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ESTIMATION OF TANGENTIAL MOMENTUM ACCOMMODATION COEFFICIENT USING MOLECULAR DYNAMICS SIMULATION
Title
ESTIMATION OF TANGENTIAL MOMENTUM ACCOMMODATION COEFFICIENT USING MOLECULAR DYNAMICS SIMULATION.
Creator
Finger, George, Kapat, Jayanta, University of Central Florida
Abstract / Description
The Tangential Momentum Accommodation Coefficient (TMAC) is used to improve the accuracy of fluid flow calculations in the slip flow regime. Under such conditions (indicated by Knudsen number greater than 0.001), the continuum assumption that a fluid velocity at a solid surface is equal to the surface velocity is inaccurate because relatively significant fluid "slip" occurs at the surface. Prior work has not led to a method to quickly estimate a value for TMAC - it is frequently assumed. In...
Show moreThe Tangential Momentum Accommodation Coefficient (TMAC) is used to improve the accuracy of fluid flow calculations in the slip flow regime. Under such conditions (indicated by Knudsen number greater than 0.001), the continuum assumption that a fluid velocity at a solid surface is equal to the surface velocity is inaccurate because relatively significant fluid "slip" occurs at the surface. Prior work has not led to a method to quickly estimate a value for TMAC - it is frequently assumed. In this work, Molecular Dynamics techniques are used to study the impacts of individual gas atoms upon solid surfaces to understand how approach velocity, crystal geometry and interatomic forces affect the scattering of the gas atoms, specifically from the perspective of tangential momentum. It is a logical step in the development of a comprehensive technique to estimate total coefficient values to be used by those investigating flows in micro- and nano-channels or on orbit spacecraft where slip flow occurs. TMAC can also help analysis in transitional or free molecular regimes of flow. The gas – solid impacts were modeled using Lennard Jones potentials. Solid surfaces were modeled with approximately 3 atoms wide by 3 atoms deep by 40 or more atoms long. The crystal surface was modeled as a Face Centered Cubic (100). The gas was modeled as individual free gas atoms. Gas approach angles were varied from 10° to 70° from normal. Gas speed was either specified directly or by way of a ratio relationship with the Lennard-Jones energy potential (Energy Ratio). In order to adequately model the trajectories and maintain conservation of energy, very small time steps (on the order of 0.0005 ô , where ô is the natural time unit) were used. For each impact the initial and final tangential momenta were determined and after a series of many impacts, a value of TMAC was calculated for those conditions. The modeling was validated with available experimental data for He gas atoms at 1770 m/s impacting Cu over angles ranging from 10° to 70°. The model agreed within 3% of the experimental values and correctly predicted that the coefficient changes with angle of approach. Molecular Dynamics results estimate TMAC values from a high of 1.2 to a low of 0.25, generally estimating a higher coefficient at the smaller angles. TMAC values above 1.0 indicate backscattering, which has been experimentally observed in numerous instances. The ratio of final to initial momenta, when plotted for a given sequence of gas atoms spaced across a lattice cycle typically follows a discontinuous curve, with continuous portions indicating forward and back scattering and discontinuous portions indicating multiple bounces. Increasing the Energy Ratio above a value of 5 tends to decrease the coefficient at all angles. Adsorbed layers atop a surface influence the coefficient similar to their Energy Ratio. The results provide encouragement to develop the model further, so as to be able in the future to evaluate TMAC for gas flows with Maxwell temperature distributions involving numerous impact angles simultaneously.
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Date Issued
2005
Identifier
CFE0000760, ucf:46567
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000760
LATTICE VIBRATION STUDY OF SILICA NANOPARTICLE IN SUSPENSION
Title
LATTICE VIBRATION STUDY OF SILICA NANOPARTICLE IN SUSPENSION.
