用于细胞固定的微纳SiO2基底研究

细胞阵列芯片在细胞生物学研究、药物筛选等生物医疗领域有着广阔的应用前景.针对芯片上细胞固定时需要化学修饰的限制,提出了仅通过表面结构实现细胞固定的方案.基于MEMS技术,采用DRlE在硅片上得到超疏水的微纳结构,通过简单的高温氧化工艺实现超亲水性的SiO2 结构表面;再通过控制BOE腐蚀时间得到不同形貌的基底表面.计算了基底表面上的循环肿瘤细胞的黏附效率,并在SEM下观察了细胞与基底的相互作用行为,探讨了粗糙表面影响细胞黏附的原因.实验结果表明:采用DRlE和高温氧化制备的微纳SiO2 基底表面能极大促进细胞黏附,可应用于细胞阵列芯片设计中.     

气化驱动的液滴在湿润性表面上的仿真研究

为了研究液滴在高温锯齿形表面时各参数对液滴摩擦学性能的影响,运用了计算流体力学研究了表面润湿性对蒸发驱动的Leidenforst液滴自推进运动的影响.结果 表明,三线接触角对液滴的悬浮和运动特性有很大的影响.表面微结构参数H/W有助于控制液滴表面的润湿性,从而提高液滴的运动速度.数值模拟结果表明,高宽比H/W=7/12时的超疏水表面具有快速运动特性.研究了温度和液滴直径等各种参数的影响,对液滴的蒸发驱动机理有了深入的认识.     

DNA在SiO2纳米粒子薄膜表面的单分子行为研究

基于应用全内反射荧光显微镜,利用YOYO-1标记的λ-DNA分子作为探针研究了SiO2纳米粒子薄膜的表面性质,在不同的pH值下,考察了pH值对单个DNA分子在其表面行为(自由运动和吸附)的影响,并采用接触角(CA)和原子力显微镜(Atomic Force Microscope,AFM)表征了SiO2纳米粒子薄膜表面的性质.实验表明,随着pH值的降低,DNA分子在其表面的吸附率随之增大.DNA分子在SiO2纳米粒子薄膜表面的吸附行为是静电作用和疏水作用共同作用的结果,但是起主导作用的是疏水作用.此外,相同pH值下,与文献中报道的DNA在玻片上的吸附率相比,DNA在SiO2纳米粒子薄膜表面的吸附率要大得多,这是由于SiO2纳米粒子的比表面积大,表面活性位点多,且疏水性能强的缘故.     

纳米防水 让手机与水绝缘

前不久小米科技联合创始人林斌在微博上展示了小米2的纳米防水涂层技术,着实让网友羡慕不已。其实,纳米防水技术并非小米2的专利,任何手机都可借助此技术获得最高IPX7级别的防水能力。纳米涂层扮演荷叶表面小米2获得了防水能力,自然得归功于其表面的纳米防水涂层。简单来说,纳米防水涂层就好像荷叶的表面,具有疏水、不吸水的表面,落在上面的     

卷对卷紫外压印超疏水薄膜的工艺及装置

为了实现大面积、批量化制备超疏水表面材料,文章开发了一种新型的卷对卷紫外压印技术并研制了相应装置.通过卷对卷微纳压印及快速光固化紫外固化胶将母版上的精细微米图形转移到目标柔性衬底上,无需复杂的制备工艺或苛刻的洁净加工环境,实现超疏水薄膜的快速、高效、批量化制备.文章着重讨论了应用于制备超疏水薄膜的卷对卷紫外压印工艺过程及对应各工艺而设计的机械功能模块.经工艺改进,选用改性的紫外固化胶,转印复制了20 μm×40 μm×17 μm(直径×间距×柱高)的微结构阵列,所得超疏水薄膜经氟化处理后与水接触角可达150°以上.最后,尝试使用该装置制备T型微纳结构阵列以获得疏水性更佳的表面材料.     

