| With the understanding of micro/nanostructures, micro/nano-structuring technology has developed into a hot topic in the research of surface modification. Femtosecond laser micro/nano-structuring technology break through the limits of processing materials and sizes, and can be controllably used to fabricate the two or three dimensional micro/nanostructures, which has become a prospect for micro/nano-structuring technology. The magnesium alloy is not only a kind of high-strength lightweight structural material, but also is expected to become a new biodegradable biomaterial, so it has broad application prospects. So far, the reaserch on fabrication of micro/nano-structure on magnesium alloy surface by femtosecond laser is limited. It is unclear for the understanding of surface morphology of fs laser ablation on magnesium alloy, and the interaction between femtosecond laser and magnesium is unknown. Therefore, in this paper we adopted the femtosecond laser micro/nano-structuing to fabricate on magnesium alloy surface, which has certain guiding significance for the development of new functional magnesium alloy surface.In this paper, AZ31 B magnesium alloy surface was ablated by femtosecond laser raster scanning. This thesis focused on the effect of fs laser processing parameters on magnesium alloy surface ablation topography. Then optical-trapping?wettability and cytotoxicity were mainly studied. The main content and conclusions were shown as following:1. Energy density and scanning speed were the mainly adjusted for surface morphology. It was obtained two kinds of surface morphologies. The typical Fs-irradiated structure comprise nano-FLIPSS structure, column structure and honeycomb hole structure. The typical Fs-inscribed structure is groove structure. The former mainly influence the ablation topography, while the latter mainly control the size of ablation structure.2. Optical reflectance in the visible range(at the wavelength of 400~800 nm) of micro/nano-structured surface was characterized to evaluate the optical-trapping performance. This thesis analyzed the influence of processing parameters on optical absorption, and then established a simplified model to analyze the surface light-trapping mechanism on four different surfaces, combing with three-dimensional surface appearance and roughness. The results showed that FLIPSS structure reduced the light absorption of magnesium alloy surface while the other three micro/nano-structures were good light-trapping structures. In the visible range the optimal light absorption of groove structure reached 93%, which had been increased by 43.1%. The optical absorption for column structure and hole structure were about 85%~90%, and the difference came from the size of column and hole.3. Contact angle was used to evaluate the wetting properties. Record the contact angle with time passing, and observe the stability of the wettability state. The surface after ablation by fs laser with FLIPSS, column structure and hole structure showed hydrophobic, and the contact angle was about 135°, while the contact angle on groove structure surface was approximately 20°. However, the hydrophobic state was not stable, which was caused by the chemical reaction between magnesium and deionized water.4. MC3T3-E1 cell were directly cultured on the micro/nano-structured surface, live/dead staining was aimed at observing the state of the cell after cultured for 24 h. SEM of cell morphology was also observed. The results found that the microstructure prepared by femtosecond laser can effectively improve the cytotoxic response and the spreading state of cell. When the surface roughness of the column structure was 1.729 ?m, the cellular toxicity was the smallest and cell spread best accompaning by pseudopodia. Further, groove structure can promote cell orientation growth. |
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