Colloidal systems find important applications ranging from fabrication of photonic crystals to direct probing of phenomena encountered in atomic crystals and glasses; topics of…
(more)
▼ Colloidal systems find important applications ranging from fabrication of photonic crystals to direct probing of phenomena encountered in atomic crystals and glasses; topics of great interest for physicists exploring a broad range of scientific, industrial and biomedical fields. The ability to accurately control particles of mesoscale size in various liquid host media is usually accomplished through optical trapping methods, which suffer limitations intrinsic to trap laser intensity and force generation. Other limitations are due to colloid properties, such as optical absorptivity, and host properties, such as viscosity, opacity and structure. Therefore, alternative and/or novel methods of colloidal manipulation are of utmost importance in order to advance the state of the art in technical applications and fundamental science.
In this thesis,
I demonstrate a magnetic-optical holonomic control system to manipulate magnetic and optical colloids in liquid crystals and show that the elastic structure inherent to nematic and cholesteric liquid crystals may be used to assist in tweezing of particles in a manner impossible in other media. Furthermore,
I demonstrate the utility of this manipulation in characterizing the structure and microrheology of liquid crystals, and elucidating the energetics and dynamics of colloids interacting with these structures.
I also demonstrate the utility of liquid crystal systems as a table top model system to probe topological defects in a manner that may lead to insights into topologically related phenomena in other fields, such as early universe cosmology, sub-atomic and high energy systems, or Skrymionic structures.
I explore the interaction of colloid surface anchoring with the structure inherent in cholesteric liquid crystals, and how this affects the periodic dynamics and localization metastability of spherical colloids undergoing a “falling” motion within the sample. These so called “metastable states” cause colloidal dynamics to deviate from Stokes-like behavior at very low Reynolds numbers and is understood by accounting for periodic landscapes of elastic interaction potential between the particle and cholesteric host medium due to surface anchoring.
This work extends our understanding of how colloids interact with liquid crystals and topological defects, and introduces a powerful method of colloidal manipulation with many potential applications.
Advisors/Committee Members: Ivan I. Smalyukh, John C. Price, Noel A. Clark, David M. Walba, Kris A. Bertness.
Subjects/Keywords: tweezing; nanowires; metastability; Materials Science and Engineering; Nanoscience and Nanotechnology; Physics
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APA ·
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MLA ·
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CSE |
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APA (6th Edition):
Varney, M. C. M. (2014). Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/114
Chicago Manual of Style (16th Edition):
Varney, Michael Christopher Mason. “Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/phys_gradetds/114.
MLA Handbook (7th Edition):
Varney, Michael Christopher Mason. “Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics.” 2014. Web. 08 Mar 2021.
Vancouver:
Varney MCM. Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/phys_gradetds/114.
Council of Science Editors:
Varney MCM. Magnetic and optical holonomic manipulation of colloids, structures and topological defects in liquid crystals for characterization of mesoscale self-assembly and dynamics. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/114
University of Colorado
11.
Martinez, Angel.
Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/129
► The study of liquid crystals has brought about many advances and innovations, not only in technology, but also in our basic understanding of the…
(more)
▼ The study of liquid crystals has brought about many advances and innovations, not only in technology, but also in our basic understanding of the world around us. For example, recent explorations of photo-induced defects and colloidal clusters in chiral nematics reveal topologically nontrivial forms in liquid crystal director fields, such as localized field structures resembling the Hopf and Seifert fibrations. In this work, we use light to control the alignment of liquid crystal director field at surfaces, to define topologically nontrivial geometric shapes of colloidal particles, and to probe the interplay between the topology of defects, director fields and surfaces. We first explore photo-responsive, azobenzene-based surface monolayers as means to optically and dynamically control boundary conditions at liquid crystal interfaces. This enables us to induce localized regions of twisted nematic field and disclination loops, which interact elastically with particle inclusions, providing a new kind of long-range, low-power colloidal manipulation as well as a means for controlling large-scale dynamics of topological defects and colloids. Using this same surface control technique, we pattern topological defects into thin films of polymerized liquid crystals, also functionalized with azobenzene. Irradiation of these films causes internal mechanical stresses that induce changes in the films' topography, depending on the patterned topology of the internal field structure within the photoresponsive liquid crystal polymer. We then employ a two-photon photo-polymerization technique to fabricate chiral, knotted and linked polymer microstructures, which we introduce into nematic liquid crystals. Based on three-photon excitation fluorescence polarizing microscopy studies, we reconstruct the surrounding 3D director field structure, revealing induced chiral, knotted and linked defect lines and fields. Using videomicroscopy, we characterize the inter-particle elastic forces that govern long range interactions and stabilize self-assembled colloidal configurations. Since there are few examples of practical realization of topological field configurations, these knotted and inter-linked colloids and fields provide a way to gain insights into behavior of other experimentally less accessible physical systems with similar symmetry and topology. Throughout the thesis, my research demonstrated that the topology of soft condensed matter can be shaped by light, laying a groundwork for experimental exploration of low-dimensional topology of fields and surfaces as well as for practical applications of topological relations in designing new forms of self-assembly.
Advisors/Committee Members: Ivan I. Smalyukh, Rafael Piestun, Noel Clark, David M. Walba, Christopher N. Bowman.
Subjects/Keywords: Colloids; Dynamic patterns; knots; links; Liquid Crystals; Topoology; Condensed Matter Physics; Physics
Record Details
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Record Details
Similar Records
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Martinez, A. (2014). Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/129
Chicago Manual of Style (16th Edition):
Martinez, Angel. “Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 08, 2021.
https://scholar.colorado.edu/phys_gradetds/129.
MLA Handbook (7th Edition):
Martinez, Angel. “Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter.” 2014. Web. 08 Mar 2021.
Vancouver:
Martinez A. Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 08].
Available from: https://scholar.colorado.edu/phys_gradetds/129.
Council of Science Editors:
Martinez A. Optical Shaping of Structural Self-Oraganization and Topology in Soft Matter. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/129
. 
Open Access Theses and Dissertations