A Study on HA Titanium Surface with Atomic Force Microscope (AFM)

Three kinds of titanium surface especially the HA surface are analyzed. Titanium was treated by 3 kinds of methods that were acid ＆ alkali, calcic solution and apathe solution. Samples were observed by optic microscope and atomic force microscope （ AFM ） . The typical surface morphology of the acid and alkali group is little holes, and on the two HA surface the tiny protuberances is typical. The surface treated by apatite solution was smoother than the two formers. The rough surface treated with acid and alkali was propitious to Ca^＋ , P^- and proteins＇ adhesion, and the relatively smooth HA surface was of benefit to the cell adhesion.

Sorting Gold and Sand(Silica) Using Atomic Force Microscope-Based Dielectrophoresis

Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures.However,the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir,which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle.Here,we propose a dielectrophoresis(DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork(QTF)-atomic force microscope(AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions.We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation,which confirmed the surfaceenhanced Raman spectroscopy(SERS).To validate the scheme,we also performed a simulation for the system and found qualitative agreement with the experimental results.The method that combines DEP,pipette-based AFM,and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning,materials sorting,and diverse advanced applications.

IMPROVED FABRICATION METHOD FOR CARBON NANOTUBE PROBE OF ATOMIC FORCE MICROSCOPY(AFM)

An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication＇s difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.

Monte Carlo method in optical atomic force microscopy

Scanning probe microscopy(SPM)is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen.Atomic force microscopy is one of the SPM family which is considered as a very versatile tool for surface imaging and measurements.A wide range of various samples can be measured regardless of being conductive,no-conductive,in vacuum,in air or in a fluid as a unique feature.One of the most challenges in atomic force microscopes(AFMs)is to evaluate the associated uncertainty during the surface measurements by AFMs.Here,an optical AFM is calibrated through the calibration of XYZ stage.The approach is to overcome difficulties experienced when trying to evaluate some uncertainty components which cannot be experimentally determined i.e.tip surface interaction forces and tip geometry.The Monte Carlo method is then used to determine the associated uncertainties due to such factors by randomly drawing the parameters according to their associated tolerances and their probability density functions(PDFs).The whole process follows supplement 2 to“the guide to the expression of the uncertainty in measurement”(GUM).The approach validated in the paper shows that the evaluated uncertainty in AFM is about 10 nm.

Carbon nanotubes as tips for atomic force microscopy

Ordinary AFM probes'characters prevent the AFM' s application in various scopes. Carbon nanotubes represent ideal AFM probe materials for their higher aspect ratio, larger Young's modulus, unique chemical structure, and well-defined electronic property. Carbon nanotube AFM probes are obtained by using a new method of attaching carbon nanotubes to the end of ordinary AFM probes, and are then used for doing AFM experiments. These experiments indicated that carbon nanotube probes have higher elastic deformation, higher resolution and higher durability. And it was also found that carbon nanotube probes ean accurately reflect the morphology of deep narrow gaps, while ordinary probes can not reflect.

基于光偏转原理的AFM光电检测系统设计

利用光偏转原理设计并实现了原子力显微镜(AFM)的光电检测系统,研究了影响光偏转噪声的影响因素。设计了新型螺旋式嵌套结构调节准直光斑,使激光发散角降低到0.053°,利用压电陶瓷特性设计了高精度三维调节结构,可以在α,β,γ方向精准调节偏转角度,36mm的聚焦焦距满足了小型化、集成化的设计目标。基于该高灵敏度光电检测系统的设计,AFM系统得到了清晰的硅材料表面台阶结构,系统分辨率达到了0.1nm,为今后的亚原子测量奠定了实验基础。

基于AFM的SBS改性沥青老化过程力学特性研究

为了探究改性沥青在老化过程中宏观与微观性能的变化,制备了掺量为5.5%的SBS改性沥青,并进行了短期与长期老化试验,分析了其基本性能指标。采用温度扫描与频率扫描试验研究了SBS改性沥青的流变性能,采用AFM试验分析了其表面微观形貌和耗散力,并结合力曲线分析了其黏附力及杨氏模量在老化前后的变化。研究结果表明,短期老化对SBS改性沥青流变性能的影响较小,长期老化对其流变性能影响显著,弹性模量和黏性模量均增大,呈现出变硬、变脆的特性;AFM试验表明SBS改性沥青在老化后高度增大,且蜂状结构尺寸增大、数量增多,黏附力和耗散力均降低,杨氏模量增大,验证了宏观流变试验的结果。

