Function Of Surface Topography Research Articles

On-Surface Domino Reactions: Glaser Coupling and Dehydrogenative Coupling of a Biscarboxylic Acid To Form Polymeric Bisacylperoxides.

Herein we report the on-surface oxidative homocoupling of 6,6'-(1,4-buta-1,3-diynyl)bis(2-naphthoic acid) (BDNA) via bisacylperoxide formation on different Au substrates. By using this unprecedented dehydrogenative polymerization of a biscarboxylic acid, linear poly-BDNA with a chain length of over 100 nm was prepared. It is shown that the monomer BDNA can be prepared in situ at the surface via on-surface Glaser coupling of 6-ethynyl-2-naphthoic acid (ENA). Under the Glaser coupling conditions, BDNA directly undergoes polymerization to give the polymeric peroxide (poly-BDNA) representing a first example of an on-surface domino reaction. It is shown that the reaction outcome varies as a function of surface topography (Au(111) or Au(100)) and also of the surface coverage, to give branched polymers, linear polymers, or 2D metal-organic networks.

Human Tumor-Associated Fibroblasts can Sense the Topography of their Environment

Cells can sense and adapt to mechanical properties of their environment. The local geometry of the extracellular matrix can control the motility, shape, and cytoskeletal structure of cells. In particular, surface topography has been shown to modulate cell morphology, migration, and proliferation. However, the underlying mechanisms by which topography is sensed by cells remain unclear. Here we investigate the effect of surface topography on the morphology and cytoskeletal dynamics of human pancreatic tumor associated fibroblast cells (TAFs). TAFs have been shown to promote the progression of pancreatic tumors, metastasis, and resistance to therapy. Mechanisms by which these cells stimulate invasiveness and metastasis of cancer cells are not well understood. We have previously shown that these cells can mechanically sense the stiffness of their environment. In this study, we used an arrangement of parallel ridges (nanopatterns), with variable spacing between the ridges, to investigate the response of pancreatic TAFs to the topography of their environment. We found that TAFs align along the direction of the ridges and modulate their shape depending on the spacing between the ridges. Fluorescence imaging of cells labeled with EGFP-palladin (an actin crosslinking protein) further revealed that actin stress fibers are organized along the nanopatterns and that the degree of this alignment is dependent on the spacing between the ridges. In order to obtain a deeper understanding of the underlying mechanisms, we tracked the movement of palladin structures in cells as this enables the measurement of cytoskeletal dynamics as a function of surface topography. Our results provide insight into the mechanisms of how cells sense and respond to substrate topography.

Evaluation of early stage human bone marrow stromal proliferation, cell migration and osteogenic differentiation on μ-MIM structured stainless steel surfaces

It is well established that surface topography greatly affect cell-surface interactions. In a recent study we showed that microstructured stainless steel surfaces characterized by the presence of defined hexagonally arranged hemisphere-like structures significantly affected cell architecture (shape and focal adhesion size) of primary human bone mesenchymal stromal cells. This study aimed at further investigating the influence these microstructures (microcline protruding hemispheres) on critical aspects of cell behaviour namely; proliferation, migration and osteogenic differentiation. As with previously reported data, we used primary human bone mesenchymal stromal cells to investigate such effects at an early stage in vitro. Cells of different patients were utilised for cell migration studies. Our data showed that an increase in cell proliferation was exhibited as a function of surface topography (hemispheres). Cell migration velocity also varied as a function of surface topography on patient specific basis and seems to relate to the differentiated state of the seeded cell population (as demonstrated by bALP positivity). Osteogenic differentiation, however, did not exhibit significant variations (both up and down-regulation) as a function of both surface topography and time in culture.

