Effect Of Surface Topography Research Articles

Bone surface mimicked PDMS membranes stimulate osteoblasts and calcification of bone matrix

Cellular microenvironments play a crucial role in cell behavior. In addition to the biochemical cues present in the microenvironments, biophysical and biomechanical properties on surfaces have an impact on cellular functionality and eventually cellular fate. Effects of surface topography on cell behavior are being studied extensively in the literature. However, these studies often try to replicate topographical features of tissue surfaces by using techniques such as chemical etching, photolithography, and electrospinning, which may result in the loss of crucial micro- and nano- features on the tissue surfaces such as bone. This study investigates the topographical effects of bone surface by transferring its surface features onto polydimethylsiloxane (PDMS) membranes using soft lithography from a bovine femur. Our results have shown that major features on bone surfaces were successfully transferred onto PDMS using soft lithography. Osteoblast proliferation and calcification of bone matrix have significantly increased along with osteoblast-specific differentiation and maturation markers such as osteocalcin (OSC), osterix (OSX), collagen type I alpha 1 chain (COL1A1), and alkaline phosphatase (ALP) on bone surface mimicked (BSM) PDMS membranes in addition to a unidirectional alignment of osteoblast cells compared to plain PDMS surfaces. This presented bone surface mimicking method can provide a versatile native-like platform for further investigation of intracellular pathways regarding osteoblast growth and differentiation.

Effect of CFRP surface topography on the adhesion and strength of composite-composite and composite-metal joints

Manufacturing carbon-fibre reinforced polymer (CFRP) composites via different techniques often leads to contrasting surface topographies. Such differences can affect any subsequent surface pre-treatments that are performed and these can ultimately affect joint strength. In the present work, CFRP adherends made using compression moulding or autoclaving were investigated. Pre-treatment techniques of acetone cleaning, plasma treatment, and grit blasting were studied. It was found that the patterned surfaces which had resulted from the vacuum autoclave moulding resulted in improved joint performance when CFRP substrates were bonded together (homogeneous bonding) compared to joints formed with flatter surfaces following compression moulding. However, when CFRP substrates were bonded to flat aluminium alloy substrates (hybrid bonding) the patterned surfaces resulted in inferior joint performance compared to the flatter CFRP substrates. It is proposed that the dissimilarity of surface topographies on the metal and composite substrates negatively influences the strength of the joint.

Effect of surface topography on dendritic growth in lithium metal batteries

Lithium (Li) metal, which has the advantages of high theoretical capacity, low redox potential, and low density, is considered an ideal anode material for next-generation battery systems. However, the dendritic morphology of Li-metal electrodeposition during the charging process remains challenging because it results in active Li depletion, poor cycling performance, and safety issues. Herein, the effect of surface topography on dendrite growth was quantitatively revealed by an electro-chemo-mechanical phase-field model. The surface topography of the Li-metal battery was measured and quantified using the arithmetic mean roughness (Ra), root mean square roughness (Rq), impulse factor (Rp), skewness, and kurtosis. The simulation results revealed that the arithmetic mean height of the bare electrode and the height of the highest tip compared to the average height were highly correlated with dendrite growth. It was also demonstrated that controlling the surface topography, applied voltage, and external pressure can effectively suppress dendritic growth. Furthermore, the exposed surface of the electrode generated by the size difference or misalignment of the electrodes induced considerable dendrite growth. We believe that our quantitative analysis provides guidance for processing the surface roughness of practical Li-metal batteries.

Joining CFRP/Ti stacks by directed energy deposition: Surface topography effects on interface formation and bonding

Compared to traditional joining techniques, the directed energy deposition (DED) technique enables the fabrication of carbon fiber reinforced polymer (CFRP)/titanium (Ti) stacks with a tailored three-dimensional (3D) Ti structure. In this work, we designed and structured four surface topographies on Ti sheets to manipulate the CFRP/Ti contact surfaces. The effects of surface topography on interfacial formation mechanism were investigated by experimental and numerical approaches. The results found that the pores dominated interfacial structures in CFRP/Ti stacks without surface patterns, yet physical gaps played a vital role in line/grid-patterned CFRP/Ti stacks. The interfacial bonding strength significantly improved when applying as-patterned Ti sheets, which was attributed to the prevented slippage or shearing by penetrated grooves as well as alleviated interfacial residual stress and distortion. This paper uncovered the interfacial formation and bonding mechanisms of CFRP/Ti stacks with different surface topographies, paving a way for improving the mechanical performance of metal/polymer stacked components used in multiple industries.