Damage of DNA ends induced by mechanical force during AFM nano-manipulation

An experimental and statistical study was carried out to explore the effects of mechanical forces on the ends of linear double-stranded DNA (dsDNA) fragments. Mechanical force was applied onto individual DNA molecules during atomic force microscope (AFM)-based picking-up manipulation. By comparing the PCR efficiency of two DNA fragments with primers either at ends or at the inner regions, it was found that the ends of DNA fragments were damaged during picking-up process.

An automated AFM for nanoindentation and force related measurements

A fully automated atomic force microscope(AFM)is presented.The mechanical motion of the AFM stage was controlled by three steppers.The fine motion of the AFM was controlled by an MCL one-axis piezo plate.A32.768kHz crystal tuning fork(TF)was used as the transducer with a probe attached.An acoustic sensor was used to measure the interactions between the probe and the sample.An SR850lock-in amplifier was used to monitor the TF signals.An additional lock-in amplifier was used to monitor the acoustic signal.A field programmable gate array(FPGA)board was used to collect the data in automatic mode.The main controller was coded with LabVIEW,which was in charge of Z-axis scan,signal processing and data visualization.A manual mode and an automatic mode were implemented in the controller.Users can switch the two modes at any time during the operation.This AFM system showed several advantages during the test operations.It is simple,flexible and easy to use.

{001} surface structure of clinotyrolite revealed by atomic force microscope (AFM)

Clinotyrolite is a mineral discovered by Ma et al. in 1980. It is a hydrous copperarsenate and similar to tyrolite in both composition and structure. Its structureformula is Cu9Ca2[（As, S）O4]（OH, O）10·10H2O. Because of a group of perfect

Nanoscale imaging with an integrated system combining stimulated emission depletion microscope and atomic force microscope

We have built an integrated imaging system by combining stimulated emission depletion(STED)microscope and atomic force microscope(AFM).The STED microscope was constructed based on the supercontinuum fiber laser and a super lateral resolution of42 nm was achieved.With this integrated imaging system,morphological features,mechanical parameters and fluorescence super resolution imaging were obtained simultaneously for both nanobeads and fixed cell samples.This new integrated imaging system is expected to obtain comprehensive information at the nanoscale for studies in nanobiology and nanomedicine.

Aligning DNA on Si surface and cutting off by tips of atomic force microscope

DNA is a kind of promising molecule as nano-lead to build or connect nano-devices due to its stable linear structure and certain conductivity. Many methods have been applied to constructing nano-patterns by using DNA molecule. In this report it is presented that l-DNA was aligned on Si substrate by using the free-flowing method and then imaged by an atomic force microscope (AFM). After the second liquid flow, a catenary-like pattern and a crossed network of l-DNA were formed. In addition, the alignedl-DNA was successfully cut off by tips of AFM.

Investigation of structural change of purple membrane in storage by transmission electron microscope and atomic force microscope

The structural change of purple membrane during storage has been investigated by means of transmission electron microscope and atomic force microscope. It is found that many liposomes have spontaneously evolved from the purple membrane sheets isolated three years ago. The membrane proteins on the liposomes, bacteriorhodopsin, are still presented as trimers in 2-D hexagonal structure, which is the same as that in natural cell membrane. However, the cytoplasmic surface of purple membrane faced outside on the liposomes.

Atomic-level characterization of liquid/solid interface

The detailed understanding of various underlying processes at liquid/solid interfaces requires the development of interface-sensitive and high-resolution experimental techniques with atomic precision.In this perspective,we review the recent advances in studying the liquid/solid interfaces at atomic level by electrochemical scanning tunneling microscope(EC-STM),non-contact atomic force microscopy(NC-AFM),and surface-sensitive vibrational spectroscopies.Different from the ultrahigh vacuum and cryogenic experiments,these techniques are all operated in situ under ambient condition,making the measurements close to the native state of the liquid/solid interface.In the end,we present some perspectives on emerging techniques,which can defeat the limitation of existing imaging and spectroscopic methods in the characterization of liquid/solid interfaces.

