单通道和多通道毛细管光学元件－技术发展水平和应用

毛细管光学元件在X射线分析中的应用已有20多年的历史,在这段时间里,毛细管光学元件的制作技术发生了很大的变化。上世纪90年代初,使用的是组装的毛细管光学元件,目前,集成的多通道毛细管光学元件已广泛地应用于市场销售的X射线分析设备中。这些元件的毛细管直径在微米量级,其光学性质可以根据几何光学的光线追迹计算进行描述。最近,由于多通道毛细管制作技术的改进,已成功制成了200 nm及以下通道尺寸的毛细管光学元件。在这样小的通道尺寸下,观察到了X射线辐射的波动效应。最后文章介绍了毛细管光学元件在X射线微荧光分析和微衍射方面的应用。     

Nano Indenter Ⅱ纳米显微力学探针

Nano Indenter Ⅱ纳米显微力学探针是我室1994年从美国 Nano Instru-ments公司引起的,目前是国内唯一一台。它是一种新型的材料微区力学性能检测系统,它使我们能够得到距材料表面几纳米至几十微米厚或亚微米范围的力学性能。从而使我们对材料微区力学性能的研究成为可能。     

微尺寸探针测量技术

原子力微探针具有极高的垂直方向位置灵敏度,其针尖半径可达几十纳米量级,这就为微纳米尺度的三维坐标测量提供了可能性.本文基于原子力微探针瞄准原理并结合二维微位移系统和高精度电容传感器,研制了微尺寸测量系统.     

基于CO2激光单点加热的微泡腔制备及其性能研究

为了简化微泡腔的制备工艺,在传统CO_2激光双向加热方案的基础上,采用CO_2激光单点加热毛细管。通过精确控制加热温度和气体流速,制备出半球形的微泡腔,进而通过调节激光光斑,增加加热面积的方式制备出球形的微泡腔。使用光学显微镜和原子力显微镜(AFM)对制备的球形微泡腔进行表征,并通过COMSOL仿真验证了所制备微泡腔的性能。所制备的微泡腔表面光滑,壁厚最薄处可达到亚微米量级。研究结果表明,通过CO_2激光单点加热制备的微泡腔的壁厚存在轻微的不均匀性,但其谐振Q值仍然较高,可广泛应用于传感领域。     

微束XRF系统中X射线聚焦光学元件研究

高性能X射线聚焦光学元件是实现亚微米分辨率微束X射线荧光分析系统(XRF)的关键器件。给出一种新型的微束XRF系统设计结构,介绍两种典型的X射线聚焦光学元件:X射线聚焦毛细管透镜和X射线组合折射透镜的结构与光学参数。数值计算比较了X射线聚焦毛细管透镜和X射线组合折射透镜的光学聚焦性能。分析结果体现了X射线聚焦组合透镜作为聚焦光学元件在焦斑大小、透过率、强度增益和检测范围等方面的优势。     

微机械的研究开发

微机械的研究开发上海交通大学徐锡林近十年里,人们应用半导体集成电路工艺相继制作出了尺寸在微米量级的微型齿轮、弹簧、连杆等,尤其是在１９８７年,两位留学美国的中国青年学人,在美国加州大学伯克利分校首次研制成功了转子直径为１００微米的硅静电微电机,虽然只...     

石英微流体器件制备仪的研制与实验研究

为获得良好微流动特性的耐高温透明微流体器件,设计了一种制备石英玻璃材质的透明微流体器件的多功能制备仪。利用玻璃材料加热到热熔融状态可进行塑形的特点对石英玻璃毛细管进行拉制、锻制、开孔、焊接,制备出微米级的微针、微管道、微三通等微流体器件。在样机上进行了基于温度、拉力二因素的实验,分析了各参数对微流体器件几何尺寸的影响。该仪器结构简单、成本低廉、功能多样化。     

硅微半球陀螺频率裂解修调工艺规律仿真分析

频率裂解是影响半球谐振陀螺性能的主要因素之一.硅微半球陀螺谐振子球壳的厚度为μm量级,半径为mm量级,小而脆弱的谐振子导致修调难度大,针对此问题,文中通过有限元仿真的方法分析了在硅半球壳谐振子唇边进行打孔对频率裂解的影响规律.得到了"应该在低频模态上打孔以减小频率裂解"、"修调的加工精度需要在微米级甚至是亚微米级"、"...     

