Search

Understanding the nanoscale electrostatic interaction between a conductive atomic force microscopy (AFM) probe and a dielectric film is central to the operation of various nanoscale dielectric microscopies and determination of dielectric properties of the film. There is no simple analytical description of the electrostatic interaction generated in the confined probe-sample geometry for neither static nor dynamic AFM modes used in dielectric measurements. An accurate description of the involved physics is obtained only by means of a finite element analysis modeling of the system. However, the alternative to using the numerical analysis is not very popular due to being slower and requiring relatively high computation resources. In this work, we revised the contributions from different parts of the AFM probe to the probe-sample capacitance by both analytical and numerical methods. We tried to reconciliate the two approaches and observed the differences as a function of geometry and material parameters. Under various noise levels, the efficiency of an analytical model was tested against a finite element analysis that captures in detail the electrostatic interaction in AFM-based dielectric measurements. The investigation was performed in both spectroscopic force-distance curves and constant height scans with measurements for deflection and frequency of the AFM probe. The obtained measurement sensitivities are relevant in selecting the optimal scanning mode and its operational parameters for a given film thicknesses and dielectric constants but also show the critical role of the numerical analysis to the correct interpretation of the measurements. [ABSTRACT FROM AUTHOR]

The accuracy of a CNC machine tool is one of the most important parameters that make the geometry and dimensions of the work pieces comply with the tolerance limits specified through the designer's technical drawing. When a machine tool is handed over to the customer it is compliant in terms of the accuracy limits specified in the documentation but, after a time interval of usage, because of the wear of the components in relative motion and machine exploitation conditions. This work suggests an innovating method of testing the accuracy of a CNC machine tool by using the "calliper", with a view to enhancing the positioning accuracy of the feed kinematic linkages. After designing and manufacturing this device, the measurement of the target points on the coordinate measuring machine is necessary, so that this device becomes a "calliper". For inspecting the machine tool, the "calliper" is located on the machine table, being measured at the target points by means of the probe with the tactile shooter that belongs to the machine. The measurement results are stored and compared to the results of the measurements performed through the coordinate measuring machine. In function of the two measurements the related corrections of the errors will be done in the software of machine tool numerical control. [ABSTRACT FROM AUTHOR]

CNC Gantry Type Machine Tools with great distance between slides (gantry milling machines, plasma and laser gantry cutting machines, vertical lathe machines, etc) are used extensively in the manufacturing of large and long components. Because this type of Machine Tool it is used to machine large parts at high speeds, significant heat will be produce at the cutting tool level and transmitted thru the tool holder to the ram or spindled and then to the ream case guideways. Heat it's also generated when using a ball screw actuation for the main axis because of the friction forces at the ball screw level. Due to material expansion, the heat generated during the machining process can influence the precision of the Machine Tool. In this paper, finite element analysis (FEA) was used to analyze the influence of the temperature on the rigidity of the Machine Tool guideways. The results of the studies performed will provide the machine tool builder with important information regarding the points that need to be address in order to help in improving thermal compensation. [ABSTRACT FROM AUTHOR]

Over the past several decades, atomic force microscopy (AFM) has advanced from a technique used primarily for surface topography imaging to one capable of characterizing a range of chemical, mechanical, electrical, and magnetic material properties with subnanometer resolution. In this review, we focus on AFM as a nanoscale mechanical property characterization tool and examine various AFM contact and intermittent contact modes that add mechanical contrast to an imaged surface. Through detailed analysis of the tip-sample contact mechanics, this contrast can be converted into quantitative measurements of various nanomechanical properties including elastic modulus, shear modulus, wear rate, adhesion, and viscoelasticity. Different AFM modes that provide such measurements are compared and contrasted in this work on a wide range of materials including ceramics, metals, semiconductors, polymers, and biomaterials. In the last few years, considerable improvements have been made in terms of fast imaging capabilities, tip preservation, and quantitative mechanics for multifrequency measurements as well as well-known AFM modes like amplitude modulation and peak-force tapping. In line with these developments, a major highlight of this review is the discussion of the operation and capabilities of one such mode, namely, intermittent contact resonance AFM (ICR-AFM). The applications of ICR-AFM to nanoscale surface and subsurface quantitative mechanical characterizations are reviewed with specific examples provided for thin polymeric films and patterned nanostructures of organosilicate dielectric materials. The combination of AFM-based mechanical characterization with AFM-based chemical spectroscopy to allow nanoscale structure-property characterization is also discussed and demonstrated for the analysis of low-k dielectric/copper nanoelectronic interconnect structures and further highlights synergistic advances in the AFM field. [ABSTRACT FROM AUTHOR]

