超疏水表面减阻特性的研究进展

超疏水表面具有减阻效果,在提高管道传输效率、降低水下航行体和微流体器件中流动阻力等方面有着广阔的应用前景。介绍超疏水表面的制备、滑移理论以及减阻特性的研究,讨论微尺度下表面润湿性、表面微结构和流场流动状态对壁面减阻的影响,对超疏水壁面减阻的物理机制进行总结,并指出气体层不连续模型和气穴模型是分别适用于光滑疏水表面和带微结构超疏水表面的减阻模型。介绍超疏水表面减阻特性的一些应用,提出将超疏水表面应用到微流体系统中面临的问题,如微通道壁面疏水性的制备及其减阻效果的耐久性。     

超疏水表面制备技术的研究进展

具有非润湿和自清洁特性的超疏水表面由于其广阔的应用前景而引起人们的极大关注.介绍超疏水状态下Wenzel和Cassie-Baxter 2种接触模型及其相互关系,讨论2种模型下表面微细结构对接触角的影响.从构造表面微细结构和低表面能物质修饰2个方面总结近年来超疏水表面制备技术的研究进展,并对超疏水表面的研究进行展望.     

超疏水表面加工技术及耐磨性能研究进展

当前制备的超疏水表面耐磨性能普遍较差,因而其在各领域的应用受到限制。研究表明微纳结构和低表面能是实现功能表面超疏水性能的关键因素,因此,首先基于超疏水表面作用机制,对超疏水表面织构进行了归纳,旨在通过优化表面织构来解决微纳结构易磨损难题;然后对超疏水表面加工技术进行了梳理总结,从成本和效率两个方面分析了降低表面能的措施,为拓展超疏水表面加工体系提供思路;进而详细总结了超疏水表面耐磨性的分析手段,并阐述了提高超疏水表面耐磨性的方法;最后,展望了耐磨性超疏水表面的未来发展前景,以期推动超疏水表面在工程中的大规模应用。     

超疏水表面制备及其在防冰中的应用

科研人员从具有超疏水性能的动植物表皮中观察到具体物理微观结构模型,通过对超疏水表面性能的进一步研究探索,发现超疏水表面具有延长水滴凝结时间、减少积冰和减小冰在固体材料表面附着力等一系列防冰优势。针对超疏水表面在防冰性能方面表现出来的突出特点,总结最近5年国内外研究人员在制备具有防冰性能的超疏水表面的研究进展。首先,对固体表面超疏水原理及其防冰原理予以阐述;随后,从制备超疏水表面的技术路线上综述了当前国内外的主流研究方向并对其防冰性能优缺点展开介绍;最后,对超疏水表面的防冰性能表现予以总结和展望。     

超疏水表面的减阻研究

为探索超疏水表面的减阻机制,利用位错刻蚀法在铝板上制备出接触角为156°、滚动角小于5°的超疏水表面,并分别以具有超疏水表面和亲水表面的铝板为基板,构建了两种流动状态可视化测试的微粒子图像测速(Particle Image Velocimetry ,PIV)微通道,通过PIV粒子图像测试技术对水在超疏水微通道和亲水微通道中的速度流动情况进行实验测定与对比,得出超疏水表面确实有减阻效果,最大减阻效果可达8.72%,并从多角度进行了解释分析.     

超疏水表面液滴的冷凝成长特性研究

利用聚二甲基硅氧烷(PDMS)为基底采用光刻技术制备了微方柱状超疏水表面,分析了冷凝条件下超疏水表面液滴的冷凝生长特征,发现液滴的生长过程可分为微液滴成核冷凝独立生长、冷凝微液滴合并生长以及大液滴生长3个阶段。超疏水表面初始合并的液滴呈Wenzel-Cassie状态和Wenzel状态,随着冷凝液滴的成长,液滴的液-固接触面积与粗糙结构表面的表观面积之比f随着冷凝液滴尺寸的增大而增大,Wenzel-Cassie状态向完全Wenzel状态转变。最后分析了超疏水性破坏的原因。     

超短脉冲激光加工超疏水功能性微结构表面

典型微结构的制备,尤其是具备特定功能性微结构表面的高效加工已成为加工制造业的研究热点。以超快皮秒脉冲激光为加工手段,实现超疏水功能性微结构表面的高效制备。试验结果显示,采用脉冲宽度为8.1ps、波长为532nm的超短皮秒脉冲激光可以一次构造出具有微纳双重结构的超疏水功能性微结构表面,其静态接触角可以高达158°,滚动角小于5°。该试验为此类功能性微结构表面的加工及应用开拓了全新的技术方法,应用前景广阔。     