基于压电纤维的微位移驱动器的研究

基于压电纤维复合材料特性研究,设计了一种新型的压电式微位移驱动器,它能够实现60μm的行程和亚微米量级的定位精度。对驱动器的电压-位移特性、分辨率以及迟滞和蠕变特性进行了实验研究,研究表明,相比于传统的压电陶瓷式微位移驱动器,这种新型的压电纤维微位移驱动器拥有更大的行程和更好的位移线性关系。本研究对压电纤维复合材料在微驱动方面的研究奠定了理论基础。     

静电驱动的亚微米悬臂梁谐振器非线性特性

当微谐振器的尺寸缩小到nm量级时其工作频率已达到MHz、GHz甚至更高,研究发现工作在高频段的谐振器具有非常明显的非线性行为。本文详细分析了亚微米尺寸的悬臂梁结构的非线性力学模     

Adhesive-free colloidal probes for nanoscale force measurements: production and characterization

We describe novel approaches for the production and characterization of epoxy- and adhesive-free colloidal probes for atomic force microscopy (AFM). Borosilicate glass microspheres are strongly attached to commercial AFM cantilevers exploiting the capillary adhesion force due to the formation of a water meniscus, and then a thermal annealing of the sphere-cantilever system at a temperature slightly below the softening point of borosilicate glass. Controlling the wettability of the surfaces involved turned out to be a crucial element for the control of surface adhesion and for the implementation of a completely adhesive-free production method of colloidal probes. Moreover, we present a statistical characterization protocol of the probe dimensions and roughness based on the AFM inverse imaging of colloidal probes on spiked gratings. We have assessed the influence of defects of the grating on the characterization of the probe, and discussed the accuracy of our characterization technique in comparison to the methods based on scanning electron or optical microscopy, or on the manual analysis of AFM inverse images.     

Probing liquid distribution in partially saturated porous materials with hydraulic admittance

The distribution of two immiscible fluids in a complex porous material during displacement is often central to understanding its function. Characterization of this distribution is traditionally determined via optically transparent flow cells. However, for opaque or thin porous materials of the order of hundreds of microns, optical visualization proves to be difficult and requires sophisticated imaging techniques that are expensive and difficult to come by. We describe here a bench-top tool that dynamically probes the hydraulic pathways leading to each free-interface within a single capillary and a bundle of seven capillaries at various saturations (i.e., hydraulic path lengths). A small volumetric displacement was applied to each interface such that the interfaces remained pinned at the capillary walls and the resultant oscillatory pressure drop was measured to determine the hydraulic admittance at each applied oscillation frequency. When the magnitude of the hydraulic admittance was plotted vs. applied oscillation frequency, a resonance peak was found for each degenerately filled capillary. The corresponding peaks were represented by a half-loop (100% filled) and full loops (partially filled) in a Nyquist plot. We compared the theoretical and measured admittance curves and found good agreement for both capillary systems at high filled states. The theoretical predictions became worse when the hydraulic path length was comparable to the capillary radius. The analysis for the hydraulic admittance of a bundle of capillaries is developed here and experimentally validated for the first time.     

Potentiostat and Cell Design for the Study of Rapid Electrochemical Systems

SUMMARY

A new potentiostat-cell system design for application to the study of very rapid electrochemical processes is described. The potentiostat provides submicrosecond transient response with very high current capability. The cell is constructed such that electrode placement can be determined very accurately and reproducibly. Very-small-diameter Luggin capillary probes have been employed to allow minimum separation between the working electrode and the reference probe, with subsequent minimization of uncompensated resistance. Probe dimensions could be varied conveniently and accurately to obtain specific characteristics. The response characteristics of the potentiostat-cell system were defined and optimized. The potential gradients near the working electrode for high-frequency control signals were measured. Controlled-potential electroanalytical methods were applied to the study of several electrode processes whose behavior could be predicted for rapid experiments.     

Qualitative and quantitative flow visualization technique using ozone

We have developed a new flow-visualization technique based on the absorption of ultraviolet light by ozone. Ozone is an excellent tracer, because as a gas it has the same effective physical properties as air. Ozone strongly absorbs the principal line (253.7 nm) of a mercury lamp, varepsilon=310 (atm cm)(-1), where I/Io=exp(-varepsiloncl) such that when an ozone-traced flow passes between a mercury lamp and a fluorescent screen, a sharp, shadow-like image of the ozone tracer is cast on the screen. Quantitative photometry can be carried out by replacing the screen with ultraviolet detectors that yield the path-integrated column density of ozone in the flow. High-speed quantitative point monitoring (10 Hz at 10 ppb O3) is possible with capillary probes and chemiluminescent analysis.     

