Three-dimensional Surface Topography Research Articles

Effects of laser-modified polystyrene substrate on CHO cell growth and alignment.

Biomaterial surface chemistry and nanoscale topography of biomaterials can significantly influence cell behavior in vitro. Polystyrene (PS) Petri dishes were subjected to Nd:YAG laser irradiation at 266 nm, which resulted in well-defined three-dimensional (3D) periodic nanoscale surface topographies and surface oxidation. The surface changes were analyzed by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and a contact-angle goniometer. The samples were then used to investigate the cell behavior of Chinese hamster ovary (CHO) cells. The surface laser modification affected the CHO cell adhesion and alignment, and caused morphological changes in comparison with unmodified PS. The results obtained from the cell-behavior studies revealed that nanoscale hydrophilic surface topography cues affected the adhesion, extension, alignment, and morphology of cells.

Wavelet analysis for corneal topographic surface characterization

Purpose. To demonstrate a mathematical method for multi-scalar decomposition of discrete corneal topography height data into a space-scale space using wavelet analysis techniques, and to demonstrate the clinical applicability of these computations in the postkeratoplasty cornea. Methods. Fifty patients with either Fuchs' dystrophy (n = 20) or keratoconus (n = 30) were seen preoperatively, at 3 months, at 1 year (before suture removal) and again at 19 ± 3 months (after suture removal) following nonmechanical trephination with an excimer laser for penetrating keratoplasty. Patients were assessed using corneal topography analysis (TMS-1), subjective refraction, and best-corrected visual acuity (VA) at each interval. Two-dimensional biorthogonal wavelets with the order 6.8 at the scales j = 1–4 revealed the following parameters: root-mean square (RMSDEV) and mean absolute (MEANDEV) deviation and maximum absolute height of the peaks or pitches (MAXPEAK) relative to the reference surface specified with the approximation component of scale j = 4. RMSDEV was correlated with the VA at various follow-up intervals. The multiscalar basis components: roughness, waviness and form were separated and recovered from the wavelet soft thresholding techniques. Peaks and pits within the three-dimensional corneal surface topography were detected and localized using the wavelet hard thresholding techniques. Results. In patients with keratoconus, the RMSDEV and the MEANDEV increased from 4.31 ± 1.25 / 5.98 ± 1.88 µm pre-operatively to the 3 months follow-up (4.98 ± 1.41 / 6.92 ± 2.16 µm) and thereafter decreased continuously to the end of the follow-up (1.87 ± 0.63 / 2.63 ± 1.07 µm), whereas in Fuchs' dystrophy the respective values started at a higher preoperative level (6.36 ± 1.24 / 7.20 ± 2.64 µm) and decreased continuously over time (2.73 ± 1.10 / 3.71 ± 1.05 µm after suture removal). In the keratoconus group, the MAXPEAK was increased at the 3 month postoperative exam (8.78 ± 2.29 µm) when compared to the preoperative value (6.55 ± 2.56 µm); however, it decreased again and returned to the preoperative level after one year (6.34 ± 2.12 µm after suture removal). In Fuchs' dystrophy, the MAXPEAK was unchanged preoperatively (8.26 ± 2.83 µm) to the 3 months follow-up, but decreased continuously to the end of the follow-up period (4.57 ± 1.36 µm). The RMSDEV was significantly lower in keratoconus than in Fuchs' dystrophy pre-operatively (P = 0.01) and after suture removal (P = 0.005) and correlated inversely with VA preoperatively (R = -0.53, P = 0.04 / R = -0.69, P = 0.02), at the 1 year exam (R = -0.61, P = 0.02 / R = -0.52, P = 0.05) and after suture removal (R = -0.73, P = 0.01 / R = -0.66, P = 0.025) in keratoconus / Fuchs' dystrophy. Conclusions. The use of wavelet analysis can provide significant clinical information by separating the raw data into the parameters: “roughness”, “waviness”, “form” and various multiscalar peaks and pits. The RMSDEV, a quantitative measure for corneal irregularity, can be used as a new approach for the prediction of potential visual acuity after penetrating keratoplasty. The decomposition of the surface elevation into fundamental components is crucial for a subsequent mathematically based extraction of clinical parameters or for topography-based flying-spot ablation of irregular corneal astigmatism.

