Specific Surface Topography Research Articles

Electrocatalytic methanol oxidation by Au nanoparticles decorated nickel tungstate/oxide nanocomplexes

The methanol oxidation reaction (MOR) serves as a critical determinant of the energy conversion efficiency within direct methanol fuel cells (DMFC). Consequently, the development of cost-effective and efficient electrocatalysts is paramount for enhancing energy conversion efficiency associated with MOR. The nanomaterials with diverse metal atomic molar ratio of (Ni:W) were synthesized via hydrothermal method for the immobilization of Au nanoparticles (Au NPs) onto the sample surface. The crystal structure of nanocomposites was confirmed through X-ray diffraction (XRD), and transmission electron microscopy (TEM) images depicted a specific surface topography. The catalytic performance of the synthesized catalysts in the MOR was assessed through electrochemical analysis. Notably, catalyst with the Ni:W atomic ratio of 2:1, displayed superior electrocatalytic performance when compared to catalysts possessing other different metal ratios. Moreover, chronoamperometry tests conducted over 7200 s and Tafel slope analysis demonstrated the enduring activity and strong resistance to toxicity of the synthesized catalysts. These results highlight the potential of nickel-tungstate bimetallic oxide as an exceptionally efficient catalyst in the field of electrocatalysis.

Effect of Stainless Steel Substrate Preparation on the Adhesion Strength and Morphology of Electrophoretically Deposited Sodium Alginate Coatings

In this study, the influence of various mechanical and chemical surface treatments on the adhesion strength and surface properties of sodium alginate coatings electrophoretically deposited (EPD) on 316L stainless steel substrates was investigated. XPS and TEM results revealed the presence of oxide layers containing elements from the substrates, with thicknesses varying from 1 to 45 nm, depending on the treatment used. Most substrates exhibited high roughness and hydrophilic properties (CA with water 62.8–82.6 deg). Sodium alginate coatings with uniform morphology were deposited with the same process parameters, i.e., 5 V and 300 s. The surface topography of the coatings was closely related to that of the substrate on which they were deposited. All coatings exhibited higher hydrophilicity (CA with water 29.5–49.7 deg) compared to the substrates (CA with water 62.8–82.6 deg). The coatings on the etched and anodized substrates demonstrated the highest adhesion strength (class 4B), attributed to the very low oxide layer thickness and the specific substrate surface topography. Mechanical interlocking was identified as the primary adhesion mechanism for these coatings. This work provides insight into optimizing surface treatments for improved adhesion of sodium alginate coatings to stainless steel substrates widely used for temporary bone implants. The results obtained will also be helpful in providing high adhesion of sodium alginate-based composite coatings to steel substrates.

Relating the surface topography of as-built Inconel 718 surfaces to laser powder bed fusion process parameters using multivariate regression analysis

The surface topography of 3D printed parts differs from that of wrought or machined parts of the same material. This work specifically focuses on Inconel 718 specimens manufactured with laser powder bed fusion (L-PBF). Predicting the surface topography of the as-built surfaces based on the L-PBF process parameters is important to manufacture parts with a specific surface topography without costly post-processing. We measure the surface topography of Inconel 718 as-built surfaces manufactured with different bulk and contour laser power, scan speed, layer thickness, and build orientation, and perform multivariate regression analysis with traditional R- and S-parameters, statistical and deterministic parameters, and even combinations of surface topography parameters, to determine which parameters most closely relate to the L-PBF process parameters. The deterministic surface topography parameters derived from a 9-point peak-identification scheme resulted in the best-fit regression equations with the highest adjusted-R2 and, thus, showed the closest relationship to the L-PBF process parameters. In contrast to the R-, S-, and statistical parameters, the deterministic approach considers the actual peaks of the surface topography rather than relying on a discrete number of traces of the surface. This conclusion is different from existing knowledge on the surface topography of as-built L-PBF surfaces, which only considers traditional R- and S-parameters.

Nonlinear effects in low-energy ion sputtering of solids

In this paper, we demonstrate that the sputtering of solids by ions of low (<30 keV) and even ultralow energies (<2 keV) is accompanied by nonlinear effects. These nonlinear effects are the result of heating a significant part of the cascades of collisions above the effective melting temperature of the material with the formation of local melts or “thermal spots” (a special case of the thermal spike regime). Nonlinear effects should primarily be observed in dense targets irradiated by heavy and cluster ions. In this paper, the question of the lifetime of such spots and their effect on the emission of secondary particles and the formation of specific surface topography is examined in detail. Another important assumption of the model is the existence of an intermediate ion sputtering regime, in that both linear cascades and thermal spots can exist simultaneously. A phenomenological model based on the effect of a rapid decrease in the cascade volume with a monotonic decrease in the energy of primary ions below 3 keV, which leads to the formation of thermal spots at ultralow energies (<2 keV), is also proposed. The suggested thermal spot model allows us to explain several experimental data that have not yet been explained in the framework of the traditional sputtering models. In particular, a simple explanation is given for the formation of pores in the surface layer during implantation and the formation of a relief on an ion-bombarded surface such as nanodots, pits (holes), and in the form of a foam-like surface. The small stationary concentration of cesium on the surface of the target sputtered by low-energy cesium ions is also explained.

