White Light Confocal Microscopy Research Articles

On the evolution of surface roughness during deformation of polycrystalline aluminum alloys

Surface roughening of polycrystalline Al–Mg alloys during tensile deformation is investigated using white light confocal microscopy. Materials are tested that differ only in grain size. A height–height correlation technique is used to analyze the data. The surface obeys self-affine scaling on length scales up to a correlation length which approximately equals the grain size and above which no height correlation is present. The self-affine scaling exponent increases initially with strain and saturates at a value around 0.9. A linear relation is observed between root-mean-square roughness and both strain and grain size. The observed roughness is explained as the result of the combined effect of a self-affine roughening on a subgrain scale and a grain scale roughening caused by orientation differences between neighboring grains.

3D-Characterisation of Sheet Metal and Roller Surfaces by Means of Confocal Microscopy

The measurement and evaluation of sheet metal surface characteristics is of increasing importance, due to the significant functional impact on finishing processes like forming and varnishing. For a comprehensive and useful description of textured topographies including nonstatistical characteristics, a simple profile evaluation based on 2D roughness parameters is no longer sufficient. The introduction of area-imaging white light confocal microscopy offers, in contrast to tactile profiling methods of comparable accuracy, the clear advantage of contact-free and extremely fast 3D data capture. The capabilities and benefits of this technology in interaction with sophisticated 3D area analysis methods are demonstrated by measurement examples of sheet metal and roller surfaces. A newly-developed mobile confocal measurement system for direct roller measurements is introduced.

Surface metrology of engineering surfaces by means of the multi-pinhole technique

Surface metrology by means of optical principles is widely used in production and research of engineering surfaces and micro-electronics parts. This paper presents the latest development in confocal white-light microscopy with multi-pinhole technique. After a brief introduction and discussion of the main features and benefits of this new confocal measurement system, the advantages and limits are described and compared with the well-established white-light interferometry technique. It can clearly be shown that, due to the physical filter technique with pinholes and the use of large-aperture microscope objectives, the confocal method is superior for engineering surfaces with steep slopes. This is illustrated by comparing the results of measurements of the white-light confocal technique with white-light interferometry.

In Vivo Laser and White-Light Confocal Microscopic Findings of Human Conjunctiva

To report in vivo laser and white-light confocal microscopic findings of human conjunctiva to investigate the potential application of these confocal microscopes as diagnostic devices for normal and pathologic conjunctiva. Two healthy volunteers, 28- and 35-year-old men, participated in this study. The temporal bulbar conjunctiva, which was approximately 5 mm away from the limbus, was examined by in vivo laser and white-light confocal microscopic analysis. Using laser confocal microscopy, at least two different cell types could be distinguished in both subjects: conjunctival superficial epithelial cells and conjunctival basal epithelial cells. In contrast, conjunctival epithelial cells could not be visualized using white-light confocal microscopy. These results indicate that laser confocal microscopy, but not white-light confocal microscopy, can be used to visualize in vivo human conjunctiva. Further investigations in a large number of normal subjects and in patients with conjunctival pathologies are required to fully evaluate the usefulness of this device in daily clinical ophthalmology.

Hydroxyapatite thin films grown by pulsed laser deposition and radio-frequency magnetron sputtering: comparative study

Hydroxyapatite (HA) thin films for applications in the biomedical field were grown by pulsed laser deposition (PLD) and radio-frequency magnetron sputtering (RF-MS) techniques. The depositions were performed from pure hydroxyapatite targets on Ti–5Al–2.5Fe (TiAlFe) alloys substrates. In order to prevent the HA film penetration by Ti atoms or ions diffused from the Ti-based alloy during and after deposition, the substrates were pre-coated with a thin buffer layer of TiN. In both cases, TiN was introduced by reactive PLD from TiN targets in low-pressure N 2. The PLD films were grown in vacuum onto room temperature substrates. The RF-MS films were deposited in low-pressure argon on substrates heated at 550 °C. The initially amorphous PLD thin films were annealed at 550 °C for 1 h in ambient air in order to restore the initial crystalline structure of HA target. The thickness of the PLD and RF-MS films were ∼1 μm and ∼350 nm, respectively. All films were structurally studied by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray spectrometry (EDS) and white light confocal microscopy (WLCM). The mechanical properties of the films were tested by Berkovich nano-indentation. Both PLD and RF-MS films mostly contain HA phase and exhibit good mechanical characteristics. Peaks of CaO were noticed as secondary phase in the GIXRD patterns only for RF-MS films. By its turn, the sputtered films were smoother as compared to the ones deposited by PLD (50 nm versus 250 nm average roughness). The RF-MS films were harder, more mechanically resistant and have a higher Young modulus.

