Investigation on Surface Plasmon Polaritons and Localized Surface Plasmon Production Mechanism in Micro-Nano Structures

The simulation mechanism of surface plasmon polaritons(SPPs)and localized surface plasmon(LSP)in different structures was studied,including the Au reflection grating(Au grating),Au substrate with dielectric ribbons grating(Au substrate grating),and pure electric conductor(PEC)substrate with Au ribbons grating(Au ribbons grating).And the characteristics of the Smith-Purcell radiation in these structures were presented.Simulation results show that SPPs are excited on the bottom surface of Au substrate grating grooves and LSP is stimulated on the upper surface both of Au ribbons grating grooves and Au grating grooves.Owing to the irreconcilable contradiction between optimizing the grating diffraction radiation efficiency and optimizing the SPPs excitation efficiency in the Au substrate grating,only 40-times enhancement of the radiation intensity was obtained by excited SPPs.However,the LSP enhanced structure overcomes the above problem and gains much better radiation enhancement ability,with about 200-times enhancement obtained in the Au ribbons grating and more than 500-times enhancement obtained in the Au grating.The results presented here provide a way of developing miniature,integratable,tunable,high-power-density radiation sources from visible light to ultraviolet rays at room temperature.

Generalized model for laser-induced surface structure in metallic glass

The details of the special three-dimensional micro-nano scale ripples with a period of hundreds of microns on the surfaces of a Zr-based and a La-based metallic glass irradiated separately by single laser pulse are investigated.We use the small-amplitude capillary wave theory to unveil the ripple formation mechanism through considering each of the molten metallic glasses as an incompressible viscous fluid.A generalized model is presented to describe the special morphology,which fits the experimental result well.It is also revealed that the viscosity brings about the biggest effect on the monotone decreasing nature of the amplitude and the wavelength of the surface ripples.The greater the viscosity is,the shorter the amplitude and the wavelength are.

Electronic Structure of Single-Crystal CaF₂(111) with Nanoscale Phases of Ca and Si

The impact of Ca and Si nano-scale structures on parameters and density of states of single-crystalline CaF2(111) was studied. It was shown that at low concentration of ions of Ar+ (D ≤ 5 × 1015 cm-2) one witnesses formation of nanoscale phases on CaF2 surface. It was revealed that these phases lead to narrowing of the forbidden band Еg between the phases by 4 - 4.5 eV. At higher concentrations (D ≈ 6 × 1016 cm-2) the surface completely is covered by Ca atoms. It was shown that deposition of θ = 10 thick Si single layer on CaF2 surface manifests island picture. The concentration of Ca and Si nano-scale phases on the surface of CaF2 and the band gap of the phases were investigated as a function of (hν) of passing light. Nano-scale phases and nano-scale films of Ca were obtained by using the technique of bombardment with ions of Ar+ of CaF2 surface. Formation of nano-scale phases were accompanied by change in the composition and structure of CaF2 zones located between the phases. These changes led to narrowing of the forbidden band of CaF2 down to 7.5 - 8 eV. The concentration of Ca and Si nano-scale phases on the surface of CaF2 and the band gap of the phases were investigated as a function of (hν) of passing light.

Surface Micro-Nano Structures on GaN Thin Films Induced by 355 nm Nanosecond Laser Irradiation

Gallium nitride(GaN)has widespread applications in the semiconductor industry because of its desirable optoelectronic properties.The fabrication of surface structures on GaN thin films can effectively modify their optical and electrical properties,providing additional degrees of freedom for controlling GaN-based devices.Compared with lithography-based techniques,laser processing is maskless and much more efficient.This paper shows how surface micronano structures can be produced on GaN thin films using 355 nm nanosecond laser irradiation.The effects of the laser pulse energy,number of pulses,and polarization direction were studied.It was found that distinct micro-nano structures were formed under different irradiation conditions,and their geometries and elemental compositions were analyzed.The results indicate that different types of surface micro-nano structures can be produced on GaN thin films in a controllable manner using 355 nm nanosecond laser irradiation.The results of our study provide valuable guidance for the surface modification of GaN-based optoelectronic devices.

Three-Dimensional Cu-Ni Composite Superamphiphobic Surface via Electrodeposition and Fluorosilane Modification

A superamphiphobic(SAP)surface was fabricated by electrodepositing Cu-Ni micro-nano particles on aluminum substrate and modifying via 1 H,1 H,2 H,2 Hperfluorodecyltrimethoxysilane.Scanning electron microscopy,X-ray diffraction,energydispersive X-ray spectroscopy,and Fourier-transform infrared spectroscopy were employed to investigate the morphology and chemical composition.The results showed that the SAP surface had three-dimensional micro-nano structures and exhibited a maximum water contact angle of 160.0°,oil contact angle of 151.6°,a minimum water slide angle of 0°and oil slide angle of 9°.The mechanical strength and chemical stability of the SAP surface were tested further.The experimental results showed that the SAP surface presented excellent resistance to wear,prominent acid-resistance and alkali-resistance,self-cleaning and anti-fouling properties.