Design and development of a new ultrasonic doppler technique for estimation of the aggregation of red blood cells

Aggregation of red blood cells (RBCs) is one of the principal hemorheological factors which plays an important role in capillary circulation. In order to study the RBC's aggregation, an ultrasound Doppler in-vitro technique, using pulsed wave monoelement pencil 4 MHz probes, has been designed. An hydraulic pump system has been implemented, establishing a laminar blood flow profile into a rectangular cross-section plexiglass tube. Adding dextrans to blood samples, red blood cells aggregation has been achieved and observed for various hematocrit values. Both the emitted and the backscattered signals, were driven to a system containing a multi-channel digital oscilloscope – of high sampling rate and processing capabilities – and a powerful PC with a high acquisition A/D card and special control software. Quantitative detection and measurement of the aggregation phenomenon can be achieved according to the experimental conditions and parameters used.     

Microfluidic on chip viscometers

We present the design and the process of fabrication of micromachined capillary on chip rheometers which have performed wall shear stress and shear rate measurements on silicon oil and ethanol-based nanofluids. The originality of these devices comes from the fact that local pressure drop measurements are performed inside the microchannels. Thus, the advantage over existing microviscometers is that they can be used with the fluid under test alone; no reference fluid nor posttreatment of the data are needed. Each on chip viscometer consists of anodically bonded silicon-Pyrex derivative microchannels equipped with local probes. The anodic bonding allows to reach relatively high pressure levels (up to approximately 10 bars) in the channels, and a broad range of shear stress and shear rate values is attainable. Dielectrophoretic and electrorheological effects can be highlighted by employing alternate microstripe electrodes patterned onto the inner side of the Pyrex wall.     

典型构筑植物表面不同湿度条件下黏附和摩擦特性研究

利用原子力显微镜的胶体探针技术,对不同湿度条件下四种具有典型构筑（光滑二维蜡质层、微褶皱、大褶皱、三维蜡质晶体）的原始植物表面以及两种氯仿处理后的植物样品表面的黏附力和摩擦力进行定量测试和分析。试验结果表明：冬青叶表面光滑二维蜡质涂层降低了其表面能和亲水特性,这不仅降低胶体探针与其表面在干燥条件下固固接触的摩擦力和黏附力,而且有效地阻碍了小湿度条件下液桥的形成,提高了其在小湿度条件下的脱附性能;荔枝叶表面微褶皱结构特征增大了固固接触的缝隙,不利于空气中的水蒸气冷凝并在毛细力的作用下形成液桥,从而在更大的湿度范围内提高了其脱附能力,脱附效果优于二维蜡质涂层;仙客来表面大褶皱特征和猪笼草表面三维蜡质晶体能有效排除接触界面附近的水蒸气,在干燥条件和高湿度条件下均能保持高效脱附功能,而猪笼草表面的微结构特征和蜡质晶体低表面能的耦合作用使其具有比仙客来表面大褶皱结构特征更优良的脱附功能。这些研究成果为仿生反黏附表面的设计和制备提供了理论依据。     

毛细管电泳的进展

在本综述中简要地介绍了毛细管电泳的发展,毛细管电泳的仪器,微型电泳仪,毛细管电泳检测器,毛细管电色谱,毛细管电泳柱,毛细管电泳的应用和毛细管电泳的手性分离。     

变径玻璃毛细管的制备及应用

提出两种用普通毛细管拉制机制备变径玻璃毛细管的新方法。通过改变炉温或拉伸比，拉制出不同形状的优势变径毛细管，并将其用于毛细管色谱柱的制备和毛细管的连接。     

变径毛细管代替毛细管组件在冷暖空调器上的应用研究

变径毛细管在正向流动和反向流动时其制冷剂流量特性不同,因而可以作为节流元件代替现有冷暖空调器中使用的毛细管组件。为实现这一目的,利用制冷剂流量试验台,先测定原毛细管组件制冷、制热时的制冷剂流量特性,然后通过调整变径毛细管规格尺寸,使变径毛细管制冷、制热时的流量特性与原毛细管组件基本一致,再安装在空调器整机上进行整机性能对比试验。试验表明,在标准工况下,新空调器与原空调器相比,其制冷量减少0.5%,制冷能效比增加0.3%,制热量减少1.1%,制热性能系数增加1.4%。因此可以得出,变径毛细管经过精确匹配,完全可以作为节流元件代替现有冷暖空调器中使用的毛细管组件。