Comparative molecular assessment of early osseointegration in implant-adherent cells

ObjectiveThe objective of our study is to identify the early molecular processes involved in osseointegration associated with a micro roughened and nanosurface superimposed featured implants. Materials and methodsThirty-two titanium implants with surface topographies exhibiting a micro roughened (AT-II) and nanosurface superimposed featured implants (AT-I) were placed in the tibiae of 8 rats and subsequently harvested at 2 and 4days after placement. Total RNA was isolated from cells adherent to retrieved implants. A whole genome microarray using the Affymetrix Rat Gene 1.1 ST Array followed by validation of select genes through qRT-PCR was used to describe the gene expression profiles that were differentially regulated by the implant surfaces. ResultsWhile significant differences at the gene level were not noted when comparing the two-implant surfaces at each time point, the microarray identified several genes that were differentially regulated at day 4 vs. day 2 for both implant surfaces. A total of 649 genes were differentially regulated at day 4 vs. day 2 in AT-I and 392 genes in AT-II implants. Functionally relevant categories related to ossification, skeletal system development, osteoblast differentiation, bone development, bone mineralization and biomineral tissue development were upregulated and more prominent at AT-I (day 4 vs. day 2) compared to AT-II. Analysis of the downregulated gene lists (day 4 vs. day 2) with average fold change >2 (were not statistically significant) revealed the biological processes involved with the inflammatory/immune response gene expression. The number of genes that were associated with the inflammatory/immune response category was greater for AT-I than AT-II. ConclusionsThe presence of nanosurface features modulated in vivo bone response. Gene regulation implicating osteogenesis as well as the inflammatory/immune responses that occur as a function of surface topography may affect bone mass shortly after implant placement.

Surface topography effect on galling resistance of coated and uncoated tool steel

Tribological evaluation of the tool steel, focused on determining coefficient of friction and critical load for galling initiation against austenitic stainless steel as a function of surface topography was carried out in a load-scanning test rig. Surfaces investigated included turned, ground, polished, shot penned and laser surface textured cold work tool steel. Additionally, effect of surface roughness and post-polishing on galling resistance of TiN and DLC coated surfaces was investigated.Results of this investigation show that by removing sharp peaks polishing of the bearing surface gives plateau-like topography and improves galling properties of forming tool steel. This becomes even more important when using hard ceramic coatings (i.e. TiN). When superbly polished contact surfaces can give similar galling resistance as otherwise obtained through contact lubrication. However, application of low friction coatings or introduction of micro-dimples with proper density and contact lubrication will result in superior galling resistance of the surface.

A Solution for Lightly Loaded Adhesive Rough Surfaces With Application to MEMS

The stiction forces that exist in microelectromechanical systems (MEMS) are characterized by surface energy and surface roughness. To simulate this contact condition, a three-dimensional fractal surface geometry and an adhesive contact model for a single asperity are used together to create a numerical adhesive rough surface solution methodology. This novel method of solution determines the characteristic adhesive contact type for each individual asperity uniquely at the time of load and area integration. Such a simulation more accurately represents the physics of the asperity-based contact. Numerical results for the adherence force are presented as a function of surface topography, interface compliance, and the work of adhesion for a MEMS interface. The magnitude of the force required to separate an adhesive rough surface interface is given in relation to a polysilicon system.

Rotation invariant classification of rough surfaces

Rotation of a rough, textured surface will not produce a simple rotation of the image texture. It follows that where image texture is a function of surface topography, existing rotation invariant texture classification algorithms are not robust to surface rotation. The effect of surface rotation on the observed image is analysed using an existing theory, a novel scheme to stabilise classification accuracy is proposed and evaluated. The scheme uses photometric stereo to estimate the surface derivatives, which are then used as the input to a classifier. Simulations indicate that, where the level of image noise is moderate or low, the approach is successful in maintaining classification accuracy. Furthermore, in some circumstances, the extra information used by the algorithm allows classification accuracy superior to that based on one image alone, even without rotation.

接触面剛性の評価法について

In this paper, the technique how to estimate the interface stiffness is discussed by considering the surface topography at the interface and material properties. The interface stiffness has a close relation to the vibratory characteristics of machine structures. The interface stiffness is originated from the spring action of micro asperities on interface in normal or parallel directions to the interface. The theoretical interface stiffness is obtained as a function of surface topography and material properties. The calculated results are compared with the experimental results. In the estimation of the interface stiffness, it must be considered that the elastic properties of micro asperities are different from that of the base material, owing to the deformation when the interface micro asperities are formed.

