Geckos are famous for the skill of switchable adhesion that they use to stick on various surface while keep their fingers super clean. In the dissertation, a unique mechanism was discovered to explain gecko self-cleaning phenomena. Using atomic force microscopy (AFM), we managed to compare the microparticle-substrate adhesion and the microparticle-seta adhesion with a single seta bonded to the AFM cantilever. A dynamic effect was approved that high pulling-off speed could increase the microparticle-substrate adhesion and thus the self-cleaning appears at high moving speed. Based on the self-cleaning theory, a gecko-inspired N-doped graphene surface with switchable adhesion was achieved, which was designed into a bio-inspired micromanipulator with a success rate over 90%. When electrical bias was applied on this biomimetic surface, the charge concentration induced an electrical double layer (ELD) on the convex surfaces, which attracts polar water molecules to form a water bridge on it, significantly enhancing the adhesion on the wrinkled graphene surface, mimicking the capillary force on beetle feet. Therefore, the bio-inspired adhesive surface can be controlled with speed, electrical bias, humidity and different material surfaces. The water attraction phenomenon on the polarized surface was further tested for the potential application of water collection and evaporation in …

The incorporation of fluorine into SiO2 has been shown to reduce the dielectric constant of the existing materials by reducing the electrical polarizability. However, the incorporation of fluorine has also been shown to decrease film stability. Therefore, new efforts have been made to find different ways to further decrease the relative dielectric constant value of the existing low-k materials. One way to reduce the dielectric constant is by decreasing its density. This reduces the amount of polarizable materials. A good approach is increasing porosity of the film. Recently, fluorinated silica xerogel films have been identified as potential candidates for applications such as interlayer dielectric materials in CMOS technology. In addition to their low dielectric constants, these films present properties such as low refractive indices, low thermal conductivities, and high surface areas. Another approach to lower k is incorporating lighter atoms such as hydrogen or carbon. Silsesquioxane based materials are among them. However, additional integration issues such as damage to these materials caused by plasma etch, plasma ash, and wet etch processes are yet to be overcome. This dissertation reports the effects of triethoxyfluorosilane-based (TEFS) xerogel films when reacted with silylation agents. TEFS films were employed because they form robust silica …

Through a series of carefully designed experiments, characterization and some modeling tools, this work is aimed at studying the role of thermal profiles on different microstructural zones and associated properties like strength and corrosion through a variation of weld parameters, thermal boundary conditions and material temper. Two different alloys belonging to the Al-Cu and Al-Cu-Li system in different temper conditions- peak aged (T8) and annealed (O) were used. A 3D-thermal pseudo mechanical (TPM) model is developed for the FSW process using heat transfer module in COMSOL Multiphysics and is based on a heat source wherein the temperature dependent yield shear stress is used for the heat generation. The precipitation and coarsening model is based on the Kampmann and Wagner theoretical framework and accounts for the competition between the various nucleation sites for both metastable and equilibrium precipitates. The model predicts different precipitate mean radius and volume fraction for the various zones in the friction stir welded material. A model for the yield strength is developed which considers contributions from different strengthening mechanisms. The predictions of the each models have been verified against experimental data and literature. At constant advance per rotation, the peak temperature decreases with a decrease in traverse …