Rough Surface Topography Research Articles

Corrosion Behavior of Aqua-Blasted and Laser-Engraved Type 316L Stainless Steel

The effect of aqua blasting and laser engraving on surface microstructure development, residual stress and corrosion resistance of type 316L stainless steel has been investigated. Aqua blasting resulted in a deformed near-surface microstructure containing compressive residual stresses. Subsequent laser engraving produced a surface layer with tensile residual stresses reaching to a depth of 200 microns. Changes of surface roughness topography were accompanied by the development of a thick oxide/hydroxide film after laser engraving. The atmospheric corrosion behavior of all surfaces with MgCl2-laden droplets was compared to their electrochemical response in 1M NaCl and 0.7 M HCl aqueous solutions. The measured total volume loss after atmospheric corrosion testing was similar for all investigated surface conditions. Laser-engraved surface exhibited the smallest number of corrosion sites, but the largest mean corrosion depth.

Experiments on the sound transmission at the water-air interface for different source-interface distances

The water-air interface is a nearly perfect reflecting boundary for acoustic waves due to the high impedance contrast between the two media. In many marine applications, ranging from geophysical measurements to bioacoustics, the sea surface has an important impact. A rough sea surface topography leads to complex scattering and interference for acoustic frequencies with similar wavelength or higher than the wavelength of the interface. In geophysical applications and infrasound the frequencies of interest often have larger wavelengths. At the same time, the source within these applications is mostly located close to the interface with respect to its wavelength. In this case, an increased transmission could be expected as experiments with acoustic transducers demonstrate [D. C. Calvo et al., J. Acoust. Soc. Am. 134, 3403-3408 (2013)]. We design two experiments with sources close to the interface while changing the distance between the source and the water-air surface. For the first experiment, a water gun, which creates large cavities, is placed in water. Second, a signal gun, as used in athletics, is positioned in air. The acoustic transmission from both sides is measured and investigated. We find an increasing transmission coefficient for lower frequencies and decreasing distance between source and interface.

Experimental analysis of rough surface topography and modifying the humidity effect in AFM images to improve the topography quality

Atomic force microscopy (AFM) is one of the most powerful tools for imaging surfaces at the nano-scale. The existence of disruptive forces in the output images that are obtained from AFM in a moist environment causes low-quality images at the nano-scale. Therefore, to enhance the quality of topography, eliminating the effect of these forces is of great importance. For this purpose, increasing accuracy in modeling and simulation of vibration behavior of AFM piezoelectric micro-cantilever (MC) and its comparison with experimental tests is important to improve the quality of images. Using modified couple stress (MCS) and classical theory, this article addresses inhomogeneous four-layered AFM MC considering Timoshenko and Euler-Bernoulli beam models in 2D modeling. In 3D modeling by using the COMSOL software, cantilever frequency and time responses were obtained and compared with different theories including classical and MCS. Laboratory tests were conducted not only to validate results but also to evaluate the effect of humidity on topography image quality in the amplitude mode. Furthermore, using simulation results based on the Timoshenko beam theory and MC behavior prediction, the capillary effect which causes noise in experimental images was filtered and the image quality which is taken by the AFM is improved.

Numerical and analytic study of rough surface morphology on the angular distribution of eroded impurity

The impact of rough surface morphology on the angular distribution of eroded impurities has been investigated with the three‐dimensional (3D) rough surface code SURO and a newly developed analytic model. The property of the rough surface structure can be described by the shadow angle of the rough surface in SURO, which is defined as the ratio of the horizontal characteristic length to the initial surface roughness. The SURO simulation results show that the influence of the rough surface on the angular distribution of eroded impurities comes into play when the shadow angle is larger than a threshold value. The larger shadow angle of the rough surface leads to a stronger shift of the angular distribution of the eroded impurities. Different rough surface topographies have been used in the SURO code to check the angular distribution of the eroded impurities. It is found that the shift tendency of the angular distribution is similar for different structures of the rough surface. Based on the numerical modelling results, an analytical model has been developed to investigate the impact of the shadow angle on the angular distribution of the eroded impurities, which shows the consistent result as the SURO simulations.

