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Hosaka, Sumio, Takayuki Takizawa, Daisuke Terauchi, You Yin y Hayato Sone. "Pico-Newton Controlled Step-in Mode NC-AFM Using a Quadrature Frequency Demodulator and a Slim Probe in Air for CD-AFM". Key Engineering Materials 497 (diciembre de 2011): 95–100. http://dx.doi.org/10.4028/www.scientific.net/kem.497.95.
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We have studied a step-in mode non-contact atomic force microscopy (NC-AFM) for precise measurement of fine and steep structure with nanometer resolution in air. When a high aspect structure is measured using step-in mode AFM with the sharpened and slim probe, it is required that AFM control has to be performed at a force of <1 nN in pico-Newton range to suppress the bending and slipping of the probe on slop. Using a home-made step-in mode NC-AFM using a quadrature frequency demodulator for resonant frequency shift of the cantilever, the NC-AFM demonstrated that Si steep structure was faithfully observed at about 2 pN in air.
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König, Thomas, Georg H. Simon, Lars Heinke, Leonid Lichtenstein y Markus Heyde. "Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy". Beilstein Journal of Nanotechnology 2 (3 de enero de 2011): 1–14. http://dx.doi.org/10.3762/bjnano.2.1.
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Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms.
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Chernoff, Ellen A. G., Donald A. Chernoff y Kevin Kjoller. "Contact and non-contact atomic-force microscopy of type I collagen". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 de agosto de 1993): 518–19. http://dx.doi.org/10.1017/s0424820100148423.
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Introduction. Type I collagen was examined using two types of atomic force microscopes (AFM) in a continuing effort to refine the process of obtaining molecular information from biological materials using scanning probe microscopy. Operating in air, a contact mode (Nanoscope II) and a non-contact mode AFM (Nanoscope III) were used to image collagen fibrils polymerized from pepsin-extracted type I bovine skin collagen adsorbed onto mica substrates. AFM is a practical method for high resolution examination of extracellular matrix material without the time consuming preparative techniques required for electron microscopy.Methods. For fibrillar collagen samples, Vitrogen 100 (Collagen Corporation, Palo Alto, CA) was prepared according to a modification of the procedure provided by Collagen Corp. for neutralized isotonic collagen gels. Monomeric collagen samples were prepared by diluting the vitrogen in 0.012M HCl.Images captured with the Nanoscope II AFM (Digital Instruments, Santa Barbara, CA) used a “J” scanner (horizontal range of 120 um).
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Carmichael, Stephen W. "Atomic Force Microscopy for Biologists". Microscopy Today 5, n.º 3 (abril de 1997): 3–4. http://dx.doi.org/10.1017/s1551929500060193.
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Atomic force microscopy (AFM) has proven to be very useful to material scientists and physicists. Biologists are only beginning to utilize the potential of this methodology. In a recent article, Tatsuo Ushiki, Jiro Hitomi, Shigeaki Ogura, Takeshi Umemoto, and Masatsugu Shigeno reviewed the applications of AFM to biologic studies.They began by reviewing the basic principles of AFM, emphasizing the value of the non-contact mode for visualizing the relatively “soft” surface of biologic specimens. They presented some examples of biologic images: DNA, chromosomes, and collagen fibrils. The specimens examined with the AFM did not need to be coated, theoretically offering a view with a smaller potential for artifacts. AFM images have the advantage of containing quantitative information about the sample height.
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Jalili, Nader, Mohsen Dadfarnia y Darren M. Dawson. "A Fresh Insight Into the Microcantilever-Sample Interaction Problem in Non-Contact Atomic Force Microscopy". Journal of Dynamic Systems, Measurement, and Control 126, n.º 2 (1 de junio de 2004): 327–35. http://dx.doi.org/10.1115/1.1767852.
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The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. The non-contact AFM offers unique advantages over other contemporary scanning probe techniques such as contact AFM and scanning tunneling microscopy, especially when utilized for reliable measurements of soft samples (e.g., biological species). Current AFM imaging techniques are often based on a lumped-parameters model and ordinary differential equation (ODE) representation of the micro-cantilevers coupled with an adhoc method for atomic interaction force estimation (especially in non-contact mode). Since the magnitude of the interaction force lies within the range of nano-Newtons to pica-Newtons, precise estimation of the atomic force is crucial for accurate topographical imaging. In contrast to the previously utilized lumped modeling methods, this paper aims at improving current AFM measurement technique through developing a general distributed-parameters base modeling approach that reveals greater insight into the fundamental characteristics of the microcantilever-sample interaction. For this, the governing equations of motion are derived in the global coordinates via the Hamilton’s Extended Principle. An interaction force identification scheme is then designed based on the original infinite dimensional distributed-parameters system which, in turn, reveals the unmeasurable distance between AFM tip and sample surface. Numerical simulations are provided to support these claims.
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Yoo, Ryan YK. "The Story behind the First Automatic Atomic Force Microscope". Microscopy Today 30, n.º 2 (marzo de 2022): 40–45. http://dx.doi.org/10.1017/s1551929522000463.
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Abstract:Over the past three decades, atomic force microscopy (AFM) has undergone a series of design changes to attain a flat XY scan and stable non-contact mode in ambient atmosphere. AFM has evolved into an ideal method for non-destructive scanning of samples with longer probe tip life, high accuracy, repeatability, and automation. Together with self-optimizing algorithms for scan parameters in the non-contact mode, AFM can become as widely adopted as other microscopies such as optical or scanning electron microscopy (SEM). Even full automation of AFM probe tip exchange is now possible with probe type recognition software and laser beam alignment on the cantilever and position-sensitive photo diode (PSPD). By separating the optics stage from the Z stage, an AFM system can be made with low mechanical noise and improved optical vision.
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Laflör, Linda, Michael Reichling y Philipp Rahe. "Protruding hydrogen atoms as markers for the molecular orientation of a metallocene". Beilstein Journal of Nanotechnology 11 (22 de septiembre de 2020): 1432–38. http://dx.doi.org/10.3762/bjnano.11.127.
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A distinct dumbbell shape is observed as the dominant contrast feature in the experimental data when imaging 1,1’-ferrocene dicarboxylic acid (FDCA) molecules on bulk and thin film CaF2(111) surfaces with non-contact atomic force microscopy (NC-AFM). We use NC-AFM image calculations with the probe particle model to interpret this distinct shape by repulsive interactions between the NC-AFM tip and the top hydrogen atoms of the cyclopentadienyl (Cp) rings. Simulated NC-AFM images show an excellent agreement with experimental constant-height NC-AFM data of FDCA molecules at several tip–sample distances. By measuring this distinct dumbbell shape together with the molecular orientation, a strategy is proposed to determine the conformation of the ferrocene moiety, herein on CaF2(111) surfaces, by using the protruding hydrogen atoms as markers.
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Ho, Huddee J. "Near Contact Mode AFM: Overcoming Surface Fluid Layer In Air And Achieve Ultra-High Resolution". Microscopy Today 6, n.º 8 (octubre de 1998): 12–15. http://dx.doi.org/10.1017/s1551929500069170.
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A major goal of Atomic Force Microscopy (AFM) is to achieve nanometer resolution on surface topography, Vibrating cantilever mode (VCM) is an important configuration of an AFU instrument, It was proposed in the first AFM paper.VCM in ultra-high vacuum (UHV) results in true AFM atomic resolution, which reveals atomic scale surface defects such as a single missing atom in a lattice. However, the VCM operation in air has many difficulties due to the surface contamination on the sample and the AFM tip. The most popular operation modes of the VCM are the non-contact mode and the Tapping mode. Both of these have limited lateral resolution in air.
