Battery-operated STM

A scanning tunnelling microscope operating with ±12 V is described. A scanning range higher than 1 μm is achieved in the three orthogonal scanning directions for that low voltage. This translator arrangement, based on the use of piezoelectric discs mounted on metallic circular plates acting like flat springs, may provide a better performance than the tube scanners or rectangular bimorphs since it allows a greater volume to be run by the tip for a given voltage.     

Increasing the scanning speed of scanning tunnelling microscopes

The scanning speed and quality of images obtained with a scanning tunnelling microscope can be increased by replacing the tunnelling tip holder with an active, high resonance frequency piezoelectric positioner. The combination tip holder and positioner has a resonance frequency near 100 kHz, allowing fast closed-loop feedback control of the STM. With appropriate electronic shielding, the active tip holder can also be used to modulate the tip to surface distance at high frequencies for work function mapping. The high speed positioner is complemented by a ‘tip-saver’ circuit which senses imminent tip-surface contact, preventing tip crashes. The circuit, when driving the fast positioner, has a response time of under 20 μs and is not subject to the oscillation problems normally associated with closed-loop feedback systems operated at high gains and large signal bandwidths.     

Implementation of a short-tip tapping-mode tuning fork near-field scanning optical microscope

We present the implementation of a short‐tip tapping‐mode tuning fork near‐field scanning optical microscope. Tapping frequency dependences of the piezoelectric signal amplitudes for a bare tuning fork fixed on the ceramic plate, a short‐tip tapping‐mode tuning fork scheme and an ordinary tapping‐mode tuning fork configuration with an 80‐cm optical fibre attached are demonstrated and compared. Our experimental results show that this new short‐tip tapping‐mode tuning fork scheme provides a stable and high Q factor at the tapping frequency of the tuning fork and will be very helpful when long optical fibre probes have to be used in an experiment. Both collection and excitation modes of short‐tip tapping‐mode tuning fork near‐field scanning optical microscope are applied to study the near‐field optical properties of a single‐mode telecommunication optical fibre and a green InGaN/GaN multiquantum well light‐emitting diode.     

一种高分辨率的光纤定位单元定位精度的测量装置

目前对光纤定位单元定位精度的检测所使用的测量手段是摄影测量,由于被测光纤的孔径非常小,使得这种测量方法的分辨率不高。该文提出了一种新的测量方法,检测装置由显微镜、CCD相机、二维精密移动平台组成。被测光纤通过显微镜放大成像于CCD中,通过对CCD所拍摄照片的实时处理,建立位置反馈机制,实时操控二维精密移动平台追随光纤运动,光纤在运动中始终成像于CCD视场中心,通过读取移动平台坐标的变化来表征光纤移动的位置变化。实验结果表明,该套测量系统的分辨率达到了0．1μm,重复定位精度1．5μm,实现了高精度的检测要求。     

Surface and internal structure correlation: high-voltage and scanning electron microscopies of wholemount alveolar walls of human lung

We found that the high-voltage electron microscope (HVEM) operating at 1–5 MeV was able to transilluminate and form a focused transmission image of whole-mounts of alveolar walls from human lung, a tissue sufficiently thin to require no embedment and sectioning. Resultant micrographs resembled a composite of scanning and transmission electron microscope images: surface and internal structure of the alveolar wall were visualized in a single micrograph. Although the scanning electron microscope extracts some subsurface information in the secondary electron mode, the HVEM produced better images of both surface and subsurface features. Lungs were fixed, dehydrated, critical point dried, and metal coated as for conventional scanning electron microscopy, then individual alveolar walls were excised by hand and mounted on transmission electron microscope grids. Regions of the alveolar wall up to 10 μm thick were delineated with the high-voltage electron microscope. Cell surface characteristics were correlated with cell type as identified by underlying cell internal structure. Whole white blood cells within capillaries of the alveolar wall were identified by the configuration of their nuclei. Features of the nucleus and surface of alveolar type II cells were recorded simultaneously. Whole red blood cells were imaged within intact capillaries that branched and wove from one alveolar surface to the other. HVEM analysis of excised alveolar septa allows definitive correlation of surface and underlying structures in single micrographs of broad portions of the alveolar wall and is an alternative to embedment, microtomy and serial section reconstruction for this uniquely thin tissue.     

