【作者】 吴勃；

【导师】 蔡兰；

【作者基本信息】 江苏大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 受自然界中生物体表面特殊功能和性能的启发,研究生物表面的微纳结构,并在人工材料表面进行仿生功能微结构的制备与性能研究是仿生学的研究热点之一。开展其研究,在工业、航空航天、军事、医疗和日常生活等领域具有重要的理论研究价值与广阔的应用前景。本文利用飞秒激光器和纳秒激光器,构造了仿生微结构表面制备实验系统,制备了一系列仿生金属微纳结构表面,对这些微纳结构表面开展了表面形成机理、表面润湿性能、表面陷光性能和表面生物相容性的研究,以期实现对仿生功能微纳结构制备和应用的指导。本文的主要研究内容和结论如下：1.构造了飞秒激光仿生微结构表面制备实验系统,在高真空环境下对不锈钢表面进行了飞秒激光微结构的制备与研究,考察了单脉冲和多脉冲激光作用下表面微结构的形成机理,并进行了大面积多尺度微纳结构的制备,在此基础上,确定了激光作用参数对表面形貌的影响规律。实验结果表明,单脉冲激光实现的烧蚀直径决定于材料的单脉冲能量阈值和所用激光的单脉冲能量,而多脉冲激光作用下形成特定微结构的能量阈值随着脉冲次数的增加而减小；激光能量密度较低时获得了典型的亚微米级激光诱导周期性表面结构(LIPSS),随激光能量密度的增强,依次形成微米级波纹和锥形钉,表面覆盖着LIPSS结构,从而组成了微米-亚微米级双尺度结构；对比扫描路径的起点和终点部位的微结构,证明高能量密度只能形成微米级粗糙结构而不能形成LIPSS结构。通过对激光作用参数进行调整可实现多种多尺度微纳结构表面,为仿生功能结构表面提供丰富的选择。2.基于润湿性能的几何分析方法,建立了多尺度微结构对润湿性能的影响模型。对经硅烷化处理后的飞秒激光微结构化不锈钢表面的润湿性能进行了检测,发现随着激光能量密度的增加,所获得微结构表面的超疏水性提高,尤其是在高能量密度激光下获得的类似荷叶表面乳突状双尺度结构的表面具有极高的表观接触角和极小的滚动角。润湿实验结果与本文建立的多尺度结构对润湿性能的影响模型的预测吻合得较好,为多尺度微纳结构超疏水功能表面的构筑和调控提供指导。3.提出了两次不同能量密度飞秒激光大面积交叉扫描的方法,在不锈钢表面获得了微米级锥状钉结合亚微米级颗粒的多尺度陷光结构；微结构表面对波长范围200-900nm的光波具有很好的吸收增强效果,XRD分析结果表明,不锈钢表面强陷光效果的原因是表面的微结构,而不是化学成分的改变；建立了多尺度微结构表面的陷光模型,并基于该模型分析了微结构的陷光机理。构造了纳秒激光微结构表面制备实验系统；在不锈钢表面进行了多脉冲微孔结构制备与光反射率测试,并确定了激光参数对微孔结构以及陷光效果的影响规律；优化设计了梅花型排列的微孔阵列陷光结构,实验结果表明其具有很好的陷光效果。金属基陷光微结构的制备与性能研究在光响应材料领域具有重要的研究价值和应用前景。4.对飞秒激光微结构化后的不锈钢表面进行了血液相容性研究,通过体外血小板粘附实验、动态凝血实验和溶血实验来评价微结构化超疏水表面的血液相容性。实验结果表明,材料表面微结构可以显著抑制血小板的粘附数量和激活比例,延长动态凝血时间,降低溶血率。本文还从微结构表面超疏水性能的角度对材料表面血液相容性的改善机理进行了研究。5.建立了表面微结构对细胞的接触导向模型,并采用了细胞培养实验对该模型进行了验证。实验结果表明：不锈钢表面的LIPSS结构具有明显的接触导向效果,细胞培养时间越长效果越明显,这与细胞接触导向模型的预测结果吻合得较好；另外发现微波纹结构还增加了细胞的粘附增殖速度。这种飞秒激光大面积扫描获得的微结构的周期远小于常见的细胞尺寸,可以用于实现各种细胞的运动控制和粘附增殖,为多尺度结构仿生微结构表面在生物医用材料中的应用提供了理论指导。更多还原