Extraction of roughness properties from captured images of surfaces

Surfaces of industrial parts need to be specified on the basis of their use and application environment. Hence, surface characterization is vital for design, manufacturing and inspection. Furthermore, the development of new industries has led to a requirement for super-smooth surfaces and for the ability to measure such surfaces accurately; therefore, the measurement of engineering surface roughness is becoming increasingly important. Many methods of measuring surface finish have been developed ranging from the simple touch comparator to sophisticated optical techniques (light scattering). The latest technology for measuring surface roughness is the computer vision systems. Unlike the stylus instruments, the optical techniques and computer vision systems have the advantages of being non-contact and are capable of measuring an area from the surface rather than a single line. This paper introduces a new technique to capture an image for a surface and then to extract the roughness heights from the captured image. A set-up consists of a charge-coupled device (CCD) video colour camera, a frame grabber, IBM-compatible PC and a microscope used to capture the images. The images were stored using the bitmap image file format (BMP). A program was written in Visual C++ to convert the captured colour images into grey scale images and then to extract the grey level for each pixel and to store it into a two-dimensional array sized to the image width and the image length. The program is capable of reading six different image file formats: these are BMP, TIFF, GIF, PCX, JPG and WMF. The grey levels range between 0 and 255. The grey level 0 represents the black colour, which represents the minimum height in the image, and the grey level 255 represents the white colour, which represents the maximum height in the image. The grey levels between 0 and 255 represent different heights according to their grey level values. After extraction of the grey levels from the image, a three-dimensional view is displayed to view the topography of the surface. The three-dimensional view can be displayed, virtually, from any point of view using the same basics as those of three-dimensional computer aided design (CAD) systems. From the three-dimensional surface topography it is easy to assess any scratches or cracks in the surface. The developed software works independently and does not need any other software. The package includes the unique feature of calculating a multitude of surface roughness parameters (59 in all) that have not been included in any other package hitherto.

Color-coded optical profilometry with >10^6 resolved depth steps

A novel, to our knowledge, approach to light-stripe triangulation configuration that allows for parallel, fast, real-time three-dimensional surface topography with an extremely large number of optically resolved depth steps is presented, analyzed, and experimentally demonstrated. The method is based on a color-coding and decoding arrangement that exploits polychromatic illumination and axially dispersing optical elements. This leads to an increase of the depth-measuring range without any decrease in the axial or the lateral resolution. Our experiments yield three-dimensional surface measurements with lateral and depth optical resolutions of <40 nm, for a depth of focus of 48 mm, resulting in 1.2 x 10(6) resolving depth steps.

Atomic Force Microscopy of RecA–DNA Complexes Using a Carbon Nanotube Tip

We report high resolution images of RecA–double stranded (ds) DNA complexes obtained by atomic force microscopy (AFM). When a carbon nanotube (CNT) tip was used, AFM images visualized the 10-nm pitch of RecA–dsDNA complexes and RecA filaments as three-dimensional surface topography without reconstruction analysis. The depth of the notch between two pitches was less than 1 nm. When adsorbed on a soft surface covered with proteins, naked DNA, RecA monomers, RecA hexamers, and short RecA filaments were all clearly resolved in one image. The high resolution images with a CNT tip provided valuable information on the initiation process of RecA-dsDNA complex formation.

Reconstruction of Laser-scanned 3D Torso Topography and Stereoradiographical Spine and Rib-cage Geometry in Scoliosis

Assessments of scoliosis are routinely done by means of clinical examination and full spinal x-rays. Multiple exposure to ionization radiation, however, can be hazardous to the child and is costly. Here, we explain the use of a noninvasive imaging technique, based on laser optical scanning, for quantifying the three-dimensional (3D) trunk surface topography that can be used to estimate parameters of 3D deformity of the spine. The laser optical scanning system consisted of four BIRIS laser cameras mounted on a ring moving along a vertical axis, producing a topographical mapping of the entire torso. In conjunction with the laser scans, an accurate 3D reconstruction of the spine and rib cage were developed from the digitized x-ray images. Results from 14 scoliotic patients are reported. The digitized surfaces provided the foundation data to start studying concordance of trunk surface asymmetry and spinal shape in idiopathic scoliosis.