Effects of Methanol on Wettability of the Non-Smooth Surface on Butterfly Wing

The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.

Bioinspired Functional Surfaces for Medical Devices

Medical devices are a major component of precision medicine and play a key role in medical treatment,particularly with the rapid development of minimally invasive surgery and wearable devices.Their tissue contact properties strongly affect device performance and patient health(e.g.,heat coagulation and slipperiness on surgical graspers).However,the design and optimization of these device surfaces are still indistinct and have no supporting principles.Under such conditions,natural surfaces with various unique functions can provide solutions.This review summarizes the current progress in natural functional surfaces for medical devices,including ultra-slipperiness and strong wet attachment.The underlying mechanisms of these surfaces are attributed to their coupling effects and featured micronano structures.Depending on various medical requirements,adaptable designs and fabrication methods have been developed.Additionally,various medical device surfaces have been validated to achieve enhanced contact properties.Based on these studies,a more promising future for medical devices can be achieved for enhanced precision medicine and human health.

Trans-scale surface wrinkling model and scaling relationship analysis of stiff film-compliant substrate structures

The self-assembly of surface-order structures based on the surface wrinkling of stiff film-compliant substrate structures(SFCS)is potentially useful in the fabrication of functional devices,the manufacture of superhydrophobic or self-cleaning surfaces,and so on.Due to the influence of the intrinsic characteristic length(g),the surface wrinkling behavior of SFCS at the micro scale is different from that at the macro scale.In this work,based on the strain gradient theory,a trans-scale surface wrinkling model for SFCS is established.First,the effectiveness of this model is verified by previous experiments.Then,based on the model and dimensional analysis,the effect of g on the surface wrinkling behavior is investigated,and the scaling relationship of surface wrinkling of SFCS at different scales is analyzed.The results show that the influence of g cannot be neglected when the film thickness decreases to the one comparable to g.At the micro scale,g will lead to the increase of the critical wrinkling wavelength and load.In addition,the scaling relationship of surface wrinkling at the micro scale will not follow the traditional one.Our study explains the underlying mechanism of the dissimilarity of surface wrinkling behaviors of SFCS at different scales and lays a theoretical foundation for the precise control of surface-order structures.

外圆鱼鳞结构化表面的研磨研究

为了在外圆工件表面上研磨出具有随行波结构特征的鱼鳞表面结构,首先基于对自然界中鱼鳞表面形貌的特征分析,建立起外圆工件沿轴向排布的鱼鳞结构化表面数学模型;其次依据外圆研磨原理以及拓扑学理论,设计出用于研磨外圆鱼鳞表面的结构化拓扑油石;然后依据外圆研磨的磨粒运动轨迹,讨论实现外圆鱼鳞结构化表面研磨的边界条件;并对外圆研磨过程进行仿真模拟,获得了具有随行波结构的鱼鳞结构化表面。研究结果表明,利用所设计的结构化拓扑油石可以实现外圆鱼鳞结构化表面的研磨;改变研磨的振幅和频率,鱼鳞结构化表面的形状参数也会变化,但其表面拓扑属性不变。

基于振动台缩尺模型的复杂体型建筑结构楼面加速度反应分布研究

楼面加速度放大系数(floor acceleration amplification,FAA)能够反映结构对地面加速度的放大,而当前的规范与研究多是依赖于历史楼面记录或者有限元分析结果,在涉及复杂体型建筑结构时计算分析和实际震害结果往往存在较大差异。以整体结构缩尺模型振动台试验记录数据为基础,通过拟合分析得到各条记录下原型结构沿高度的FAA分布。基于类拟地震反应谱形状模型,得到具有一定保证率的FAA分布曲面,针对不同结构类型分别提出了相应的计算公式,相比于规范能够更好地反映出复杂体型建筑结构的FAA分布特征。定性地探索了场地卓越周期变化对该类型建筑结构FAA分布特征的影响。