White-Light and Laser Confocal Microscopic Findings of Rabbit Conjunctiva

To report laser and white-light confocal microscopic findings of ex vivo rabbit conjunctiva to investigate the potential application of these confocal microscopes as diagnostic devices for normal and pathologic conjunctiva. Three male albino rabbits were killed and six eyeballs were removed with as much bulbar conjunctiva as possible. The bulbar conjunctiva approximately 5 mm away from the limbus was then subjected to an ex vivo laser and white-light confocal microscopic analysis. Using laser confocal microscopy, conjunctival epithelial cells, subepithelial conjunctival vessels, and sclera were clearly observed. By contrast, white-light confocal microscopy yielded images of conjunctival epithelium, subepithelial layers, and sclera that were not clearly defined. This study indicates that laser confocal microscopy has a superior ability to visualize ex vivo, non-fixed conjunctiva when compared with white-light confocal microscopy. It also suggests that the laser confocal microscope might be a useful, non-invasive, in vivo, "quasi-cytological" device for observing and diagnosing the conjunctival condition in humans.

Electron microscopy studies of octa-calcium phosphate thin films obtained by pulsed laser deposition

Octa-calcium phosphate (OCP), Ca8(HPO4)2(PO4)4·5H2O, is present as transient compound in the precipitation of hydroxyapatite (HA) and biological apatites. Because of these characteristics, OCP plays a crucial role in the in-vivo mineralization of human bones and teeth. The use of OCP in developing new generations of bone prosthesis stands therefore for an innovative challenge. This paper reports studies of OCP structures grown in the form of thin films by pulsed laser deposition (PLD) with emphasis on electron microscopy investigations. OCP films were grown on etched Ti substrates, using an UV KrF* excimer laser source (λ=248 nm, τ≥20 ns). Films were deposited in low-pressure (50 Pa) water vapors environment on substrates heated at 20–180 °C. We performed annealing treatments in water vapors and ambient pressure at substrate temperatures identical to those used during deposition. Comprehensive structural and morphological investigations were carried out with different based-electron microscopy procedures. Grazing incidence X-ray diffraction (GIXRD) and white light confocal microscopy were also applied to characterize the films. Ca/P atomic ratio of films was determined by energy dispersive X-ray spectrometry, electron energy loss spectroscopy and X-ray photoelectron spectroscopy. The obtained films generally exhibit an amorphous structure, as evidenced by GIXRD. Nevertheless, cross-section transmission electron microscopy investigations provide supplementary information about the film characteristics and material crystallization in small domains. OCP nanoparticles coalesce and grow perpendicular to the substrate in a tree-like structure, comparable to a coral reef.

Microstructure, surface topography and mechanical properties of slip cast and powder injection moulded microspecimens made of zirconia

Abstract Investigations on ceramic microspecimens made of Y2O3-stabilized ZrO2 produced by slip casting or micro powder injection moulding are introduced. During the production of the microspecimens, feedstocks and sintering conditions were varied. Differently moulded specimens were examined with respect to their microstructure and surface topography using light microscopy, scanning electron microscopy (SEM) and confocal white light microscopy. Additionally, the mechanical characteristics were investigated by three-point bending tests using a micro universal testing device. The statistical analysis was realised by means of the Weibull theory and interpreted by the aid of SEM images of fracture surfaces. This research allowed to understand correlations between different feedstocks used, process parameters like the sintering conditions applied and the resulting characteristics as well as material properties of the microspecimens. These results could be used to improve the production process.