Tribological problems in electrical contacts

Electrical contacts are considered from the point of view of tribological behaviour, and their classification is presented. The main problems in friction, wear and lubrication in connection with the field of application are examined. Contact resistance of electrical contacts is evaluated as a function of surface topography, load and mechanical properties of materials. The interrelation of electrical performances with friction and wear is discussed taking into account material properties and lubricant effects.

Detection of abandoned coal mine workings and underground voids by microgravity : Butler, D Min EngngV41, N4, April 1989, P245–247

Subsurface density changes can be detected by very precise surface gravity measurements. A feasibility study, combined with field experience using modern instruments, will indicate the probability of success. In addition to projected anomaly parameters, surface conditions that effect the survey precision must be evaluated. Examples with excavated zones at 9m (30ft) of depth and +-22 microgal error are compared to the same model at 30 m (98 ft) of depth. The figures illustrate anomaly detectability. The survey error is a function of surface topography and lateral density variation in the very near surface.

Cobalt modified iron oxides: dependence of surface topography on preparation method and resulting influence on magnetic properties

Depending on which method of synthesis is adopted for the deposition of a cobalt ferrite layer on gamma -Fe/sub 2/O/sub 3/ particles, very different surface topographies of the modified particles are observed in electron micrographs. The modifying layers are either grown as smooth epitaxially crystallized films or as a coating of more or less isolated ferrite particles. In the later case, significantly lower H/sub c/-enhancements after modification are observed. The layer is still magnetically strongly interacting with the core particle of gamma -Fe/sub 2/O/sub 3/. To explain the results, differences in magnetostatic energy as a function of surface topography are discussed. >

On the squeeze effect of a lubricant between two rough surfaces. (2nd report. Rectangular contact surfaces).

The squeezing of a lubricant between two rough surfaces having rectangular contact area is examined. Firstly, the approximate equation of squeeze flow is introduced for smooth rectangular surfaces. This approximate equation is a function only of the aspect ratio of the rectangular surface, and it agrees well with the exact calculation by the theory of Reynolds. Then, the approximate equation is extended to the case of a rough rectangular surface. The calculation of lubricant squeezing by the extended equation agrees well with the experimental results. The squeeze coefficient is the criterion for the load-carrying capacity of the contact surface due to the lubricant squeezing. This coefficient is obtained as a function of surface topography and lubricating film thickness. The representative equation of the squeeze coefficient for the rectangular surface is the same as that for the circular surface. The fundamental information is important for improving the dynamic characteristics of sliding elements.

On the squeeze effect of a lubricant between two rough surfaces. (1st report. Circular contact surfaces).

The clarification of the squeezing mechanism of a lubricant which flows between rough surfaces is quite important for the improvement of the dynamic characteristics of sliding elements, and for the elimination of stick-slip vibration. In the present study, the surface roughness effect on the squeezing mechanism is examined experimentally using rough surfaces of circular contact area. The distance between two surfaces, that is, the lubricant film thickness treated in this study, is widely distributed. When the distance becomes small and the surface roughness effect cannot be neglected, micro-squeezing of the lubricant may occur. It is seen in the experiment that the effect of surface roughness on lubricant squeezing is remarkable. The squeezing of the lubricant is simulated by assuming a surface asperity model and by extending the theory of Reynolds. The simulated result is quantitatively agreeable with the experimental results. The load-carrying capacity of the circular contact surface is obtained as the function of surface topography and the initial film thickness.

On the Squeeze Effect of Lubricant Between Two Rough Surfaces

The clarification of the squeezing mechanism of lubricant, which flows between rough surfaces, is quite important for the improvement of the dynamic characteristics of sliding elements, and for the elimination of stick-slip vibration. In the present study, the surface roughness effect on the squeezing mechanism is examined. In the first place, the approximate equation of squeeze flow is introduced for flat surfaces. Then, the approximate equation is extended to the case of rough surface. The calculation of lubricant squeezing by the extended equation agrees well with the experimental results in both cases of circular and rectangular surfaces. The squeeze coefficient is the criterion for the load carrying capacity of the contact surface due to the lubricant squeezing. Then, this coefficient is obtained as a function of surface topography and oil film thickness. The representative equation of the squeeze coefficient for the rectangular surface is the same as for the circular surface. The fundamental information is important to improve the dynamic characteristics of sliding elements.