Surface morphology and wear mechanisms of four clinically relevant biomaterials after hip simulator testing

The surfaces of worn components hold clues to the underlying wear mechanisms. Previous evidence suggested that the absolute wear rates of acetabular components in a hip simulator were related to mechanical behavior; we hypothesized that the surface morphology of the liners might also be sensitive to mechanical properties. A noncontact, three-dimensional surface topography measurement system based on white light interferometry was used to quantify the surface morphology of ultra-high molecular weight polyethylene, polytetrafluoroethylene, high-density polyethylene, and polyacetal liners, and their corresponding femoral heads, after 3 million cycles in a multi-directional hip simulator. Comparisons were made with the fatigue soaked and control (as machined) components. Statistically significant power law relationships were observed between the arithmetic mean surface roughness (Ra) of the worn acetabular liners and the volumetric wear rate in the hip simulator (p < 0.01, r2 = 0.52). Significant relationships were also observed between Ra and the elastic and large deformation mechanical behavior of the liner materials, measured directly from the wear-tested liners using the small punch test (p < 0.01, r2 = 0.54–0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the mechanical behavior of the polymeric materials. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 447–459, 2000.

Development of a lifting wavelet representation for surface characterization

This paper reviews the existing numerical analysis methods and their problems in surface metrology. Based on the requirements of functional analysis of surfaces, this paper proposes a lifting wavelet representation for extraction of different components of a surface. The theory of the lifting wavelet is introduced and a fast algorithm is developed. Different frequency components of the surface can be separated, extracted and then reconstructed according the intended requirements of functional analysis. The surface textures can be highlighted and multi-scalar topographical features can be identified and clearly recovered. In order to verify the behaviour of the new model, a computer simulation based on sinusoidal and triangular waveforms is used. Case studies are conducted using a series of typical surfaces of engineering and bioengineering, such as planes, cylinders and curves, measured by contact (stylus) and non-contact (phase-shifting interferometry) instruments, to demonstrate the feasibility and applicability of using the lifting wavelet model in the analysis of these surfaces.

A Comparative Study on the Three-Dimensional Surface Topography for the Polished Surface of Femoral Head

Several surface topographic techniques have been widely used in many manufacturing engineering fields for studying the surface characteristics for the practical application of manufactured surfaces. In this paper, a polished surface of a femoral head is considered for the comparative study, where the stylus based technique, the autofocused optical measurement technique, the interferometric technique, and scanning probe microscopy are applied. After the operational principles are introduced, some practical comparative measurements are reported for the polished surface. Some useful comparisons and conclusions are drawn from the comparative study. General guidelines for the 3D surface topography are also given for practical application.

Characterization of surface topography by confocal microscopy: II. The micro and macro surface irregularities

In part I, considering the autofocus and intensity methods of measurement, the principles and performance of a confocal microscope were discussed. In this part, the details of the experiments, conducted to measure and assess micro and macro surface irregularities of various machined planar and cylindrical surfaces, using a confocal scanning optical microscope (CSOM) are described. The three-dimensional surface topographies of various machined planar surfaces and also the form errors, like roundness and cylindricity, are measured and analysed. The significance of the set of new parameters, proposed for characterizing three-dimensional surface roughness and roundness measurements, is indicated. The effect of filtering on the variation in values of three-dimensional surface-topography parameters is studied. The performance of the CSOM is compared with those of conventional stylus and interferometric methods. The system is shown to have a great number of advantages in terms of three-dimensional surface mapping of planar and cylindrical surfaces and recognition of details and analysis for characterization of surfaces.

Characterization of surface topography by confocal microscopy: I. Principles and the measurement system

Surface topography and, in particular, roughness and form, plays an important role in determining the functional performance of engineering parts. The measurement and understanding of surface topography is rapidly attracting the attention of the physicist, the biologist and the chemist as well as the engineer. Optics in general played an important role in measurement and, with the advent of opto-mechatronics, it is once again at the forefront of measurement. In this paper, the principles and performance of a confocal microscope, together with the measurement system, are described. Suitable fixtures are developed and integrated with the computer system for generating three-dimensional surface and form data. Software for data acquisition, analysis of various parameters including new parameters and visualization of surface geometrical features has been developed. Both the intensity and the auto-focus methods are used to measure two-dimensional surface roughness by use of the system and results are presented. The measurement and characterization of three-dimensional surface topography and form error will be presented in part II of this paper.