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Rius, Gemma, Matteo Lorenzoni, Soichiro Matsui, Masaki Tanemura y Francesc Perez-Murano. "Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes". Beilstein Journal of Nanotechnology 6 (19 de enero de 2015): 215–22. http://dx.doi.org/10.3762/bjnano.6.20.
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Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.
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Lübbe, Jannis, Matthias Temmen, Philipp Rahe y Michael Reichling. "Noise in NC-AFM measurements with significant tip–sample interaction". Beilstein Journal of Nanotechnology 7 (1 de diciembre de 2016): 1885–904. http://dx.doi.org/10.3762/bjnano.7.181.
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The frequency shift noise in non-contact atomic force microscopy (NC-AFM) imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip–sample interactions. The total noise power spectral density D Δ f (f m) is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip–sample interaction, by the coupling between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure D Δ f (f m) for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip–sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops.
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Evans, Christopher T., Sara J. Baldock, John G. Hardy, Oliver Payton, Loren Picco y Michael J. Allen. "A Non-Destructive, Tuneable Method to Isolate Live Cells for High-Speed AFM Analysis". Microorganisms 9, n.º 4 (25 de marzo de 2021): 680. http://dx.doi.org/10.3390/microorganisms9040680.
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Suitable immobilisation of microorganisms and single cells is key for high-resolution topographical imaging and study of mechanical properties with atomic force microscopy (AFM) under physiologically relevant conditions. Sample preparation techniques must be able to withstand the forces exerted by the Z range-limited cantilever tip, and not negatively affect the sample surface for data acquisition. Here, we describe an inherently flexible methodology, utilising the high-resolution three-dimensional based printing technique of multiphoton polymerisation to rapidly generate bespoke arrays for cellular AFM analysis. As an example, we present data collected from live Emiliania huxleyi cells, unicellular microalgae, imaged by contact mode High-Speed Atomic Force Microscopy (HS-AFM), including one cell that was imaged continuously for over 90 min.
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Rodriguez, D. J., A. V. Kotosonova, H. A. Ballouk, N. A. Shandyba, O. I. Osotova y A. S. Kolomiytsev. "Fabrication of probe tips via the FIB method for nanodiagnostics of the surface of solids by atomic force microscopy". Journal of Physics: Conference Series 2086, n.º 1 (1 de diciembre de 2021): 012204. http://dx.doi.org/10.1088/1742-6596/2086/1/012204.
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Abstract In this work, we carried out an investigation of commercial atomic force microscope (AFM) probes for contact and semi-contact modes, which were modified by focused ion beam (FIB). This method was used to modify the original tip shape of silicon AFM probes, by ion-etching and ion-enhance gas deposition. we show a better performance of the FIB-modified probes in contrast with the non-modified commercial probes. These results were obtained after using both probes in semi-contact mode in a calibration grating sample.
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Leitner, Michael, Hannah Seferovic, Sarah Stainer, Boris Buchroithner, Christian H. Schwalb, Alexander Deutschinger y Andreas Ebner. "Atomic Force Microscopy Imaging in Turbid Liquids: A Promising Tool in Nanomedicine". Sensors 20, n.º 13 (2 de julio de 2020): 3715. http://dx.doi.org/10.3390/s20133715.
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Tracking of biological and physiological processes on the nanoscale is a central part of the growing field of nanomedicine. Although atomic force microscopy (AFM) is one of the most appropriate techniques in this area, investigations in non-transparent fluids such as human blood are not possible with conventional AFMs due to limitations caused by the optical readout. Here, we show a promising approach based on self-sensing cantilevers (SSC) as a replacement for optical readout in biological AFM imaging. Piezo-resistors, in the form of a Wheatstone bridge, are embedded into the cantilever, whereas two of them are placed at the bending edge. This enables the deflection of the cantilever to be precisely recorded by measuring the changes in resistance. Furthermore, the conventional acoustic or magnetic vibration excitation in intermittent contact mode can be replaced by a thermal excitation using a heating loop. We show further developments of existing approaches enabling stable measurements in turbid liquids. Different readout and excitation methods are compared under various environmental conditions, ranging from dry state to human blood. To demonstrate the applicability of our laser-free bio-AFM for nanomedical research, we have selected the hemostatic process of blood coagulation as well as ultra-flat red blood cells in different turbid fluids. Furthermore, the effects on noise and scanning speed of different media are compared. The technical realization is shown (1) on a conventional optical beam deflection (OBD)-based AFM, where we replaced the optical part by a new SSC nose cone, and (2) on an all-electric AFM, which we adapted for measurements in turbid liquids.
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von Schmidsfeld, Alexander, Tobias Nörenberg, Matthias Temmen y Michael Reichling. "Understanding interferometry for micro-cantilever displacement detection". Beilstein Journal of Nanotechnology 7 (10 de junio de 2016): 841–51. http://dx.doi.org/10.3762/bjnano.7.76.
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Interferometric displacement detection in a cantilever-based non-contact atomic force microscope (NC-AFM) operated in ultra-high vacuum is demonstrated for the Michelson and Fabry–Pérot modes of operation. Each mode is addressed by appropriately adjusting the distance between the fiber end delivering and collecting light and a highly reflective micro-cantilever, both together forming the interferometric cavity. For a precise measurement of the cantilever displacement, the relative positioning of fiber and cantilever is of critical importance. We describe a systematic approach for accurate alignment as well as the implications of deficient fiber–cantilever configurations. In the Fabry–Pérot regime, the displacement noise spectral density strongly decreases with decreasing distance between the fiber-end and the cantilever, yielding a noise floor of 24 fm/Hz0.5 under optimum conditions.
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Gien, Helena, Michael Morse, Micah J. McCauley, Jonathan P. Kitzrow, Karin Musier-Forsyth, Robert J. Gorelick, Ioulia Rouzina y Mark C. Williams. "HIV-1 Nucleocapsid Protein Binds Double-Stranded DNA in Multiple Modes to Regulate Compaction and Capsid Uncoating". Viruses 14, n.º 2 (25 de enero de 2022): 235. http://dx.doi.org/10.3390/v14020235.
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The HIV-1 nucleocapsid protein (NC) is a multi-functional protein necessary for viral replication. Recent studies have demonstrated reverse transcription occurs inside the fully intact viral capsid and that the timing of reverse transcription and uncoating are correlated. How a nearly 10 kbp viral DNA genome is stably contained within a narrow capsid with diameter similar to the persistence length of double-stranded (ds) DNA, and the role of NC in this process, are not well understood. In this study, we use optical tweezers, fluorescence imaging, and atomic force microscopy to observe NC binding a single long DNA substrate in multiple modes. We find that NC binds and saturates the DNA substrate in a non-specific binding mode that triggers uniform DNA self-attraction, condensing the DNA into a tight globule at a constant force up to 10 pN. When NC is removed from solution, the globule dissipates over time, but specifically-bound NC maintains long-range DNA looping that is less compact but highly stable. Both binding modes are additionally observed using AFM imaging. These results suggest multiple binding modes of NC compact DNA into a conformation compatible with reverse transcription, regulating the genomic pressure on the capsid and preventing premature uncoating.
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Croshaw, Jeremiah, Thomas Dienel, Taleana Huff y Robert Wolkow. "Atomic defect classification of the H–Si(100) surface through multi-mode scanning probe microscopy". Beilstein Journal of Nanotechnology 11 (7 de septiembre de 2020): 1346–60. http://dx.doi.org/10.3762/bjnano.11.119.
