Towards a nanomechanical basis for temporary adhesion in barnacle cyprids (Semibalanus balanoides)

Cypris larvae of barnacles are able to use a rapidly reversible temporary adhesion mechanism for exploring immersed surfaces. Despite decades of research interest, the means by which cyprids maintain attachment with surfaces prior to permanent settlement remain poorly understood. Here, we present novel observations on the morphology of 'footprints' of a putative adhesive secretion deposited by cyprids during surface exploration. Atomic force microscopy (AFM) was used to image footprints at high resolution and to acquire measurements of interaction forces. R-CH3- and R-NH2-terminated glass surfaces were used for comparison of footprint morphology, and it was noted that on R-NH2 each footprint comprised three times the volume of material deposited for footprints on R-CH3. Direct scaling of adhesion forces derived from AFM measurements did not adequately predict the real attachment tenacity of cyprids, and it is suggested that a mixture of 'wet' and 'dry' adhesive mechanisms may be at work in cyprid adhesion. High-resolution images of cyprid footprints are presented that correlate well with the known morphology of the attachment structures.     

Classification of the pre-settlement behaviour of barnacle cyprids

Barnacle cyprids exhibit a complex swimming and exploratory behaviour on surfaces and settlement is a consequence of extensive surface probing and selection of suitable settlement sites. In this work, the behaviour of cyprids in their pre-settlement phase was studied by three-dimensional video stereoscopy. With this technique, three-dimensional trajectories were obtained that were quantitatively analysed. The velocity during vertical sinking of cyprids of Balanus amphitrite was used with a modified form of Stokes'' law to calculate their mean body density. Furthermore, a classification of the swimming patterns allowed the extension of existing models describing cyprid locomotion and swimming behaviour. The patterns were characterized with respect to their occurrence, transition between patterns and their velocity distribution, and motions were identified that led to surface contacts. This analysis provides a classification framework, which can assist future attempts to identify behavioural responses of cyprids to specific settlement cues.     

Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy

Submicrometer-sized particles of poly(N-isopropylacrylamide) (PNIPAM) are synthesized by surfactant-free radical polymerization. The morphology and nanomechanical properties of individual, isolated PNIPAM microgel particles at the silicon/air and silicon/water interfaces, below and above the PNIPAM volume-phase-transition temperature (VPTT), are probed by atomic force microscopy. In air, and in water below the VPTT, the PNIPAM spheres are flattened and adopt a pancakelike shape. Interestingly, above the VPTT the microgels adopt a more spherical form with increased height and decreased width, which is attributed to reduced interactions of the particles with the substrate. The elastic modulus calculated from force-indentation curves obtained for individual microgel spheres reveals that the stiffness of the particle's surface decreases by two orders of magnitude upon swelling in water. Additionally, the modulus of the PNIPAM spheres in water increases by one order of magnitude when crossing the VPTT from the swollen to the collapsed states, indicating a more compact chain packing at the particle surface.     

Application of dynamic impedance spectroscopy to atomic force microscopy

Abstract

Atomic force microscopy (AFM) is a universal imaging technique, while impedance spectroscopy is a fundamental method of determining the electrical properties of materials. It is useful to combine those techniques to obtain the spatial distribution of an impedance vector. This paper proposes a new combining approach utilizing multifrequency scanning and simultaneous AFM scanning of an investigated surface.     

原子力显微镜与X射线光电子能谱对ITO表面改性的研究

采用氧气等离子体(OP)处理对氧化铟锡(ITO)薄膜进行表面改性,通过原子力显微镜(AFM)、X射线光电子能谱(XPS)和四探针等测试手段对薄膜样品进行表征,研究了OP处理对ITO表面性质的影响.实验结果表明OP处理有效去除了ITO表面的污染物,优化了ITO表面的化学组分,降低了ITO表面的粗糙度和方块电阻,改善了ITO的表面形态.与此同时,通过XPS监测研究了OP处理后ITO表面化学组分随老化时间的变化,结果显示经过优化的化学组分随老化时间增加而逐渐退化.另外,以OP处理后经过不同老化时间的ITO样品作为空穴注入电极,制备了有机电致发光器件(OELD),通过测试器件的电压-电流-亮度特性,进一步研究了ITO表面性质对于OELD光电性能的影响.     

原子力显微镜及在膜科学技术研究中的应用

随着科学技术的进步 ,新型的观测仪器的出现为研究提供了先进的手段 .介绍了原子力显微镜的基本探测原理及在膜科学技术中的应用 ,由于原子力显微镜具有空前的高分辨率 ,为其在膜的表面形态与结构等的观测方面开启了一扇新的大门 .     