The role of macrophage polarization on fibroblast behavior-an in vitro investigation on titanium surfaces.

This study investigated the effect of smooth and rough titanium surface topographies on macrophage polarization and their influence on gingival fibroblast behavior cultured on titanium surfaces. RAW 264.7 macrophages were seeded on smooth (pickled titanium (PT)) and rough Sand-blasted with Large grit particles followed by Acid-etching (SLA) titanium surfaces and first investigated for macrophage polarization towards tissue-inflammatory M1 macrophages or wound-healing M2 macrophages. Thereafter, culture media collected from macrophages on both surfaces were cultured with gingival fibroblasts seeded on their respective topographies. All experiments were performed in triplicate with three independent experiments. Macrophages seeded on SLA surfaces polarized towards tissue-inflammatory M1 macrophages at early time points. Immunofluorescent staining and RT-PCR analysis demonstrated higher levels of iNOS and gene expression of IL-1β, IL-6, and TNF-alpha on SLA surfaces at 3days when compared to both tissue culture plastic (TCP) and PT surfaces (p<0.001). Very little differences were found between smooth PT surfaces and TCP. Interestingly, proliferation assay (CCK-8) suggested that conditioned media (CM) from macrophages seeded on SLA surfaces drastically inhibited gingival fibroblast proliferation at 3 and 5days (p<0.001). Meanwhile, CM from macrophages cultured on SLA surfaces also significantly reduced collagen 1 synthesis on SLA surfaces at 14days as assessed by immunofluorescent staining (p<0.001). The results from this study demonstrate that the polarization of macrophages towards a pro-inflammatory (M1) phenotype on SLA surfaces may have a negative impact on gingival fibroblast behavior on titanium surfaces. Future strategies to better modulate macrophage polarization should be investigated to support a favorable immune response and encourage tissue integration. As SLA surfaces have a potential to shift macrophages towards tissue-inflammatory M1 macrophages, this might be a negative impact for soft tissue healing. Therefore, SLA surfaces should be kept within the bone, as when in contact with soft tissue, they are prone to support a lack of soft tissue integration leading to inflammation.

Ag nanoparticles decorated ion-beam-assisted TiO2 thin films for tuning the water splitting activity from UV to visible light harvesting

Abstract In this study, tuning of the photoelectrochemical (PEC) water splitting activity from UV to visible region was achieved on RF magnetron sputtered TiO 2 thin films grown under various Ar ion-beam energies (0, 60 and 110 eV). We propose a new strategy of energetic Ar ion-beam projection towards the substrate surface during the film growth. The resulting TiO 2 films were decorated with silver (Ag) nanoparticles for efficient plasmon-enhanced PEC water splitting activity under visible light illumination. Firstly, the ion-beam-energy induced a well-defined anatase TiO 2 (101) phase with improved crystallinity, which is key factor responsible for the enhanced PEC activity. Interestingly, XPS studies revealed the presence of Ti 3+ states along with the Ti 4+ ones, which sensitively influence the UV and visible light absorption. Furthermore, AFM images revealed rough surface topography of the films, which is highly desirable for large area exposure to the electrolyte. In addition, the UV–vis transmittance spectra showed a stronger red shift in the optical absorption edge and a reduced band gap, which are crucial factors for charge carrier generation. Studies on Ag nanoparticles decorated TiO 2 films show that, due to the transfer of surface plasmon energy from the Ag nanoparticles to TiO 2 , efficient visible light water splitting activity was achieved. This is about five times higher than that observed for TiO 2 films under UV light. Comprehensively, this novel approach could pave the way for efficient visible-light-driven PEC water splitting activity.

Regulation of RAW264.7 macrophage polarization on smooth and rough surface topographies by galectin-3.