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The combination of scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) allows enhanced extraction and correlation of properties not readily available via a single imaging mode. We demonstrate this through the characterization and classification of several commonly found defects of the hydrogen-terminated silicon (100)-2 × 1 surface (H–Si(100)-2 × 1) by using six unique imaging modes. The H–Si surface was chosen as it provides a promising platform for the development of atom scale devices, with recent work showing their creation through precise desorption or placement of surface hydrogen atoms. While samples with relatively large areas of the H–Si surface are routinely created using an in situ methodology, surface defects are inevitably formed reducing the area available for patterning. By probing the surface using the different interactivity afforded by either hydrogen- or silicon-terminated tips, we are able to extract new insights regarding the atomic and electronic structure of these defects. This allows for the confirmation of literature assignments of several commonly found defects, as well as proposed classifications of previously unreported and unassigned defects. By combining insights from multiple imaging modes, better understanding of their successes and shortcomings in identifying defect structures and origins is achieved. With this, we take the first steps toward enabling the creation of superior H–Si surfaces through an improved understanding of surface defects, ultimately leading to more consistent and reliable fabrication of atom scale devices.
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MOUTLANA, MALESELA K. y SARP ADALI. "Fundamental frequencies of a nano beam used for atomic force microscopy (AFM) in tapping mode". MRS Advances 3, n.º 42-43 (2018): 2617–26. http://dx.doi.org/10.1557/adv.2018.321.
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ABSTRACTIn this study we investigate the motion of a torsionally restrained beam used in tapping mode atomic force microscopy (TM-AFM), with the aim of manufacturing at nano-scale. TM-AFM oscillates at high frequency in order to remove material or shape nano structures. Euler-Bernoulli theory and Eringen’s theory of non-local continuum are used to model the nano machining structure composed of two single degree of freedom systems. Eringen’s theory is effective at nano-scale and takes into account small-scale effects. This theory has been shown to yield reliable results when compared to modelling using molecular dynamics.The system is modelled as a beam with a torsional boundary condition at one end; and at the free end is a transverse linear spring attached to the tip. The other end of the spring is attached to a mass, resulting in a single degree of freedom spring-mass system. The motion of the tip of the beam and tip mass can be investigated to observe the tip frequency response, displacement and contact force. The beam and spring–mass frequencies contain information about the maximum displacement amplitude and therefore the sample penetration depth and this allows
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Lübbe, Jannis, Matthias Temmen, Philipp Rahe, Angelika Kühnle y Michael Reichling. "Determining cantilever stiffness from thermal noise". Beilstein Journal of Nanotechnology 4 (28 de marzo de 2013): 227–33. http://dx.doi.org/10.3762/bjnano.4.23.
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We critically discuss the extraction of intrinsic cantilever properties, namely eigenfrequency f n , quality factor Q n and specifically the stiffness k n of the nth cantilever oscillation mode from thermal noise by an analysis of the power spectral density of displacement fluctuations of the cantilever in contact with a thermal bath. The practical applicability of this approach is demonstrated for several cantilevers with eigenfrequencies ranging from 50 kHz to 2 MHz. As such an analysis requires a sophisticated spectral analysis, we introduce a new method to determine k n from a spectral analysis of the demodulated oscillation signal of the excited cantilever that can be performed in the frequency range of 10 Hz to 1 kHz regardless of the eigenfrequency of the cantilever. We demonstrate that the latter method is in particular useful for noncontact atomic force microscopy (NC-AFM) where the required simple instrumentation for spectral analysis is available in most experimental systems.
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CRISTIAN ION, TUDORA, MARIOARA ABRUDEANU, SERGIU STANCIU, DANIEL CONSTANTIN ANGHEL, GABRIELA ADRIANA PLAIASU, VASILE RIZEA, MARGARETA COTEATA, MIHAI DUMITRU y NICANOR CIMPOESU. "Activation of CuAlNi SMAs using a solar energy". Journal of Engineering Sciences and Innovation 5, n.º 12 (3 de junio de 2020): 123–28. http://dx.doi.org/10.56958/jesi.2020.5.2.3.
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"Shape memory alloys are special materials that can perform mechanical work during martensitic transformation. CuAlNi shape memory alloys have gained attention based on them high transformation temperatures domain and can be considered as HTSMAs (high temperature shape memory alloys). The thermal component in order to achieve martensitic transformation can be obtained from sun using a solar concentrator. The heating/cooling process was registered and analyzed during the experiments. Material surface was analyzed before and after thermal shocks by microstructure point of view using scanning electron microscopy (SEM VegaTescan LMH II, SE detector) and atomic force microscopy (AFM EasyScan II, non-contact mode). The experiments follow the material behavior during fast heating and propose the possibility of activating smart materials using the sun heat for aerospace applications. "
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Börås, Linda y Paul Gatenholm. "Surface Composition and Morphology of CTMP Fibers". Holzforschung 53, n.º 2 (1 de marzo de 1999): 188–94. http://dx.doi.org/10.1515/hf.1999.031.
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Summary The aim of this study was to investigate the surface composition and morphology of Chemithermomechanical pulp (CTMP) fibers from spruce. The fibers were exposed to a sequence of mild treatments such as washing, peroxide bleaching and extraction. The effects of treatments on fiber bulk composition and surface properties were investigated. All treatments did not significantly result in changes in total lignin and carbohydrate content. However, the extractives were stepwise removed. With the Electron Spectroscopy for Chemical Analysis (ESCA) technique, a gradual reduction of unoxidized carbon in the C1s resolved peak was shown, which was correlated to the removal of non-carbohydrates. Variations in surface topography among the analyzed samples were displayed with Atomic Force Microscopy (AFM) imaging of fibers in tapping mode. The wetting properties of all pulps were measured by Dynamic Contact Angle (DCA) on the single fibers. The advancing contact angle decreased and the hysteresis is also reduced, as a result of treatments. ESCA, AFM and contact angle analyses suggest that the extractives are distributed as globular particles at the fiber surface. Phase imaging AFM indicated the presence of lignin as irregular patches at the surface. A model of the CTMP fiber surface based on experimental findings in this work is proposed.
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Leinen, Philipp, Matthew F. B. Green, Taner Esat, Christian Wagner, F. Stefan Tautz y Ruslan Temirov. "Virtual reality visual feedback for hand-controlled scanning probe microscopy manipulation of single molecules". Beilstein Journal of Nanotechnology 6 (16 de noviembre de 2015): 2148–53. http://dx.doi.org/10.3762/bjnano.6.220.
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Controlled manipulation of single molecules is an important step towards the fabrication of single molecule devices and nanoscale molecular machines. Currently, scanning probe microscopy (SPM) is the only technique that facilitates direct imaging and manipulations of nanometer-sized molecular compounds on surfaces. The technique of hand-controlled manipulation (HCM) introduced recently in Beilstein J. Nanotechnol. 2014, 5, 1926–1932 simplifies the identification of successful manipulation protocols in situations when the interaction pattern of the manipulated molecule with its environment is not fully known. Here we present a further technical development that substantially improves the effectiveness of HCM. By adding Oculus Rift virtual reality goggles to our HCM set-up we provide the experimentalist with 3D visual feedback that displays the currently executed trajectory and the position of the SPM tip during manipulation in real time, while simultaneously plotting the experimentally measured frequency shift (Δf) of the non-contact atomic force microscope (NC-AFM) tuning fork sensor as well as the magnitude of the electric current (I) flowing between the tip and the surface. The advantages of the set-up are demonstrated by applying it to the model problem of the extraction of an individual PTCDA molecule from its hydrogen-bonded monolayer grown on Ag(111) surface.
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Crismaru, Mihaela, Lia A. T. W. Asri, Ton J. A. Loontjens, Bastiaan P. Krom, Joop de Vries, Henny C. van der Mei y Henk J. Busscher. "Survival of Adhering Staphylococci during Exposure to a Quaternary Ammonium Compound Evaluated by Using Atomic Force Microscopy Imaging". Antimicrobial Agents and Chemotherapy 55, n.º 11 (29 de agosto de 2011): 5010–17. http://dx.doi.org/10.1128/aac.05062-11.