Development of a numerical modelling method to predict the seismic signals generated by wind farms

In efforts to reduce greenhouse gas emissions, renewable energies have been increasingly leveraged to generate power; in particular, the number of wind turbines has risen sharply in recent years and continues to grow. However, being mechanically coupled to the earth, wind turbines also generate ground vibrations, which can have adverse effects on the capability of seismic observatories to detect and analyse earthquakes; nevertheless, the distances at which these signals modulate seismic records are disputed between the operators of wind farms and seismic observatories. Here, to quantify the noise signal amplitudes at distant seismometers, we develop the first numerical model to predict the seismic wavefield emitted by wind farms and simulate the complex effects of wavefield interferences, surface topography and attenuation. This modelling approach can reliably quantify the influences of multiple wind turbines on ground motion recordings and thus provide necessary information to aid decision-making in advance of wind farm installation.

Effect of the crystallographic c-axis orientation on the tribological properties of the few-layer PtSe2

Two-dimensional (2D) transition metal dichalcogenides are potential candidates for ultrathin solid-state lubricants in low-dimensional systems owing to their flatness, high in-plane mechanical strength, and low shear interlayer strength. Yet, the effects of surface topography and surface chemistry on the tribological properties of 2D layers are still unclear. In this work, we performed a comparative investigation of nanoscale tribological properties of ultra-thin highly-ordered PtSe2 layers deposited on the sapphire substrates with the in-plane and out-of-plane crystallographic orientation of the PtSe2c-axis flakes, and epitaxial PtSe2 layers. PtSe2c-axis orientation was found to has an impact on the nanotribological, morphological and electrical properties of PtSe2, in particular the change in the alignment of the PtSe2 flakes from vertical (VA) to horizontal (HA) led to the lowering of the coefficient of friction from 0.21 to 0.16. This observation was accompanied by an increase in the root-mean-square surface roughness from 1.0 to 1.7 nm for the HA and VA films, respectively. The epitaxial films showed lower friction caused by lowering adhesion when compared to other investigated films, whereas the friction coefficient was similar to films with HA flakes. The observed trends in nanoscale friction is attributed to a different distribution of PtSe2 structure.

Assessing the combined effect of surface topography and substrate rigidity in human bone marrow stem cell cultures.

The combined effect of surface topography and substrate rigidity in stem cell cultures is still under‐investigated, especially when biodegradable polymers are used. Herein, we assessed human bone marrow stem cell response on aliphatic polyester substrates as a function of anisotropic grooved topography and rigidity (7 and 12 kPa). Planar tissue culture plastic (TCP, 3 GPa) and aliphatic polyester substrates were used as controls. Cell morphology analysis revealed that grooved substrates caused nuclei orientation/alignment in the direction of the grooves. After 21 days in osteogenic and chondrogenic media, the 3 GPa TCP and the grooved 12 kPa substrate induced significantly higher calcium deposition and alkaline phosphatase (ALP) activity and glycosaminoglycan (GAG) deposition, respectively, than the other groups. After 14 days in tenogenic media, the 3 GPa TCP upregulated four and downregulated four genes; the planar 7 kPa substrate upregulated seven genes and downregulated one gene; and the grooved 12 kPa substrate upregulated seven genes and downregulated one gene. After 21 days in adipogenic media, the softest (7 kPa) substrates induced significantly higher oil droplet deposition than the other substrates and the grooved substrate induced significantly higher droplet deposition than the planar. Our data pave the way for more rational design of bioinspired constructs.

Effect of machining-induced surface topography on corrosion behaviors of 304 austenitic stainless steel in pre-stress grinding

Effect of machining-induced surface topography on corrosion behaviors of 304 austenitic stainless steel in pre-stress grinding

Meshing Characteristics of Spur Gears Considering Three-Dimensional Fractal Rough Surface under Elastohydrodynamic Lubrication

Taking the effect of actual surface topography under elastohydrodynamic lubrication (EHL) conditions on the contact state of gear pairs into consideration, a combination model with the analytical sliced method and two-dimensional (2D) EHL model is proposed to characterize the three-dimensional (3D) meshing characteristics of spur gears. Firstly, the surface topology of gears is tested by a surface profiler, which reflects that the topography of tooth surface accords with fractal characteristics. Thus, by adopting the Weierstrass–Mandelbrot (W-M) fractal function, the gear surface is characterized. Secondly, the numerical 2D EHL model with fractal roughness is established, and distributions of oil film pressure (OFP) and oil film thickness (OFT) at different meshing positions are obtained. Finally, considering the different topography distributions in the direction of face width, time-varying mesh stiffness (TVMS) is calculated based on the analytical sliced method. Thus, the influence of 3D surface topography can be considered. The Hertz contact stiffness is substituted by the time-varying lubricating oil film stiffness (OFS). The influences of tooth surface topography and lubricant film characteristics on meshing characteristics are investigated. The results show that the 3D rough tooth surface may be well characterized by a fractal function with random phase. Moreover, there is a great difference in the distribution of OFP and OFT between rough and smooth surfaces, which certainly influences the gear meshing characteristics.