Creator
Sachdeva, Parveen, Kumar, Ranganathan, University of Central Florida
Abstract / Description
In recent years considerable research has been done in the area of "nanofluids". Nanofluids are colloidal suspensions of nanometer size metallic or oxide particles in a base fluid such as water, ethylene glycol. Nanofluids show enhanced heat transfer characteristics compared to the base fluid. The thermal transport properties of nanofluids depend on various parameters e.g. interfacial resistance, Brownian motion of particles, liquid layering at the solid-liquid interface and clustering of...
Show moreIn recent years considerable research has been done in the area of "nanofluids". Nanofluids are colloidal suspensions of nanometer size metallic or oxide particles in a base fluid such as water, ethylene glycol. Nanofluids show enhanced heat transfer characteristics compared to the base fluid. The thermal transport properties of nanofluids depend on various parameters e.g. interfacial resistance, Brownian motion of particles, liquid layering at the solid-liquid interface and clustering of nanoparticles. In this work atomic scale simulation has been used to study possible mechanisms affecting the heat transfer characteristics of nanofluids. Molecular dynamics simulation for a single silica nanoparticle surrounded by water molecules has been performed. Periodic boundary condition has been used in all three directions. The effect of nanoparticle size and temperature of system on the thermal conductivity of nanofluids has been studied. It was found that as the size of nanoparticle decreases thermal conductivity of nanofluid increases. This is partially due to the fact that as the diameter of nanoparticle decreases from micrometer to nanometer its surface area to volume ratio increases by a factor of 103. Since heat transfer between the fluid and the nanoparticle takes place at the surface this enhanced surface area gives higher thermal conductivity for smaller particles. Thermal conductivity enhancement is also due to the accumulation of water molecules near the particle surface and the lattice vibration of the nanoparticle. The phonon transfer through the second layer allows the nanofluid thermal conductivity to increase by 23%-27% compared to the base fluid water for 2% concentration of nanosilica.
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Date Issued
2006
Identifier
CFE0001278, ucf:46897
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001278
COARSE GRAINED MONTE CARLO SIMULATION OF THE SELF-ASSEMBLY OF THEHIV-1 CAPSID PROTEIN
Title
COARSE GRAINED MONTE CARLO SIMULATION OF THE SELF-ASSEMBLY OF THEHIV-1 CAPSID PROTEIN.
Creator
Weber, Jeffrey, Chen, Bo, University of Central Florida
Abstract / Description
In this study, a Monte Carlo simulation was designed to observe the self-assembly of the HIV-1 capsid protein. The simulation allowed a coarse grained model of the capsid protein with defined interaction sites to move freely in three dimensions using the Metropolis criterion. Observations were made as to which parameters affected the assembly the process. The ways in which the assembly were affected were also noted. It was found that proper dimerization of the capsid protein was necessary in...
Show moreIn this study, a Monte Carlo simulation was designed to observe the self-assembly of the HIV-1 capsid protein. The simulation allowed a coarse grained model of the capsid protein with defined interaction sites to move freely in three dimensions using the Metropolis criterion. Observations were made as to which parameters affected the assembly the process. The ways in which the assembly were affected were also noted. It was found that proper dimerization of the capsid protein was necessary in order for the lattice to form properly. It was also found that a strong trimeric interface could be responsible for double-layered assemblies. Further studies may be conducted by further varying of parameters or reworking the dynamics of the simulation. The possible causes of curvature within the assembly still need to be researched further.
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Date Issued
2014
Identifier
CFH0004618, ucf:45316
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004618
SIMULATION STUDIES OF SELF-ASSEMBLY AND PHASE DIAGRAMOF AMPHIPHILIC MOLECULES
Title
SIMULATION STUDIES OF SELF-ASSEMBLY AND PHASE DIAGRAMOF AMPHIPHILIC MOLECULES.
Creator
Bourov, Geuorgui, Bhattacharya, Aniket, University of Central Florida
Abstract / Description
The aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system...