Recognition of topographical features induces phenotypic changes in macrophages although the receptors and signaling pathways are not completely characterized. As integrin molecules in focal adhesions/podosomes are in intimate contact with topography and topography modulates the NFkB pathway through cholesterol enriched raft-associated adhesive signaling structures we hypothesized that a cell-surface signaling complex comprised of galectin-3 together with its ligand CD98 and integrinβ1 is important for topography-directed lineage determination. This study used polished, sand blasted and acid etched (SLA) surfaces and two novel grooved topographies (G1 and G2) produced by anisotropic etching of Si <1 1 0> to evaluate the role of galectin-3 in macrophage polarization in RAW 264.7 macrophages, as determined by gene expression and morphology. In the presence of the galectin-3 inhibitor, lactose, the M2 marker (mannose receptor) was down-regulated while the M1 marker (iNOS) was up-regulated on smooth and rough surfaces. This skewing of phenotype suggests a role for galectin-3 in macrophage polarization towards the M2 phenotype. Additionally, we evaluated the role of PI3K on polarization using PI3K inhibitor LY294002. We found that the M2 marker was down-regulated on both PO (surface polished) and G1 surfaces implicating PI3K in lineage determination. We also found that surface topography altered cell morphology; macrophages had a larger area on G2 surfaces. Lactose treatment significantly reduced the cell area on all topographies suggesting that the galectin-3 is also involved in signaling complexes triggering the rearrangement of the actin cytoskeleton. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2499-2509, 2017.

An experimental and theoretical study on soft chemically grown CuS thin film for photosensor application

Herein we report, the photosensitivity of in-situ chemical bath deposition (CBD) grown CuS thin film for the first time, also comparatively very short deposition time of 40min and much lower bath temperature i.e. 45°C are reported. The structural, surface topographical, optical, electronic and electrical properties of as-grown CuS thin film have been investigated. The XRD analysis revealed the formation of Orthorhombic (Covellite) structure with preferential growth along [113] direction having ~14nm average crystallite size. Raman spectrum indicating a sharp peak at 474cm−1 confirms the formation of CuS covellite structure. Polycrystalline nature of the film has been confirmed from the concentric ring pattern obtained from TEM–SAED and AFM revealed the rough surface topography with RMS roughness of ~27nm. The bond lengths of Cu(1)-S(1) and S(1)-S(1) were obtained from the DFT calculations based on GGA approximation, suggest S-S bond is much stronger as compared to Cu-S bond; these results are in good agreement with the Raman result. The film shows higher absorbance in the visible region with a band gap of 2.2eV. The electrical properties show a drastic increase in current after light illumination of 50 W which increases with increasing light intensity and tends to attain a saturation state around 200 W. The highest photosensitivity of ~66% has been calculated for 200 W with fast response time of ~34s and a complete recovery. These results represent CuS thin films promising candidature for photosensor application.

Dynamic modeling of oblique non-uniform piezoelectric MC in liquid with various percentages of glycerin in the presence of rough surface

One of the most useful applications of an AFM is imaging of biological particles in a liquid medium. The increase of the topography accuracy in a liquid medium requires accurate dynamic modeling of a Microcantilever (MC). This article investigates the accurate dynamic modeling of the non-uniform AFM piezoelectric MC with rectangular geometry in the amplitude mode in liquid medium for rough surfaces. To increase the accuracy of the modeling, the Modified couple stress (MCS) theory in the liquid medium according to the Timoshenko beam model has been used. Moreover, the differential quadrature (DQ) method has been used for solving equations, because in comparison with the other methods it has a high speed in solving equations and is accurate in the number of fewer elements. In addition, the accurate force modeling has been established by considering the shear forces caused by liquid on the sides of the piezoelectric MC by solving the Navier-Stokes equations, and by considering the hydrodynamic force, squeeze force and applied forces between the sample surface and the MC tip. The results illustrate that utilizing higher vibration modes affect the quality of rough surface topography with the step roughness in the liquid medium and increase the quality of surfaces topography in the tapping mode, especially in the second MC vibration mode. Moreover, it should be noted that the sensitivity of the MC vibration amplitude to the piezoelectric MC angle is higher in comparison with other investigated parameters.

