Combined-dynamic mode “dip-pen” nanolithography and physically nanopatterning along single DNA molecules

Atomic force micriscope (AFM)-based dip-pen nanolithography (DPN) is an emerging approach for constructing nanostructures on material surfaces such as gold, silicon and silicon oxide. Although DPN is a powerful technique, it has not shown its ability of direct-writing and patterning of nanostructures on surfaces of soft materials, for example biomacromolecules. Direct depositing on soft surfaces becomes possible with the introduction of a combined-dynamic mode DPN rather than mostly used contact mode DPN or tapping mode DPN. In this report, the combined dynamic mode DPN is used for direct depositing protein ink on DNA molecules at the nanometer scale.     

Design and fabrication of superconducting HEB mixer

This paper describes the design and fabrication of superconducting hot electron bolometer （HEB） mixer based on ultra-thin superconducting NbN films. The high quality films were epitaxially grown on high resistance Si substrates. The device was fabricated by magnetron sputtering, electron beam lithography （EBL）, reactive ion etching （RIE）, lithography, and so on. The device＇s resistance-temperature （R-T） curves and current-voltage （I-V） curves were studied. The results of THz response of the device are presented. Y-factor technique was used to measure the device＇s noise temperature. When the device was irradiated with a laser radiation of 2.5 THz, the obtained lowest noise temperature of the device was 2213 K.     

Non-invasive scanning ion-selective electrode technique and its applications to the research of higher plants

The process of various ions and molecules getting into and out of cells is critical for plant survival. The non-invasive scanning ion-selective electrode technique (SIET) is a non-invasive method to obtain the information of ions/molecules across membranes in plant. This technique can measure the absolute concentration of ions and molecules, and also their fluxes and directions of movement. The samples to be analyzed can be a single cell, a piece of tissue, a whole organ and even an intact seedling. This article reviews the recent progress made in plant physiology by using this technique and discusses its potentials in future studies on plant physiology.     

AlGaN/GaN heterostructure field transistor for label-free detection of DNA hybridization

This paper demonstrates electrical detection of single strand deoxyribonucleic acid (ssDNA) conjugation by AlGaN/GaN hetero-structure field effect transistor (HFET) biological sensors. The probe ssDNA molecules are modified by thiol groups. The immobilization of probe molecules is achieved by S-Au bonding on a thin layer of gold film in the sensing area. The immobilization and hybridization process are firstly implemented on Si surfaces and checked by fluorescent and atomic force microscopy (AFM) imaging. The hybridization process is monitored on AlGaN/GaN HFETs. Time-dependent current change is observed when a matched ssDNA solution is applied, while no response is observed for a mismatched ssDNA sequence. The DNA hybridization process is dominated by the conjugation between matched ssDNA sequences in the first few tens of seconds. After that, the hybridization process is dominated by mass transfer processes and saturation of the immobilized probe ssDNA molecules.     

Effective Factors on Forming Precision in Patternless Casting Manufacturing Technique

The patternless casting manufacturing (PCM) technique, which adopts a new concept of double scanning method, combines the principle of discreteness and deposition with resin-bonded sand technique. This paper is to evaluate the dimensional accuracy of sand mould on PCM. The two important factors-the liquid penetration rule in the space of particles and the shape and dimension of the agglomeration unit body, which influence the process parameters such as scanning speed, layer thickness, liquid flux on dimension accuracy, and surface qualities, were investigated systematically, thus the theoretical basis for these parameters was provided. Experiments on rapid manufacturing of sand mould were carried out, and the results of the free penetration and the constraint penetration well verified the relationship of the two factors and the process parameters.     

Formation of superthick Al-based amorphous ribbon

The Al-Ni-La-Ce-Pr-Nd amorphous ribbon with a super-thickness of 140μm has been produced by the melt spinning technique.The thickness is as twice as that achieved by the melt spinning technique in the corresponding period (the largest thickness of 65μm）.The crystallization was characterized by using a differential scanning calorimetry.The activation energies are calculated based on the Kissinger equation and the effects of the La,Ce,Pr and Nd on the glass forming ability of Al-based alloy are discussed in the paper.     