Show moreThe aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system behavior is consistent with theoretical predictions, experiments and lattice simulation models. We demonstrate that by modifying the geometry of the molecules, self-assembled aggregates are altered in a way close to theoretical predictions. In several two and three dimensional off-lattice Brownian Dynamics simulations, the influence of the shape of the amphiphilic molecules on the size and form of the aggregates is studied systematically. Model phospholipid molecules, with two hydrophobic chains connected to one hydrophilic head group, are simulated and the formation of stable bilayers is observed. In addition, (practically very important) mixtures of amphiphiles with diverse structures are studied under different mixing ratios and molecular structures. We find that in several systems, with Poisson distributed chain lengths, the effect on the aggregation distribution is negligible compared to that of the pure amphiphilic system with the mean length of the Poisson distribution. The phase diagrams of different amphiphilic molecular structures are investigated in separate simulations by employing the Gibbs Ensemble Monte Carlo method with an implemented configurational-bias technique. The computer simulations of the above mentioned amphiphilic systems are done in an area where physics, biology and chemistry are closely connected and advances in applications require the use of new theoretical, experimental and simulation methods for a better understanding of their self-assembling properties. Obtained simulation results demonstrate the connection between the structure of amphiphilic molecules and the properties of their thermodynamically stable aggregates and thus build a foundation for many applications of the remarkable phenomena of amphiphilic self-assembly in the area of nanotechnology.
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Date Issued
2005
Identifier
CFE0000695, ucf:46491
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000695
MOLECULAR DYNAMICS STUDY OF THERMAL CONDUCTIVITY ENHANCEMENT OF WATER BASED NANOFLUIDS
Title
MOLECULAR DYNAMICS STUDY OF THERMAL CONDUCTIVITY ENHANCEMENT OF WATER BASED NANOFLUIDS.
Creator
Sachdeva, Parveen, Kumar, Ranganathan, University of Central Florida
Abstract / Description
A systematic investigation using molecular dynamics (MD) simulation involving particle volume fraction, size, wettability and system temperature is performed and the effect of these parameters on the thermal conductivity of water based nanofluids is discussed. Nanofluids are a colloidal suspension of 10 -100 nm particles in base fluid. In the last decade, significant research has been done in nanofluids, and thermal conductivity increases in double digits were reported in the literature. This...
Show moreA systematic investigation using molecular dynamics (MD) simulation involving particle volume fraction, size, wettability and system temperature is performed and the effect of these parameters on the thermal conductivity of water based nanofluids is discussed. Nanofluids are a colloidal suspension of 10 -100 nm particles in base fluid. In the last decade, significant research has been done in nanofluids, and thermal conductivity increases in double digits were reported in the literature. This anomalous increase in thermal conductivity cannot be explained by classical theories like Maxwell's model and Hamilton-Crosser model for nanoparticle suspensions. Various mechanisms responsible for thermal conductivity enhancement in nanofluids have been proposed and later refuted. MD simulation allows one to predict the static and dynamic properties of solids and liquids, and observe the interactions between solid and liquid atoms. In this work MD simulation is used to calculate the thermal conductivity of water based nanofluid and explore possible mechanisms causing the enhancement. While most recent MD simulations have considered Lennard Jones (LJ) potential to model water molecule interactions, this work uses a flexible bipolar water molecule using the Flexible 3 Center (F3C) model. This model maintains the tetrahedral structure of the water molecule and allows the bond bending and bond stretching modes, thereby tracking the motion and interactions between real water molecules. The choice of the potential for solid nanoparticle reflects the need for economic but insightful analyses and reasonable accuracy. A simple two body LJ potential is used to model the solid nanoparticle. The cross interaction between the solid and liquid atoms is also modeled by LJ potential and the Lorentz-Berthelot mixing rule is used to calculate the potential parameters. The various atomic interactions show that there exist two regimes of thermal conductivity enhancement. It is also found that increasing particle size and decreasing particle wettability cause lower thermal conductivity enhancement. In contrast to the previous studies, it is observed that increasing system temperature does not enhance thermal conductivity significantly. Such enhancement with temperature is proportional to the conductivity enhancement of base fluid with temperature. This study demonstrates that the major cause of thermal conductivity enhancement is the formation of ordered liquid layer at the solid-liquid interface. The enhanced motion of the liquid molecules in the presence of solid particles is captured by comparing the mean square displacement (MSD) of liquid molecules in the nanofluid to that of the base fluid molecules. The thermal conductivity is decomposed into three modes that make up the microscopic heat flux vector, namely kinetic, potential and collision modes. It was observed by this decomposition analyses that most of the thermal conductivity enhancement is obtained from the collision mode and not from either the kinetic or potential mode. This finding also supports the observation made by comparing the MSD of liquid molecules with the base fluid that the interaction between solid and liquid molecules is important for the enhancement in thermal transport properties in nanofluids. These findings are important for the future research in nanofluids, because they suggest that if smaller, functional nanoparticles which have higher wettability compared to the base fluid can be produced, they will provide higher thermal conductivity compared to the regular nanoparticles.