A more inclusive and detailed measurement of various physical interactions is enabled by the advance of high-speed data digitization. For surface potential characterization, this was demonstrated recently in terms of open-loop amplitude modulation Kelvin probe force microscopy (OL AM-KPFM). Its counterpart, namely open-loop frequency modulation Kelvin probe force microscopy (OL FM-KPFM), is examined here across different materials and under various bias voltages in the form of OL sideband FM-KPFM. In this implementation the changes in the amplitude and resonance frequency of the cantilever were continuously tracked as a conductive AFM probe was modulated by a 2 kHz AC bias voltage around the first eigenmode frequency of the cantilever. The contact potential difference (CPD) between the AFM probe and sample was determined from the time series analysis of the high-speed 4 MHz digitized amplitude and frequency signals of the OL sideband FM-KPFM mode. This interpretation is demonstrated to be superior to the analysis of the parabolic bias dependent response, which is more commonly used to extract the CPD in OL KPFM modes. The measured OL sideband FM-KPFM amplitude and frequency responses are directly related to the electrostatic force and force-gradient between the AFM probe and sample, respectively. As a result, clear distinction was observed for the determined CPD in each of these cases across materials of different surface potentials, with far superior spatial resolution when the force-gradient detection was used. In addition, the CPD values obtained from OL sideband FM-KPFM amplitude and frequency measurements perfectly matched those determined from their closed-loop AM-KPFM and FM-KPFM counterparts, respectively. [ABSTRACT FROM AUTHOR]

In the current industry, industrial robots are gaining more and more ground to classical positioning methods, especially due to the ratio of workspace / volume of the industrial robot. For this reason, methods of minimization of trajectory errors are necessary. Among the multitudes of factors that affect the trajectory precision is the difference between the programmed transient regime and the measured transient regime of the kinematic link used in the structure of the industrial robots. In this paper is presented the method of measurement the transient regimes of the end-effector and a method of compensation of the trajectory error. [ABSTRACT FROM AUTHOR]

The purpose of this article is to present the research on the influence of the dimensional deviations of the mechanical elements in the kinematic structures of the SCARA industrial robots regarding the positioning precision and trajectory error. In this article the direct kinematics method is used to calculate the positioning of the end-effector and generate the trajectory simulation with and without dimensional deviations. [ABSTRACT FROM AUTHOR]

Olfactory responses are intensely enhanced with the addition of endogenous and engineered primarily-elemental small zinc nanoparticles (NPs). With aging, oxidation of these Zn nanoparticles eliminated the observed enhancement. The design of a polyethylene glycol coating to meet storage requirements of engineered zinc nanoparticles is evaluated to achieve maximal olfactory benefit. The zinc nanoparticles were covered with 1000 g/mol or 400 g/mol molecular weight polyethylene glycol (PEG). Non-PEGylated and PEGylated zinc nanoparticles were tested by electroolfactogram with isolated rat olfactory epithelium and odorant responses evoked by the mixture of eugenol, ethyl butyrate and (±) carvone after storage at 278 K (5 oC), 303 K (30 oC) and 323 K (50 oC). The particles were analyzed by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and laser Doppler velocimetry. Our data indicate that stored ZnPEG400 nanoparticles maintain physiologically-consistent olfactory enhancement for over 300 days. These engineered Nanoparticles support future applications in olfactory research, sensitive detection, and medicine. [ABSTRACT FROM AUTHOR]

Recent trends in the machine tools domain have focused on improving the manufacturing performances by increasing the feed rates and acceleration values. In this context, the stiffness of the constructive elements which form the mechanical part of the kinematic feed chains need to be studied in order to determine the machine tool dynamic behavior. This study plays a very important role in the correct dimensioning of the feed chain structure and in establishing an optimum control law for the closed-loop system. The present paper presents an experimental study which demonstrates the influence of the whole kinematic feed chain stiffness on the positioning precision of the moving table. Experimental tests were carried out on a test bed which uses the indirect position measuring system, in which case all the external disturbances affecting the mechanical part are found in the values of the positioning precision parameters. [ABSTRACT FROM AUTHOR]

Friction represents one of the major sources of disturbing forces which affect the functioning of the kinematic feed chains from CNC machine tools. Its influence reflects on the positioning precision values, having a negative impact on the table movement and leading to stationary errors, stick-slip motion and trajectory errors. The present paper presents an experimental analysis regarding the influence of the friction forces which appear in the linear rolling guideways on the positioning precision of kinematic feed chains. The rolling guideways present the advantages of a good behavior in terms of axis stability at low speeds and also for achieving high positioning speeds. Concerning the friction coefficient values, rolling and hydrostatic guideways are most suitable for the construction of high speed and high precision kinematic feed chains; in these cases, the friction coefficient has small values, which maintain quasi-constant against the feed rate [ABSTRACT FROM AUTHOR]