Ultrasonic evaluation of the pitch of periodically rough surfaces from back side

The geometrical features of internal surfaces are important parameters in the field of non-destructive testing such as corrosion inspection or artistic qualities of material surfaces. Although stylus profiling and optical scattering are commonly used for measuring both random and periodically rough surface topography, they are only applicable to accessible surfaces. However, there are many cases in which the surface to be evaluated is inaccessible. For example, integrity monitoring of inner surfaces of pipes is required to ensure proper functions and safeguard quality. Unfortunately, little attention has been paid to the measurement of inaccessible periodic surfaces. Since inaccessible surfaces do not permit contact or optical measurement, application of ultrasonic technique from back side is an appropriate candidate among others. In this paper, an ultrasonic pulse-echo technique is investigated to evaluate the pitch of periodically rough surfaces which is inaccessible or hidden on the back side. The pitch of back surface profile is evaluated based on the diffraction grating theory for oblique incidence of P-wave, SV-wave, and SH-wave. The applicability of the proposed technique was verified by both numerical simulation and experiment. It is found that the angle of incidence should be larger than 45° to enhance the accuracy. SH-wave shows better results compared with SV-wave due to the effect of mode conversion. Moreover, using SH-wave is an effective way for evaluation of the pitch because SH-wave is more sensitive than P-wave with shorter wavelength. On the other hand, P-wave is the best solution to obtain the highest resolution of measurement with higher signal to noise ratio.

Surface roughness effects on plasma near a divertor plate and local impact angle

The impact of rough surface topography on the electric potential and electric field is generally neglected due to the small scale of surface roughness compared to the width of the plasma sheath. However, the distributions of the electric potential and field on rough surfaces are expected to influence the characteristics of edge plasma and the local impact angle. The distributions of plasma sheath and local impact angle on rough surfaces are investigated by a two dimension-in-space and three dimension-in-velocity (2d3v) Particle-In-Cell (PIC) code. The influences of the plasma temperature andsurface morphology on the plasma sheath, local impact angle and resulting physical sputtering yield on rough surfaces are investigated.

Modeling and analysis of titanium alloy in wire-cut EDM using Grey relation coupled with principle component analysis

This research work presents the comparative usage of brass and molybdenum wires in the Wire electrical discharge machining (WEDM) process study on surface roughness and material removal rate (MRR) performance of titanium alloy. The optimum parameters of the model such as pulse current, pulse on-time and pulse off-time have been determined through L9 orthogonal array of Taguchi design of experiment methodology. Wear rate of brass wire is found to increase with rise in input energy in machining titanium alloy than in the case of molybdenum wire. The experimental analysis showed that the combination of higher levels of pulse current is essential to achieve simultaneous maximisation of MRR and minimisation of surface roughness by using Grey relational analysis coupled with principal component analysis. The surface roughness topography has been described by performing scanning electron microscope study. The WEDM machined surface revealed that craters are found on the machined surface of titanium alloy when using brass wire than the high strength, high wire tension and more erosion resistant molybdenum wire.

Effect of tool surface topography on friction with carbon fibre tows for composite fabric forming

The effect of tool surface roughness topography on tow-on-tool friction relevant to the dry forming of composite fabrics is investigated. A comprehensive range of tool average surface roughness Ra values from 0.005 to 3.2 μm was used in friction testing with carbon fibre tows. The measured slope of these surfaces, which is the critical surface topographical characteristic, increased significantly with increasing roughness amplitude. Friction was found to be sensitive to roughness topography for very smooth surfaces (Ra<0.1μm) and increased with decreasing roughness slope and amplitude. For rougher surfaces (Ra>0.1μm), friction was relatively insensitive to roughness slope and amplitude. A finite element idealisation of the tow-on-tool contact was used to explain these results in terms of the level of tow-tool conformance. Smooth surfaces have low slopes which allow good conformance, and hence high real contact area and friction. Rougher surfaces have high slopes, particularly at shorter wavelengths, which prevents good conformance. In this case, point contact between fibres and surface dominates, leaving the resulting friction less sensitive to roughness.