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Date Issued
2009
Identifier
CFE0002944, ucf:47969
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002944
Understanding the Role of Defects in the Radiation Response of Nanoceria
Title
Understanding the Role of Defects in the Radiation Response of Nanoceria.
Creator
Kumar, Amit, Seal, Sudipta, Heinrich, Helge, Cho, Hyoung, Leuenberger, Michael, Zhai, Lei, Devanathan, Ram, University of Central Florida
Abstract / Description
Nanoscale cerium oxide (nanoceria) have shown to possess redox active property , and has been widely studied for potential use in catalysis, chemical-mechanical planarization, bio-medical and solid oxide fuel cell (SOFC), etc. The redox state of nanoceria can be tuned by controlling the defects within the lattice and thus its physical and chemical properties. Perfect ceria lattice has fluorite structure and the research in last decade has shown that oxide and mixed oxide systems with...
Show moreNanoscale cerium oxide (nanoceria) have shown to possess redox active property , and has been widely studied for potential use in catalysis, chemical-mechanical planarization, bio-medical and solid oxide fuel cell (SOFC), etc. The redox state of nanoceria can be tuned by controlling the defects within the lattice and thus its physical and chemical properties. Perfect ceria lattice has fluorite structure and the research in last decade has shown that oxide and mixed oxide systems with pyrochlore and fluorite have better structural stability under high energy radiation. However, the current literature shows a limited number of studies on the effect of high energy radiation on nanoceria. This dissertation aims at understanding the phenomena occurring on irradiation of nanoceria lattice through experiments and atomistic simulation.At first, research was conducted to show the ability to control the defects in nanoceria lattice and understand the effect in tailoring its properties. The defect state of nanoceria was controlled by lower valence state rare earth dopant europium. Extensive materials characterization was done using high resolution transmission electron microscopy (HRTEM), UV-Visible spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to understand the effect of dopant chemistry in modifying the chemical state of nanoceria. The defects originating in the lattice and redox state was quantified with increasing dopant concentration. The photoluminescence property of the control and doped nanoceria were evaluated with respect to its defect state. It was observed that defect plays an important role in modifying the photoluminescence property and that it can be tailored in a wide range to control the optical properties of nanoceria.Having seen the importance of defects in controlling the properties of nanoceria, further experiments were conducted to understand the effect of radiation in cerium oxide thin films of different crystallinity. The cerium oxide thin films were synthesized using oxygen plasma assisted molecular beam epitaxy (OPA-MBE) growth. The thin films were exposed to high energy radiation over a wide range of fluence (1013 to 1017 He+ ions/cm3). The current literature does not report the radiation effect in nanoceria in this wide range and upto this high fluence. The chemical state of the thin film was studied using in-situ XPS for each dose of radiation. It was found that radiation induced defects within both the ceria thin films and the valence state deviated further towards non-stoichiometry with radiation. The experimental results from cerium oxide thin film irradiation were studied in the light of simulation. Classical molecular dynamics and Monte Carlo simulation were used for designing the model ceria nanoparticle and studying the interaction of the lattice model with radiation. Electronic and nuclear stopping at the end of the range were modeled in ceria lattice using classical molecular dynamics to simulate the effect of radiation. It was seen that displacement damage was the controlling factor in defect production in ceria lattice. The simulation results suggested that nanosized cerium oxide has structural stability under radiation and encounters radiation damage due to the mixed valence states. A portion of the study will focus on observing the lattice stability of cerium with increasing concentration of the lower valence (Ce3+) within the lattice. With this current theoretical understanding of the role of redox state and defects during irradiation, the surfaces and bulk of nanoceria can be tailored for radiation stable structural applications.