Fabrication of Nanoscale Active Plasmonic Elements Using Atomic Force Microscope Tip-Based Nanomachining

Atomic force microscopy(AFM)is a widely adopted imaging and surface analysis technique that provides resolutions on the nanometer scale.AFM tip-based nanomachining has recently been adopted for the fabrication of arbitrarily shaped nanoscale structures.A major challenge of using AFM tip-based machining for the sculpting of nanoscale plasmonic structures is the build-up of displaced material along the sides of the channels.Here we apply this nanomechanical machining method to create active plasmonic elements and present the strategy we have been using to avoid the formation of such debris.Furthermore,a number of post-manufacturing treatments that can potentially be used to reduce the amount of debris surrounding the fabricated structures are discussed.

Microfluidic bacterial traps for simultaneous fluorescence and atomic force microscopy

The atomic force microscope has become an established research tool for imaging microorganisms with unprecedented resolution.However,its use in microbiology has been limited by the difficulty of proper bacterial immobilization.Here,we have developed a microfluidic device that solves the issue of bacterial immobilization for atomic force microscopy under physiological conditions.Our device is able to rapidly immobilize bacteria in well-defined positions and subsequently release the cells for quick sample exchange.The developed device also allows simultaneous fluorescence analysis to assess the bacterial viability during atomic force microscope imaging.We demonstrated the potential of our approach for the immobilization of rod-shaped Escherichia coli and Bacillus subtilis.Using our device,we observed buffer-dependent morphological changes of the bacterial envelope mediated by the antimicrobial peptide CM15.Our approach to bacterial immobilization makes sample preparation much simpler and more reliable,thereby accelerating atomic force microscopy studies at the single-cell level.

Electrocondensation and Evaporation of Attoliter Water Droplets: Direct Visualization Using Atomic Force Microscopy

Working with a biased atomic force microscope(AFM)tip in the tapping mode under ambient atmosphere,attoliter(10^(-18) L)water droplet patterns have been generated on a patterned carbonaceous surface.This is essentially electrocondensation of water leading to charged droplets,as evidenced from electrostatic force microscopy measurements.The droplets are unusual in that they exhibit a highly corrugated surface and evaporate rather slowly,taking several tens of minutes.

Atomic Force Microscopy of Calcite Surface

Both atomic force microscope (AFM) and scanning tunneling microscope (STM) are devices for investigating material surfaces down to atomic-scale in real space. But unlike STM, AFM can be used to study not only conductors and semiconductors but also insulators. So it has a wider application range than STM. As most minerals are insulators,

基于AFM的虚拟纳米手操作策略研究

针对纳米操作过程中存在的不确定性及AFM单探针带来的纳米粒子的稳定操作问题,提出了虚拟纳米手操作策略。该策略采用蒙特卡洛方法描述粒子的不确定性,在纳米粒子推动操作的运动学模型基础上,对AFM探针的作用参数进行规划,模拟多探针并行操作效果,将粒子的中心位置限制在规定误差范围内,从而可以避免操作过程中粒子的丢失,实现粒子的稳定高精度纳米操作,仿真结果与实验操作结果相对比,验证了虚拟纳米手操作方法的有效性。

动态AFM悬臂的高阶谐振特性研究及实验

为了提高动态原子力显微镜(AFM)的灵敏度、分辨率、扫描速度等,基于硅悬臂器件具有多阶谐振模态的特性,提出一种利用硅悬臂高阶谐振而进行扫描测量的高阶谐振表面测量方法,并对相应动态AFM悬臂的高阶谐振特性进行了理论和实验研究。分析了高阶谐振悬臂的工作原理,给出了悬臂的振动方程和振型函数,从理论上证明了高阶谐振悬臂较其初级谐振模式具有更高灵敏度和更高空间分辨率;由于频率的提高,悬臂的动态测量性能明显改善。基于自制的轻敲式AFM,通过实验证实了高阶谐振现象的存在;实验测得的一阶二阶谐振悬臂的灵敏度,空间分辨率和最小可探测力梯度分别为8 V/μm,17 V/μm;1.33 nm,0.47 nm;1.80×10-7N/m,0.54×10-7N/m,实验结果与理论分析结论一致;通过二阶谐振扫描获得了光栅试样表面轮廓图,证明了该高阶谐振特性研究的正确性及利用高阶谐振特性进行扫描测量的可行性。