This thesis develops various theoretical and computational models to understand the motion of nanoparticles in nanochannels, and to study the ionic current traces due to translocating particles through a nanopore. Investigating and understanding the interactions that control the dynamics of nanoparticles will expedite the implementation of nanochannels for various applications, such as filtration, detection, and characterization of nanoparticles. The computational modeling gives us the means to further understand the capabilities of nanochannels and shed light on some of the phenomena seen in experiments.
The first stage of this work involved calculating analytical solutions of continuum electrostatics in trapezoidal nanochannels. The Poisson-Boltzmann equation was used to calculate the electrostatic potential distribution analytically for the nanochannel immersed in an electrolyte solution, which contributes to the electrostatic and dielectrophoretic forces acting on a spherical particle placed in the channel. The analytical study of electrostatic and dielectrophoretic forces acting on a negatively charged particle in the corner of a negatively charged nanochannel shows a competing effect. We discovered the net force acting on a nanoparticle can be attractive at the vertex when the dielectrophoretic force dominates over the electrostatic force for some solution concentrations and geometric angles of the vertex.
The second stage involved computational studies of the electroosmotic fluid flow for cylindrical nanochannels, also known as nanopores. In this study different nanopore geometries, membrane charges, and electrolyte concentrations were considered and compared with the analytical solutions of an infinitely long pore. The solution of the electroosmotic fluid flow was obtained by solving self-consistently the Poisson-Nernst-Planck and Navier-Stokes equations. This study finds that an induced pressure is created from the expansion and contraction of the fluid flow at the pore entrance/exit, which plays an important role in modifying the fluid flow profile. This induced pressure modifies the fluid flow profile by creating a local minimum in the flow along the pore's axis and becomes a maximum when the pore's length is about the size of the pore's diameter. An analytical solution was modified to incorporate the induced pressure.
The third stage of this thesis developed a novel computational scheme to model a nanoparticle's movement through a nanopore. We self-consistently calculate the electrostatic and hydrodynamic forces a particle experiences at various locations within a nanopore and incorporate these forces into a Brownian dynamics model. The value of the ionic current is determined based on the particle's location after each simulated time step to give a realistic ionic current as seen in experiments. By repeating these simulations many times, analysis of the ionic current traces can be performed similar to how it is done in experiments.
|Commitee:||Helenbrook, Brian, Roy, Dipankar, Scrimgeour, Jan, ben-Avraham, Daniel|
|School Location:||United States -- New York|
|Source:||DAI-B 80/03(E), Dissertation Abstracts International|
|Keywords:||cylindrical nanochannels, dielectrophoretic force, electrostatic potential distribution|
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