利用电化学阻抗技术测试界面污染对涂层防护性能的影响

本工作采用交流阻抗技术与腐蚀电位监测,研究低碳钢基体表面污染面积(NaCl盐水污染)对醇酸清漆在0.5mol/LNaCl水溶液中防护性能的影响,并探讨有机涂层的失效机制。实验表明基体表面处理的好坏对有机涂层防护性能有着至关重要的影响。基体表面污染,不仅会削弱有机涂层的防护性能,而且能够加速涂层失效过程。     

基于全自动热喷涂技术的电力设备零部件涂层制备工艺研究

变电设施常常服役于空气环境中,容易受到腐蚀的影响,对设备进行表面改性处理可以大幅改善设施的防腐蚀性能,提升其使用寿命。全自动热喷涂技术作为一种新型表面改性方式,是通过热源将合金加热至熔融或半熔融状态并涂覆与基体表面的技术。本文对其工艺参数进行了系统研究,发现当喷涂速度为0.1m/s,涂层厚度最大(700μm)、孔隙最小(2.1%)、性能最佳。喷涂距离对涂层孔隙率的影响较大,在距离为180mm,孔隙率达到最低(4.3%),此外还可根据对涂层厚度需求以及孔隙率的大小选择合适的喷涂电压和电流。对最佳参数条件下热喷涂铝涂层的试样进行盐雾试验。发现涂层表面会发生氧化腐蚀,生成以Al(OH)₃为主的腐蚀产物并在涂层表面形成致密的氧化膜。此外,产生的腐蚀产物还可以填补热喷涂过程中形成的孔隙,阻止腐蚀介质继续向涂层内部渗入。     

脉冲偏压对镍钛牙弓丝相变点温度的影响

错牙合畸形是世界各国均呈较高发病率的口腔疾病,表现为牙列、颌骨和颅面的畸形,口腔正畸是目前最有效的治疗方法。正畸牙弓丝是正畸治疗中的关键部件,而镍钛牙弓丝因具有形状记忆和超弹性性能在牙齿正畸中得到广泛使用。随着临床应用对牙弓丝提出新的性能需求,新型表面涂层也不断涌现。在镍钛牙弓丝表面引入氮化钛涂层可降低表面摩擦系数和摩擦力、提高耐磨性与生物安全性。物理气相沉积是工业上常用的氮化钛制备技术,但镍钛丝的相变点温度对周围环境温度变化敏感。为避免物理气相沉积过程中升温造成镍钛牙弓丝形状记忆效应和超弹性性能丢失,该研究将传统靶台上加载的直流偏压替换为脉冲式负偏压,可降低离子的注入沉积能量,为保留镍钛牙弓丝的优异力学性能创造条件。通过调整靶台加载负偏压的频率和占空比制备得到不同氮化钛涂层的镍钛牙弓丝,并比较其宏观和微观形貌、相变点温度发现,低频、低占空比处理条件制备的氮化钛涂层-镍钛牙 弓丝更适合于临床应用。     

H-POSS表面润湿性的分子动力学模拟

采用分子动力学模拟方法研究了水滴在多面体低聚倍半硅氧烷(H-POSS)固体表面的润湿性能,H-POSS分子和水分子分别采用COMPASS力场和SPC力场模型。模拟得到H-POSS基体密度为1.84g/cm~3,且X射线衍射模拟发现基体具有明显衍射峰,表现出晶体特性,说明COMPASS力场适用于H-POSS基体的构建与研究。H-POSS表面水接触角的模拟值为104.9°,具有疏水性能。通过直接水解法由三氯硅烷(HSiCl_3)实验合成出H-POSS样品,傅立叶红外表征(FT-IR)发现,在2260、1142和871cm~(-1)波数位置出现吸收峰,证实了所合成的样品为H-POSS。其表面水接触角的实验值为109.3°,与模拟值的相对误差仅为4%,说明分子动力学方法可应用于计算H-POSS材料表面润湿性。模拟结果还表明体系温度影响H-POSS材料的表面润湿性,增大体系温度,表面疏水性能降低。     

基于PC控制的防腐电源设计

应用PC技术、电力电子交流技术和微电子技术并将神经网络控制理论和方法引入到防腐电源设计中,是本文所研究的关键,采用这种方法设计了贩新型防腐电源,可以得到无静差、无超调的优良性能,它对金属防腐的保护具有实际意义。     