A fractal study of sound propagation characteristics in roughened porous materials

The influence of rough elements of porous materials on sound propagation characteristics in roughened porous materials is investigated. Rough surface topography on the roughened porous materials is simulated by the fractal geometry theory, in which relative roughness is defined clearly as a function of the fractal dimension, porosity, average diameter and diameter ratio of the hexagonal elements on pore wall of the porous materials. Based on the sound propagation model of the smooth porous materials, a sound propagation model of the roughened porous materials is built. The effective density and bulk modulus, acoustic impedance and propagation constant, flow resistivity and sound absorption coefficient of the roughened porous materials are derived and discussed as a function of the relative roughness. It is demonstrated that the sound absorption coefficient of the roughened porous materials is improved as the relative roughness increases. The model predictions for the sound absorption coefficient of the roughened porous materials are well agreed with that of the existing test results.

Simple model of surface roughness for binary collision sputtering simulations

It has been shown that surface roughness can strongly influence the sputtering yield – especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the “density gradient model”) which imitates surface roughness effects. In the model, the target’s atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient – leading to increased sputtering yields, similar in effect to surface roughness.

Preventing probe induced topography correlated artifacts in Kelvin Probe Force Microscopy

Kelvin Probe Force Microscopy (KPFM) on samples with rough surface topography can be hindered by topography correlated artifacts. We show that, with the proper experimental configuration and using homogeneously metal coated probes, we are able to obtain amplitude modulation (AM) KPFM results on a gold coated sample with rough topography that are free from such artifacts. By inducing tip inhomogeneity through contact with the sample, clear potential variations appear in the KPFM image, which correlate with the surface topography and, thus, are probe induced artifacts. We find that switching to frequency modulation (FM) KPFM with such altered probes does not remove these artifacts. We also find that the induced tip inhomogeneity causes a lift height dependence of the KPFM measurement, which can therefore be used as a check for the presence of probe induced topography correlated artifacts. We attribute the observed effects to a work function difference between the tip and the rest of the probe and describe a model for such inhomogeneous probes that predicts lift height dependence and topography correlated artifacts for both AM and FM-KPFM methods. This work demonstrates that using a probe with a homogeneous work function and preventing tip changes is essential for KPFM on non-flat samples. From the three investigated probe coatings, PtIr, Au and TiN, the latter appears to be the most suitable, because of its better resistance against coating damage.

ENERGY ABSORPTION IN A LOAD–UNLOAD CYCLE OF KNEE IMPLANT USING FRACTAL MODEL OF ROUGH SURFACES

Roughness measurement of knee implant surfaces is investigated. The study of roughness measurement show that the topography of knee implant surface is multi-scale and surface spectra follows a power law behavior. A magnification of rough surface topography implies that there is no difference between original and magnified profile of implant surface. For implant surface, statistical parameters such as variance of height, curvature, and slope are found to be scale-dependent. Fractal representation of implant surface shows that the size-distribution of the multi-scale contacts spots follows a power law and is characterized by the fractal dimension of implant surface. Fractal surface description of the rough surfaces of knee implant is used to obtain force–displacement relationship of the contact force. Using an approximate function through the fusion of two piecewise functions, energy absorption of a knee implant in a single cycle of load–unload is obtained.

Engineering Porous Poly(lactic acid) Scaffolds with High Mechanical Performance via a Solid State Extrusion/Porogen Leaching Approach.

