基于原子力显微镜的纳米加工研究

以原子力显微镜(AFM)作为加工工具对单晶硅进行了基于金刚石针尖的纳米加工试验,运用不同的方法对纳米加工区域的特性、材料在不同垂直载荷下的去除机理及切屑形成特征进行了系统的研究和分析,提出了一种在纳米尺度下研究加工机理的新方法。在此基础上,应用有限元法对AFM纳米加工中存在于金刚石针尖和被加工材料之间的接触作用机制进行了计算仿真。     

Improvement of Local Surface Quality by Using Single Abrasive Abrasion Process

AFM-based wear process actually is single abrasive abrasion process. It is widely employed in the surface micro/nano machining for fabrication of structures at the nanometer scale exhibiting high removing ability of nanometer scale materials. In this study, application of AFM-based single abrasive abrasion process in the local surface quality (surface roughness) improvement was studied. Merged holes were fabricated using an AFM diamond tip with different wear parameters on the surface of germanium (Ge) machined by conventional ultra-precision diamond turning. Results showed that cracks left by diamond turning can be removed and the local surface quality can be improved. Also effects of the wear parameters on the surface roughness were investigated. The optimized parameters of the abrasion process for improving the surface quality were provided. It is verified that AFM-based single abrasive abrasion process is a novel approach to modify or repair local surface on the surface of parts manufactured by other methods.     

Contact mechanics and tip shape in AFM-based nanomechanical measurements

Stiffness-load curves obtained in quantitative atomic force acoustic microscopy (AFAM) measurements depend on both the elastic properties of the sample and the geometry of the atomic force microscope (AFM) tip. The geometry of silicon AFM tips changes when used in contact mode, affecting measurement accuracy. To study the influence of tip geometry, we subjected ten AFM tips to the same series of AFAM measurements. Changes in tip shape were observed in the scanning electron microscope (SEM) between individual AFAM tests. Because all of the AFAM measurements were performed on the same sample, variations in AFAM stiffness-load curves were attributed to differences in tip geometry. Contact-mechanics models that assumed simple tip geometries were used to analyze the AFAM data, but the calculated values for tip dimensions did not agree with those provided by SEM images. Therefore, we used a power-law approach that allows for a nonspherical tip geometry. We found that after several AFAM measurements, the geometry of the tips at the very end is intermediate between those of a flat punch and a hemisphere. These results indicate that the nanoscale tip-sample contact cannot easily be described in terms of simple, ideal geometries.     

基于原子力显微镜扫描的金刚石刀具纳米刃口轮廓测量方法研究

基于扫描探针理论,本文介绍了一种超精神加工金刚石刀具刃口锋锐轮廓的测量方法,给出了测量图象并分析了测量结果,首次对金刚石刀具刃口轮廓参数进行了ＡＦＭ扫描原理下的初步评定。这一方法可提高金刚石刀具刃口锋锐度的测量准确度,对进一步分析刃口参数如何影响超精密加工表面质量具有指导意义。     

碳纳米管原子力显微镜针尖的制作研究

研究在光学显微镜下，运用两个独立的三维工作台分别控制针尖和碳纳米管的位置，将碳纳米管吸附在传统的原子力显微镜针尖上。首先将碳纳米管粘附在导电的胶带上，然后用涂胶的针尖与其接触将碳纳米管粘附到针尖上，最后运用电蚀的方法优化碳纳米管针尖的长度，以达到高分辨率的要求。运用制作的碳纳米管针尖对硅表面的深槽进行成像，获得了传统针尖无法得到的信息。     

The immobilization of animal cells using the cysteine-modified RGD oligopeptide

RGD peptide sequence is an effective cell recognition motif and used to enhance the cell adhesion on desired solid material for cell immobilization. We have synthesized CRGD, CRGD-multiple-armed peptide (MAP), RGD-MAP-C and evaluated their comparative efficacy for cell immobilization. Each peptide was assembled on gold surface and investigated by the atomic force microscopy (AFM) technique in the contact mode. The viability of immobilized animal cells was examined by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Our results showed that RGD-MAP-C in comparison to others was the most effective proliferation of cells on the gold surface. The goal of this present work is integration to the nano-pattern cell chip bioplatform for biomedical assays or provide valuable insights into cell biology and design of biomaterials. This RGD-MAP-C can be applicable to the nano-pattern cell chip platform.     

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.     