An investigation of the influence of microstructure surface topography on the imaging mechanism to explore super-resolution microstructure

Vision-based precision measurement is limited by the optical resolution. Although various super-resolution algorithms have been developed, measurement precision and accuracy are difficult to guarantee. To achieve nanoscale resolution measurement, a super-resolution microstructure concept is proposed which is based on the idea of a strong mathematical mapping relationship that may exist between microstructure surface topography features and the corresponding image pixel intensities. In this work, a series of microgrooves are ultra-precision machined and their surface topographies and images are measured. A mapping relationship model is established to analyze the effect of the microgroove surface topography on the imaging mechanism. The results show that the surface roughness and surface defects of the microgroove have significant effects on predicting the imaging mechanism. The optimized machining parameters are determined afterward. This paper demonstrates a feasible and valuable work to support the design and manufacture super-resolution microstructure which has essential applications in precision positioning measurement.

Effect of surface topography on mechanical properties of steel-polycarbonate joints by laser direct joining

Effect of surface topography on mechanical properties of steel-polycarbonate joints by laser direct joining

Thermal ridges – Formation of hillock-like structures in deformed bulk nickel

The effect of surface topography on grain boundary migration has been the focus of numerous studies due to its importance for microstructure evolution in thin films. In this work we have studied grain boundaries in samples of pure bulk Ni after mild cold deformation and a subsequent anneal. The surface topography in the vicinity of grain boundaries featured large protrusions formed during the anneal with a striking resemblance to downscaled terrestrial mountains. We coined the term 'thermal ridges' to describe these protrusions. Their size decreases with increasing annealing time and degree of deformation. We developed a kinetic model of ridges based on the original Mullins’ model of mobile grain boundary grooves modified to account for high surface anisotropy. The combination of our experimental and modeling results sheds new light on the phenomenon of hillock formation in thin polycrystalline films.

Preparation and characterization of two novel osteoinductive fishbone-derived biphasic calcium phosphate bone graft substitutes.

Many studies have reported on the conversion of natural resources into xenografts with hydroxyapatite (HA) as major component, but the extraction of biphasic calcium phosphate (HA/β-TCP) from animal bones and transformation into bone graft substitutes are rarely reported. In this research, two kinds of fish bones were made into granular porous biphasic calcium phosphate bone graft substitutes with particle sizes between 500 to 1000μm through a series of preparation procedures (Salmo salar calcined at 900°C named Sa900 and Anoplopoma fimbria calcined at 800°C named An800). The chemical composition was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The morphology and porous structure of the scaffolds were comparatively analyzed by scanning electron microscopy (SEM) and mercury porosimeter. The specific surface area of materials was measured by the nitrogen adsorption technique based on BET theory. Cytotoxicity and ectopic osteogenesis were also carried out to investigate the biocompatibility and osteoinductive potential of these materials. The results showed that both fishbone-derived scaffolds were composed of HA and β-TCP with different proportions, and numerous interconnected pores with different sizes were observed at the surface of materials. An800 had higher total porosity reaching 74.8% with higher interconnectivity and micropores mostly distributed at 0.27μm and 0.12μm, while Sa900 had a higher specific surface area and higher intraparticle porosity with nanopores mostly distributed at 0.07μm. CCK-8 assays and Live/dead staining demonstrated excellent biocompatibility. Material-induced osteoid formation were observed on the interface of both internal pores and periphery of materials after implantation in muscle pouch of Wistar rats for 8weeks which indicated some extent of osteoinductive potential of materials. The possible mechanism of material-induced osteogenesis and the effects of chemical composition, surface topography, and spatial structure on osteogenesis were also discussed in this paper.

Interaction of surface topography and taper mismatch on head-stem modular junction contact mechanics during assembly in modern total hip replacement.