【Abstract】 The surface of the organism in nature has a variety of special functions. Acquiring inspiration by investigating microstructure of living beings surface, and fabricating bionic functional microstructure are one of the hotspots of biomimics. The investigation has wide application prospect in several fields such as industrial, aerospace, military, medical and daily life.In this paper, the preparation experimental system of biomimetic microstructure has been constructed with femtosecond laser and nanosecond laser. Various microstructures have been fabricated on stainless steel using the experimental system. The formed mechanism, hydrophobicity, optical character, and biocompatibility of these topography on stainless steel surface have been studied to achieve preparation and application of bionic functional microstructure. The main content and conclusion of this thesis are as follows:1. The preparation experimental system of biomimetic microstructure was constructed with femtosecond laser. Preparation of biomimetic microstructure using laser on stainless steel surface in high vacuum was investigated. The formed mechanism of microstructure using single pulse and multiple pulses was studied. Large area multi-scale microstructure has been obtained by scanning with femtosecond laser. With these experiments, the effect of laser parameters on the microstructure was determined. The results of these experiments suggest that the single-pulse laser ablation diameter depends on single pulse energy and single pulse energy threshold. Multiple pulse experiment indicates that the energy threshold of specific microstructure decreases with the number of laser pulses increasing. With low laser fluence, we fabricated typical laser-induced periodic surface structures (LIPSS) on the submicron level. With laser fluence increasing, we fabricated periodic ripples and periodic cone-shaped spikes on the micron scale, both covered with LIPSS. These surface topography are micro- and submicron double-scale structures. By comparing topography at the starting point and that at the end point, it is obvious that microstructure of high laser fluence can only lead to roughness on the micron scale instead of LIPSS. This controllable multi-scale microstructure preparation and investigation provide abundant choise for bionic functional microstructure fabrication.2. Based on the geometry analysis method, an influence model of multi-scale microstructure on wettability was established. The wettability of the stainless steel surface, after microstructured with femtosecond laser flowed silanizing, was examined. The results suggest that with laser fluence increasing, the superhydrophobicity of the microtructured surface is enhanced, particularly the lotus-leaf-like papillary double-scale structure surface of high laser fluence has extremely high apparent contact angle (CA) and extremely low sliding angle (SA). The uniformity between the calculated value and the experimental result indicates that the influence model can be used to guide designing multi-scale superhydrophobic microstructure.3. Through a large area microstruture fabricating method comprising two scanning with different fluence femtosecond laser, a multi-scale light trapping structure with cone-shaped micro-spikes and submicro-particles was obtained. The microstructure surface has an extremly low reflectivity in the wavelength range of 200-900 nm. The XRD result suggests that strongly enhanced optical absorption of the stainless steel surfaces should be attributed to the micro- and nano-structures on the surfaces rather than the surfaces’ chemical changes. We established an optical absorption model of multi-scale microstructure surface. Based on the model, the light trapping mechanism of the microstructure was analysed. The preparation experimental system of microstructure was constructed with nanosecond laser. The reflectivity of the microholes fabricated on the stainless steel surface using nanosecond laser was examined. The effect of laser parameters on the microstructure and light trapping function was determined. We designed a light trapping structure of microholes quincuncial distributing on the sample surface. The experimental result suggests that the structure surface has an extremly low reflectivity. The preparation and study of light trapping structure on metal have significant research value and application prospect in the field of optical response materials. 4. Blood compatibility for stainless steel superhydrophobic surface microstructured using femtosecond laser was studied through the platelet adhesion experiment, dynamic coagulation and hemolysis test experiment. The results of these experiments suggest that the microstructures on the sample’s surface can significantly decrease the number of adhered and activated platelets, extend the dynamic clotting time and decrease haemolysis ratio. In addition, we investigated the function of the microstructure to blood compatibility from the point of superhydrophobicity.5. We established a contact guidance model to reveal how the microstructure can influence cell growth and attachment. The model was validated by cell culture experiment. The results are in good agreement with the predictions, suggesting that the LIPSS have significant contact guidance effect, which was enhanced with extending of the cell cultured time. In addition, the LIPSS could increase the speed of the cells adhesion and proliferation. The period of the LIPSS fabricated using femtosecond laser is much smaller than the common cell size. Therefore, the microstructure can be used to implement a variety of cell adhesion, proliferation and motion control. The study provides a theoretical guidance for multi-scale biomimetic microstructure surface in biomedical applications.更多还原