Water distribution at solid/liquid interfaces visualized by frequency modulation atomic force microscopy

Interfacial phenomena at solid/water interfaces play an important role in a wide range of industrial technologies and biological processes. However, it has been a great challenge to directly probe the molecular-scale behavior of water at solid/water interfaces. Recently, there have been tremendous advancements in frequency modulation atomic force microscopy (FM-AFM), enabling its operation in liquids with atomic resolution. The high spatial and force resolutions of FM-AFM have enabled the visualization of one-dimensional (1D) profiles of the hydration force, two-dimensional (2D) images of hydration layers and three-dimensional (3D) images of the water distribution at solid/water interfaces. Here I present an overview of the recent advances in FM-AFM instrumentation and its applications to the study of solid/water interfaces.     

Water distribution at solid/liquid interfaces visualized by frequency modulation atomic force microscopy

Abstract

Interfacial phenomena at solid/water interfaces play an important role in a wide range of industrial technologies and biological processes. However, it has been a great challenge to directly probe the molecular-scale behavior of water at solid/water interfaces. Recently, there have been tremendous advancements in frequency modulation atomic force microscopy (FM-AFM), enabling its operation in liquids with atomic resolution. The high spatial and force resolutions of FM-AFM have enabled the visualization of one-dimensional (1D) profiles of the hydration force, two-dimensional (2D) images of hydration layers and three-dimensional (3D) images of the water distribution at solid/water interfaces. Here I present an overview of the recent advances in FM-AFM instrumentation and its applications to the study of solid/water interfaces.     

Atomic force microscopy and X-ray photoelectron spectroscopy evaluation of adhesion and nanostructure of thin Cr films

Chromium (Cr) thin films were deposited on float glass using electron beam (e-beam) physical vapor deposition and radio frequency (RF) magnetron sputtering techniques. Surface morphology of these Cr films was studied using atomic force microscopy (AFM). The e-beam deposited Cr films consisted of isolated surface mounds while in RF sputtered samples, these mounds combined to form larger islands. Lower surface adhesive properties were observed for e-beam deposited films, as determined from AFM force-distance curves, presumably due to the nanostructural differences. Similar amounts of adsorbed atmospheric carbonaceous contaminants and water vapor were detected on samples deposited using both methods with e-beam deposited samples having additional carbide species, as determined by X-ray photoelectron spectroscopy data. The dominant crystallographic plane in both e-beam deposited and RF sputtered Cr thin films was (110) of body-centered cubic Cr metal structure as determined from X-ray diffraction data. Weak (211) reflection was also observed in RF sputtered samples and was attributed to a different thin Cr film condensation and growth mechanism which resulted in nanostructural differences between films deposited using two different methods.     

Atomic force microscopy and atomic force acoustic microscopy characterization of photo-induced changes in some Ge-As-S amorphous films

Amorphous Ge₂₇As₁₃S₆₀, Ge₁₄As₂₇S₅₉ and Ge₁₆As₂₆S₅₈ thin films were prepared by thermal evaporation. Well annealed films were photodarkened by the photons with energy little exceeding the band gap energy. Using Atomic Force Microscopy we observed significant photoexpansion of studied films. Atomic Force Acoustic Microscopy revealed domains like structure of the surface and near surface parts of the samples which one was found to be more disintegrated after illumination.     

Long Jumps of an Organic Molecule Induced by Atomic Force Microscopy Manipulation

Non‐contact atomic force microscopy at cryogenic temperatures is used for the controlled lateral manipulation of individual 3,4,9,10‐perylene‐tetracarboxylicacid‐dianhydride (PTCDA) molecules on the Ag(111) surface. The molecules are moved along the [‐110] direction of the Ag lattice in the regime of repulsive tip‐molecule forces performing discrete jumps that span distances from single to multiple lattice spacings. The analysis of the two‐dimensional force field measured before and during the manipulation reveals that the displacement beyond nearest neighbor sites cannot be explained by long range tip‐molecule forces but instead has to involve an energy transfer to translational modes of the molecule. Combined with the results of the simultaneous measurement of the energy dissipation, these findings allow to identify a likely manipulation mechanism and provide insight into the process of energy transfer between excited large molecules and metal surfaces. Furthermore, implications for the theoretical treatment of NC‐AFM based molecule manipulation are discussed.     

Atomic force microscopy and the mechanism of fatigue crack growth

Fatigue crack test was performed using a grain-orientated 3% silicon iron under constant amplitude loading. Growth behaviour of the fatigue crack and slip deformation behaviour near the crack tip were observed in detail by using an atomic force microscope. In the lower K region, only one preferential slip system of this material operated and the fatigue crack grew along that slip plane. It was found that constraint of slip deformation due to cyclic strain hardening resulted in crack arrest and crack branching. The fatigue crack grew in a zigzag manner as a result of such successive crack branching and deflection. In the high K region, two preferential slip systems operated simultaneously to an almost identical extent and the fatigue crack grew in a direction perpendicular to the loading axis. The slipping distance in one loading cycle was measured quantitatively by using the image processing technique and the crack growth mechanism is discussed.     