Implant failure due to fretting corrosion at the head-stem modular junction is an increasing problem in modular total hip arthroplasty. The effect of varying microgroove topography on modular junction contact mechanics has not been well characterized. The aim of this study was to employ a novel, microgrooved finite element (FEA) model of the hip taper interface and assess the role of microgroove geometry and taper mismatch angle on the modular junction mechanics during assembly. A two-dimensional, axisymmetric FEA model was created using a modern 12/14 taper design of a CoCrMo femoral head taper and Ti6Al4V stem taper. Microgrooves were modeled at the contacting interface of the tapers and varied based on height and spacing measurements obtained from a repository of measured retrievals. Additionally, taper angular mismatch between the head and stem was varied to simulate proximal- and distal-locked engagement. Forty simulations were conducted to parametrically evaluate the effects of microgroove surface topography and angular mismatch on predicted contact area, contact pressure, and equivalent plastic strain. Multiple linear regression analysis was highly significant (p < 0.001; R2 > 0.74) for all outcome variables. The regression analysis identified microgroove geometry on the head taper to have the greatest influence on modular junction contact mechanics. Additionally, there was a significant second order relationship between both peak contact pressure (p < 0.001) and plastic strain (p < 0.001) with taper mismatch angle. These modeling techniques will be used to identify the implant parameters that maximize taper interference strength via large in-silico parametric studies.

Effects of surface topography at different scales on the dispersion of the wetting data for sessile water droplets on nitrided austenitic stainless steels

Plasma nitriding is used to increase the durability of steels. The wettability of nitrided surfaces is poorly studied. The ability of nitriding in modifying the wetting and evaporation of sessile droplets on austenitic stainless steel is studied. Transferred plasma for nitriding provides independent substrate biasing giving the opportunity to tailor the surface before and during the nitriding treatments. It was shown that a cleaning treatment (ArH2 plasma) produces topographical modifications of the surface by selective sputtering of the grains giving contact angles between 80 and 90°. Similar results are obtained when the nitriding treatments are carried out with a rather high bias voltage. It is explained using the skewness (Ssk) topographical roughness parameter which reveals the asymmetry of the profile. The more the Ssk is, the higher the contact angle is. During nitriding treatments, the very high internal stresses leads to the formation of spikes at the grain boundaries. Pinning of the three-phase contact line on peaks localized at grain boundaries are responsible for high contact angles. For nitriding treatments carried out with lower bias, surface contamination occurs and a discontinuous oxynitride layer is formed. The nanostructure formed by these oxides gives contact angles up to 120°.

Graphene-Coated PVDF Membranes: Effects of Multi-Scale Rough Structure on Membrane Distillation Performance.

Graphene-coated membranes for membrane distillation have been fabricated by using a wet-filtration approach. Graphene nanoplatelets have been deposited onto PVDF membrane surfaces. Morphology and physicochemical properties have been explored to evaluate the changes in the surface topography and related effects on the membrane performance in water desalination. The membranes have been tested in membrane distillation plants by using mixtures of sodium chloride and humic acid. The multi-scale rough structure of the surface has been envisaged to amplify the wetting and fouling resistance of the graphene-coated membranes so that a better flux and full salt rejection have been achieved in comparison with pristine PVDF. Total salt rejection and an increase of 77% in flux have been observed for coated membrane with optimized graphene content when worked with NaCl 0.6 M (DCMD, ΔT ≈ 24 °C) over a test period of 6 h. The experimental findings suggest these novel graphene-coated membranes as promising materials to develop functional membranes for high-performing water desalination.

Mesh-like electrospun membrane loaded with atorvastatin facilitates cutaneous wound healing by promoting the paracrine function of mesenchymal stem cells

BackgroundFunctional electrospun membranes are promising dressings for promoting wound healing. However, their microstructure and drug loading capacity need further improvements. It is the first time to design a novel mesh-like electrospun fiber loaded with atorvastatin (ATV) and investigated its effects on paracrine secretion by bone marrow-derived mesenchymal stem cells (BMSCs) and wound healing in vivo.MethodsWe fabricated a mesh-like electrospun membrane using a copper mesh receiver. The physical properties of the membranes were evaluated by SEM, FTIR spectroscopy, tensile strength analysis, and contrast angle test. Drug release was measured by plotting concentration as a function of time. We tested the effects of conditioned media (CM) derived from BMSCs on endothelial cell migration and angiogenesis. We used these BMSCs and performed RT-PCR and ELISA to evaluate the expressions of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF) genes and proteins, respectively. The involvement of FAK and AKT mechanotransduction pathways in the regulation of BMSC secretion by material surface topography was also investigated. Furthermore, we established a rat model of wound healing, applied ATV-loaded mesh-like membranes (PCL/MAT) seeded with BMSCs on wounds, and assessed their efficacy for promoting wound healing.ResultsFTIR spectroscopy revealed successful ATV loading in PCL/MAT. Compared with random electrospun fibers (PCL/R) and mesh-like electrospun fibers without drug load (PCL/M), PCL/MAT induced maximum promotion of human umbilical vein endothelial cell (HUVEC) migration. In the PCL/MAT group, the cell sheet scratches were nearly closed after 24 h. However, the cell sheet scratches remained open in other treatments at the same time point. The PCL/MAT promoted angiogenesis and led to the generation of longer tubes than the other treatments. Finally, the PCL/MAT induced maximum gene expression and protein secretion of VEGF and b-FGF. As for material surface topography effect on BMSCs, FAK and AKT signaling pathways were shown to participate in the modulation of MSC morphology and its paracrine function. In vivo, PCL/MAT seeded with BMSCs significantly accelerated healing and improved neovascularization and collagen reconstruction in the wound area compared to the other treatments.ConclusionsThe mesh-like topography of fibrous scaffolds combined with ATV release creates a unique microenvironment that promotes paracrine secretion of BMSCs, thereby accelerating wound healing. Hence, drug-loaded mesh-like electrospun membranes may be highly efficacious for wound healing and as artificial skin. It is a promising approach to solve the traumatic skin defect and accelerate recovery, which is essential to developing functional materials for future regenerative medicine.