单点激光连续扫描测振的薄壁圆筒件模态测试

针对薄壁圆筒构件模态测试的需求,提出了基于单点激光连续扫描测振的薄壁圆筒构件模态测试方法。根据纯模态分析理论,在研究两端固定细弦自由振动的基础上,理论上建立了单点激光测振仪在两端固定的自由振动细弦上做连续扫描所得的振动信号和弦的模态振型之间的关系,研究了并提出了激光测振仪输出信号的处理方法。搭建了单点激光连续扫描测振的薄壁圆筒构件模态测试平台,对薄壁圆筒构件进行了模态实测,获得了薄壁圆筒构件前五阶固有频率和相应的模态振型,并对测试结果进行了有限元模态分析验证。结果表明,模态振型一致,固有频率误差在5%以内,证明了提出方法的正确性和有效性。     

一种仿生型无阀压电泵

针对传统的容积型流阻差式无阀压电泵具有吸入周期和排出周期,存在着流动脉动大、流量小的问题,提出一种新型的鱼鳍摆动式无阀压电泵。模仿在鱼类中巡游速度最快的金枪鱼的鱼体结构,设计了压电双晶片结构的压电振子,并将其尾鳍设计成柔性叶片状。分析了压电双晶片结构悬臂梁的受力变形、模态振型在机电转换效率方面的关系。研制了泵的样机并测量了激励电压在100 V时泵的流量。实验结果表明:振子工作在1阶振型时,泵水效应不明显;振子工作在2阶振型时,谐振频率为740 Hz,泵的流量为266 mL/min;振子工作在3阶振型时,谐振频率为1 280 Hz,泵的流量为105 mL/min。     

压电双晶片执行器驱动位移模型研究

通过对压电双晶片执行器的受力分析，推导出弹性梁双面对称粘贴和单面粘贴压电片驱动位移模型的计算公式。通过计算机数值模拟，分析了弹性梁厚度及材料特性对驱动位移的影响。实验研究证明了所建模型的正确性，为双晶片结构中压电片和弹性梁的选择提供了理论依据。     

Infrared scanning for biomedical applications

The great interest in using infrared imaging for biological and medical applications is motivated by the harmless interaction of small doses of infrared radiation with biological objects and by the technical ability of infrared digital cameras to generate, produce, store, and display the resultant images in situ. In this study, we review the state of the art of infrared (IR) imaging in comparison with well established medical imaging techniques such as ultrasound and x-rays. We demonstrate for the first time that by using IR transmitted light, one can observe bones, tendons, cartilages, and other tissues. The IR long-focus scanning microscope was built to allow two modes of scanning. The first mode is when illumination of a biological object is performed at the same angle of view with different IR wavelengths lambda. The second mode is when, for fixed wavelength lambda, scanning of the source of light around the object is performed. We discuss the special image processing methods and potential applications of the new scanner for medical diagnostics. This novel, low-cost IR imaging system (hardware and software) allows one to scan biological objects such as human arms, legs, palms, and fingers to differentiate tissues, tendons, muscles, ligaments, blood vessels, bones, and cartilages. Some of these objects cannot be detected by conventional x-rays.     

Dilute aldehyde treatment on aldehyde-fixed cells for observing chromosomes in situ with the scanning electron microscope

A new preparation method is introduced to reveal intracellular structures in the scanning electron microscope and its application to mitotic cells in root meristems of Vicia faba is demonstrated. The root tips are fixed with a mixture of formaldehyde and glutaraldehyde and the fixed tissues are frozen and fractured in liquid nitrogen. They are then incubated successively in dilute solutions of aldehyde (formaldehyde or glutaraldehyde) and osmium tetroxide. By this treatment, the excess cell-matrix is removed from the fractured surface of the cell, and a deep view into the cell-interior can be obtained with the scanning electron microscope. Varied levels of substructure are observed on the surface of chromosomes.     

