Interaction and Self-Assembly of Nanoparticles for Biomedical, Nanodevice, and Material Applications.

Abstract

The goal of this thesis is to investigate the use of nanoparticles as a means of self-assembly into target structures and as candidates for a variety of applications such as advanced materials, nanodevices, and drug delivery systems. Materials with a well-organized distribution and an orientation provide superior properties that cannot be achieved by the current uniformly or randomly dispersed nanocomposites. An approach to rigorously calculate the driving force for core-shell nanoparticles, taking into account the thermal motion, may suggest a significant degree of the experimental control and contribute to materialization of the distinguished properties. Electrostatic interactions also demonstrate that organizing different nanoparticles systematically into ordered binary superlattices can lead to functional materials. The work elucidates how parameters including permittivity, volume fraction, particle size, and the frequency of the field can be utilized to control the morphology of the superlattice structures. The study explores a wide range of superlattices from functional gradient columns to an alternating chain-network. Poly (amidoamine) dendrimer nanoparticles have been employed extensively in biomedical applications such as drug delivery systems. They disrupt cell membranes and allow the transportation of agent materials into cells. The results of a three dimensional phase field model demonstrate that an amine-terminated G7 dendrimer, which has positive charges on the surface, causes a hole in the membrane. The molecules removed from the membrane encircle the dendrimer and form a dendrimer-filled membrane vesicle. This behavior is significantly reduced for smaller dendrimers. An acetamide-terminated dendrimer, which has a neutral charge, does not induce a hole effectively. Relatively larger particles, such as liquid droplets, also have diverse applications such as ‘lab-on-a-chip’ systems for biomedical diagnostics. A phase field model, combining the thermodynamics and hydrodynamics, predicts a dynamic motion of a droplet on designed electrodes, which is an important factor for designing devices. Furthermore, it predicts the instability occurrence at a high field strength, which is observed from experiments. A parametric study, combined with a stability analysis, shows a tendency of the instability to depend on the surface energy and the strength of the applied field.