Fabrication of gold nanoelectrodes based on nanolithography electrochemically through a conductive AFM tip

Gold nanoelectrodes were fabricated by approach of combining surface self-assembly with nanolithography electrochemically through a conductive AFM tip. The controllahle structure with width and distance in nanometer as a template was constructed by nanolithography patterning process, which was accomplished by a conductive AFM tip on certain highly ordered long-tail organosilane monolayers. Then through adsorption of Cd^2＋ and exposure of the Cd^2＋-loaded surface to gaseous H2S, CdS nanowires were generated in a template-controlled self-assembly process. Finally, metallic gold nanowires were conversed from CdS nanowires by treatment with the aqueous solution of HAuCl4 via a redox chemical process, which had good conductivity proved by C-AFM.     

The effect of heat treatment on the structure and morphology of poly （p-phenylene benzobisoxazole） fiber

The effect of heat treatment on the structure of Poly（p-phenylene benzobisoxazole） （PBO） fiber was studied by wide angle X-ray diffraction （WAXD） and differential scanning calorimetry-（DSC）, which resuits in confirmation of secondary crystallization in the heat treatment process. The effect of heat treatment on the structure and morphology of PBO fiber＇ s surface was investigated with X-ray photoelectron spectroscopic analysis （XPS）, scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The results show that heat treatment not only has an effect on the composition of PBO fiber＇s surface, but also improves the microstmcture of PBO fiber, makes fiber more regular.     

Effect of interface morphology on the mechanical properties of titanium clad steel plates

Interface morphology has important influence on the bond quality of titanium clad steel plates. The mechanical properties of titanium clad steel plates with wavy and straight interfaces were investigated by tensile-shear tests and bending tests. The interface morphology of the plates was examined by optical microscopy (OM) and scanning electron microscopy (SEM). The experimental results show that the shear strength of a wavy interface is higher than that of a straight interface. A wavy interface is the guarantee for obtaining high shear strength to provide a greater shear resistance. During the macrobending process, cracks appear in the swirl of the wave tip and ferrotitanium intermetallics. For in-situ observing the bending process by SEM, the wave tip of a wavy interface and the massive ferrotitanium intermetallics of a straight interface are places where cracks initiate and propagate. The results are the same as those observed in the macrobending process. Because of high hardness, the wave tip and the massive ferrotitanium intermetallics are hard in terms of compatible deformation.     

Compound machining of silicon carbide ceramics by high speed end electrical discharge milling and mechanical grinding

A compound process that integrates end electrical discharge (ED) milling and mechanical grinding to machine silicon carbide (SiC) ceramics is developed in this paper. The process employs a turntable with several uniformly-distributed cylindrical copper electrodes and abrasive sticks as the tool, and uses a water-based emulsion as the machining fluid. End electrical discharge milling and mechanical grinding happen alternately and are mutually beneficial, so the process is able to effectively machine a large surface area on SiC ceramic with a good surface quality. The machining principle and characteristics of the technique are introduced. The effects of polarity, pulse duration, pulse interval, open-circuit voltage, discharge current, diamond grit size, emulsion concentration, emulsion flux, milling depth and tool stick number on performance parameters such as the material removal rate, tool wear ratio, and surface roughness have been investigated. In addition, the microstructure of the machined surface under different machining conditions is examined with a scanning electron microscope and an energy dispersive spectrometer. The SiC ceramic was mainly removed by end ED milling during the initial rough machining mode, whereas it is mainly removed by mechanical grinding during the later finer machining mode; moreover, the tool material can transfer to the workpiece surface during the compound process.     

使用碳纳米管AFM针尖的蛋白质高分辨率成像

原子力显微镜(AFM)是分析生物分子结构的有效手段,而目前使用的探针针尖的性质限制了高分辨率图像的获得。该文将碳纳米管安装到原子力显微镜的传统针尖上,制作出碳纳米管针尖以解决这个问题。运用碳纳米管针尖在大气常温条件下获得了由3个单元组成的小鼠抗体IgG蛋白质的Y形结构,并且分子的尺寸与X射线晶体衍射的结果非常接近,这种效果用传统针尖是无法获得的。获得的蛋白质分子超微结构的高分辨率图像为研究蛋白质分子功能提供了有价值的信息。     

Erasable electrostatic lithography for quantum components

Quantum electronic components--such as quantum antidots and one-dimensional channels--are usually defined from doped GaAs/AlGaAs heterostructures using electron-beam lithography or local oxidation by conductive atomic force microscopy. In both cases, lithography and measurement are performed in very different environments, so fabrication and test cycles can take several weeks. Here we describe a different lithographic technique, which we call erasable electrostatic lithography (EEL), where patterns of charge are drawn on the device surface with a negatively biased scanning probe in the same low-temperature high-vacuum environment used for measurement. The charge patterns locally deplete electrons from a subsurface two-dimensional electron system (2DES) to define working quantum components. Charge patterns are erased locally with the scanning probe biased positive or globally by illuminating the device with red light. We demonstrate and investigate EEL by drawing and erasing quantum antidots, then develop the technique to draw and tune high-quality one-dimensional channels. The quantum components are imaged using scanned gate microscopy. A technique similar to EEL has been reported previously, where tip-induced charging of the surface or donor layer was used to locally perturb a 2DES before charge accumulation imaging.     

