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  • 1.
    Groth, Margareta Ring
    et al.
    Luleå tekniska universitet.
    Mannelquist, Anders
    Luleå tekniska universitet.
    Comparison of fractal analyses methods and fractal dimension for pre-treated stainless steel surfaces and the correlation to adhesive joint strength2001In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 73, no 3, p. 347-355Article in journal (Refereed)
    Abstract [en]

    The fractal dimensions of six differently mechanically pre-treated stainless steel samples were investigated using five fractal algorithms. The surfaces were analyzed using a profiler, atomic force microscopy (AFM), scanning electron microscopy (SEM) and light microscopy (LM), and thereafter adhesively bonded and tested in single-overlap joints to test their tensile strength. All samples showed different fractal behavior, depending on the microscopic methods and fractal algorithms. However, the overall relation between fractal dimension and tensile strength is qualitatively the same, except for the SEM images. This verifies that tensile strength is correlated to fractal dimension, although only within the length-scale of the profiler and the light microscope (,0.5-100 7m). The AFM method was excluded in this comparison, since the limitation in the z-direction for the AFM scanner made it difficult to scan the rougher parts of the blasted samples. The magnitude of the surfaces is a parameter not often considered in fractal analysis. It is shown that the magnitude, for the Fourier method, is correlated to the arithmetic average difference, Ra, but only weakly to the fractal dimension. Hence, traditional parameters, such as Ra, tell us very little about the spatial distribution of the elevation data

  • 2.
    Mannelquist, Anders
    Luleå tekniska universitet.
    Fractal analysis and surface characterization by atomic force microscopy and other methods1999Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This licentiate thesis focuses on fractal analysis of surfaces measured with atomic force microscopy (AFM) and other microscopic methods, and the correlation between fractal dimensions and tensile strength for pre-treated stainless-steel surfaces. The disadvantage is that the probe biases the image and the roughness measurement. This has been investigated on simulated fractal surfaces scanned with a simulated pyramidal standard AFM tip, and we demonstrate that the fractal dimension is, underestimated, explaining why higher fractal dimensions are rarely reported in the AFM literature. The results of the simulations are applied to real fractal graphite samples, to shown how the simulations can be used to derive real fractal dimensions. Other surfaces with fractal behavior are pre-treated stainless-steel surfaces used to test the adhesion strength in a single joint lap. The weak relation between traditional roughness parameters and strength of the bond has made the use of fractal analysis appealing. These ideas are tested and evaluated by four microscopic methods and five fractal algorithms. We show that there is a relationship between fractal dimension and tensile strength at the length scale of the profiler i.e., 0.5 - 100 micrometer, and that the conventional parameter Ra is strongly connected to the magnitude of the surface.

  • 3.
    Mannelquist, Anders
    Luleå tekniska universitet.
    Near-field scanning optical microscopy and fractal characterization with atomic force microscopy and other methods2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is devoted to the development of near-field scanning optical microscopy (NSOM) for aqueous solutions and to fractal characterization of steel surfaces with atomic force microscopy (AFM) and other methods. NSOM combines optical properties from a light microscope and the technique of scanning probe microscopy, SPM (invented in the early 1980’s). With an appropriately configured scanning quartz pipette coated with aluminum, an NSOM can be constructed to operate in aqueous solution for applications in biology. Many of the technical limitations associated with a scanning pipette were circumvented, by the help of a small modulation of the distance between the pipette and the sample. This alternating current (AC) method allows the pipette to be positioned very close to the sample surface and is robust in obtaining reproducible NSOM images in solution. This approach is also compatible with fluorescence imaging and fluorescence resonance energy transfer (FRET), and should further facilitate the use of NSOM in various areas of cell biology, where high resolution is considered to be critical. Technical details of this design, and a further characterization of the system, are discussed in the context of biological applications as well as fundamental limitations in comparison to other systems. Based on the current technology, it is concluded that better than 50-nm resolution should be achievable with this technique for fluorescence and FRET imaging of biological specimens. The second part of the thesis is devoted to fractal analysis of data from AFM and other microscopic methods, such as scanning electron microscopy (SEM), light microscopy (LM) and profilometer. Fractal analysis is often necessary for studying surfaces with scale-invariant roughness, as is the case for many pre-treated steel surfaces. However, fractal parameters are influenced by the finite-sized tip geometry of the AFM stylus, and the dependence on AFM tip radius and surface height magnitude is analyzed according to different fractal methods. The result shows that fractal dimension is in general underestimated when the tip size is in comparison with features on the surface which may explain why higher fractal dimensions are seldom reported in the literature. When applied to mechanically pre-treated stainless steel samples, fractal dimension can be correlated to tensile strength for single overlap joints. This was shown within a length scale of ~0.5 - 100 µm, for profilometer profiles, using the Fourier and the Hurst algorithms, and for light microscope images, using a texture algorithm. In addition, the magnitude of the surface roughness, a parameter not often considered in fractal analysis, was shown to correlate to the arithmetic average difference, Ra. Hence, traditional parameters such as Ra tell very little about the spatial distribution of elevation data, in contrast to fractal dimension, and are not as easily correlated to tensile strength. Moreover, fractal dimension is closely related to the surface contact angle for a fluid, a parameter also important for adhesion, both for instant strength and durability properties. By comparing contact angle and adhesive data with fractal dimension, calculated from AFM and profilometer data for the steel surfaces, it can be shown that the surfaces can be qualitatively ranked according to anticipated adhesive properties.