In the field of cutting processes, the current trend is to produce more and more in the shortest time. A solution to this consists of shortening the total machining time by increasing the motion speeds of the tool supply systems that equip the machining centers, thus minimizing the idle time needed for replacing the tools during the machining process. Actual idle times needed for replacing the tools through the supply systems are high, especially for machining housing type work pieces on boring and milling machining centres. With the help of the method being proposed through this work, the motion times of the moving elements in the structure of the tool supply systems can be decreased, by following up, at the same time, their dynamic behavior. [ABSTRACT FROM AUTHOR]

The total machining time for a part produced on machining centers is influenced, besides the actual machining time, by the auxiliary times which include the automatic changing of the tools. In order to increase the productivity of machining centers, the research presented in this paper has focused on enhancing the movement speed of an automatic tool feeding system. Increasing the movement speed of the mechanism`s components has led to the appearance of unwanted side effects, such as shocks and vibrations. In order to minimize these effects, we have proposed and tested a new solution to adjust the braking regime. [ABSTRACT FROM AUTHOR]

In order to shorten the auxiliary times regarding tool and workpiece changing, conventional machine tools are equipped with automatic tool changers and automatic pallet changers, thus becoming machining centers. Reducing the time consumed with the change of the workpiece to follow in machining implies the existence of another table - i.e. the pallet - on which the workpiece is positioned and clamped, while on the working area of the machine another part is manufactured. This paper is presenting a new automatic pallet changer mechanism which is hydraulically driven, along with its guiding and transmission systems. [ABSTRACT FROM AUTHOR]

Growing performance demands in the mechanical manufacturing field have lead to a great development of the machine tools domain, regarding especially the productivity and the manufacturing precision. When equipping a machine tool with an automatic tool changer and an automatic pallet mechanism, the obtained result is a machining center. For small series products, milling machining centers fulfill the precision and productivity requirements, through the advantages of a reduced auxiliary time and reduced operating errors. This paper presents a new technical solution of the rotary table indexing mechanism used on milling machining centers, which offers a very high positioning precision, by using a curvic coupling and a hydraulically driven table clamp/unclamp mechanism. [ABSTRACT FROM AUTHOR]

A necessary step in advancing the use of polyethyleneglycol (PEG)surface coatings in critical biotechnological applications such ascancer treatments is to provide direct and reliable nanoscale propertycharacterization. Measurements for such characterization are currentlyprovided by scanning probe methods, which are capable of assessingheterogeneity of both surface coverage and properties with nanoscalespatial resolution. In particular, atomic force microscopy (AFM) canbe used to detect and quantify the heterogeneity of surface coverage,whereas atomic force spectroscopy can be used to determine mechanicalproperties, thereby revealing possible heterogeneity of propertieswithin coatings. In this work, AFM and force spectroscopy were usedto characterize the morphology and mechanical properties of thiol-functionalizedPEG surface coatings on flat gold substrates in aqueous PEG solution.Thiol-functionalized PEG offers a direct and simple method of attachmentto gold substrates without intermediate anchoring layers and thereforecan be exploited in developing PEG-functionalized gold nanoparticles.AFM was used to investigate the morphology of the PEG coatings asa function of molecular weight; the commonly observed coverage wasin the form of sparse, brushlike islands. Similarly, force spectroscopywas utilized to study the mechanical properties of the PEG coatingsin compression and tension as a function of molecular weight. A constitutivedescription of the mechanical properties of PEG brushes was achievedthrough a combinatorial analysis of the statistical responses acquiredin both compression and tension tests. Such a statistical characterizationprovides a straightforward procedure to assess the nanoscale heterogeneityin the morphology and properties of PEG coverage. [ABSTRACT FROM AUTHOR]

In this work, the ultimate bending strengths of as-grown Si and fully oxidized Si nanowires (NWs) were investigated by using a new atomic force microscopy (AFM) bending method. NWs dispersed on Si substrates were bent into hook and loop configurations by AFM manipulation. The adhesion between NWs and the substrate provided sufficient restraint to retain NWs in imposed bent states and allowed subsequent AFM imaging. The stress and friction force distributions along the bent NWs were calculated based on the in-plane configurations of the NWs in the AFM images. As revealed from the last-achieved bending state, before fracture, fracture strengths close to the ideal strength of materials were attained in these measurements: 17.3 GPa for Si NWs and 6.2 GPa for fully oxidized Si NWs. [ABSTRACT FROM PUBLISHER]