串联弯曲臂压电微电机机理初步研究

把两片压电双晶片(PZT Bimorph)串联在一起,构成串联弯曲臂.一端固定,另一端自由时,在相位差为π/2的一定频率的方波信号驱动下,弯曲臂的自由端将形成类似椭圆的运动轨迹.以串联弯曲臂为驱动元件,可用来驱动与其端面相接触的转子转动,构成串联弯曲臂式压电微电机.本文将对串联弯曲臂的驱动机理进行分析,在新的微小尺寸驱动机理研究的椭圆运动的基础上,研制了串联弯曲臂压电微电机的样机,并且对样机的性能参数进行测试,转速可以达到110rpm,输出转矩可以达到22.5μNm.     

Fast scanning mode and its realization in a scanning acoustic microscope

The scanning speed of the two-dimensional stage dominates the efficiency of mechanical scanning measurement systems. This paper focused on a detailed scanning time analysis of conventional raster and spiral scan modes and then proposed two fast alternative scanning modes. Performed on a self-developed scanning acoustic microscope (SAM), the measured images obtained by using the conventional scan mode and fast scan modes are compared. The total scanning time is reduced by 29% of the two proposed fast scan modes. It will offer a better solution for high speed scanning without sacrificing the system stability, and will not introduce additional difficulties to the configuration of scanning measurement systems. They can be easily applied to the mechanical scanning measuring systems with different driving actuators such as piezoelectric, linear motor, dc motor, and so on. The proposed fast raster and square spiral scan modes are realized in SAM, but not specially designed for it. Therefore, they have universal adaptability and can be applied to other scanning measurement systems with two-dimensional mechanical scanning stages, such as atomic force microscope or scanning tunneling microscope.     

Quality assessment of atomic force microscopy probes by scanning electron microscopy: correlation of tip structure with rendered images

While image quality from instruments such as electron microscopes, light microscopes, and confocal laser scanning microscopes is mostly influenced by the alignment of optical train components, the atomic force microscope differs in that image quality is highly dependent upon a consumable component, the scanning probe. Although many types of scanning probes are commercially available, specific configurations and styles are generally recommended for specific applications. For instance, in our area of interest, tapping mode imaging of biological constituents in fluid, double ended, oxide-sharpened pyramidal silicon nitride probes are most often employed. These cantilevers contain four differently sized probes; thick- and thin-legged 100 microm long and thick- and thin-legged 200 microm long, with only one probe used per cantilever. In a recent investigation [Taatjes et al. (1997) Cell Biol. Int. 21:715-726], we used the scanning electron microscope to modify the oxide-sharpened pyramidal probe by creating an electron beam deposited tip with a higher aspect ratio than unmodified tips. Placing the probes in the scanning electron microscope for modification prompted us to begin to examine the probes for defects both before and after use with the atomic force microscope. The most frequently encountered defect was a mis-centered probe, or a probe hanging off the end of the cantilever. If we had difficulty imaging with a probe, we would examine the probe in the scanning electron microscope to determine if any defects were present, or if the tip had become contaminated during scanning. Moreover, we observed that electron beam deposited tips were blunted by the act of scanning a hard specimen, such as colloidal gold with the atomic force microscope. We also present a mathematical geometric model for deducing the interaction between an electron beam deposited tip and either a spherical or elliptical specimen. Examination of probes in the scanning electron microscope may assist in interpreting images generated by the atomic force microscope.     

