Influence Of Surface Topography Research Articles

Directed Differentiation of Adipose-Derived Stem Cells Using Imprinted Cell-Like Topographies as a Growth Factor-Free Approach.

The influence of surface topography on stem cell behavior and differentiation has garnered significant attention in regenerative medicine and tissue engineering. The cell-imprinting method has been introduced as a promising approach to mimic the geometry and topography of cells. The cell-imprinted substrates are designed to replicate the topographies and dimensions of target cells, enabling tailored interactions that promote the differentiation of stem cells towards desired specialized cell types. In fact, by replicating the size and shape of cells, biomimetic substrates provide physical cues that profoundly impact stem cell differentiation. These cues play a pivotal role in directing cell morphology, cytoskeletal organization, and gene expression, ultimately influencing lineage commitment. The biomimetic substrates' ability to emulate the native cellular microenvironment supports the creation of platforms capable of steering stem cell fate with high precision. This review discusses the role of mechanical factors that impact stem cell fate. It also provides an overview of the design and fabrication principles of cell-imprinted substrates. Furthermore, the paper delves into the use of cell-imprinted polydimethylsiloxane (PDMS) substrates to direct adipose-derived stem cells (ADSCs) differentiation into a variety of specialized cells for tissue engineering and regenerative medicine applications. Additionally, the review discusses the limitations of cell-imprinted PDMS substrates and highlights the efforts made to overcome these limitations.

Microbiological aspects and challenges of dairy powders – II: Biofilm/biofouling

Biofilms generated during production of dairy/whey powders can cause contamination, spoilage and equipment failures, posing a significant challenge in the agri‐food sector. Factors including temperature, protein composition, equipment structures and surface topography influence biofilm formation and resistance to cleaning and sanitation. Several species of bacteria are well adapted to these challenges, posing the most pressing concerns of dairy whey process. Despite efforts to improve cleaning‐in‐place strategies, bacteria persist in difficult‐to‐clean areas. This review provides insights into bacterial biofouling in dairy protein powders, highlighting the mechanism of biofilm formation, predominant bacterial genera, critical processing steps and strategies to manage biofilm formation during the manufacturing process.

Multiscale simulation scheme by using a finite-difference derivative framework for lubrication surface

To exactly describe lubrication problems modelling micro-scale influence in rough lubricated contact is unavoidable. In this study a novel computational scheme for lubricated problem is presented based on two-scale homogenization method, which facilitates solving the two-scale problem. Homogenization model of mass fluxes is implemented at the micro-scale domain, and represents the influence of surface topography. A linearization method is developed to derive finite derivatives of mass fluxes at the micro-scale domain defined by scale separation. The key strength of the proposed procedure is the finite difference derivative coupling which represents the lubricated problem inclusive of the effect of surface topography. The effectiveness of the proposed multiscale scheme is validated by comparing with the deterministic method. The numerical results show that increasing topography amplitude can improve the performance of journal bearing in terms of load carrying capacity and friction coefficient.

The influence of surface topography and microstructure of zirconia on initial bacterial adhesion of streptococcus mutans– in vitro study

The purpose of this research in this paper is to study the physical and chemical characteristics of the surfaces and the topography of the surfaces of zirconium materials used for the processing of fixed prosthetic works and their influence on the surface adhesion of Streptococcus mutans bacteria. The samples used for examination are produced from zircon material, they are divided into two groups, the first group after sintering are polished without glaze, while the second group, after sintering, are covered with a layer of glaze. For the realization of the experimental part of this research, the following methods and analyzes were used: surface roughness measurement (SR), contact angle measurement, surface free energy determination (SFE), biofilm formation and preparation for scanning with a microscope electronic (SEM) Specimens produced from zirconia, polished but unglazed showed higher contact angle values 90.340, while glazed samples showed lower values than unglazed ones 61.640, Surface free energy measurements of zirconia samples polished without glaze showed significantly lower values (24.31mJ/m2 ) compared to the values obtained in the zircon samples covered with glaze (40.66mJ/m2 ), The surface roughness values are higher in unglazed zirconia samples and is 0.65μm, while in the polished and glazed zirconia samples, the roughness of the surfaces is less 0.29μm, SEM analysis results show that the smallest number of attached bacteria is found on the surfaces of samples with unglazed zircon (8 bacteria), while in samples with zircon covered with glaze, a much larger number of bacteria (26 bacteria) were found on their surfaces. The roughness of the surfaces was shown to have no effect on the bacterial surface adhesion of these samples.