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ABSTRACTEffects of a quaternary ammonium compound (QAC) on the survival of adhering staphylococci on a surface were investigated using atomic force microscopy (AFM). Four strains with different minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) for the QAC were exposed to three different concentrations of the QAC in potassium phosphate buffer (0.5×, 1×, and 2× MBC) while adhering to glass. Adhering staphylococci were repeatedly imaged with AFM in the contact mode, and the cell surface was found to wrinkle upon progressive exposure to the QAC until bacteria disappeared from the substratum. Higher concentrations of QAC yielded faster wrinkling and the disappearance of bacteria during imaging. Two slime-producing staphylococcal strains survived longer on the surface than two non-slime-producing strains despite similar MICs and MBCs. All staphylococci adhering in unscanned areas remained adhering during exposure to QAC. Since MICs and MBCs did not relate to bacterial cell surface hydrophobicities and zeta potentials, survival on the surface is probably not determined by the direct interaction of QAC molecules with the cell surface. Instead, it is suggested that the pressure of the AFM tip assists the incorporation of QAC molecules in the membrane and enhances their bactericidal efficacy. In addition, the prolonged survival under pressure from slime-producing strains on a surface may point to a new protective role of slime as a stress absorber, impeding the incorporation of QAC molecules. The addition of Ca2+ions to a QAC solution yielded longer survival of intact, adhering staphylococci, suggesting that Ca2+ions can impede the exchange of membrane Ca2+ions required for QAC incorporation.
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Ruppert, Michael G., Daniel Martin-Jimenez, Yuen K. Yong, Alexander Ihle, André Schirmeisen, Andrew J. Fleming y Daniel Ebeling. "Experimental analysis of tip vibrations at higher eigenmodes of QPlus sensors for atomic force microscopy". Nanotechnology 33, n.º 18 (10 de febrero de 2022): 185503. http://dx.doi.org/10.1088/1361-6528/ac4759.
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Abstract QPlus sensors are non-contact atomic force microscope probes constructed from a quartz tuning fork and a tungsten wire with an electrochemically etched tip. These probes are self-sensing and offer an atomic-scale spatial resolution. Therefore, qPlus sensors are routinely used to visualize the chemical structure of adsorbed organic molecules via the so-called bond imaging technique. This is achieved by functionalizing the AFM tip with a single CO molecule and exciting the sensor at the first vertical cantilever resonance mode. Recent work using higher-order resonance modes has also resolved the chemical structure of single organic molecules. However, in these experiments, the image contrast can differ significantly from the conventional bond imaging contrast, which was suspected to be caused by unknown vibrations of the tip. This work investigates the source of these artefacts by using a combination of mechanical simulation and laser vibrometry to characterize a range of sensors with different tip wire geometries. The results show that increased tip mass and length cause increased torsional rotation of the tuning fork beam due to the off-center mounting of the tip wire, and increased flexural vibration of the tip. These undesirable motions cause lateral deflection of the probe tip as it approaches the sample, which is rationalized to be the cause of the different image contrast. The results also provide a guide for future probe development to reduce these issues.
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Alibakhshi, Amin, Sasan Rahmanian, Shahriar Dastjerdi, Mohammad Malikan, Behrouz Karami, Bekir Akgöz y Ömer Civalek. "Hyperelastic Microcantilever AFM: Efficient Detection Mechanism Based on Principal Parametric Resonance". Nanomaterials 12, n.º 15 (28 de julio de 2022): 2598. http://dx.doi.org/10.3390/nano12152598.
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The impetus of writing this paper is to propose an efficient detection mechanism to scan the surface profile of a micro-sample using cantilever-based atomic force microscopy (AFM), operating in non-contact mode. In order to implement this scheme, the principal parametric resonance characteristics of the resonator are employed, benefiting from the bifurcation-based sensing mechanism. It is assumed that the microcantilever is made from a hyperelastic material, providing large deformation under small excitation amplitude. A nonlinear strain energy function is proposed to capture the elastic energy stored in the flexible component of the device. The tip–sample interaction is modeled based on the van der Waals non-contact force. The nonlinear equation governing the AFM’s dynamics is established using the extended Hamilton’s principle, obeying the Euler–Bernoulli beam theory. As a result, the vibration behavior of the system is introduced by a nonlinear equation having a time-dependent boundary condition. To capture the steady-state numerical response of the system, a developed Galerkin method is utilized to discretize the partial differential equation to a set of nonlinear ordinary differential equations (ODE) that are solved by the combination of shooting and arc-length continuation method. The output reveals that while the resonator is set to be operating near twice the fundamental natural frequency, the response amplitude undergoes a significant drop to the trivial stable branch as the sample’s profile experiences depression in the order of the picometer. According to the performed sensitivity analysis, the proposed working principle based on principal parametric resonance is recommended to design AFMs with ultra-high detection resolution for surface profile scanning.
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Kislyuk, Alexander M., Tatiana S. Ilina, Ilya V. Kubasov, Dmitry A. Kiselev, Alexander A. Temirov, Andrei V. Turutin, Mikhail D. Malinkovich, Andrey A. Polisan y Yury N. Parkhomenko. "Tailoring of stable induced domains near a charged domain wall in lithium niobate by probe microscopy". Modern Electronic Materials 5, n.º 2 (1 de junio de 2019): 51–60. http://dx.doi.org/10.3897/j.moem.5.2.51314.
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Ferroelectric lithium niobate (LiNbO3) crystals with an engineered domain structure have a number of applications in optical systems for generation of multiple laser radiation harmonics, acoustooptics, precision actuators, vibration and magnetic field sensors, including those for high-temperature applications, and prospectively, in non-volatile computer memory. We have studied the effect of charged domain boundary on the formation of induced domain structures in congruent lithium niobate (LiNbO3) crystals at the non-polar x-cut. Bi- and polydomain ferroelectric structures containing charged “head-to-head” and “tail-to-tail” type domain boundaries have been formed in the specimens using diffusion annealing in air ambient close to the Curie temperature and infrared annealing in an oxygen free environment. The surface potential near the charged domain wall has been studied using an atomic force microscope (AFM) in Kelvin mode. We have studied surface wedge-shaped induced microscopic domains formed at the charged domain boundary and far from that boundary by applying electric potential to the AFM cantilever which was in contact with the crystal surface. We have demonstrated that the morphology of the induced domain structure depends on the electrical conductivity of the crystals. The charged “head-to-head” domain boundary has a screening effect on the shape and size of the domain induced at the domain wall. Single wedge-shaped domains forming during local repolarization of reduced lithium niobate crystals at the AFM cantilever split into families of microscopic domains in the form of codirectional beams emerging from a common formation site. The charged domain wall affects the topography of the specimens by inducing the formation of an elongated trench, coincident with the charged boundary, during reduction annealing.
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McMaster, T. J., M. M. Smits, S. J. Haward, J. R. Leake, S. Banwart y K. V. Ragnarsdottir. "High-resolution imaging of biotite dissolution and measurement of activation energy". Mineralogical Magazine 72, n.º 1 (febrero de 2008): 115–20. http://dx.doi.org/10.1180/minmag.2008.072.1.115.
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AbstractWe have used a direct imaging technique, in situ atomic force microscopy(AFM) to observe the earliest stages of the dissolution of a biotite surface byoxalic acid at temperatures close to ambient conditions, using a speciallydesigned AFM liquid cell and non-invasive intermittent contact mode of operation. From the nm-resolution data sets in x, yand z dimensions, we have measured dissolution rates and determined activation energies for the process as a function of temperature, via a mass-loss calculation. The value of Ea obtained, 49±2 kJ mol-1, appears to be too high to indicate a diffusion-controlled process and is more in line with expectations based on a process limited by the rate of ligand-induced metal cation detachment from the (001) surface. This is consistent with visual observations of the relative rates of etch-pit formation and growth, and accepted knowledge of the biotite crystal structure. Separate calculations based on planar area etch-pit growth, and measurements of etch-pit perimeters confirm this result, and also indicate substantiallyhigher activation energy, up to 80 kJ mol-1, when the edge pits are in an incipient stage.