Wear of Polysilicon Surface Micromachines Operated in High Vacuum

The evolution of wear at sidewall surfaces of polysilicon microelectromechanical systems was investigated in high vacuum under controlled normal load and sliding speed conditions. The static adhesion force was used as an indicator of the changes in wear characteristics occurring during oscillatory sliding contact. Measurements of the static adhesion force as a function of sliding cycles and scanning electron microscopy observations of micromachines from the same batch process subjected to nominally identical testing conditions revealed two distinctly different tribological patterns, namely, low-adhesion/high-wear behavior and high-adhesion/low-wear behavior. The static adhesion force and wear behavior were found to be in direct correlation with the micromachine operational lifetime. Transmission electron microscopy, selected area diffraction, and energy dispersive X-ray spectroscopy yielded insight into the origin, microstructure, and composition of wear debris and agglomerates adhered onto the sliding surfaces. Results demonstrate a strong dependence of micromachine operational life on the removal of the native oxide film and the organic monolayer coating as well as the formation of agglomerates consisting of organic coating material and wear debris.     

Surface microfluidics fabricated by photopatternable superhydrophobic nanocomposite

Surface microfluidics can be of potential use in a variety of emerging applications, including biological and chemical analysis, cellular detection and manipulation, high-throughput pharmaceutical screening, and etc. In comparison with the conventional closed-channel microfluidic system, surface microfluidics shows the distinct advantages of simple construction, direct surface access, no cavitation or interphase obstruction, clear optical path, easy fluidic packaging, and device reusability. In this article, we first present surface microfluidic networks microfabricated by a single-step lithographic process using a novel superhydrophobic photosensitive nanocomposite formula. The photopatternable superhydrophobic nanocomposite (PSN) incorporates PTFE nanoparticles into a SU-8 matrix, in which superhydrophobicity (contact angle of above 160°) is primarily contributed by the extremely low chemical energy and nano-topology of PTFE nanoparticles, while the SU-8 polymer matrix offers photopatternability (lithographic resolution of 10 μm) and substrate adhesion. Moreover, an additive intermediate layer with hydrophilic sidewall considerably reduces flow resistance while improving the substrate adhesion, as a crucial improvement from the previous surface flow configuration. Furthermore, self-propelled microfluidic networks driven by surface tension-induced pressure gradient have been fabricated and characterized to demonstrate the applicability of the novel nanocomposite fabrication approach.     

Investigating the effects of surface superhydrophobicity on moisture ingression of nanofiber-reinforced bio-composite structures

Superhydrophobic coatings have been involved in many industrial applications because they exhibit high water repellency. These coatings can usually improve the surface properties of materials by reducing corrosion, adhesion, deicing, defrosting, and wetting, and increasing self-cleaning. In this study, superhydrophobic coatings were applied on the surfaces of carbon, Kevlar, and glass fiber composites to eliminate the absorption of moisture into the composite structures. The superhydrophobic coatings consist of two coats: bottom (or base) and top. The coated composite coupons were subjected to moisture ingression tests in deionized water until the samples reach their moisture equilibrium, which may vary between 4 and 6 weeks, and then the ingression tests were compared with the bare composite coupons. The water contact angles (WCAs) and thicknesses of the composite samples were measured at the beginning and end of the tests. The moisture gain of all composite coupons was measured as a function of immersion times. Heat treatment tests were performed on the samples to observe the moisture gain. In order to characterize the coated surfaces, WCA tests and Fourier transform infrared spectrometry analyses were also conducted. Test results demonstrated that when the surface of composites was coated with superhydrophobic coatings, the moisture absorption was much less in comparison to the non-coated composite coupons. This study can provide several benefits to the composite industry in general, and the aircraft and wind turbine industries in particular, in terms of moisture elimination, weight savings, and structural integrity of composites.