  • 4.
    Mannelquist, Anders
    et al.
    Luleå tekniska universitet.
    Almqvist, Nils
    Fredriksson, Sverker
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Influence of tip geometry on fractal analysis of atomic force microscopy images1998In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 66, no Supplement 1, p. S 891-S 895Article in journal (Refereed)
    Abstract [en]

    Fractal analysis of data from atomic force microscopy (AFM) is often necessary for studying surfaces with scale-invariant roughness. However, the fractal parameters are influenced by the finite-sized tip geometry of the AFM stylus. We make an extended study of such little-known effects. The so-called successive random algorithm is used to generate by computer ideal fractal surfaces with known fractal dimensions and varying height magnitudes. Tip-distorted AFM images are simulated from the ideal surfaces for the case of a strictly geometrical interaction between surface and tip. The AFM-induced error, taken as the difference in estimated parameters between ideal and distorted images, is shown to be largest for small scan sizes and high fractal dimensions. The dependence on AFM tip radius and surface height magnitude is analyzed by the structure function, variance and a Fourier method. The latter is shown to be unreliable for analyzing AFM images. We exemplify how the results can be applied to AFM images of real surfaces.

  • 5.
    Mannelquist, Anders
    et al.
    Luleå tekniska universitet.
    Iwamoto, H
    University of Virginia School of Medicine.
    Szabo, G
    University of Virginia School of Medicine.
    Shao, Z
    University of Virginia School of Medicine.
    Near field optical microscopy in aqueous solution: implementation and characterization of a vibrating probe2002In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 205, no 1, p. 53-60Article in journal (Refereed)
    Abstract [en]

    Near field optical microscopy (NSOM) is one of the possible solutions to circumvent the diffraction limit, but the control of the optical probe in solution has been a technical challenge for practical applications. Most recently, it has been shown that the pipette used in the scanning ion conductance microscope can be modified to form a high resolution near field optical probe. When combined with a novel distance modulation mechanism, a robust near field microscope can be constructed for operation in aqueous solution. In this paper, we present technical details of this design and a further characterization of the NSOM system for imaging in solution. Fundamental limitations of this approach in comparison to other systems are also discussed. Based on the current technology, it is concluded that better than 50 nm resolution should be achievable with this technique for fluorescence, as well as fluorescence resonance energy transfer, imaging of biological specimens.

  • 6.
    Mannelquist, Anders
    et al.
    Luleå tekniska universitet.
    Iwamoto, Hideki
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Szabo, Gabor
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Shao, Zhifeng
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Near-field optical microscopy with a vibrating probe in aqueous solution2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 14, p. 2076-2078Article in journal (Refereed)
    Abstract [en]

    We show that with an appropriately configured scanning quartz pipette coated with aluminum, a near-field scanning optical microscope (NSOM) can be constructed to operate in aqueous solution for applications in biology. Many of the technical limitations associated with a scanning pipette were circumvented by introducing a small modulation of the distance between the pipette and the sample. We show that this ac method allows the pipette to be positioned very close to the sample surface and is robust in obtaining reproducible NSOM images in solution. This approach is also compatible with fluorescence imaging and fluorescence resonance energy transfer, and should further facilitate the use of NSOM in various areas of cell biology where high resolution is considered to be critical.

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