A knotty issue concerning the poor mechanical properties exists in the porogen leaching approach to porous scaffolds, despite its advantage in tuning pore structure. To address this hurdle, solid state extrusion (SSE) combined with porogen leaching was utilized to engineer porous scaffolds of poly(lactic acid) (PLA). Advances introduced by poly(ethylene glycol) (PEG) caused the PLA ductile to be processed and, on the other hand, enabled the formation of interconnected pores. Thus, a well-interconnected porous architecture with high connectivity exceeding 97% and elevated porosity over 60% was obtained in the as-prepared PLA scaffolds with the composition of NaCl higher than 75.00 wt % and PEG beyond 1.25 wt %. More strikingly, the pore walls of macropores encompassed countless micropores and rough surface topography, in favor of transporting nutrients and metabolites as well as cell attachment. The prominent compressive modulus of the PLA scaffolds was in the range of 85.7–207.4 MPa, matching the normal modulus of human trabecular bone (50–250 MPa). By means of alkaline modification to improve hydrophilicity, biocompatible porous PLA scaffolds exhibited good cell attachment. These results suggest that the SSE/porogen leaching approach provides an eligible clue for fabricating porous scaffolds with high mechanical performance for use as artificial extracellular matrices.

Novel grooved substrata stimulate macrophage fusion, CCL2 and MMP-9 secretion.

Rough surface topographies on implants attract macrophages but the influence of topography on macrophage fusion to produce multinucleated giant cells (MGC) and foreign body giant cells (FBGC) is unclear. Two rough novel grooved substrata, G1 and G2, fabricated by anisotropic etching of Silicon <110> crystals without the use of photolithographic patterning, and a control smooth surface (Pol) were produced and replicated in epoxy. The surfaces were compared for their effects on RAW264.7 macrophage morphology, gene expression, cyto/chemokine secretion, and fusion for one and five days. Macrophages on grooved surfaces exhibited an elongated morphology similar to M2 macrophages and increased cell alignment with surface directionality, roughness and cell culture time. Up-regulated expression of macrophage chemoattractants at gene and protein level was observed on both grooved surfaces relative to Pol. Grooved surfaces showed time-dependent increase in soluble mediators involved in cell fusion, CCL2 and MMP-9, and an increased proportion of multinucleated cells at Day 5. Collectively, this study demonstrated that a rough surface with surface directionality produced changes in macrophage shape and macrophage attractant chemokines and soluble mediators involved in cell fusion. These in vitro results suggest a possible explanation for the observed accumulation of macrophages and MGCs on rough surfaced implants in vivo. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2243-2254, 2016.

Role of prostaglandin E2 in the modulation of Wnt canonical signaling in cells on microstructured titanium surfaces.

Rough surface topography enhances the activation of Wnt canonical signaling, a pathway required for osteoblast differentiation. The present study investigated the effects of the modulation of prostaglandin E2 (PGE2) signaling on osteoblastic differentiation on titanium surfaces for endosseous implants with different topographies. C2C12 cells were plated on polished or acid-etched/sand-blasted (SLA) titanium discs and stimulated with 1 μM PGE2 or 100 nM cyclooxygenase inhibitor indomethacin. Activation of Wnt canonical signaling was measured with a reporter system. Gene expression was measured in the same cell system by real-time polymerase chain reaction (RT-PCR). Osteoblastic MC3T3 cells were then plated on polished or SLA titanium discs with or without indomethacin, and their proliferation and the expression of osteoblast-specific genes was assessed by RT-PCR. Cell morphology was furthermore studied on SEM, and cell adhesion was assessed by fluorescent labeling of focal adhesion. PGE2 decreased Wnt signaling stimulation in cells growing on polished or SLA surfaces, while indomethacin increased the expression of Wnt target genes in C2C12 and MC3T3 cells, by reporter assay. Moreover, indomethacin increased the expression of early differentiation marker alkaline phosphatase in MC3T3 cells on polished discs and of late marker osteocalcin in cells on SLA titanium. Prostaglandin signaling affects the activation of Wnt canonical pathway in osteoblastic and mesenchymal cells on microstructured surfaces.