The paper is a synthetic study of the author's results regarding the possibility and advantages of the practical use of sexual pheromones. Synthetic sexual pheromones have been proved by ecological studies to be an efficient method both for the monitoring and control of pest insects. The efficient practical use of pheromones depends on the knowledge we have about the biology, ecology and behaviour of the target species. We present the concrete results obtained during the study of some species of harmful Lepidoptera Noctuidae in agroecosystems (with special reference to Mamestra brassicae L.), the research activity taking place from 1980 to 2000. The role of chemical mediators in general is suggested as ecotechnologies protecting the ecosystems and the environment. [ABSTRACT FROM AUTHOR]

Atomic force acoustic microscopy (AFAM) was used to quantitatively determine material indentation moduli by measuring local mechanical responses. A dual reference method has been shown to be capable of extracting the modulus of a material within 3% of the calculated expected value without any assumptions of the probe’s mechanical properties. The use of this developed method also allows for the calculation of the maximum precision in the quantitative determination of the indentation modulus of materials using AFAM. A parallel analysis of the single and dual reference AFAM techniques isolates the inaccuracy induced by the assumption that the indentation modulus of the atomic force microscopy probe used is the same as bulk silicon. [ABSTRACT FROM AUTHOR]

A fundamental study of two turbulent, directly opposed impinging jets in a stagnant ambient fluid, unconfined or uninfluenced by far-field walls, is presented. By experimental investigation and numerical modeling the fundamental characteristics of direct impingement of two turbulent axisymmetric round jets under seven different geometrical and flow-rate configurations (L* =L/d = {5,10,20}, where L is nozzle to nozzle separation distance and d is nozzle diameter, and Re = ρU0d/µ = {1500, 4500, 7500, 11000}, where ρ is fluid density, µ is dynamic viscosity of fluid, and U0 is average initial velocity of fluid) are discussed. Flow visualization and velocity measurements performed using various laser-based techniques have revealed the effects of Reynolds number Re and dimensionless nozzle to nozzle separation L* on the complex flow structure. Similarity analysis of the initial freejet development and developing radial jet found Re = 11 x 10³ and L* = 20 as the only case where the freejets exhibit a self-preserving development. However, the jets show significant growth with axial and radial distance for Re = 7.5 x 10³ and L* = 20. All other experimental cases show little or no axial growth as a result of shorter development length. When used to simulate the present flow, the standard k-ε turbulence model showed little disagreement between computed and experimental mean velocities and poor predictions as far as the jet growth rates are concerned. [ABSTRACT FROM AUTHOR]

The intermittent contact resonance atomic force microscopy (ICR-AFM) mode proposed here is a new frequency modulation technique performed in scanning force controlled AFM modes like force volume or peak force tapping. It consists of tracking the change in the resonance frequency of an eigenmode of a driven AFM cantilever during scanning as the AFM probe intermittently contacts a surface at a controlled applied maximum force (setpoint). A high speed data capture was used during individual oscillations to obtain detailed contact stiffness–force curve measurements on a two-phase polystyrene/poly(methyl methacrylate) film with sub-micrometer size domains. Through a suitable normalization, the measurements were analyzed by linear fits to provide an improved quantitative characterization of these materials in terms of their elastic moduli and adhesive properties. [ABSTRACT FROM AUTHOR]

In this work, a new procedure is demonstrated to retrieve the conservative and dissipative contributions to contact resonance atomic force microscopy (CR-AFM) measurements from the contact resonance frequency and resonance amplitude. By simultaneously tracking the CR-AFM frequency and amplitude during contact AFM scanning, the contact stiffness and damping were mapped with nanoscale resolution on copper (Cu) interconnects and low-k dielectric materials. A detailed surface mechanical characterization of the two materials and their interfaces was performed in terms of elastic moduli and contact damping coefficients by considering the system dynamics and included contact mechanics. Using Cu as a reference material, the CR-AFM measurements on the patterned structures showed a significant increase in the elastic modulus of the low-k dielectric material compared with that of a blanket pristine film. Such an increase in the elastic modulus suggests an enhancement in the densification of low-k dielectric films during patterning. In addition, the subsurface response of the materials was investigated in load-dependent CR-AFM point measurements and in this way a depth dimension was added to the common CR-AFM surface characterization. With the new proposed measurement procedure and analysis, the present investigation provides new insights into characterization of surface and subsurface mechanical responses of nanoscale structures and the integrity of their interfaces. [ABSTRACT FROM AUTHOR]

Abstract: Structure–property relationships for methyl-terminated alkyl self-assembled monolayers (SAMs) are developed using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM). NEXAFS C K-edge spectra are used to compute the dichroic ratio, which provides a quantitative measure of the molecular structure. AFM data are analyzed with an elastic adhesive contact model, modified by a first-order elastic perturbation method to include substrate effects, to extract the monolayer mechanical properties. Using this approach, the measured mechanical properties are not influenced by the substrate, which allows universal structure–property relationships to be developed for methyl-terminated alkyl SAMs. [Copyright &y& Elsevier]