     

Coatings of indium tin oxide nanoparticles on various flexible polymer substrates: Influence of surface topography and oscillatory bending on electrical properties

Abstract— Coatings of indium tin oxide (ITO) nanoparticles on different flexible polymer substrates were investigated with respect to the achievable sheet resistance and their electrical behavior under oscillatory bending. As substrate materials, polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), and polyimide (PI) were chosen, the surface resistances on the different polymer substrates were compared as a function of annealing temperature and surface topography. The surface topography, which has a strong influence on the surface resistance, was characterized by means of a white‐light confocal (WL‐CF) microscope. On the PET substrate, which exhibits the smoothest surface, the coating of ITO nanoparticles shows the lowest sheet resistance of 2 kΩ/□ for a layer thickness of 3 μm and an annealing temperature of 200°C. Furthermore, the electrical behavior of coatings of ITO nanoparticles under oscillatory bending was investigated using a special device. These coatings show a cyclic change of the conductivity which can be explained by an alternating compression and extension of crack flanks under the applied stress. Due to the growing number of cracks with increasing number of cycles, a decrease of the conductivity is observed in the bent state as well as in the balanced state. For a small bending radii, the decrease of the conductivity is stronger due to more cracks caused by the higher tensile stresses in the layer. The electrical behavior of the coatings of the annealed ITO nanoparticles on PET films under oscillatory bending was compared with commercially available sputtered ITO coatings. The annealed coatings of ITO nanoparticles demonstrate better electrical properties under oscillatory bending than coatings of sputtered ITO. The different electrical behavior under oscillatory bending can be related to differences in crack formation.     

Investigation of anti-stiction coating for ohmic contact MEMS switches with thiophenol and 2-naphthalenethiol self-assembled monolayer

Anti-stiction coating with a conductive self-assembled monolayer (SAM) formed by π-conjugated bonds was investigated for ohmic contact microelectromechanical system (MEMS) switches with low-load contacts. SAMs of thiophenol (C₆H₅SH, TP) or 2-naphthalenethiol (C₁₀H₇SH, 2NT) were coated on Au samples with different surface roughness to investigate the effects of the surface asperities on the adhesion force and contact resistance. The adhesion force was measured using a silicon tipless cantilever in the relative humidity range of 10-85% and the contact resistance was measured in the contact force range of 0-70 μN using a conductive tipless cantilever coated with Au for the SAM coated samples and compared with those for a Au sample surface. The adhesion force measurements indicate that the TP and 2NT coatings can prevent a liquid meniscus from forming on device surfaces due to their hydrophobic character caused by the protruding aromatic group. In addition, it was confirmed that these coatings could reduce van der Waals forces more than Au coating. Contact resistance measurements revealed that an electric current begins to flow with smaller contact force for TP and 2NT coated samples than for Au coated samples. The measured contact resistances of the SAM and Au coated samples were comparable. Based on these results, SAMs of TP and 2NT have excellent potential as anti-stiction coating for MEMS switch contacts.     

Fabrication of anti‐reflection coatings on plastics using the spraying layer‐by‐layer self‐assembly technique

Abstract— Anti‐reflection (AR) coatings on plastic substrates have been extensively investigated with the development of large‐area LCD and LED displays. A robust AR coating on plastics requires strong adhesion to the substrate, precise thickness and refractive index, and abrasion resistance. In this paper, abrasion‐resistant AR coatings were fabricated on polycarbonate substrates using the layer‐by‐layer spraying deposition of poly(allylamine hydrochloride) (PAH) and silica nanoparticles. The adhesion between the substrates and coatings was enhanced by treating the polycarbonate surfaces with aminopropyltrimethoxylsilane (APTS). The porous low‐refractive‐index PAH/silica‐nanoparticles multilayers were constructed by the layer‐by‐layer spraying of PAH and silica‐nanoparticles aqueous solutions onto the functionalized substrates. The subsequent treatment of the porous coatings with tetrahydroxylsilane leads to stable abrasion‐resistant AR coatings. The resultant AR coatings can reduce the reflection from 5 to 0.3%. The reported technique provides a cost‐effective method for large‐scale production of AR coatings on plastic substrates.     