The influence of surface topography on thermal contact resistance of 7075-T6/beryllium bronze

The calculation of thermal contact resistance is crucial for studying heat transfer between solids. Surface topography has a significant impact on thermal contact resistance, however, the influence of surface topography parameters on thermal resistance is still limited to the parameters such as roughness. The effect of other topography parameters still lacks. Therefore, in this paper, randomly non-Gaussian rough surfaces with specified root mean square roughness value, kurtosis, skewness, and wave lengths are generated by two-dimensional digital filtering method combined with Johnson transformation system. The contact mechanical deformation, heat transfer performance and thermal contact resistance between 7075-T6 and beryllium bronze QBe2 are studied using ABAQUS. The results show that thermal contact resistance is correlated with real contact area. The thermal contact resistance decreases with the increase of pressure, and gradually gets a rise with the increase of root mean square roughness value. Normal distribution of asperities, the isotropic surface, and zero or a low negative value of skewness all can enhance heat transfer efficiency. Our results provide guidance for designing surface topography when heat transfer need be considered in application.

Influence of surface topography on the surface film resistance in earth plasters

In this paper, the influence of the surface topography on the surface film resistance that occurs during mass transfer was investigated for earth plasters. Raw earth plaster samples have been made in order to achieve different surface topography. First, the mass transfer wet-cup procedure has been conducted on these raw earth plasters to determine the value of the surface film resistance Zs. Two wind tunnels have been designed to control the nature and the speed of the ventilation flow above the wet-cups to determine the influence of the flow and speed of ventilation on Zs. Results have shown that Zs was not depending on the ventilation speed in laminar mode and that is was about the size of the roughness Ra of the plaster. In a second time, the convective heat transfer coefficient h has been measured by a heat transfer experiment and a FEM model. The heat/mass transfer analogy from Chilton–Colburn has been used to estimate the surface film resistance during heat exchanges Zs∗. Results have shown that Zs and Zs∗ could not be compared.

Stratified topography theory to understand frictional electrification for sliding triboelectric nanogenerators

Researchers are used to investigating the influence of surface topography on the frictional electrification of sliding triboelectric nanogenerators TENGs from the perspective of a single-stratum topography; however, a stratified feature has shared reality in closer relationships. Here, we characterize the stratified feature of the topographies for the sliding TENGs, and link them to the electrification voltages, finding that the frictional electrification strongly depends on the characteristics of the small-scale component in a stratified topography, which suggest us to develop a stratified electrification model for mechanism reveal. Based on the dependence, we also succeed in identifying the stratified topographic characteristics with frictional electrification signals by machine learning including support vector machine and convolutional neural network, which can be envisioned as a tool for topography measurement. This is the first demonstration of a stratified topography theory for sliding TENGs, providing new insights into the mechanism reveal and functional application of frictional electrification.

Impact of Surface Roughness on the Impingement of Urea–Water Solution Droplets

The understanding of impingement processes is crucial for optimizing automotive selective catalytic reduction (SCR) systems. An accurate description of this behavior helps design exhaust systems and increases the validity of modeling approaches. A component test bench was set up, featuring a droplet chain generator for producing droplet sizes typically found in the urea–water solution sprays of SCR systems. A heatable impingement plate with an interchangeable surface enabled investigation of the influence of surface roughness. Data were acquired using a high-speed camera and image postprocessing. The droplet–wall interaction could be described using different regimes. An approach to characterizing impingement behavior based on weighted-regime superposition enabled gradual transitions between regimes, instead of step-like changes. It was observed that the surface roughness increased the droplet–solid contact area and generated thermal-induced secondary droplets at lower temperatures. A region of enhanced mechanical disintegration of the droplet was found, caused by peaks of the surface shearing off parts of the droplet. The probability of a droplet rebounding from the wall was reduced on a rough surface, due to the interference of the surface spikes with the droplet’s spreading and contracting motion. Additionally, the influence of surface topography was investigated using a shot-peened surface. Caused by this surface’s reduced root mean square slope, the aforementioned enhancement of mechanical disintegration was not observed.