Growth of calcium phosphate thin films by in situ assisted ultraviolet pulsed laser deposition

Calcium phosphate (CaP) thin films including hydroxyapatite were intensively studied in order to optimize the technology of the bone prostheses manufacturing. A drawback in the CaP films processing is the poor mechanical characteristics, especially hardness, tensile strength and adherence to the metallic substrate. We report a new method for the growth of high quality CaP films with substantial improvement of the mechanical properties: pulsed laser deposition (PLD) assisted by in situ ultraviolet (UV) radiation emitted by a low pressure Hg lamp. The depositions were made on Si and Ti-5Al-2.5Fe alloys in very low ambient oxygen at pressures of 10 −2 to 10 −1 Pa with the substrates maintained at 500–600 °C temperature. The films were analyzed by electron microscopy, white light confocal microscopy (WLCM), grazing incidence X-ray diffraction and Berkovich nanoindentation. The films were crystalline and exhibited remarkable mechanical characteristics with values of hardness and Young modulus of 6–8 and 150–170 GPa, respectively, which are uncommonly high for the CaP ceramics. The UV lamp radiation enhanced the gas reactivity and atoms mobility during processing, while the tensile strength between the film’s grains and the bonding strength at the CaP film-substrate interface were increased.

Mechanical properties improvement of pulsed laser-deposited hydroxyapatite thin films by high energy ion-beam implantation

Major problems in the hydroxyapatite (HA), Ca 5(PO 4) 3OH, thin films processing still keep the poor mechanical properties and the lack in density. We present a study on the feasibility of high energy ion-beam implantation technique to densify HA bioceramic films. Crystalline HA films were grown by pulsed laser deposition (PLD) method using an excimer KrF ∗ laser ( λ=248 nm , τ FWHM ≥20 ns ). The films were deposited on Ti–5Al–2.5Fe alloys substrates previously coated with a ceramic TiN buffer layer. After deposition the films were implanted with Ar + ions at high energy. Optical microscopy (OM), white light confocal microscopy (WLCM), grazing incidence X-ray diffraction (GIXRD) and Berkovich nanoindentation in normal and scratch options have been applied for the characterization of the obtained structures. We put into evidence an enhancement of the mechanical characteristics after implantation, while GIXRD measurements confirm that the crystalline structure of HA phase is preserved. The improvement in mechanical properties is an effect of a densification after ion treatment as a result of pores elimination and grains regrowth.

Morphology of corneal nerves using confocal microscopy.

The aim of the current study was to evaluate the distribution and morphology of corneal nerves as seen by means of white light confocal microscopy. This study analyzed images of corneal nerves that were obtained using the Tomey Confoscan slit scanning confocal microscope (40x/0.75 objective lens). The images were classified according to their location within the cornea. The objective and subjective evaluation of the images involved measuring, grading, or judging a number of parameters from both individual pictures and from each single nerve fiber within any image. The in vivo observations made in this work are in agreement with those of previous histologic studies. The general scheme of corneal innervation is described as originating from thick and straight stromal nerve trunks that extend lateral and anteriorly and give rise to plexiform arrangements of progressively thinner nerve fibers at several levels within the stroma. From there, nerve fibers perforate Bowman's layer and eventually form a dense neural plexus just beneath the basal epithelial cell layer, which is characterized by tortuous and thin beaded nerve fibers interconnected by numerous nerve elements; nerve fibers from this plexus are known to be responsible for the innervation of the epithelium. This study provides convincing evidence of the suitability of confocal microscopy to image corneal nerves, the only drawback being the limited resolution in terms of the differentiation of the ultrastructure of nerve bundles.

Confocal microscopy in cornea guttata and Fuchs’ endothelial dystrophy

AIMS To report the appearances of cornea guttata and Fuchs’ endothelial dystrophy from white light confocal microscopy. METHODS Seven eyes of four consecutive patients with cornea guttata were prospectively examined....