T细胞与K562细胞共培养的AFM观察

人类机体的免疫系统很难彻底清除肿瘤细胞,了解T淋巴细胞杀伤肿瘤细胞的整个过程的机理,将为提高免疫系统杀灭肿瘤的效率提供知识基础。本文采用原子力显微镜与倒置显微镜在细胞层面上观察T淋巴细胞进攻杀伤人慢性粒细胞性白血病细胞株——K562细胞的过程,并对T细胞与K562细胞共培养前后的表面形貌和生物机械性质进行表征。结果显示,与培养前相比,共培养后2种细胞数目之和减少,2种细胞的表面形貌和机械力学性质均出现很大差异,表现为:K562细胞,平均粗糙度(Ra)降低,细胞平均高度(Mh)降低,细胞表面出现5～8 cm的孔洞,有的细胞甚至完全破裂溶解。多个T细胞的统计分析结果显示,共培养前,T细胞为静息状态,而共培养后Ra和Mh都显著增加。该方法为研究免疫系统与肿瘤相互作用的机制提供重要的切入点。     

Facilitating the pickup of individual DNA molecules by AFM nanomanipulation with tips mechanically worn on bare mica

The tip is one of the critical factors to improve the efficiency in picking up individual DNA molecules from solid substrates based on atomic force microscope (AFM) nanomanipulation. We found that wearing AFM tips on certain solid substrates in advance to nanomanipulation operation would largely improve the pickup efficiency, which was ascribed to the increasing affinity of the tip to the DNA molecules along with the increase of the tip radius after wearing. It was demonstrated that bare mica was superior to APTES-modified mica to keep the tip clean while wearing, which was crucial for DNA pickup during AFM nanomanipulation.     

MEMS微悬臂梁构件变形规律的AFM试验研究

采用原子力显微镜测试了微悬臂梁构件的弯曲变形规律。发现构件的弹性支撑是试验数据和理论计算出现误差的主要原因。引入支撑扭转等效刚度对探针-样品等效刚度计算公式进行修正。修正结果对大有效长度的构件与实测结果吻合良好。对短有效长度微悬臂梁,其误差原因主要为支撑的影响以及测试探针的大变形,论文进一步提出研究的建议。     

Fabrication of hierarchical micro/nanostructures via scanning probe lithography and wet chemical etching

In this study, we propose a simple and effective method for fabricating hierarchical silicon structures via the combination of scanning probe lithography (SPL) and wet chemical etching. Here, silicon oxide structures were protruded from a 100-oriented silicon surface, followed by the passivation of silicon nitride by AFM tip-induced local oxidation. Based on the two-dimensional (2D) silicon oxide patterns, three-dimensional (3D) microstructures with high aspect ratios were formed by wet etching with HF and KOH. A variety of combinations of SPL and the etching process allowed us to fabricate diverse silicon-based structures such as deep-etched microstructures and multi-terraced nanostructures.     

AFM针尖对胶原样品表面一种损伤现象的研究

用AFM对吸附于云母表面的胶原蛋白的研究过程中，观察到一种AFM针尖对样品损伤现象。在小范围的扫描过程中．胶原蛋白在AFM针尖的作用下。产生了明显的移动。改变了其原来平整、均匀分布的表面特征。此现象文献中也曾有报道，在本实验中能重复出现。本文进一步分析讨论这种现象产生的原因，对比了不同成像模式下AFM针尖对样品表面的影响。结果表明，用Tapping Mode(TM)，扫描过程对样品表面几乎不产生影响，但是Non Contact Mode(NCM)在扫描过程中对样品表面产生了损伤作用。证明了TM模式更适合于对生物样品的研究。实验还发现这种损伤的程度和扫描范围的大小、针尖扫描的方向有着很大关系。     

Finishing effect of abrasive flow machining on micro slit fabricated by wire-EDM

This experimental research use the method of abrasive flow machining (AFM) to evaluate the characteristics of various levels of roughness and finishing of the complex shaped micro slits fabricated by wire electrical discharge machining (Wire-EDM). An investigative methodology based on the Taguchi experimental method for the micro slits of biomedicine was developed to determine the parameters of AFM, including abrasive particle size, concentration, extrusion pressure and machining time. The parameters that influenced the machining quality of the micro slits were also analyzed. Furthermore, in the shape precision of the micro slit fabricated by wire-EDM and subsequently fine-finished by AFM was also elucidated using a scanning electron microscope (SEM). The significant machining parameters and the optimal combinations of the machining parameters were identified by ANOVA (analysis of variation) and the S/N (-to-noise) ratio response graph. ANOVA was proposed to obtain the surface finishing and the shape precision in this study.     