Experimental Investigations on the Influence of Surface Topography in Sliding Wear Behaviour of Sustainable Polymeric Composites

Experimental Investigations on the Influence of Surface Topography in Sliding Wear Behaviour of Sustainable Polymeric Composites

Waviness Affects Friction and Abrasive Wear

Abrasive wear can have a detrimental effect on machinery, especially in the mining and construction industries. To prolong machinery lifetime and cut down energy consumption, a thorough understanding of abrasive wear is essential: surface topography measurement and interpretation (including form, waviness, and roughness) are vitally important. However, the potentially crucial influence of surface topography intricacies on tribological behavior has been obscured since roughness and waviness are considered simple scalar quantities in most cases (e.g., roughness Ra and waviness Wt). In this work, the complete waviness profile of the sliding track was used to shed light on the influence of surface topography on abrasive wear. Bearing steel (100Cr6, AISI 52100) pins and disks were tribologically tested in a flat-on-flat contact with Al2O3-based slurries as interfacial medium. Using slurries with two different particle sizes, 5 and 13 μm, we found that friction fluctuates only with small abrasive particles (5-µm slurry) and relatively low waviness disks. It was found that even small surface deviations (albeit minimized and controlled for) can significantly increase the friction coefficient—up to 91%. Remarkably, not only are frictional fluctuations strongly correlated with the disk’s initial waviness profile, but these small fluctuations correlate with unevenly distributed high wear. These findings enhance our understanding of the friction wear structure and provide the basis for exploring how surfaces can be optimized for better tribological performance.Graphical

The Densification Characteristics of Polished Fused Silica Glass and Its Scattering Characteristics

Optical surface scattering is an important subject in the field of optics. Previous studies of surface scattering mainly focused on the influence of surface topography and often ignored the influence of the mechanical property’s change caused by polished surface densification. In this paper, we study the mechanical property of fused silica glass in detail and analyze the scattering behaviour of actual fused silica glass’s surface with sub-angstrom roughness, considering the topography and the change of refractive index. Experimental results show that there is a negative correlation between the height and modulus on the surface of roughly polished fused silica glass, and the correlation coefficient γ = −0.29 was determined. After super−polishing, the mechanical properties of the sample surface become significantly uniform with a roughness of Rq = 0.06 nm and Ra = 0.05 nm, and the correlation coefficient becomes γ = −0.02. Moreover, the nanoindentation test proves that silica glass surfaces have been densified during polishing. Based on the densification characteristics, the bidirectional reflectance distribution function (BRDF) was simulated by the finite element method. The result indicates that the densification characteristics will increase the scattering intensity. This work not only deepens the understanding of the properties of polished optical surfaces but also the surface scattering characteristics of optical elements.

Influence of Gutta-Percha Surface on Enterococcus faecalis Initial Adhesion In Vitro: An Atomic Force Microscopy Study.

The aim of this study was to evaluate the influence of surface topography of gutta-percha (GP) cones and plasticized disks of GP on the initial adhesion of Enterococcus faecalis (E. faecalis). The GP cones (Tanari and Dentsply brands) were cut 3 mm from the apical portion and fixed on a glass slide. To make the disks, the cones were thermoplasticized in standardized molds. The specimens were divided into groups according to the shape of the GP and the presence or absence of the bacteria. For contamination, the strain of E. faecalis (ATCC 29212) was used. The surface topography was analyzed using an atomic force microscope (AFM). The surface, roughness, and waviness parameters were evaluated by the Kruskal-Wallis and Dunn test. The comparison between disks and cones showed significant differences, where the cones were rougher, with a higher value attributed to the Dentsply cone (DC group). The same was observed for the waviness. After contamination, there was greater bacterial accumulation in cones, especially in their valleys, but both the surface and the topography became more homogeneous and smoother, with no differences between disks and cones of both brands. The topographic surface of the GP, at the micro and nanoscale, influences the initial adhesion of E. faecalis, with a greater tendency for contamination in regions associated with the presence of roughness and waviness. In this context, plasticization of GP is indicated, as it reduces surface irregularities compared to cones, contributing to less retention of bacteria.

Influences of surface topography of porous titanium scaffolds manufactured by powder bed fusion on osteogenesis

Powder bed fusion (PBF) has emerged as a useful metal-three-dimensional (3D) printing technology for manufacturing porous structures; it has been widely employed for the production of medical implants. Multiple previous reports have suggested that the bone ingrowth characteristics of porous structures, among the most important factors for medical implants, are affected by 3D printing parameters (e.g., pore shape). The topography of 3D-printed metal surfaces can also influence cellular responses, including osteoblast differentiation. The surface topography may change according to the shape of the printed pores. Nevertheless, it remains unclear how the surface topography changes. In addition, it is still unknown how the pore shape and the resulting surface topography can further impact the bone ingrowth efficiency of the porous structure. Therefore, to better understand the relationship, we prepared Ti–6Al–4V specimens with different pore shapes (i.e., circular, triangular, and rectangular) using the PBF method, then analyzed the surface topographies of these 3D scaffolds based on curvature and roughness profiles. Through subsequent in vitro studies, we investigated how changes in pore shape and surface topography affect the activity of Saos-2 human osteosarcoma cells. The results of this study confirmed that the curvature radii and local surface roughness change according to pore shape because of the characteristics of PBF. Furthermore, differences in local surface topography and pore shape led to differences in cell proliferation and differentiation. Through our findings, we anticipate that the meticulous design of pore shape and sophisticated control of the processing parameters, such as laser speed and paths, in the fabrication of orthopedic and dental implants will result in significantly enhanced bone ingrowth efficiency.