Quantification of bacteria on abiotic surfaces by laser scanning cytometry: an automated approach to screen the antifouling properties of new surface coatings

Bacterial biofilms are a persistent source of contamination, and much effort has been invested in developing antifouling surfaces or coatings. A bottleneck in developing such coatings is often the time-consuming task of screening and evaluating a large number of surface materials. An automated high-throughput assay is therefore needed. In this study, we present a promising technique, laser scanning cytometry (LSC), for automated quantification of bacteria on surfaces. The method was evaluated by quantifying young Staphylococcus xylosus biofilms on glass surfaces using LSC and comparing the results with cell counts obtained by fluorescence microscopy. As an example of application, we quantified bacterial adhesion to seven different sol-gel-based coatings on stainless steel. The surface structure and hydrophobicity of the coatings were analyzed using atomic force microscopy and water contact angle measurements. Among the coatings tested, a significant reduction in adhesion of S. xylosus was observed only for one coating, which also had a unique surface microstructure. LSC was particularly sensitive for quantification at low cell densities, and the adhered bacteria could be quantified both as cell number and as area coverage. The method proved to be an excellent alternative to microscopy for fast and reproducible quantification of microbial colonization on abiotic surfaces.     

Spin coating of hydrophilic polymeric films for enhanced centrifugal flow control by serial siphoning

In this paper, we implement rotational flow control on a polymeric microfluidic “lab-on-a-disc” platform by combining serial siphoning and capillary valving for sequential release of a set of on-board stored liquid reagents into a common (assay) channel. The functionality of this integrated, multi-step, multi-reagent centrifugal assay platform critically depends on the capability to establish very reproducible, capillary-driven priming of the innately only weakly hydrophilic siphon microchannels made from common poly(methyl methacrylate) (PMMA) substrates. Due to the relatively high contact angle of the native PMMA substrate, it was practically impossible to ensure sequential release of on-board stored reagents using the capillary-driven serial siphon valves. In this work, we demonstrate that spin-coated hydrophilic films of poly(vinyl alcohol) (PVA) and (hydroxypropyl)methyl cellulose (HPMC) provide stable contact angles on PMMA substrates for more than 60 days. The deposited films were characterized using contact angle measurements, surface energy calculations and X-ray photoelectron spectroscopy spectra. The PVA and HPMC films reduced the water contact angle of the PMMA substrate from 68° to 22° and 27° while increasing their surface energies from 47 to 62 and 57 mN m^?1, respectively. On the centrifugal microfluidic platform, the films were validated to enable the effective and reproducible priming of the serial siphon microchannels at low rotational frequencies while ensuring that the in-line capillary valves are not opened until their respective burst frequencies are passed. Furthermore, the biocompatibility of the proposed surface modification method was examined, and the platform was used to run a sandwich immunoassay for the detection of human immunoglobulin G, and its performance was proven to be comparable to dynamic coating using surfactants.     

Contact line dynamics of a superhydrophobic surface: application for immersion lithography

The dynamic contact line behavior of water on nanotextured rough hydrophobic and superhydrophobic surfaces is studied and contrasted to smooth hydrophobic surfaces for application in immersion lithography. Liquid loss occurs at the receding meniscus when the smooth substrate is accelerated beyond a critical velocity of approximately 1 m/s. Nanotexturing the surface with average roughness values even below 10 nm results in critical velocity larger than 2.5 m/s, the upper limit of the apparatus. This unexpected increase in critical velocity is observed for both sticky hydrophobic and slippery superhydrophobic surfaces. The authors attribute this large increase in critical velocity both in increased receding contact angle and in increased slip length for such nanotextured surfaces.     

Liquid-state motion sensing

This paper demonstrates a liquid droplet-based motion sensing system which has the advantages of simple fabrication, low power consumption and digital signal processing. The sensor consists of a dielectric substrate patterned with an array of microelectrodes, and a saline droplet as the proof mass. Once an external linear acceleration is applied, the inertial force moves the droplet on the micropatterned substrate. The acceleration is determined from the movement profile detected by the microelectrodes. In order to enhance the threshold and the sensitivity of motion sensing, two surface treatment approaches are utilized to create superhydrophobic surfaces. The result shows that the minimal sliding angle that can move a 20 μl droplet on the superhydrophobic surface is lower than 1°, corresponding to a threshold of lower than 0.017 g. A lumped-parameter model is developed to estimate the dynamic behavior of the proposed system. The result shows that the frequency response of the droplet-based sensor is more significant at low frequencies than at high frequencies, which is distinct from solid-state accelerometers. Measurement under a constant acceleration shows that the predicted value derived from the measurement has a good match with the actual applied acceleration, validating the proposed system as a viable alternative for motion sensing.