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Lee, Jae Jong, Soo Yeon Park, Seung Woo Lee y In Deok Jeon. "Electronic Transport Properties of Chemical Gas Sensor Using Conducting Polymer PAni". Key Engineering Materials 326-328 (diciembre de 2006): 1363–66. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1363.
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The conducting polymer PAni is coated on Au electrode sample by spin coater on 500rpm and 3000rpm for 5sec and 30sec. Then, it was drying 10min at 180C. The layer thickness was 140~200nm. The electrodes were fabricated the resist pattern by electron beam writing machine which was performed on a Raith75 e-Line on the PMMA 950K, thickness 100nm. The electrodes were written at an electron does of 200uAs/cm2 and developed for 40sec in a 1:3 MIBK (methyl-isobutyl-ketone): IPA (isopropyl alcohol) solution. Metal lift-off of the PMMA in acetone was preceded by an e-beam evaporation consisting of 50Å Cr and 250Å Au. Electrical measurements were performed on low-noise commercial probe stations equipped. We measured distance between the electrodes ranges from a few tens of nanometer to hundreds nanometer by AFM (Atomic Force Microscopy) which was done with silicon tips in non-contact mode on a PSIA, XE-100.
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Aubriet, Valentin, Kristell Courouble, Olivier Bardagot, Renaud Demadrille, Łukasz Borowik y Benjamin Grévin. "Hidden surface photovoltages revealed by pump probe KPFM". Nanotechnology 33, n.º 22 (8 de marzo de 2022): 225401. http://dx.doi.org/10.1088/1361-6528/ac5542.
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Abstract In this work, we use pump-probe Kelvin probe force microscopy (pp-KPFM) in combination with non-contact atomic force microscopy (nc-AFM) under ultrahigh vacuum, to investigate the nature of the light-induced surface potential dynamics in alumina-passivated crystalline silicon, and in an organic bulk heterojunction thin film based on the PTB7-PC71BM tandem. In both cases, we demonstrate that it is possible to identify and separate the contributions of two different kinds of photo-induced charge distributions that give rise to potential shifts with opposite polarities, each characterized by different dynamics. The data acquired on the passivated crystalline silicon are shown to be fully consistent with the band-bending at the silicon-oxide interface, and with electron trapping processes in acceptors states and in the passivation layer. The full sequence of events that follow the electron–hole generation can be observed on the pp-KPFM curves, i.e. the carriers spatial separation and hole accumulation in the space charge area, the electron trapping, the electron–hole recombination, and finally the electron trap-release. Two dimensional dynamical maps of the organic blend photo-response are obtained by recording the pump-probe KPFM curves in data cube mode, and by implementing a specific batch processing protocol. Sample areas displaying an extra positive SPV component characterized by decay time-constants of a few tens of microseconds are thus revealed, and are tentatively attributed to specific interfaces formed between a polymer-enriched skin layer and recessed acceptor aggregates. Decay time constant images of the negative SPV component confirm that the acceptor clusters act as electron-trapping centres. Whatever the photovoltaic technology, our results exemplify how some of the SPV components may remain completely hidden to conventional SPV imaging by KPFM, with possible consequences in terms of photo-response misinterpretation. This work furthermore highlights the need of implementing time-resolved techniques that can provide a quantitative measurement of the time-resolved potential.
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Bubendorf, Alexandre, Stefan Walheim, Thomas Schimmel y Ernst Meyer. "A robust AFM-based method for locally measuring the elasticity of samples". Beilstein Journal of Nanotechnology 9 (2 de enero de 2018): 1–10. http://dx.doi.org/10.3762/bjnano.9.1.
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Investigation of the local sample elasticity is of high importance in many scientific domains. In 2014, Herruzo et al. published a new method based on frequency-modulation atomic force microscopy to locally determine the elasticity of samples (Nat. Commun. 2014, 5, 3126). This method gives evidence for the linearity of the relation between the frequency shift of the cantilever first flexural mode Δf 1 and the square of the frequency shift of the second flexural mode Δf 2 2. In the present work, we showed that a similar linear relation exists when measuring in contact mode with a certain load F N and propose a new method for determining the elastic modulus of samples from this relation. The measurements were performed in non-dry air at ambient temperature on three different polymers (polystyrene, polypropylene and linear low-density polyethylene) and a self-assembled monolayer of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) on a silicon oxide substrate perforated with circular holes prepared by polymer blend lithography. For all samples the relation was evidenced by recording Δf 1, Δf 2 and F N as a function of the Z-displacement curves of the piezoelectric scanner. The occurence of a plastic deformation followed by an elastic deformation is shown and explained. The necessary load F N for measuring in the elastic domain was assessed for each sample, used for mapping the frequency shifts Δf 1 and Δf 2 and for determining the elastic modulus from Δf 2 2/Δf 1. The method was used to give an estimate of the Young’s modulus of the FDTS thin film.
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Bobić, Zoran, Sanja Kojić, Goran M. Stojanović, Vladimir Terek, Lazar Kovačević y Pal Terek. "Nanotopography Evaluation of NiTi Alloy Exposed to Artificial Saliva and Different Mouthwashes". Materials 15, n.º 23 (6 de diciembre de 2022): 8705. http://dx.doi.org/10.3390/ma15238705.
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Nitinol (NiTi) alloy is a widely used material for the production of orthodontic archwires. Its corrosion behavior in conditions that exist in the oral cavity still remains a great characterization challenge. The motivation behind this work is to reveal the influence of commercially available mouthwashes on NiTi orthodontic archwires by performing non-electrochemical corrosion tests and quantifying the changes in the nanotopography of commercially available NiTi orthodontic wires. In this study, we examined the behavior of NiTi alloy archwires exposed for 21.5 days to different corrosive media: artificial saliva, Eludril®, Aquafresh®, and Listerine®. The corrosion was characterized by contact mode atomic force microscopy (AFM) before and after the corrosion tests. A novel analysis methodology was developed to obtain insight into locations of material gain or material loss based on standard surface roughness parameters Sa, Sdr, Ssk, and S10z. The developed methodology revealed that fluoride-containing mouthwashes (Aquafresh® and Listerine®) dominantly cause material loss, while chloride-containing mouthwash (Eludril®) can cause both material loss and material gain. The sample exposed to artificial saliva did not display significant changes in any parameter.
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Евсиков, И. Д., С. В. Митько, П. Ю. Глаголев, Н. А. Дюжев y Г. Д. Демин. "Анализ эмиссии электронов с одиночного кремниевого катода в квазивакуумную (воздушную) среду методом атомно-силовой микроскопии". Журнал технической физики 90, n.º 11 (2020): 1931. http://dx.doi.org/10.21883/jtf.2020.11.49986.136-20.
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Using atomic force microscopy (AFM), we experimentally examined the features of field-electron emission from a single point-type silicon cathode into a quasi-vacuum (air) medium. In the non-contact AFM operating mode, the current – voltage characteristics (CVCs) of a single cathode with a nanometer radius of curvature of the tip were measured at distances of 10 nm and 20 nm between the cathode tip and the top of the measuring probe. The electric field distribution was simulated both on the surface of the tip of a single cathode and on the surface of the tips of individual cathodes within the array, based on which a theoretical estimate of the field enhancement factor as a function of the cathode-probe distance was made. The field-enhancement factor calculated from the experimental CVCs in the Fowler-Nordheim coordinates is several orders of magnitude higher than its value obtained from theoretical calculations. Such a mismatch between the experimental data and the simulation results indicates the need to take into account additional quantum-size effects, which play an important role in the formation of the field-electron emission current in the nanoscale gap. In particular, deformation of the silicon emitter tip can occur at this scale due to the penetration of a strong electric field into its surface region, which, in turn, causes the distortion of the potential barrier at the interface with the quasi-vacuum medium.