The influence of surface topography on mixed plasto-elastohydrodynamic lubrication in point contacts

Surface topography plays an important role in mixed lubrication. However, the influence of the surface topography's morphological characteristics on lubrication performance is still not fully understood. In this article, we employ digital filtering and the Johnson transformation system, and we use a mixed plasto-elastohydrodynamic lubrication model to simulate the lubricated contact between rough spherical surfaces with different morphological characteristic parameters. The influence of skewness, kurtosis, and the wavelength factor, that is, the ratio between the autocorrelation lengths in the transversal and longitudinal directions, on contact pressure, film thickness, and von Mises (subsurface) stress, is examined with the mixed plasto-elastohydrodynamic lubrication model. The results confirm that plastic deformation leads to lower pressure distribution, distributed over a larger contact area than the pure elastohydrodynamic lubrication solution. Moreover, it is found that an increase in the kurtosis may improve the lubrication performance, while the opposite is true for the skewness and the wavelength factor. We believe that the insights obtained by means of the numerical simulations presented herein, would facilitate the design and manufacturing processes of the surfaces used for machine elements operating in the mixed plasto-elastohydrodynamic lubrication regime.

Effect of substrate surface roughness on the microstructure and properties of laser surface cladding of Tribaloy T-400 on mild steel

This study reports a maiden systematic investigation of the effect of substrate surface roughness on the microstructure and relevant mechanical properties following laser surface cladding (LSC) of Co-based Tribaloy T-400 alloy on mild steel substrate. Before LSC, controlled and distinctly different degrees of surface roughness was introduced on the mild steel plates by sandblasting and belt grinding. The roughness of the sandblasted substrate was considerably higher which resulted in significantly higher laser energy absorption during LSC. As a result, although the deposited clads in either case were defect-free and of the same composition, both depth of melting of the substrate and degree of intermixing between the substrate and clad were considerably higher in the clad deposited on the sandblasted substrate. A detailed analysis of the microstructure and composition across the clad and alloyed (or intermixing) zone revealed that substantial change in composition due to solute intermixing, surface alloying, and dilution of Fe-content had completely altered the microstructure, elemental distribution, and phase aggregate of the clad. Co, Mo, and Si-containing MgZn2 type hard primary Laves phase, present in large amounts in the clad deposited on mild steel substrate following belt grinding, was not observed in the clad developed by LSC on the sandblasted substrate. As the high hardness of T-400 clad usually arises due to the presence of a large quantity of primary Laves phase, the clad deposited on mild steel after belt grinding recorded almost 40 % higher hardness and 67 % lower wear rate. In addition, corrosion resistance of the clad deposited after belt grinding was also marginally higher. Thus, surface roughness prior to laser irradiation is an important parameter to ensure the desired microstructure and properties of the clad, besides clad composition and laser process parameters employed in LSC. This important aspect of influence of surface topography on properties of the clad is often ignored or rarely highlighted in LSC of metallic systems.

Effect of surface roughness on laser surface alloying of additively manufactured 17-4PH stainless steel

In the present work, the evolution of the final microstructure in 17-4PH stainless steel additively manufactured and subjected to the laser surface alloying with boron and nitrogen is described with special emphasis on the influence of surface topography and roughness. It was shown that character of the surface topography, and hence the surface roughness of the additively manufactured samples plays a major role in the development of microstructure during laser surface alloying. Dendritic microstructure of a solid solution with a small amount of eutectic in the interdendritic space was observed in a laser-melted zone (LMZ) of so-called smooth samples. In contrast, fully eutectic microstructure was revealed in the LMZ of the rough samples. This resulted in significantly different microhardness of the LMZ of both samples, i.e. 317.0 ± 12.7 and 636.7 ± 18.5 HV0.1 for the smooth and rough samples. The microstructural features and varying microhardness were found to be attributed to the different degree of the steel alloying primarily with boron in the LMZ, significantly affected by the initial roughness of the sample surface. This mechanism can be used to enhance laser surface alloying of the additively manufactured products.