Development of Scanning Acoustic Microscopy System for Evaluating the Resistance Spot Welding Quality

ABSTRACT Scanning acoustic microscopy (SAM) system (TSAM-400) was designed and developed for evaluating the quality of resistance spot welding (RSW) joints of 1.5 mm-thick SUS 316 stainless steel sheets under different welding parameters. Indentation and nugget information (diameter and shape) were used for evaluating the RSW quality. SAM A-scan signals were used to calculate the indentation. The nugget diameter was determined in the C-scan image. Internal information (nugget shape, splashes, and defects) was visualized in the B- and C-scan images. In addition, the spot weld area was treated to examine the surface topography effect. The nugget diameters of treated and untreated areas were measured and compared to conclude that the surface topography effect can be neglected in the quality evaluation by SAM system. By implementing TSAM-400, some specimens were successfully tested with a scanning area of 55 × 15 mm2, and a scanning time of 33.5 s corresponding to a B-scan frame rate of 4.5 Hz, and a resolution of 0.1 × 0.1 mm2. Finally, the good input parameters for welding two 1.5 mm-thick SUS 316 were determined by analyzing the results from TSAM-400.

Anisotropic tribological behavior of LSI based 2.5D needle-punched carbon fiber reinforced Cf/C–SiC composites

Cf/C–SiC composites were fabricated via liquid silicon infiltration with 2.5D needle-punched carbon fiber reinforced Cf/C composites. The effect of surface topography and carbon content of the Cf/C–SiC composites on the tribological properties was researched by the ball-on-disk reciprocating tribometer. The results indicate that different fiber layers and cross-section of the composites have various surface topography and show significant differences in the friction and wear properties. By the wear morphology and model analyses, the reason for the tribological anisotropy of the composites is that the distribution of carbon and SiC phases in the composites are inhomogeneous caused by the difference of the carbon fiber orientation and the relative content in each layer. Moreover, the wear rate of the short-cut fiber web layer was the lowest and there is an obvious linear decrease in coefficient of friction with increase of carbon content. The present work explains why the tribological properties of the composites are inconsistent and provides a way to adjust the friction properties of composite materials by optimizing the friction surface.

Parametric Effects on Pool Boiling Heat Transfer and Critical Heat Flux: A Critical Review

Abstract Pool boiling heat transfer offers high-performance cooling opportunities for thermal problems of electronics limited with high heat fluxes. Therefore, many researchers have been extensively studying over the last six decades. This paper presents a critical literature review of various parametric effects on pool boiling heat transfer and critical heat flux (CHF) such as pressure, subcooling, surface topography, surface orientation, working fluid, and combined effects. To achieve an optimal heat removal solution for a particular problem, each of these parameters must be understood. The governing mechanisms are discussed separately, and various options related to the selection of appropriate working fluids are highlighted. A broad summary of correlations developed until now for predicting CHF is presented with their ranges of validity. While proposed correlations for predicting CHF have been quite promising, they still have a considerable uncertainty (±25%). Finally, a correlation proposed by Professor Avram Bar-Cohen and his team (thermal management of electronics (TME) correlation) is compared with the experimental dataset published in previous studies. It shows that the uncertainty band can be further narrowed down to ±12.5% for dielectric liquids by using TME correlation. Furthermore, this correlation has been enhanced to predict CHF values underwater above 50 W/cm2 by applying a genetic algorithm, and new perspectives for possible future research activities are proposed.