Surface morphology and wear mechanisms of four clinically relevant biomaterials after hip simulator testing.

The surfaces of worn components hold clues to the underlying wear mechanisms. Previous evidence suggested that the absolute wear rates of acetabular components in a hip simulator were related to mechanical behavior; we hypothesized that the surface morphology of the liners might also be sensitive to mechanical properties. A noncontact, three-dimensional surface topography measurement system based on white light interferometry was used to quantify the surface morphology of ultra-high molecular weight polyethylene, polytetrafluoroethylene, high-density polyethylene, and polyacetal liners, and their corresponding femoral heads, after 3 million cycles in a multi-directional hip simulator. Comparisons were made with the fatigue soaked and control (as machined) components. Statistically significant power law relationships were observed between the arithmetic mean surface roughness (R(a)) of the worn acetabular liners and the volumetric wear rate in the hip simulator (p < 0.01, r(2) = 0.52). Significant relationships were also observed between R(a) and the elastic and large deformation mechanical behavior of the liner materials, measured directly from the wear-tested liners using the small punch test (p < 0.01, r(2) = 0.54-0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the mechanical behavior of the polymeric materials.

Detection of Rokitamycin-Induced Morphostructural Alterations in Helicobacter pylori by Atomic Force Microscopy

The subinhibitory and suprainhibitory concentrations of many antibiotics are capable of interfering with the morphology of bacteria, thus disrupting the integrity of their structures and reducing bacterial virulence. Studies of this type have so far been performed using optical or scanning electron microscopes, but a new type of lens-free microscope, the atomic force microscope (AFM), has recently been introduced which is capable of investigating fine three-dimensional surface topography. The present study made use of this new technique to investigate the morphological alterations in Helicobacter pylori as a bacterial specimen exposed or not to different concentrations of rokitamycin. The produced images clearly show that AFM is a very useful tool for obtaining fine-quality three-dimensional images of bacterial morphology. The breakthrough in applying this new type of microscopy is also due to the fact that the images can be digitally collected at very high resolution in the z-axis, without the need to adopt the critical point-drying method or vacuum conditions, and without the need to coat the surface of the sample with a metal layer, a result not otherwise attainable with other microscopy techniques.

Texture prediction of milled surfaces using texture superposition method

It is difficult to evaluate surface error in three- or multi-axis milling due to the complexity of the machining geometry. This paper presents texture superposition method to evaluate the surface asperity of milled surfaces. In order to derive overall surface generation mechanism of three different types of endmill cutters including a ball endmill, a filleted (torus-shaped) endmill, and a flat endmill, a generalized cutter model is proposed by introducing the fillet radius as a variable. The surface roughness is determined by the maximum height of the effective scallop including the effects of cutter marks and conventional scallops. The runout effect caused by the geometric inaccuracy of a cutter is added to make the predicted surface closer to the actual machined surface. Through these steps, three-dimensional surface topography, according to given cutting conditions and cutter types, can be formed. From machining experiments with a three-axis machining center, validity of the developed method was verified. The method proposed in this paper can be used to improve the efficiency of three- or multi-axis milling and to generate optimal cutter paths and cutting conditions.

The spectral element method for elastic wave equations—application to 2-D and 3-D seismic problems

A spectral element method for the approximate solution of linear elastodynamic equations, set in a weak form, is shown to provide an efficient tool for simulating elastic wave propagation in realistic geological structures in two- and three-dimensional geometries. The computational domain is discretized into quadrangles, or hexahedra, defined with respect to a reference unit domain by an invertible local mapping. Inside each reference element, the numerical integration is based on the tensor-product of a Gauss–Lobatto–Legendre 1-D quadrature and the solution is expanded onto a discrete polynomial basis using Lagrange interpolants. As a result, the mass matrix is always diagonal, which drastically reduces the computational cost and allows an efficient parallel implementation. Absorbing boundary conditions are introduced in variational form to simulate unbounded physical domains. The time discretization is based on an energy-momentum conserving scheme that can be put into a classical explicit-implicit predictor/multicorrector format. Long term energy conservation and stability properties are illustrated as well as the efficiency of the absorbing conditions. The accuracy of the method is shown by comparing the spectral element results to numerical solutions of some classical two-dimensional problems obtained by other methods. The potentiality of the method is then illustrated by studying a simple three-dimensional model. Very accurate modelling of Rayleigh wave propagation and surface diffraction is obtained at a low computational cost. The method is shown to provide an efficient tool to study the diffraction of elastic waves and the large amplification of ground motion caused by three-dimensional surface topographies. Copyright © 1999 John Wiley & Sons, Ltd.

