Matching Items (4)
Description
ABSTRACT The unique structural features of deoxyribonucleic acid (DNA) that are of considerable biological interest also make it a valuable engineering material. Perhaps the most useful property of DNA for molecular engineering is its ability to self-assemble into predictable, double helical secondary structures. These interactions are exploited to design a variety of DNA nanostructures, which can be organized into both discrete and periodic structures. This dissertation focuses on studying the dynamic behavior of DNA nanostructure recognition processes. The thermodynamics and kinetics of nanostructure binding are evaluated, with the intention of improving our ability to understand and control their assembly. Presented here are a series of studies toward this goal. First, multi-helical DNA nanostructures were used to investigate how the valency and arrangement of the connections between DNA nanostructures affect super-structure formation. The study revealed that both the number and the relative position of connections play a significant role in the stability of the final assembly. Next, several DNA nanostructures were designed to gain insight into how small changes to the nanostructure scaffolds, intended to vary their conformational flexibility, would affect their association equilibrium. This approach yielded quantitative information about the roles of enthalpy and entropy in the affinity of polyvalent DNA nanostructure interactions, which exhibit an intriguing compensating effect. Finally, a multi-helical DNA nanostructure was used as a model `chip' for the detection of a single stranded DNA target. The results revealed that the rate constant of hybridization is strongly dominated by a rate-limiting nucleation step.
ContributorsNangreave, Jeanette (Author) / Yan, Hao (Thesis advisor) / Liu, Yan (Thesis advisor) / Chen, Julian J.-L. (Committee member) / Seo, Dong Kyun (Committee member) / Arizona State University (Publisher)
Created2011
Description
Deoxyribonucleic acid (DNA) has emerged as an attractive building material for creating complex architectures at the nanometer scale that simultaneously affords versatility and modularity. Particularly, the programmability of DNA enables the assembly of basic building units into increasingly complex, arbitrary shapes or patterns. With the expanding complexity and functionality of DNA toolboxes, a quantitative understanding of DNA self-assembly in terms of thermodynamics and kinetics, will provide researchers with more subtle design guidelines that facilitate more precise spatial and temporal control. This dissertation focuses on studying the physicochemical properties of DNA tile-based self-assembly process by recapitulating representative scenarios and intermediate states with unique assembly pathways.
First, DNA double-helical tiles with increasing flexibility were designed to investigate the dimerization kinetics. The higher dimerization rates of more rigid tiles result from the opposing effects of higher activation energies and higher pre-exponential factors from the Arrhenius equation, where the pre-exponential factor dominates. Next, the thermodynamics and kinetics of single tile attachment to preformed “multitile” arrays were investigated to test the fundamental assumptions of tile assembly models. The results offer experimental evidences that double crossover tile attachment is determined by the electrostatic environment and the steric hindrance at the binding site. Finally, the assembly of double crossover tiles within a rhombic DNA origami frame was employed as the model system to investigate the competition between unseeded, facet and seeded nucleation. The results revealed that preference of nucleation types can be tuned by controlling the rate-limiting nucleation step.
The works presented in this dissertation will be helpful for refining the DNA tile assembly model for future designs and simulations. Moreover, The works presented here could also be helpful in understanding how individual molecules interact and more complex cooperative bindings in chemistry and biology. The future direction will focus on the characterization of tile assembly at single molecule level and the development of error-free tile assembly systems.
First, DNA double-helical tiles with increasing flexibility were designed to investigate the dimerization kinetics. The higher dimerization rates of more rigid tiles result from the opposing effects of higher activation energies and higher pre-exponential factors from the Arrhenius equation, where the pre-exponential factor dominates. Next, the thermodynamics and kinetics of single tile attachment to preformed “multitile” arrays were investigated to test the fundamental assumptions of tile assembly models. The results offer experimental evidences that double crossover tile attachment is determined by the electrostatic environment and the steric hindrance at the binding site. Finally, the assembly of double crossover tiles within a rhombic DNA origami frame was employed as the model system to investigate the competition between unseeded, facet and seeded nucleation. The results revealed that preference of nucleation types can be tuned by controlling the rate-limiting nucleation step.
The works presented in this dissertation will be helpful for refining the DNA tile assembly model for future designs and simulations. Moreover, The works presented here could also be helpful in understanding how individual molecules interact and more complex cooperative bindings in chemistry and biology. The future direction will focus on the characterization of tile assembly at single molecule level and the development of error-free tile assembly systems.
ContributorsJiang, Shuoxing (Author) / Yan, Hao (Thesis advisor) / Liu, Yan (Thesis advisor) / Hayes, Mark (Committee member) / Wang, Xu (Committee member) / Arizona State University (Publisher)
Created2016
Description
Surface exploration of the Moon and Asteroids can provide important information to scientists regarding the origins of the solar-system and life . Small robots and sensor modules can enable low-cost surface exploration. In the near future, they are the main machines providing these answers. Advanced in electronics, sensors and actuators enable ever smaller platforms, with compromising functionality. However similar advances haven’t taken place for power supplies and thermal control system. The lunar south pole has temperatures in the range of -100 to -150 oC. Similarly, asteroid surfaces can encounter temperatures of -150 oC. Most electronics and batteries do not work below -40 oC. An effective thermal control system is critical towards making small robots and sensors module for extreme environments feasible.