具有沉浸感的毛笔书写行为实时仿真

提出一种毛笔书写行为的实时仿真技术.在毛笔的几何外形方面,采用了骨骼蒙皮的建模方式,并提出一种骨骼旋转参数的快速算法,从而实现了笔头在运动过程中的弯曲和扭转两种变形效果;在水墨效果方面,采用了基于粒子系统的墨水扩散模型,能够灵活地控制墨迹在纸面上的浸染效果.基于上述技术,使用头戴显示器和力反馈设备,实现了一个毛笔书写仿真系统,具有很好的实时性和沉浸感.      

中性笔出墨量与笔头结构匹配

为解决优质进口墨水与笔头匹配问题并保证中性笔的书写性能,基于有限元分析法,考虑中性墨水流变特性、笔头结构参数及加工误差等对出墨量的影响,建立中性墨水与笔头匹配的出墨量仿真模型并进行修正。结果表明,该出墨量模型的仿真结果与实际测试结果相近。该模型为中性墨水与笔头结构匹配出墨量的有效仿真提供了一种新方法,有助于提高出墨量仿真结果的准确性。     

Manipulation of atoms across a surface at room temperature

Since the realization that the tips of scanning probe microscopes can interact with atoms at surfaces, there has been much interest in the possibility of building or modifying nanostructures or molecules directly from single atoms. Individual large molecules can be positioned on surfaces, and atoms can be transferred controllably between the sample and probe tip. The most complex structures are produced at cryogenic temperatures by sliding atoms across a surface to chosen sites. But there are problems in manipulating atoms laterally at higher temperatures--atoms that are sufficiently well bound to a surface to be stable at higher temperatures require a stronger tip interaction to be moved. This situation differs significantly from the idealized weakly interacting tips of scanning tunnelling or atomic force microscopes. Here we demonstrate that precise positioning of atoms on a copper surface is possible at room temperature. The triggering mechanism for the atomic motion unexpectedly depends on the tunnelling current density, rather than the electric field or proximity of tip and surface.     

乙醇为承载液时IDO指纹显现液的性能及应用

使用乙醇替代CFC-113/HFE7100作为1,2-茚二酮（IDO）承载液,考察了该配方对常用纸张和墨迹上指纹的显现性能.结果表明：指纹显现性能无明显差异;除油性圆珠笔字迹外,常用的中性签字笔、碳素、蓝黑、纯蓝墨迹以及激光打（复）印件和报纸字迹均不影响指纹显现.     

高强度激光三倍频增透膜的制备

激光技术的发展对增透膜的要求越来越高.采用溶胶-凝胶工艺,运用提拉法镀膜技术与氨处理的后处理工艺,制备了高强度的纳米多孔SiO2增透膜.利用分光光度计研究了提拉速度对透射光谱的影响.结果表明,可以通过控制提拉速度来控制薄透射峰值的位置.经过氨处理,薄膜的机械强度比未采用氨处理的薄膜大大增强,并利用红外光谱、原子力显微镜(AFM)等分析手段分析了薄膜强度增强的机理.最后在石英玻璃基底上镀制了激光三倍频增透膜,该薄膜在355nm处透射率为99.58％,满足了实际应用的需要.     

A novel colloid probe preparation method based on chemical etching technique

Several fundamental problems in hydrophobic force measurements using atomic force microscope (AFM) are discussed in this paper. A novel method for colloid probe preparation based on chemical etching technology is proposed, which is specially fit for the unique demands of hydrophobic force measurements by AFM. The features of three different approaches for determining spring constants of rectangular cantilevers, including geometric dimension, Cleveland and Sader methods are compared. The influences of the sizes of the colloids on the measurements of the hydrophobic force curves are investigated. Our experimental results showed that by selecting colloid probe with proper spring constant and tip size, the hydrophobic force and the complete hydrophobic interaction force curve can be measured by using AFM.