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Date Issued
2012
Identifier
CFE0004396, ucf:49375
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004396
STRUCTURAL, ELECTRONIC, VIBRATIONAL AND THERMODYNAMICAL PROPERTIES OF SURFACES AND NANOPARTICLES
Title
STRUCTURAL, ELECTRONIC, VIBRATIONAL AND THERMODYNAMICAL PROPERTIES OF SURFACES AND NANOPARTICLES.
Creator
Yildirim, Handan, Rahman, Talat S., University of Central Florida
Abstract / Description
The main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the ÂÂ"bottom-upÃ&...
Show moreThe main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the ÂÂ"bottom-upÂÂ" approach for which the knowledge gathered at the scale of atoms and NPs serves as a base to build, at the macroscopic scale, materials with desired physical and chemical properties. We use a variety of theoretical and computational tools with different degrees of accuracy to study problems in different time and length scales. Interactions between the atoms are derived using both Density Functional Theory (DFT) and Embedded Atom Method (EAM), depending on the scale of the problem at hand. For some cases, both methods are used for the purpose of comparison. For revealing the local contributions to the vibrational dynamics and thermodynamics for the systems possessing site-specific environments, a local approach in real-space is used, namely Real Space GreenÂÂ's Function method (RSGF). For simulating diffusion of atoms/clusters and growth on metal surfaces, Molecular Statics (MS) and Molecular Dynamics (MD) methods are employed.
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Date Issued
2010
Identifier
CFE0003064, ucf:48300
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003064
Chemistry and dissipation at mineral surfaces in the space environment
Title
Chemistry and dissipation at mineral surfaces in the space environment.
Creator
Tucker, William, Schelling, Patrick, Britt, Daniel, Kara, Abdelkader, Coffey, Kevin, University of Central Florida
Abstract / Description
The composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation,...
Show moreThe composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation, experimental results are first presented which demonstrate that mineral grains subjected to high temperatures in a reducing environment lead to iron nanoparticles which are strongly catalytic for the formation of complex organic species. Next, results obtained using molecular-dynamics simulations demonstrate that uncoordinated surface atoms in metallic nanoparticles result in plastic deformation, strong dissipation and adhesion during collisions. This can be contrasted with previous simulations which demonstrate significantly weaker dissipation when surface atoms are passivated. Calculations of critical sticking velocities demonstrate that simple coarse- grain models are insufficient for predicting the adhesive behavior of sub-micron sized grains. Next, results are presented describing a computational study illuminating the role of surface chemistry on adhesion and dissipation for iron nanoparticle collisions, which in the case of free radical adsorbates may also contribute to the creation of more complex species. Lastly, to further elucidate dissipation, the direct coupling of harmonic vibrational modes in the dissipation process is established. The results demonstrate broad participation of low and high-frequency modes during a collision during a timescale less than time required for particles to rebound. Hence, our results demonstrate extremely strong likelihood of adhesion during collisions. This approach provides a way to use density-functional theory calculations to directly compute dissipative couplings at mineral interfaces.
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Date Issued
2019
Identifier
CFE0007545, ucf:52592
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007545
Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface
Title
Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface.
Creator
Thakore, Vaibhav, Hickman, James, Mucciolo, Eduardo, Rahman, Talat, Johnson, Michael, Behal, Aman, Molnar, Peter, University of Central Florida
Abstract / Description
Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron...
Show moreExtracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signal-to-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.
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Date Issued
2012
Identifier
CFE0004797, ucf:49718
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004797