高强重载汽车大梁钢表面麻坑问题的研究与改进

高强重载汽车大梁钢表层氧化铁皮在开平矫直过程中破碎、脱落导致后续矫直过程中氧化铁皮压入形成大小不一的表面麻坑。本文研究精轧入口温度、轧制速度、冷却速率和卷取温度等工艺因素与氧化铁皮厚度之间对应关系。结果表明:精轧入口温度在1040℃以下时氧化铁皮厚度随着入口温度的上升而缓慢增加,在1040℃以上时氧化铁皮厚度随着入口温度的升高而急剧增加;随着轧制速度的加快,带钢表面生成的氧化铁皮变薄;较大速率冷却可以抑制氧化铁皮的长大、增厚;在560~630℃,卷取温度越高,氧化铁皮越厚。通过优化加热制度,提高轧制速度,优化层流冷却速率和卷取温度等措施,大梁钢表面麻坑缺陷得到有效控制。

空间自由曲面砌体拱壳的结构设计与试验研究

目前我国在薄壳砌体结构设计方面并无相应的指导标准,薄壳砌体结构的相关案例也较少,设计时无相应参考。重庆市黄桷坪涂鸦街美术廊为一个自由曲面壳体结构,为满足视觉要求,采用砖砌拱壳结构形式,为目前国内跨度最大的自由曲面无筋砌体拱壳结构,壳体采用多孔陶土砖和高延性混凝土砌筑。采用数值分析、材料试验、足尺荷载试验的方法,从结构的形态确立、材料试验、砌筑方式、静力分析、稳定性分析和足尺荷载试验等方面,全面介绍了项目中的关键问题。结果表明,本工程采用无筋砖砌拱壳结构是可行的,为后续类似工程提供了案例参考和设计思路。

仿生鱼鳞结构对风管气流影响数值研究

基于RSM模型,通过数值模拟的方法研究鱼鳞结构在风管中的减阻特性。对比上凸型鱼鳞排布、上凸型单个鱼鳞排布及下凹型单个鱼鳞排布在风管中的减阻率。结果表明,上凸型鱼鳞排布与上凸型单个鱼鳞排布相比平滑风管,使风管内的阻力增大。而下凹型单个鱼鳞排布能够对风管减阻起到效果。当修改下凹形单个鱼鳞排布的深度h(h=1mm,3mm,5mm),排布间距L不变时,h=5mm时,减阻效果最佳,最大减阻率为2.5%。当修改下凹形单个鱼鳞结构的排布间距L(L=2cm,2.5cm,3cm),深度h不变时,当L=3cm时,对风管的减阻能力最佳,最大减阻率为2.8%。

静压转台导轨油膜静态性能分析与优化

为解决大型重载静压转台承载性能不足的问题,以ZT45SW型转台底座导轨油垫为研究对象,针对测试过程中油膜无法浮起的现象,设计了扇形、圆形、回形、双回形4种油腔,基于FLUENT仿真分析,研究了不同工况对4种油膜的静态性能(承载力、刚度、最大温升、平均温升)的影响规律,确定了各油垫适用的工况。综合对比,双回形腔油膜的静态性能最佳,基于响应面法对油腔结构尺寸优化后,减小了油膜压力集中的现象,提高了油膜静态性能;通过实验验证了仿真模型的准确性。

基于面波走时的三维结构面波直接成像:方法综述与应用

利用面波频散数据进行各向同性和各向异性横波速度结构成像是研究全球和区域构造变形、获取地壳上地幔和近地表精细结构的一种非常有效的方法.传统的基于频散数据的面波成像通常采用两步法,即首先反演二维相速度或群速度分布图,然后再基于格点的纯路径频散反演格点下方的一维横波速度模型,之后再拼合成三维速度模型.在本文中我们较为详细地综述新发展的基于面波频散走时的三维面波直接成像方法体系,即面波一步法成像.该方法体系包括通过所有路径、不同频率的面波频散走时直接反演三维各向同性横波速度结构的方法(DSurfTomo)、直接反演三维方位各向异性横波速度结构的方法(DAzimSurfTomo),以及直接反演三维径向各向异性横波速度结构的方法(DRadiSurfTomo).新的面波直接成像方法计算不同周期的面波射线路径,从而更好地考虑复杂结构下面波射线路径弯曲对成像精度的影响.随后我们介绍面波直接成像方法的应用实例,包括地壳上地幔及地壳浅部的多尺度各向同性和各向异性横波速度结构的成像,这些成像研究为认识区域构造演化、孕震构造、断裂带浅部结构、成矿构造、城市地下结构等提供了重要的约束.最后我们讨论面波直接成像方法的频散数据及模型参数化问题,以及基于有限频理论的面波直接成像和面波全波形成像,讨论并展望在面波直接成像方法框架下面波频散数据与其他地震或地球物理数据的联合成像问题.