原子力显微镜在合成膜表征中的应用

原子力显微镜(AFM)在其发明不久即应用于膜科学领域，并以其无可比拟的优势获得了广泛的应用．它不仅可以定性地表征膜的表面三维形貌，还能定量地研究膜表面的粗糙度、孔径大小和分布及球粒尺寸．综述了近年来原子力显微镜在合成膜表征中的应用，对其中几个重要方面进行了举例介绍．     

Antibacterial action of lipidic nanoemulsions using atomic force microscopy and scanning electron microscopy on Escherichia coli

The present study demonstrates the mechanism of bactericidal effect rendered by cationic and non-cationic lipidic emulsions using atomic force microscopy (AFM) and scanning electron microscopy. The AFM images of treated Escherichia coli cells indicated the conformational alteration from rod-shaped bacteria to a fluid-flattened structure with the presence of pore in the centre of bacterium, indicating the cell lysis. Root mean square roughness increased substantially due to exposure of underlying rugose peptidoglycan layer when treated with non-cationized lipidic nanoemulsions (NCLE). The cationised-lipidic-emulsion (CLE) treated E. coli cells frequently showed division septa along the length of E. coli which was not visible in non-cationised treated bacterial cells. The enhanced adhesion between CLE and negatively charged bacteria leads to lesser time required to kill the bacteria as compared to NCLE.     

Multifrequency imaging in the intermittent contact mode of atomic force microscopy: beyond phase imaging

The cantilever dynamics in single-frequency scanning probe microscopy (SPM) are undefined due to having only two output variables, which leads to poorly understood image contrast. To address this shortcoming, generalized phase imaging scanning probe microscopy (GP-SPM), based on broad band detection and multi-eigenmode operation, is developed and demonstrated on diamond nanoparticles with different functionalization layers. It is shown that rich information on tip-surface interactions can be acquired by separating the response amplitude, instant resonance frequency, and quality factor. The obtained data allow high-resolution imaging even in the ambient environment. By tuning the strength of tip-surface interaction, different surface functionalizations can be discerned.     

Atomic force microscopy study of Mo (110) surface topology after high temperature homoepitaxy

In this paper we report experimental results on investigation of Mo (110) single crystals surface topology carried out using AFM technique after high-temperature homoepitaxy within the frame of deposition rates 1-40 ML/s and in the interval of substrate temperatures 1900 °C-2300 °C. The systems of atomically flat steps on the surface of single crystal samples were observed. Typical height of the steps was in the range 1-4 of (110) parallel lattice plane spacing, with width being about 50-70 nm. High temperature homoepitaxy of Mo leads to formation of micro-crystals with dimensions up to 150 μ in width and few micrometres in height. Huge monatomic steps up to 5-10 μ in width were observed on flat (110) Mo micro-crystal planes slightly declined to the substrate surface. The root-mean-square (RMS) roughness of the micro-crystal surfaces achieves the values of 0.2 nm which is determined by the presence of monoatomic steps. The residual pattern of spiral growth was also observed on the top of (110) micro-crystal surfaces.     

X-ray photoelectron spectroscopy and conducting atomic force microscopy investigations on dual ion beam sputtered MgO ultrathin films

Ultrathin films of MgO (~ 6 nm) were deposited on Si(100) using dual ion beam sputtering in different partial pressures of oxygen. These thin films were characterized by X-ray photoelectron spectroscopy (XPS) for chemical state analysis and conducting atomic force microscopy for topography and local conductivity map. No trace of metal Mg was evidenced in these MgO films. The XPS analysis clearly brought out the formation of oxygen interstitials and Mg(OH)₂ primarily due to the presence of residual water vapors in the chamber. An optimum value of oxygen partial pressure of ~ 4.4 × 10^− 2 Pa is identified with regard to homogeneity of film and stoichiometry across the film thickness (O:Mg::0.93-0.97). The local conductivity mapping investigations also established the film homogeneity in respect of electrical resistivity. Non-linear local current-voltage curves revealed typical tunneling characteristics with barrier width of ~ 5.6 nm and barrier height of ~ 0.92 eV.     

Surface evaluation of whey protein films by atomic force microscopy and water vapour permeability analysis

The atomic force microscopy (AFM) technique is a powerful tool for studying surfaces and has been used to provide qualitative and quantitative information about nanometer‐scale matter properties that are often inaccessible by any other experimental technique. In this work AFM was used to evaluate the surfaces of edible films produced with whey protein concentrate (WPC). The morphology and the roughness of the films were analysed. The effects of WPC and plasticizer concentration were characterized in terms of water vapour permeability (WVP) and roughness parameters. Roughness was calculated through the images captured with AFM. AFM can be useful to identify structural changes of the film resulting from sample preparation. The results showed a relation between water vapour permeability and area roughness, through different sample preparation. The analyses of topography through roughness obtained with AFM, demonstrated the correlation between the morphology of the film, obtained with nanometer resolution and WVP. Copyright © 2004 John Wiley & Sons, Ltd.