静电气喷磁响应复合微结构功能表面制备研究

提出一种静电气喷法制备磁响应超疏水复合微结构表面以实现微流控液滴传输与驱动应用。首先利用静电气喷法将微米级羰基铁粉和PDMS (Polydimethylsiloxane)混合喷涂到置于磁场中的基底以构建磁响应超疏水表面,热固化后再在表面喷涂纳米碳粉以形成磁响应超疏水复合微结构表面;通过扫描电镜和显微镜分析复合微结构表面形貌,通过接触角测量仪检测功能表面的湿润性,利用液滴与表面的接触和碰撞实验测试表面的黏附性能,以磁响应特性为基础的复合微结构功能表面进行液滴驱动和定向分配应用测试。磁响应超疏水表面和复合微结构表面表现出不同的形貌和性能,喷涂纳米碳粉可以获得微纳米复合结构从而显著提升表面的疏水性和降低表面的黏附性。利用静电气喷法简单有效地制备出的磁响应超疏水复合微结构表面具有优异的超疏水性能和极低的黏附性,从而能实现不同液滴操作,具有广泛的应用前景。     

基于电化学加工方法的铝基超疏水表面制备技术研究

鉴于金属铝表面存在微米级的晶界和纳米级的位错,在外加电场和电解液的作用下,晶界位错处因具有更高的位能会使得阳极优先溶解,进而形成微纳米结构相结合的粗糙表面,提出一种新的铝基超疏水表面的电化学制备方法,实验研究了其加工质量、加工效率和加工条件之间的关系,结果显示电化学加工方法能够在铝基底上制备出多阶层微/纳米结构,可用作超疏水表面基底。电化学加工比化学刻蚀法有更好的可控性,同时比光刻等方法更经济。所加工表面经过低表面能材料修饰后呈现超疏水的特性,与水滴的接触角达到167°,滚动角小于3°。     

微纳双重结构表面的接触角模型及其润湿性研究

依据超疏水、自清洁荷叶表面具有的微米乳突和纳米鞭毛双重结构,设计类似荷叶表面的微/纳双重结构,建立对应的Wenzel、Cassie接触角模型,分析微纳双重结构及其结构参数对表面润湿性的影响。研究表明,对于单级微观结构,具有细长(较大的柱高与柱边长比)微观结构的粗糙表面疏水效果更好;对于微纳双重结构,二级纳米结构的出现降低了实现超疏水性的柱高与柱边长比的阈值,微纳双重结构可以大大提高表面的疏水性能。     

Precision nano-fabrication and evaluation of a large area sinusoidal grid surface for a surface encoder

This paper describes the fabrication of a large area sinusoidal grid surface, which is used as the measurement reference of a surface encoder for multi-axis position measurement. The profile of the grid surface is a superposition of sinusoidal waves in the X-direction and the Y-direction with spatial wavelengths of 100 μm and amplitudes of 100 nm. Diamond turning with a fast tool servo (FTS) was chosen as the fabrication method. The constructed FTS, which employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitance probe as the feedback sensor, was confirmed to have a bandwidth of approximately 2.5 kHz and a tool displacement accuracy of several nanometers in the closed-loop mode. Experiments of fabricating the sinusoidal grid surface were performed on a commercially available precision diamond turning machine. An aluminum alloy workpiece was vacuum chucked on the spindle and the FTS was mounted on the X-slide. Efforts were made to position the tool tip to the center of the spindle (center-alignment) since it was verified that the center-alignment is important for the fabrication accuracy of the sinusoidal grid surface. An evaluation technique based on the two-dimensional (2D) discrete Fourier transform (DFT) of interference microscope images was also developed to evaluate the fabricated grid surface effectively. The fabrication result of a grid surface over an area of 150 mm has indicated the effectiveness of the fabrication system.     

表面改性非球面碳化硅反射镜的加工

为了获得高质量光学表面的非球面碳化硅(SiC)反射镜,对碳化硅反射镜表面改性技术以及离子束辅助沉积(IBAD)Si改性后的非球面碳化硅反射镜的加工技术进行研究。首先,简要介绍了碳化硅反射镜表面改性技术以及本文所采用的离子束辅助沉积(IBAD)Si的改性方法。然后,通过采用氧化铈、氧化铝以及二氧化硅等各种抛光液对离子束辅助沉积(IBAD)Si的碳化硅样片进行抛光试验。试验结果表明氧化铈抛光液的抛光效率较高,使用二氧化硅抛光液抛光后的样片表面质量最好。最后,在上述实验的基础上,采用计算机控制光学表面成型（CCOS）技术对尺寸为650mm×200mm的表面改性离轴非球面碳化硅(SiC)反射镜进行加工,最终的检测结果表明离轴非球面碳化硅(SiC)反射镜实际使用口径内的面形精度（RMS值）优于λ/50（λ=0.6328μm）,表面粗糙度优于1nm（Rq值）,满足设计技术指标的要求。     