An Overview of the Stability and Fretting Corrosion of Microgrooved Necks in the Taper Junction of Hip Implants.

Fretting corrosion at the head-neck interface of modular hip implants, scientifically termed trunnionosis/taperosis, may cause regional inflammation, metallosis, and adverse local tissue reactions. The severity of such a deleterious process depends on various design parameters. In this review, the influence of surface topography (in some cases, called microgrooves/ridges) on the overall performance of the microgrooved head-neck junctions is investigated. The methodologies together with the assumptions and simplifications, as well as the findings from both the experimental observations (retrieval and in vitro) and the numerical approaches used in previous studies, are presented and discussed. The performance of the microgrooved junctions is compared to those with a smooth surface finish in two main categories: stability and integrity; wear, corrosion, and material loss. Existing contradictions and disagreements among the reported results are reported and discussed in order to present a comprehensive picture of the microgrooved junctions. The current research needs and possible future research directions on the microgrooved junctions are also identified and presented.

Elastic reverse time migration method in vertical transversely isotropic media including surface topography

AbstractCompared with acoustic seismic data, multi‐wave and multi‐component seismic data can offer some special media properties. Elastic reverse time migration is a high‐precision migration method to image multi‐wave and multi‐component seismic data. Anisotropy widely exists in the earth, and it is important to take anisotropy into account and correct the anisotropy effect for obtaining high‐quality image results during migration. However, accurate elastic reverse time migration in anisotropic media is still a challenging task, particularly for areas with irregular surface topography. To resolve these issues, a new elastic reverse time migration method is developed to correct the anisotropy effect in vertical transversely isotropic media with surface topography. We first use the modified pseudo‐acoustic wave equations of vertical transversely isotropic media to assist the elastic wavefield separation in vertical transversely isotropic media for suppressing the crosstalk artefacts between different wave modes and further generating high‐quality images. We then use a topography‐related filter to remove the influence of surface topography on the migration results of elastic reverse time migration. The advantage of the proposed topography‐related filter is that we do not need to make any changes to the conventional finite‐difference method based on regular grids but can calculate the wavefield in the areas with irregular surface topography efficiently. The synthetic examples with different surface topographies models demonstrate that our proposed elastic reverse time migration method can correct the anisotropy effect effectively, remove the influence of surface topography on elastic reverse time migration results, and generate high‐quality images.

Shot Peening Induced Corrosion Resistance of Magnesium Alloy WE43

Mechanical surface treatments like shot peening provide a pathway to stabilize degradation of magnesium alloys without compositional change. The resultant subsurface grain refinement, twin dislocations, and nanoprecipitation improves fatigue life but lowers corrosion resistance of magnesium. The lower corrosion resistance is justified by an increase in surface roughness after shot peening. However, a skewed estimate of surface area is expected to justify the inconsistent corrosion behavior of shot peening magnesium compared to other mechanical surface treatments. The objective of this research was to understand the influence of surface topography due to shot peening on the corrosion kinetics of a magnesium alloy WE43. Results showed that the corrosion resistance increased after shot peening WE43 when using an adjusted surface area that better accounts for the topographical features under exposure to corrosion attack.

Effect of Surface Topology on the Apparent Thermal Diffusivity of Thin Samples at LFA Measurements.

This paper deals with the problem of the influence of surface topography on the results of thermal diffusivity measurements when determined using the instantaneous surface heat source method, also called the pulse method. The analysis was based on numerical tests carried out using Comsol Multiphysics software. The results of experimental investigations on the actual material structure using an electron microscope, an optical microscope and a profilometer were used to develop a numerical model. The influence of the non-uniformity of the surface of the tested sample on the determined values of half-time of the thermal response of the sample’s rough surface to the impulse forcing on the opposing flat surface was determined by developing the data for simulated measurements. The effect of the position of the response data reading area on the obtained simulation results was also analyzed. The obtained results can be used to improve the accuracy of experimental heat transfer studies performed on thin-film engineering structures depending on the uniformity and parallelism of the material applied to engineering structures. The difference in half-life determination error results for various analyzed models can be as high as 16.7%, depending on the surface from which the responses of the heating impulse are read. With an equivalent model in which 10% of the material volume corresponds to the rough part as a single inclusion, hemisphere, the error in determining thermal diffusivity was equal to 3.8%. An increase in the number of inclusions with smaller weight reduces an error in the determination of thermal diffusivity, as presented in the paper.