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Teodorowicz, Patrycja, Małgorzata Tokarska-Rodak, Estera Michaluk, Marta Zarębska, Dorota Plewik, Tomasz Grudniewski y Mariusz Sacharczuk. "Assessment of nanomechanical properties of Candida albicans as an element of the oral mycobiota in healthy subjects – a preliminary study". Animal Science Papers and Reports 41, n.º 2 (1 de junio de 2023): 165–78. http://dx.doi.org/10.2478/aspr-2023-0006.
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Abstract In a healthy physiological state, the mucous membrane of the oral cavity creates a suitable environment for the colonization of Candida spp. yeasts. The aim of the study was to analyze the nanomechanical properties of C. albicans cells derived from the oral cavity of healthy people in a biofilm produced in laboratory conditions. Candida spp. were sampled from the oral cavity of healthy individuals. The process of biofilm formation was analyzed using classic microscopic observation enriched with SEM (scanning electron microscope) and the nanomechanical properties of the cells were assessed with the use of the atomic force microscopy technique (AFM). From all isolated strains in the samples collected of the oral cavity healthy people was detected 79% C. albicans. Other isolated species belonged to the group „non-albicans”. The observations of C. albicans carried out in 24-h cultures revealed a tendency of the cells to form a biofilm structure with multilayer cell systems. The diameter of C. albicans cells in this structure was 5.75 µm, and the length of the pseudohyphae was 17.08 µm. The presence of an extracellular substance surrounding the C. albicans cells was detected. The mean value of the adhesion force determined for C. albicans cells was 4.01 nN. Areas with increased hardness (Force Modulation Mode signal; FMM signal) were found mainly in the zones of cells in contact with the glass substrate. The analysis of Candida cells in liquid samples gives satisfactory results, as it prevents unfavorable changes in the cell surface and thus provides more reliable results. The quality of the biofilm is probably related to the nanomechanical properties of C. albicans cells and may consequently contribute to the stability of the biofilm structures and their susceptibility or resistance to antifungal drugs. The presence of Candida spp. especially in companion animals (dogs, cats) poses a risk of their transmission to the human organism. For this reason, it is advisable to undertake additional research to analyze the ability of zoonotic-origin Candida spp. to form biofilms with comparison of the biofilm-formation capacity of species isolated from humans.
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Iwatsuki, Masashi, Kazuyuki Suzuki, Shin-ich Kitamura y Mike Kersker. "Comparative Surface Studies at Atomic Resolution with Ultrahigh Vacuum Variable-Temperature Atomic Force and Scanning Tunneling Microscopes". Microscopy and Microanalysis 5, n.º 3 (mayo de 1999): 208–15. http://dx.doi.org/10.1017/s143192769900015x.
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With the ultrahigh vacuum variable-temperature scanning tunneling microscope (UHV-VT-STM), atomic-level observation has been achieved. An ultrahigh vacuum atomic force microscope (UHV-AFM) has also been developed, with success in obtaining atom images where observation in noncontact (NC) mode with a frequency modulation (FM) detection method was attempted. Using the FM detection method in the constant oscillation amplitude of the cantilever excitation mode, we have obtained atomic-resolution images of Si(111) 7 × 7 structures and Si(100) 2 × 1 structures and other structures together with STM images in an ultrahigh vacuum environment. Also shown here are contact potential difference (CPD) images using the NC-AFM method.
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Woodward, John T. "Choosing a Cantilever for In Situ Atomic Force Microscopy". Microscopy Today 11, n.º 2 (abril de 2003): 42–43. http://dx.doi.org/10.1017/s1551929500052500.
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What is the best cantilever for intermittent contact mode (often called Tapping Mode™) atomic force microscope (AFM) imaging under water? This is a question I hear often and one that recently generated some interesting discussion on an AFM newsgroup (more on the newsgroup below). The ability of the AFM to image samples En physiologically relevant environments has made it a popular technique in the biological sciences. However, because scanning the AFM tip in contact mode easily perturbs many biological samples, it was the advent of intermittent contact modes that lead to AFM's widespread use in biology.
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Glover, Christopher C., Jason P. Killgore y Ryan C. Tung. "Scanning speed phenomenon in contact-resonance atomic force microscopy". Beilstein Journal of Nanotechnology 9 (21 de marzo de 2018): 945–52. http://dx.doi.org/10.3762/bjnano.9.87.
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This work presents data confirming the existence of a scan speed related phenomenon in contact-mode atomic force microscopy (AFM). Specifically, contact-resonance spectroscopy is used to interrogate this phenomenon. Above a critical scan speed, a monotonic decrease in the recorded contact-resonance frequency is observed with increasing scan speed. Proper characterization and understanding of this phenomenon is necessary to conduct accurate quantitative imaging using contact-resonance AFM, and other contact-mode AFM techniques, at higher scan speeds. A squeeze film hydrodynamic theory is proposed to explain this phenomenon, and model predictions are compared against the experimental data.
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Katsube, Daiki, Shoki Ojima, Eiichi Inami y Masayuki Abe. "Atomic-resolution imaging of rutile TiO2(110)-(1 × 2) reconstructed surface by non-contact atomic force microscopy". Beilstein Journal of Nanotechnology 11 (10 de marzo de 2020): 443–49. http://dx.doi.org/10.3762/bjnano.11.35.
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The structure of the rutile TiO2(110)-(1 × 2) reconstructed surface is a phase induced by oxygen reduction. There is ongoing debate about the (1 × 2) reconstruction, because it cannot be clarified whether the (1 × 2) structure is formed over a wide area or only locally using macroscopic analysis methods such as diffraction. We used non-contact atomic force microscopy, scanning tunneling microscopy, and low-energy electron diffraction at room temperature to characterize the surface. Ti2O3 rows appeared as bright spots in both NC-AFM and STM images observed in the same area. High-resolution NC-AFM images revealed that the rutile TiO2(110)-(1 × 2) reconstructed surface is composed of two domains with different types of asymmetric rows.
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De Falco, Gianluigi, Fiorenzo Carbone, Mario Commodo, Patrizia Minutolo y Andrea D’Anna. "Exploring Nanomechanical Properties of Soot Particle Layers by Atomic Force Microscopy Nanoindentation". Applied Sciences 11, n.º 18 (11 de septiembre de 2021): 8448. http://dx.doi.org/10.3390/app11188448.
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In this work, an experimental investigation of the nanomechanical properties of flame-formed carbonaceous particle layers has been performed for the first time by means of Atomic Force Microscopy (AFM). To this aim, carbon nanoparticles with different properties and nanostructures were produced in ethylene/air laminar premixed flames at different residence times. Particles were collected on mica substrates by means of a thermophoretic sampling system and then analyzed by AFM. An experimental procedure based on the combination between semi-contact AFM topography imaging, contact AFM topography imaging and AFM force spectroscopy has been implemented. More specifically, a preliminary topological characterization of the samples was first performed operating AFM in semi-contact mode and then tip-sample interaction forces were measured in contact spectroscopy mode. Finally, semi-contact mode was used to image the indented surface of the samples and to retrieve the projected area of indents. The hardness of investigated samples was obtained from the force–distance curves measured in spectroscopy mode and the images of intends acquired in semi-contact mode. Moreover, the Young’s modulus was measured by fitting the linear part of the retraction force curves using a model based on the Hertz theory. The extreme force sensitivity of this technique (down to nNewton) in addition to the small size of the probe makes it extremely suitable for performing investigation of mechanical properties of materials at the nanoscale. The experimental procedure was successfully tested on reference materials characterized by different plastic behavior, e.g., polyethylene naphthalate and highly oriented pyrolytic graphite. Both hardness and Young’s modulus values obtained from AFM measurements for different soot particle films were discussed.
