Abstract

This dissertation aims to develop a new technique for fabrication of three-dimensional (3-D) interwoven nanofibrous platforms using femtosecond laser ablation of solids in ambient conditions. In the first part, the mechanism of ablation of solids by multiple femtosecond laser pulses in ambient air is described in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles for laser ablation by multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Later, the formation mechanism of the nanofibrous structures during laser ablation of targets in the presence of air is discussed. The results indicate that femtosecond laser ablation of solids at air background yields crystalline nanostructures. It’s also shown that this technique allows synthesis of 3-D nanostructures on a wide range of materials including synthetic and natural materials. Later, potential practice of the proposed technique for integration of nanostructures on transparent platforms as well as inside microstructures toward device fabrication is investigated. Presented studies show that integrated nanostructure inside microchannels can be fabricated in one single step using this technique. Finally, to address the potential use of the nanostructures for biomedical application, several studies are performed to evaluate the bioactivity and biocompatibility of the nanostructures. The fabricated nanostructures incorporate the functions of 3-D nano-scaled topography and modified chemical properties to improve osseointegration, while at the same time leaving space for delivering other functional agents.

Highlights

  • Nanotechnology is considered as a key technology of current century, as it influences microelectronic technologies and biological, medical, and chemical industries

  • The results showed that femtosecond laser ablation of Ti target at air background resulted in the formation of crystalline titania nanostructures

  • The results showed that laser pulse repetition could control the density, size, and pore size of engineered nanofibrous structure

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Summary

Introduction

Nanotechnology is considered as a key technology of current century, as it influences microelectronic technologies and biological, medical, and chemical industries. Nanotechnology is defined as the fabrication and characterization of devices with precision scale down to atomic or molecular level. Structures with basic structural units, grains, particles, fibers or other constituent components smaller than 100 nm in at least one dimension are considered nanostructures [1]. Nanostructures have drawn great attention due to the unique physical and chemical properties exhibited when the size of particles are in the order of sub 100 nm. Nanostructures can be in forms of nanoparticles, nanoclusters, nanocrystals, nanotubes, nanofibers, nanowires, nanorods, nanofilms, etc. Synthesized nanostructures have numerous potential applications in the fabrication of nano-devices in microelectronic, biomedical, photonic fields, tissue engineering and filtration technologies

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