An analysis of the three-dimensional surface topography of textured cold-rolled steel sheets

The surface topography of cold-rolled steel sheet affects its press-forming behaviour and also influences the appearance of the end product after painting. In this study, the three-dimensional surface topography of several steel sheets processed by different technologies has been measured. Using statistical and signal processing techniques, two-dimensional power spectral density function, two-dimensional autocorrelation function and two three-dimensional characteristic parameters of the surface topography of each steel sheet are obtained separately. Through analyzing these parameters and charts of the functions, an investigation on three-dimensional surface topography of these steel sheets is performed.

Geoscience Laser Altimeter System waveform simulation and its applications

AbstractTo study the relationship between surface topography and satellite laser altimetry waveform, a numerical model that simulates an ideal satellite laser altimeter has been developed. It has a Gaussian beam pattern and a Gaussian pulse shape. Different three-dimensional surface topographies have been used in the simulation to generate waveforms. Using a non-linear least-squares method, the generated waveforms were fitted to theoretical models to calculate surface roughness and surface slope. The outputs from the models were then compared with the values calculated from the given assumed surfaces. There is no way to distinguish between a horizontal, randomly rough surface and a smoothly sloping surface from waveform fitting alone. However, if either the surface roughness or the surface slope can be acquired independently, the other one can be determined through waveform fitting.

Three-dimensional surface characterization for orthopaedic joint prostheses.

This study attempts to investigate a range of 'better' methods for the characterization of the three-dimensional (3D) surface topography of orthopaedic joint prostheses. In this paper, a new characterization tool for the comprehensive identification and evaluation of functional features of these surface topographies is presented. For identification, the surface topography is investigated in a space-scale space, by employing wavelet analysis. The roughness, waviness and form involved in surface topography are consequently separated and recovered respectively. The multiscalar topographical features are identified and captured. The errors caused as a consequence of three-dimensional measurement methods can be reduced. After identification, the three-dimensional surface assessment techniques previously reported by Stout and co-workers are used for the quantitative evaluation of various surface roughness features of the orthopaedic joint prostheses. Moreover, the functional properties, such as bearing area, material volume and void volume which are significantly effected by large peaks, pits and scratches are studied and the location of isolated peaks, pits and scratches in the different scales is also clearly characterized. In this work, measurement of the femoral heads and acetabular cups is carried out to demonstrate the applicability of the characterization technique for the three-dimensional surface topography of orthopaedic joint prostheses.

三次元表面凹凸データの横方向間隔パラメータに関する研究

This paper deals with lateral spacing parameters of the three-dimensional surface topography data. To begin with, the method for calculating the mean surface wavelength was introduced being based on auto-correlation analysis for the virtual surface composed of orthogonal sine waves. By applying this technique to measured data, a fairly good correlation was obtained between the mean surface wavelength and lateral spacing of adjacent asperities. Additionally, the method for deciding the calculation region of the local slope and the summit shape was developed and the necessary condition for sampling interval was shown.

Contact analysis of elastic-plastic fractal surfaces

Rough surfaces are characterized by fractal geometry using a modified two-variable Weierstrass–Mandelbrot function. The developed algorithm yields three-dimensional fractal surface topographies representative of engineering rough surfaces. This surface model is incorporated into an elastic-plastic contact mechanics analysis of two approaching rough surfaces. Closed form solutions for the elastic and plastic components of the total normal force and real contact area are derived in terms of fractal parameters, material properties, and mean surface separation distance. The effects of surface topography parameters and material properties on the total deformation force are investigated by comparing results from two- and three-dimensional contact analyses and elastic and elastic-perfectly plastic material behaviors. For normal contact of elastic-perfectly plastic silica surfaces and range of surface interference examined, the interfacial force is predominantly elastic and the real contact area is approximately one percent of the apparent contact area or less, depending on the mean interfacial distance. The analysis can be easily modified to account for anisotropic fractal surfaces and different material behaviors.