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Katsube, Daiki, Ryota Shimizu, Yoshiaki Sugimoto, Taro Hitosugi y Masayuki Abe. "Identification of OH groups on SrTiO3(100)-( 13×13)-R33.7° reconstructed surface by non-contact atomic force microscopy and scanning tunneling microscopy". Applied Physics Letters 122, n.º 7 (13 de febrero de 2023): 071602. http://dx.doi.org/10.1063/5.0139493.
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Atomic resolution imaging of a SrTiO3(100)-([Formula: see text])-R33.7° reconstructed surface using non-contact atomic force microscopy (NC-AFM) and its simultaneous measurement with scanning tunneling microscopy (STM) is presented. Simultaneous STM and NC-AFM imaging reveals three patterns of image contrast depending on the tip apex condition and the relationship between the SrTiO3(100)-([Formula: see text])-R33.7° surface reconstructed structure and the NC-AFM image contrast. The NC-AFM image contrast variation is deduced from the tip apex polarity on the basis of an analysis of two images with opposite contrast. This interpretation is consistent with the results of simultaneous imaging of the SrTiO3(100)-([Formula: see text])-R33.7° surface. Furthermore, the results and interpretation identified an OH group, which is one of the surface defects, and this adsorption site.
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Vanitparinyakul, S., P. Pattamang, A. Chanhom, B. Tunhoo, T. Thiwawong, S. Porntheeraphat y J. Nukeaw. "Study of PDMS Compounds Using the Adhesion Force Determined by AFM Force Distance Curve Measurements". Advanced Materials Research 93-94 (enero de 2010): 141–44. http://dx.doi.org/10.4028/www.scientific.net/amr.93-94.141.
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The atomic force microscope(AFM) was used to perform surface force measurements in contact mode to investigate surface properties of model systems at the nanoscale. Three different Polydimethylsiloxane (PDMS) compounds were observed. The first consisted of pure PDMS, the second of PDMS blend with the nanoparticles Zinc Oxide(PDMS/ZnO) and the third of PDMS blend with the nanoparticles Zinc Oxide and toluene solvent(PDMS/ZnO/toluene), respectively. Surface morphology and the adhesion force were investigated by using atomic force microscopy. Force–distance curve measurement was performed in a contact mode, which used tip as silicon nitride. Moreover, we found a significantly different of the adhesion force when modified by nanoparticles ZnO and toluene solvent.
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Gotszalk, Teodor Paweł, Paweł Janus, Andrzej Marek Marendziak, Piotr Czarnecki, Jacek Mikołaj Radojewski, Roman F. Szeloch, Piotr B. Grabiec y Ivo W. Rangelow. "Diagnostics of micro- and nanostructure using the scanning probe microscopy". Journal of Telecommunications and Information Technology, n.º 1 (30 de marzo de 2005): 41–46. http://dx.doi.org/10.26636/jtit.2005.1.293.
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In this paper we summarize the results of our research concerning the diagnostics of micro- and nanostructure with scanning probe microscopy (SPM). We describe the experiments performed with one of the scanning probe microscopy techniques enabling also insulating surfaces to be investigated, i.e., atomic force microscopy (AFM). We present the results of topography measurements using both contact and non-contact AFM modes, investigations of the friction forces that appear between the microtip and the surface, and experiments connected with the thermal behaviour of integrated circuits, carried out with the local resolution of 20 nm.
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Dandavate, Chetan. "False Engagements in AFM". Microscopy Today 7, n.º 2 (marzo de 1999): 26–27. http://dx.doi.org/10.1017/s1551929500063914.
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In scanning microscopes, like the Atomic Force Microscope (AFM), used in contact mode, scanning begins with engaging the tip with the sample at some contact force, which can be adjusted by the setpoint* (this is common to Digital Instruments' AFMs). It may differ for other brands. For a system that detects the motion of the cantilever with a laser beam, the setpoint basically gives an idea of the voltage difference between the top and bottom photo detectors, When the tip comes into contact, the feedback circuit adjusts the tip deflection according to the required contact force, This is the method commonly followed for the constant deflection method.
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Katsube, Daiki, Hayato Yamashita, Satoshi Abo y Masayuki Abe. "Combined pulsed laser deposition and non-contact atomic force microscopy system for studies of insulator metal oxide thin films". Beilstein Journal of Nanotechnology 9 (21 de febrero de 2018): 686–92. http://dx.doi.org/10.3762/bjnano.9.63.
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We have designed and developed a combined system of pulsed laser deposition (PLD) and non-contact atomic force microscopy (NC-AFM) for observations of insulator metal oxide surfaces. With this system, the long-period iterations of sputtering and annealing used in conventional methods for preparing a metal oxide film surface are not required. The performance of the combined system is demonstrated for the preparation and high-resolution NC-AFM imaging of atomically flat thin films of anatase TiO2(001) and LaAlO3(100).
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Zhao, Xiaocui, Nils O. Petersen y Zhifeng Ding. "Comparison study of live cells by atomic force microscopy, confocal microscopy, and scanning electrochemical microscopy". Canadian Journal of Chemistry 85, n.º 3 (1 de marzo de 2007): 175–83. http://dx.doi.org/10.1139/v07-007.
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In this report, three kinds of scanning probe microscopy techniques, atomic force microscopy (AFM), confocal microscopy (CM), and scanning electrochemical microscopy (SECM), were used to study live cells in the physiological environment. Two model cell lines, CV-1 and COS-7, were studied. Time-lapse images were obtained with both contact and tapping mode AFM techniques. Cells were more easily scratched or moved by contact mode AFM than by tapping mode AFM. Detailed surface structures such as filamentous structures on the cell membrane can be obtained and easily discerned with tapping mode AFM. The toxicity of ferrocenemethanol (Fc) on live cells was studied by CM in reflection mode by recording the time-lapse images of controlled live cells and live cells with different Fc concentrations. No significant change in the morphology of cells was caused by Fc. Cells were imaged by SECM with Fc as the mediator at a biased potential of 0.35 V (vs. Ag/AgCl with a saturated KCl solution). Cells did not change visibly within 1 h, which indicated that SECM was a noninvasive technique and thus has a unique advantage for the study of soft cells, since the electrode scanned above the cells instead of in contact with them. Reactive oxygen species (ROS) generated by the cells were detected and images based on these chemical species were obtained. It is demonstrated that SECM can provide not only the topographical images but also the images related to the chemical or biochemical species released by the live cells.Key words: live cells, atomic force microscopy, confocal microscopy, scanning electrochemical microscopy.
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Beltrán, F. J. Espinoza, J. Muñoz-Saldaña, D. Torres-Torres, R. Torres-Martínez y G. A. Schneider. "Atomic force microscopy cantilever simulation by finite element methods for quantitative atomic force acoustic microscopy measurements". Journal of Materials Research 21, n.º 12 (diciembre de 2006): 3072–79. http://dx.doi.org/10.1557/jmr.2006.0379.