In this work, the feasibility of using thermochemical storage materials as a possible thermal control solution is analyzed for small robots and sensor modules for lunar and asteroid surface environments. The presented technology will focus on using resources that is readily generated as waste product aboard a spacecraft or is available off-world through In-Situ Resource Utilization (ISRU).
In this work, a sensor module for extreme environment has been designed and prototyped. Our intention is to have a network of tens or hundreds of sensor modules that can communicate and interact with each other while also gathering science data. The design contains environmental sensors like temperature sensors and IMU (containing accelerometer, gyro and magnetometer) to gather data. The sensor module would nominally contain an electrical heater and insulation. The thermal heating effect provided by this active heater is compared with the proposed technology that utilizes thermochemical storage chemicals.
Our results show that a thermochemical storage-based thermal control system is feasible for use in extreme temperatures. A performance increase of 80% is predicted for the sensor modules on the asteroid Eros using thermochemical based storage system. At laboratory level, a performance increase of 8 to 9 % is observed at ambient temperatures of -32oC and -40 oC.
In this work, the feasibility of using thermochemical storage materials as a possible thermal control solution is analyzed for small robots and sensor modules for lunar and asteroid surface environments. The presented technology will focus on using resources that is readily generated as waste product aboard a spacecraft or is available off-world through In-Situ Resource Utilization (ISRU).
In this work, a sensor module for extreme environment has been designed and prototyped. Our intention is to have a network of tens or hundreds of sensor modules that can communicate and interact with each other while also gathering science data. The design contains environmental sensors like temperature sensors and IMU (containing accelerometer, gyro and magnetometer) to gather data. The sensor module would nominally contain an electrical heater and insulation. The thermal heating effect provided by this active heater is compared with the proposed technology that utilizes thermochemical storage chemicals.
Our results show that a thermochemical storage-based thermal control system is feasible for use in extreme temperatures. A performance increase of 80% is predicted for the sensor modules on the asteroid Eros using thermochemical based storage system. At laboratory level, a performance increase of 8 to 9 % is observed at ambient temperatures of -32oC and -40 oC.
ContributorsRabade, Salil Rajendra (Author) / Thangavelautham, Jekanthan (Thesis advisor) / Huang, Huei Ping (Thesis advisor) / Rykaczweksi, Konrad (Committee member) / Arizona State University (Publisher)
Created2016
Description
I studied the properties of novel Co2FeAl0.5Si0.5 (CFAS), ZnGeAs2, and FeS2 (pyrite) thin films for microelectronic applications ranging from spintronic to photovoltaic. CFAS is a half metal with theoretical spin polarization of 100%. I investigated its potential as a spin injector, for spintronic applications, by studying the critical steps involved in the injection of spin polarized electron populations from tunnel junctions containing CFAS electrodes. Epitaxial CFAS thin films with L21 structure and saturation magnetizations of over 1200 emu/cm3 were produced by optimization of the sputtering growth conditions. Point contact Andreev reflection measurements show that the spin polarization at the CFAS electrode surface exceeds 70%. Analyses of the electrical properties of tunnel junctions with a superconducting Pb counter-electrode indicate that transport through native Al oxide barriers is mostly from direct tunneling, while that through the native CFAS oxide barriers is not. ZnGeAs2 is a semiconductor comprised of only inexpensive and earth-abundant elements. The electronic structure and defect properties are similar in many ways to GaAs. Thus, in theory, efficient solar cells could be made with ZnGeAs2 if similar quality material to that of GaAs could be produced. To understand the thermochemistry and determine the rate limiting steps of ZnGeAs2 thin-film synthesis, the (a) thermal decomposition rate and (b) elemental composition and deposition rate of films were measured. It is concluded that the ZnGeAs2 thin film synthesis is a metastable process with an activation energy of 1.08±0.05 eV for the kinetically-limited decomposition rate and an evaporation coefficient of ~10-3. The thermochemical analysis presented here can be used to predict optimal conditions of ZnGeAs2 physical vapor deposition and thermal processing. Pyrite (FeS2) is another semiconductor that has tremendous potential for use in photovoltaic applications if high quality materials could be made. Here, I present the layer-by-layer growth of single-phase pyrite thin-films on heated substrates using sequential evaporation of Fe under high-vacuum followed by sulfidation at S pressures between 1 mTorr and 1 Torr. High-resolution transmission electron microscopy reveals high-quality, defect-free pyrite grains were produces by this method. It is demonstrated that epitaxial pyrite layer was produced on natural pyrite substrates with this method.
ContributorsVahidi, Mahmoud (Author) / Newman, Nathan (Thesis advisor) / Alford, Terry (Committee member) / Singh, Rakesh (Committee member) / Chen, Tingyong (Committee member) / Arizona State University (Publisher)
Created2013