表面活性剂及复配在云母片上吸附的AFM研究

借助原子力显微镜对十二烷基硫酸钠(SDS)/十六烷基三甲基溴化铵(CTAB)及其复配溶液在云母表面的吸附以及吸附后不同的表面形貌和微摩擦特性进行了研究,探讨了摩擦力与表面形貌的关系。结果表明,SDS与CTAB表面活性剂分子都以纳米级颗粒吸附于云母表面;摩擦力受表面形貌的影响,但不成一一对应关系;在0.8和2倍临界胶束浓度(CMC)下,SDS/CTAB=1∶1复配溶液在云母表面吸附后的润滑效应较其它配比好。     

基于原子力显微镜的线宽粗糙度测量

给出采用原子力显微镜(Atomic force microscope,AFM)测量线宽粗糙度(Line width roughness,LWR)的分析步骤。分析线宽和LWR及其偏差随刻线横截面位置的高度变化的关系,线宽及其偏差和LWR及其偏差随刻线横截面位置的高度值增加而减小。分别采用四种边缘提取算子提取了碳纳米管针尖AFM测量的刻线顶部线宽边缘,计算了刻线顶部线宽和LWR,顶部线宽和LWR测量结果对边缘提取算子不敏感。结合被测单晶硅台阶的顶表面和底表面加工方法,提出采用各扫描线轮廓高度相等的方法校正AFM压电驱动器的z向非线性。比较了采用普通氮化硅探针针尖、超尖针尖以及碳纳米管针尖AFM测量名义线宽为1 000 nm刻线LWR的结果,显示采用三种针尖的LWR测量结果存在差异,但考虑到AFM分辨率,可认为测量结果基本相同。因此,为更精确描述刻线边缘,必须提高AFM分辨率。     

Effect of the molecular weight on deformation states of the polystyrene film by AFM single scanning

Nanobundles patterns can be formed on the surface of most thermoplastic polymers when the atomic force microscope (AFM)‐based nanomechanical machining method is employed to scratch their surfaces. Such patterns are reviewed as three‐dimensional sine‐wave structures. In the present study, the single‐line scratch test is used firstly to study different removal states of the polystyrene (PS) polymer with different molecular weights (MWs). Effects of the scratching direction and the scratching velocity on deformation of the PS film and the state of the removed materials are also investigated. Single‐wear box test is then employed to study the possibility of forming bundle structures on PS films with different MWs. The experimental results show that the state between the tip and the sample plays a key role in the nano machining process. If the contact radius between the AFM tip and the polymer surface is larger than the chain end‐to‐end distance, it is designated as the “cutting” state that means the area of both side ridges is less than the area of the groove and materials are removed. If the contact radius is less than the chain end‐to‐end distance, it is designated as the “plowing” state that means the area of both side ridges is larger than the area of the groove and no materials are removed at all. For the perfect bundles formation on the PS film, the plowing state is ideal condition for the larger MW polymers because of the chains’ entanglement. SCANNING 35:308‐315, 2013. © 2012 Wiley Periodicals, Inc.     

Atomic force microscopy of histological sections using a new electron beam etching method

In order to examine histological sections of the rat vomeronasal epithelium with the atomic force microscope (AFM), we developed an electron beam etching method that improves the resolution of AFM images. This method results in AFM images comparable to those obtained with the transmission electron microscope (TEM). Ultrathin tissue sections embedded in epoxy resin were observed before and after the treatment with electron beam radiation. Before electron beam treatment, epithelial structures such as the microvilli surface, dendritic processes, the supporting cell layers and the neuronal cell layers were all visible using the AFM. However, only a few subcellular structures could also be resolved. The AFM images were not as clear as those obtained with the TEM. After electron beam treatment, however, the resolution of AFM images was greatly improved. Most of the subcellular structures observed in TEM images, including the inner membrane of mitochondria, ciliary-structure precursor body, junctional complexes between the neurons and supporting cells, and individual microvilli were now visible in the AFM images. The electron beam treatment appeared to melt the embedding resin, bringing subcellular structures into high relief. The result of this study suggests that electron beam etching of histological samples may provide a new method for the study of subcellular structure using the AFM.     

Optimization of the film coating process for polymer blends by the grey-based Taguchi method

The purpose of this paper is to find the optimum conditions of the film coating process for polymer blends and the influence of major processing parameters on the morphological properties of the material surface has been discussed. The surface roughness is regarded as the target characteristic of the smaller-the-better system. In order to achieve the aim of the multiple-response process of robustness, the grey-based Taguchi method is proposed. Nine experimental trials based on the L₉(3⁴) orthogonal array are conducted to determine the optimum processing conditions, the significant factor levels, and the percent contributions together with the analysis of variance (ANOVA). Also, confirmation experiments are performed to verify that the experimental results are reproducible. Moreover, atomic force microscopy (AFM) can be carried out with 3D atomic resolution in air for the measurement and analysis of the precision surface .