磨削的结构化鱼鳞表面的摩擦特性研究

为了获得磨削后结构化鱼鳞表面的摩擦特性,首先设计拓扑结构化鱼鳞表面,然后对表面建立流体动压润滑模型,并利用流体仿真软件进行分析,研究对比磨削加工后不同粗糙度的单元鱼鳞凹坑的油膜承载力以及摩擦系数,并且整体分析结构化鱼鳞表面的压力和摩擦系数随油膜厚度变化的规律。研究表明:在给定的结构化表面参数范围内,磨削粗糙度越低的结构化鱼鳞表面单元的润滑效果越好;整体来看,结构化鱼鳞表面的润滑效果具有显著的累积效应;选择合适参数的结构化鱼鳞表面可以提高油膜承载力和降低摩擦系数,从而起到改善摩擦副润滑效果的作用。

预制钢筋混凝土墙板加固砌体试验研究

为研究加固后砌体结构的抗震性能,本文对全缩尺模型下的预制混凝土墙板加固法与现浇面层加固法的加固效果进行对比分析,并对局部后浇带措施替代传统后浇带连接法的可行性进行研究。结果表明:1)合理配筋设计的局部后浇带可以替代现场通长后浇带的连接措施;2)缩尺模型下的预制混凝土构件加固砌体可有效提高砌体抗震性能。本文研究成果可为类似砌体结构加固方法的设计与研究提供一定的借鉴与参考。

旋带掩模电解织构化圆柱表面及其润湿性分析

在圆柱面工件上高效、低成本地创制功能化极端润湿性表面仍面临重大技术挑战。对此提出旋带掩模电解织构技术。该技术直接选用市售带状柔性电绝缘多孔高分子编织布为活动掩模,以中性盐Na NO3溶液为电解液,基于旋带电解印制方式对金属圆柱表面进行织构化处理。介绍其工作原理,分析圆柱表面微织构形貌与几何廓形的演化过程,试验探究极间电压、旋带速度、加工次数等对表面织构特征的影响,评测氟化后的不同微结构特征的织构化表面的润湿性。结果表明:圆柱表面织构特征显著受加工次数的影响,随加工次数的增加,圆柱表面经历“反复复制”掩模印制阵列凹凸微结构、阵列凹凸微结构叠错-细化、微纳米分级结构分级化等表面微织构化演化过程;用时仅需249 s制备的外径49 cm、长50 cm的SUS304圆柱面(氟化后)微-纳米分级结构表面对水/甘油/十六烷的接触角分别为160.4°、158.5°、153.6°、滚动角分别为2.1°、5.6°、8.6°;呈现优异的超双疏极端润湿性且机械耐久性好。旋带掩模电解织构技术在圆柱面工件制取机械耐久性极端润湿性功能表面方面呈现高效、低成本、便于实施等优势。

建筑物单体结构化重建的变尺度网格基元提取法

现有的区域生长算法提取平面基元不准确不规则,忽略了尺度较小的几何结构。本文提出了一种建筑物单体结构化重建的变尺度网格基元提取方法,采用多尺度区域生长算法从网格不同尺度大小的几何结构中提取出对应的平面基元,提升了平面基元提取的准确性和完整性。通过平面基元拓扑优化进一步改善平面基元的拓扑质量,提升多边形表面模型的重建精度;并采用面积优先级策略提高共面平面基元合并效率。试验结果表明,本文方法能够更准确地进行平面基元的提取,保留了建筑物较小尺度的几何结构,生成了更简洁紧凑、结构化的建筑物多边形表面模型。

Superhydrophobic Purple Orchid Leaves:Variation in Surface Morphology During the Vegetation Stages Leading to Diversity in Wettability

Learning hydrophobic phenomena from nature is always a promising approach to design the superhydrophobic surface.Purple orchid leaf which processes superhydrophobicity is an ideal plant model,and through mimicking its structure,the surface with excellent hydrophobicity is able to be obtained.However,the unclear of the diversity in wettability during the different vegetation stages and the absence of its relation to the surface morphology limits the further enhancement of the inspired structure.Here,we analyze the wettability difference as the leaf grows from tender to mature and then to senescent.Combining with the variation of surface morphology and chemical composition,the well-developed micro-scale basic unit bumps with dense nano-scale waxy layer on the surface are proven to be responsible for the best hydrophobicity of the mature leaf.The presence of the undeveloped or damaged micro-nano hierarchical structure reduces the formation of air pockets at the interface,leading to the decrease of the wettability for leaves at other stages.Moreover,by fabricating artificial leaves,the nano-waxy layer is proved to be more effective than that of the micro-bumps on the surface wettability.The results of study are of a great significance for guiding the design and fabrication of plant-inspired bionic superhydrophobic surface.