基于HART协议的智能电气阀门定位器

二线制智能电气阀门定位器是阀门定位器的主流发展方向。本文详细阐述了基于MSP430单片机的智能阀门定位器软硬件设计，给出了HART协议通讯的实现方法，提出了阀门定位器低功耗设计中应采取的软硬件技术措施。实际应用表明，该定位器的主要技术性能明显优于传统的阀门定位器。     

开放式多功能扫描探针显微镜系统

开放式多功能扫描探针显微镜、集成扫描隧道显微镜、原子力显微镜、横向力显微镜和静电力显微镜．具有接触、半接触和非接触工作模式，可进行作用力、电流、电位、光能量等参数的高度局域综合测量,具有极高的开放性和可扩展性，支持用户进行二次开发。     

基于ADAMS焊接变位机受迫振动分析及优化研究

目前的自动化焊接设备中,不少点焊设备的变位机均为点焊、装卸等多工位设计,变位机在点焊的同时,另一端正在装卸工件等工序。工件装卸所产生的振动对点焊精度产生影响,高精度的变位机产品开发中必须对其认真考虑。文中以点焊和装卸两工位的变位机为例,基于ADAMS/Vibration功能模块对其进行了受迫振动分析,从而模拟了整个焊接过程中工件的装卸对点焊过程的影响,并以最小频域响应为目标,基于一个自编制仿真脚本,对振动分析进行了参数化设计,从而得到满足目标函数管件厚度的最优解,为高精度变位机的产品开发做一个研究,具有一定的理论价值。     

单点式位移平台激光共聚焦扫描荧光显微镜

为了获得细胞图像,利用Visual Studio C#开发了移动位移平台的控制程序,使用位移平台单点扫描的方式设计激光共聚焦扫描显微镜(laser confocal scanning microscope,LCSM)。为了获得高分辨率的位移,位移由精度可以达到1nm的压电陶瓷驱动器驱动。设计了梳状和矩形两种扫描路径,通过程序设计位移补偿的方法弥补了机械运动的偏差。利用算术平均值的数字滤波方法处理数据采集卡采集的数据以减小随机噪声的影响。实验结果证明,利用C#程序控制的单点式平台扫描LCSM具有较好地测量效果。     

An evanescent-field optical microscope

The classic diffraction limit of resolution in optical microscopy (～γ/2) can be overcome by detecting the diffracted field of a submicrometre-size probe in its near field. The present stage of this so-called scanning near-field optical microscopy (SNOM) is reviewed. An evanescent-field optical microscope (EFOM) is presented in which the near-field regime is provided by the exponentially decaying evanescent field caused by total internal reflection at a refractive-index transition. A sample placed in this field causes a spatial variation of the evanescent field which is characteristic for the dielectric and topographic properties of the sample. The evanescent field is frustrated by a dielectric probe and thus converted into a radiative field. In our case the probe consists either of an etched optical fibre or of a highly sharpened diamond tip. The probe is scanned over the sample surface with nanometre precision using a piezo-electric positioner. The distance between probe and sample is controlled by a feedback on the detected optical signal. The resolution of the microscope is determined by both the gradient of the evanescent field and the sharpness of the tip. Details of the experimental set-up are discussed. The coupling of the evanescent field to the submicrometre probe as a function of probe-sample distance, angle of incidence and polarization has been characterized quantitatively. The observed coupling is generally in agreement with presented theoretical calculations. Microscopy has been performed on a regular latex sphere structure, which clearly demonstrates the capacity of the evanescent-field optical microscope for nanometre-scale optical imaging. Resolution is typically 100 nm laterally and 10 nm vertically. The technique is promising for biological applications, especially if combined with optical spectroscopy.     

The “SOMSEM”—An SEM-based scanning optical microscope

No one form of microscopy is ideal for all applications and, in general, significant advances are made by correlating several techniques. In this paper, a scanning optical microscope is discussed which is based on the SEM and is entirely compatible with it. This new hybrid instrument, known as the SOMSEM, has been demonstrated using a converted SEM specimen stage and a standard Cambridge Stereoscan 250 Mk II microscope. The operating principles have been verified, and silicon MOS (metal oxide semiconductor) devices have been successfully imaged using the OBIC (optical beam induced current) mode thus avoiding electron beam damage. Potential applications and future developments are briefly discussed.