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Measurements of vibrational spectra of atomic force microscopy (AFM) microprobes in contact with a sample allow a good correlation between resonance frequencies shifts and the effective elastic modulus of the tip-sample system. In this work we use finite element methods for modeling the AFM microprobe vibration considering actual features of the cantilever geometry. This allowed us to predict the behavior of the cantilevers in contact with any sample for a wide range of effective tip-sample stiffness. Experimental spectra for glass and chromium were well reproduced for the numerical model, and stiffness values were obtained. We present a method to correlate the experimental resonance spectrum to the effective stiffness using realistic geometry of the cantilever to numerically model the vibration of the cantilever in contact with a sample surface. Thus, supported in a reliable finite element method (FEM) model, atomic force acoustic microscopy can be a quantitative technique for elastic-modulus measurements. Considering the possibility of tip-apex wear during atomic force acoustic microscopy measurements, it is necessary to perform a calibration procedure to obtain the tip-sample contact areas before and after each measurement.
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NEJAT PISHKENARI, HOSSEIN y ALI MEGHDARI. "TEMPERATURE DEPENDENCE STUDY OF NONCONTACT AFM IMAGES USING MOLECULAR DYNAMICS SIMULATIONS". International Journal of Modern Physics: Conference Series 05 (enero de 2012): 418–32. http://dx.doi.org/10.1142/s2010194512002309.
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The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have employed the well-known NC-AFM model and carried out realistic non-equilibrium MD 3D simulations of atomic scale imaging at different close approach positions to the surface.
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Yamanaka, Kazushi. "Ultrasonic Force Microscopy". MRS Bulletin 21, n.º 10 (octubre de 1996): 36–41. http://dx.doi.org/10.1557/s0883769400031626.
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As an imaging method of elastic properties and subsurface features on the microscopic scale, the scanning acoustic microscope (SAM) provides spatial resolution comparable or superior to that of optical microscopes. Nondestructive evaluation methods of defects and elastic properties on the microscopic scale were developed by using the SAM, and they have been widely applied to various fields in science and technology. One major problem in acoustic microscopy is resolution. The best resolution of SAM with water as the coupling fluid has been 240 nm at a frequency of 4.4 GHz. At a more conventional frequency of 1 GHz, the resolution is about 1 μm. Therefore the resolution of SAM is not always sufficient for examining nanoscale defects and advanced micro/nanodevices.For materials characterization on the nanometer scale, atomic force microscopy (AFM) was developed and extended in order to observe elastic properties in force-modulation mode. In the force-modulation mode, the sample is vibrated, and the resultant cantilever-deflection vibration is measured and used to produce elasticity images of objects. The lateral force-modulation AFM can evaluate the friction force or the shear elasticity in real time. However in the force-modulation mode, it is difficult to analyze stiff objects such as metals and ceramics.When the sample is vertically vibrated at ultrasonic frequencies much higher than the cantilever resonance frequency, the tip cannot vibrate due to the inertia of the cantilever. However by modulating the amplitude of the ultrasonic vibration, deflection vibration of the cantilever at the modulation frequency is excited due to the rectifier effect of the nonlinear force curves. Based on the tip-sample indentation during ultrasonic vibration, we developed ultrasonic force microscopy (UFM) for contact elasticity and subsurface imaging of rigid objects using a soft cantilever with a stiffness of the order of 0.1 N/m.
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Yamasue, Kohei y Yasuo Cho. "Boxcar Averaging Scanning Nonlinear Dielectric Microscopy". Nanomaterials 12, n.º 5 (26 de febrero de 2022): 794. http://dx.doi.org/10.3390/nano12050794.
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Scanning nonlinear dielectric microscopy (SNDM) is a near-field microwave-based scanning probe microscopy method with a wide variety of applications, especially in the fields of dielectrics and semiconductors. This microscopy method has often been combined with contact-mode atomic force microscopy (AFM) for simultaneous topography imaging and contact force regulation. The combination SNDM with intermittent contact AFM is also beneficial for imaging a sample prone to damage and using a sharp microscopy tip for improving spatial resolution. However, SNDM with intermittent contact AFM can suffer from a lower signal-to-noise (S/N) ratio than that with contact-mode AFM because of the shorter contact time for a given measurement time. In order to improve the S/N ratio, we apply boxcar averaging based signal acquisition suitable for SNDM with intermittent contact AFM. We develop a theory for the S/N ratio of SNDM and experimentally demonstrate the enhancement of the S/N ratio in SNDM combined with peak-force tapping (a trademark of Bruker) AFM. In addition, we apply the proposed method to the carrier concentration distribution imaging of atomically thin van der Waals semiconductors. The proposed method clearly visualizes an anomalous electron doping effect on few-layer Nb-doped MoS2. The proposed method is also applicable to other scanning near-field microwave microscopes combined with peak-force tapping AFM such as scanning microwave impedance microscopy. Our results indicate the possibility of simultaneous nanoscale topographic, electrical, and mechanical imaging even on delicate samples.
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Kheirodin, Mohsen, Hossein Nejat Pishkenari, Ali Moosavi y Ali Meghdari. "Study of Biomolecules Imaging Using Molecular Dynamics Simulations". Nano 10, n.º 07 (octubre de 2015): 1550096. http://dx.doi.org/10.1142/s1793292015500964.
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The process of imaging a biomolecule by atomic force microscope (AFM) is modeled using molecular dynamics (MD) simulations. Since the large normal force exerted by the tip on the biosample in contact and tapping modes may damage the sample structure and produce irreversible deformation, the noncontact mode of AFM (NC-AFM) is employed as the operating mode. The biosample is scanned using a carbon nanotube (CNT) as the AFM probe. CNTs because of their small diameter, high aspect ratio and high mechanical resistance attract many attentions for imaging purposes. The tip–sample interaction is simulated by the MD method. The protein, which has been considered as the biomolecule, is ubiquitin and a graphene sheet is used as the substrate. The effects of CNT's geometric parameters such as the CNT height, the diameter, the tilt angle, the flexibility and the number of layers on the image quality have been evaluated.
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SHEN, ZIYONG, SAIJIN LIU, SHIMIN HOU, ZENGQUAN XUE y ZHENNAN GU. "MANIPULATION OF CARBON NANOTUBE BUNDLES WITH CONTACT MODE ATOMIC FORCE MICROSCOPY". International Journal of Nanoscience 01, n.º 05n06 (octubre de 2002): 575–79. http://dx.doi.org/10.1142/s0219581x02000693.
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The cutting and splitting of carbon nanotube bundles were realized with an atomic force microscopy (AFM) in contact mode. The results of manipulating were found depending on the tip–bundle interaction and bundle–substrate interaction. With an optimal force load of AFM tip, the lateral force applied on the nanotube bundle could overcome the adhesive interaction between nanotubes within the bundle, consequently separating individual nanotubes from the bundle. The threshold of the tip force load was found to be ~45 nN in our experiments. This technique provides new possibilities for the controllable manipulation of carbon nanotubes.
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Janigian, D., E. Morales, T. Muir, B. Garcia y J. Vesenka. "Topographic Comparison of G-Wire DNA Imaged by Hydration Scanning Tunneling and Atomic Force Microscopy as a Function of Humidity". Microscopy and Microanalysis 4, S2 (julio de 1998): 302–3. http://dx.doi.org/10.1017/s1431927600021632.
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The tendency of poly-G oligonucleotides to undergo self-assembly into helical nucleic acid tetramers have been termed G-quartets. Also known as G-wires, these structures retain their crystallographic determined dimensions better than duplex DNA when imaged with the atomic force microscope (AFM). Relative humidity has been known to affect both the resolution and measured height DNA strands on mica. The results below aim to develop a model that can be used to define the mechanical properties of G-wires by scanning probe microscopy investigations. G-wires were examined under a wide range of relative humidity to determine their tolerance to shear forces under the AFM, and to establish imaging conditions for hydration scanning tunneling microscopy (HSTM).The relative humidity dependence of G-wires were taken with 125 μm long, 20 μm wide silicon nitride cantilevers in contact AFM mode (spring constant ∼ 0.4 N/m) (Fig. 1).