Micro/Nano Structured Materials for Enhanced Device Performance and Antibacterial Applications

Micro/nanostructured materials have been used extensively for various applications due to their unique chemical, physical, and mechanical properties. In this thesis we report the fabrication and characterization of micro/nanostructured materials with antibacterial properties. Plastics are used in a wide range of medical components such as prosthetics, implants, catheters, and syringes. However, contaminating bacteria can attach to plastic surfaces and grow and form biofilms that lead to healthcare associated infections. The consequences on patients and their families are serious, as infections can extend hospital stays, create long-term disability, increase healthcare costs, and even result in unnecessary deaths. Two strategies for creating antibacterial surfaces are (1) anti-biofouling surfaces that make the bacterial attachment process difficult and (2) bactericidal surfaces that kill bacteria cells that come in proximity of or contact the surface. We demonstrate that a fluorine etch chemistry may be utilized to create lotus leaf-inspired, low surface energy, hierarchical micro-structure/nanofibrils in Polypropylene (PP). Our anti-biofouling PP surfaces exhibit a 99.6% reduction of E. coli cell adhesion compared to untreated PP. We also fabricated bactericidal surfaces consisting of uniform and regular nanostructured arrays. The interest in mechanical bactericidal effect has recently increased, as the bacteria cells grow drug resistance. Nanosphere lithography and combination of reactive ion etching and deep reactive ion etching were utilized to prepare these substrates. The pitch, diameter, taper, and height of the nanostructures are controlled. The bactericidal effect of these structures is investigated and significant enhancement in killing is observed. We also report fabrication of micro/nanostructured materials to improve device performance. Our simulation results show that absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays over a broad range of tilt angles. The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% of the ideal double pass thin film. Incorporation of these structures could improve the efficiency of solar cells.