Effects of heat flux on dropwise condensation on a superhydrophobic surface

The condensation heat transfer efficiencies of superhydrophobic surfaces that have ∼160° contact angle under atmospheric conditions were investigated experimentally. The departing diameter and the contact angle hysteresis of droplets were measured by capturing front and tilted side views of condensation phenomena with a high speed camera and an endoscope, respectively. Condensation behaviors on the surface were observed at the micro-scale using an Environmental scanning electron microscope (ESEM). Apparently-spherical droplets formed at very low heat flux q″ ∼20 kW/m² but hemispherical droplets formed at high q″ ∼440 kW/m². At high q″, heat transfer coefficients were lower on the superhydrophobic surface than on a hydrophobic surface although the superhydrophobic surface is water repellent so droplets roll off. The results of contact angle hysteresis and ESEM image revealed that the reduced heat transfer of the surface can be attributed to the large size of departing droplets caused by adhesive condensed droplets at nucleation sites. The results suggest that the effect of q″ or degree of sub-cooling of a condensation wall determine the droplet shape, which is closely related to removal rates of condensates and finally to the heat transfer coefficient.

     

Fabrication of microgrooves on a curved surface by the confocal measurement system using pulse laser and continuous laser

In order to fabricate microgrooves on a curved surface, the curved surface was measured with a confocal system and then it was used for laser microprocessing. This paper proposes a new method of using a pulse laser for the confocal system to measure the curved surface. It also compares the conventional way of using a continuous laser and a new way of using the pulse laser with the confocal system. Using the data measured with the pulse laser for fabrication, microgrooves were fabricated on a curved surface. The width of the fabricated microgroove was 10 μm and the depth was 27 μm. The microgroove fabricated on a curved surface as a part of this study can be used in injection molding to manufacture a micropatterned plastic surface at a low cost. This plastic surface can be applied for a superhydrophobic surface, a self-cleaning surface, or a biochip.     

利用曲面计算全息图进行非球面检测

研究了利用曲面计算全息图进行非球面检测.分析了曲面计算全息图的衍射特性,给出了曲面计算全息图与传统检测方法相结合检测凹非球面和凸非球面的原理及特点,并进行了具体设计.利用激光直接写入设备,在口径为110mm、曲率半径为504mm的曲面基底上制作出了计算全息图,并对金刚石车床车削的凸面非球面进行了检测.利用两步测量法解决了凸非球面的中心部位难以检测的难题,同时利用旋转相减法消除了调节误差,非球面的面形精度为234nm(P-V),与金刚石车床的精度相符.     

基于偏微分方程的断层间表面的重构

断层间表面重构作为科学计算可视化领域的一个重要研究方向,在医学、地质学、生物学等领域有着广泛的应用。针对基于偏微分方程（PDE）的断层间表面重构,提出了基于一张PDE曲面的断层间表面重构和基于组合PDE曲面的断层间表面重构两种方法。实验结果表明,PDE重构断层间轮廓线表面避免了连接函数的构造,而且基于组合PDE曲面的断层间表面重构方法能方便地实现轮廓线间表面的一阶或一阶以上的参数连续。     

High-resolution wide-field surface plasmon microscopy

This paper describes the application of a Köhler illuminated high‐resolution wide‐field microscope using surface plasmons to provide the image contrast. The response of the microscope to a grating structure in both the Fourier and the image planes is presented to demonstrate image formation by surface waves. The effect of spatial filtering in the back focal (Fourier) plane to enhance image constrast is described. We also discuss how the surface wave contrast mechanism affects the imaging performance of the microscope and discuss factors that can be expected to lead to even greater improvements in lateral resolution and sensitivity.     

吹扫捕集/GC-MS联用法分析地表水中挥发性有机物

建立了吹扫捕集—气质谱联用仪同时测定地表水中22种挥发性有机物的方法。NIST标准谱库检索定性,外标法定量。各组分得到了较好的分离,在0.5～100μg/L浓度范围内线性关系良好,标准曲线线性相关系数在0.993～0.9992之间,回收率在85%～102%之间。方法准确,精密度良好,满足地表水质分析检测的要求。     

X PS － EDS 联用技术分析金电极表面焊接不良的原因

金电极焊接不良,影响产品质量,焊接不良产生的原因通常与表面存在污染物有关。本实验采用能谱仪（EDS）结合X－射线光电子能谱仪（XPS）对样品表面成分进行分析。分析结果表明,样品由Au、C、O、N等元素组成,而表面污染物中含有F元素,F1s的结合能为688.5ev ,而C1s的结合能在291.7ev处有拟合峰,表明表面存在C F2污染,C F2污染是金电极焊接不牢的原因。