Friction of flat and micropatterned interfaces with nanoscale roughness

The dry friction of surfaces with nanoscale roughness and the possibility of using micropatterning to tailor friction by manipulating contact area is investigated. Square wave patterns produced on samples from silicon wafers (and their unstructured equivalent) were slid against unstructured silicon counter surfaces. The width of the square wave features was adjusted to vary the apparent feature contact area. The existence of nanoscale roughness was sufficient to ensure Amontons’ first law (F = μP) on both structured & unstructured samples. Somewhat counterintuitively, friction was independent of the apparent feature contact area making it difficult to tailor friction via the feature contact area. This occurred because, even though the apparent feature contact area was adjusted, the surface roughness and nominal flatness at the contact interface was preserved ensuring that the real contact area and thereby the friction, were likewise preserved. This is an interesting special case, but not universally applicable: friction can indeed be adjusted by structuring provided the intervention leads to a change in real contact area (or interlocking)– and this depends on the specific surface geometry and topography.

Effect of Hydrothermal (Sr)-Hydroxyapatite Coatings on the Corrosion Resistance and Mg2+ Ion Release to Enhance Osteoblastic Cell Responses of AZ91D Alloy.

The biomedical applications of Mg-based alloys are limited by their rapid corrosion rate in the body fluid. In this study, the hydrothermal synthesis is employed to produce protective bioactive hydroxyapatite coating (HAC) and strontium-substituted hydroxyapatite coating (Sr-HAC) to further enhance the corrosion resistance and in vitro biocompatibility of biodegradable AZ91D Mg alloy in physiological environments. For comparison, the brucite Mg(OH)2 prepared by the alkaline pre-treatment is designated as a control group. Experimental evidences of XRD and XPS analysis confirm that Sr2+ ions can be incorporated into HA crystal structure. It is noted that the hydrothermally synthesized Sr-HAC conversion coating composed of a specific surface topography with the nanoscaled flake-like fine crystallites is constructed on the AZ91D Mg alloy. The hydrophilicity of Mg substrate is effectively enhanced with the decrease in static contact angles after performing alkaline and hydrothermal treatments. Potentiodynamic polarization measurements reveal that the nanostructured Sr-HAC-coated specimens exhibit superior corrosion resistance than HAC and alkaline pre-treated Mg(OH)2. Moreover, immersion tests demonstrate that Sr-HAC provides favorable long-term stability for the Mg alloy with decreasing concentration of released Mg2+ ions in the SBF and the reduced corrosion rate during the immersion length of 30 days. The cells cultured on Sr-HAC specimens exhibit higher viability than those on the alkaline-pre-treated Mg(OH)2 and HAC specimens. The Sr-substituted HA coating with a nanostructured surface topography can help to stimulate the cell viability of osteoblastic cells.

Synthesis of micro/meso porous carbon for ultrahigh hydrogen adsorption using cross-linked polyaspartic acid

In addition to the specific surface area, surface topography and characteristics such as the pore size, pore size distribution, and micro/mesopores ratio are factors that determine the performance of porous carbons (PCs) in the fields of energy, catalysis, and adsorption. Based on the mechanism of weight loss of polyaspartic acid at high temperatures, this study provided a new method for adjusting the surface morphology of PCs by changing the cross-linking ratio of the precursor, where cross-linked polyaspartic acid was used as precursor without additional activating agents. N2 adsorption analysis indicated that the specific surface area of the obtained PCs was as high as 1458 m2 · g−1, of which 1200 m2 · g−1 was the contribution of the microporous area and the highest pore volume was 1.13 cm3 · g−1, of which the micropore volume was 0.636 cm3 · g−1. The thermogravimetric analysis results of the precursor, and also the scanning electron microscopy and Brunauer—Emmet—Teller analysis results of the carbonization product confirmed that the prepared PCs presented multilevel pore structure, and the diameters of most pores were 0.78 and 3.97 nm; moreover, the pore size distribution was relatively uniform. This conferred the PCs the ultrahigh hydrogen adsorption capacity of up to 4.52 wt-% at 77 K and 1.13 bar, in addition to their great energy storage and catalytic potential.

Influence of the Drive Plate with Different Surface Textures on the Property of Carbonyl Iron‐Based Magnetorheological Fluid

Aiming to study the effect of drive plate with different surface topographies on the wear property of magnetorheological fluid (MRF), some specific experiments are carried out and analyzed in this paper. Firstly, experiment materials and test methods for MRF are elaborated, and four different surface topography drive plates are designed and manufactured. MRF test‐bed is built up to test the rheological properties of MRF. Moreover, the surface morphology of particles is taken using a scanning electron microscope (SEM). Finally, experimental results show that there are remarkable influences on tribological properties of carbonyl iron‐based MRF with different drive plates. Therefore, the drive plate with specific surface topography can meet the needs of different MRF transmission systems.

Textured materials with extreme wettability for water harvesting from aerosols

The creation of methods for complete and cost-effective collection of water droplets from an aerosol which arises as a by-product of the low-potential heat uptake from industrial devices, is one of the key tasks of rational use of water resources contributing to the improvement of the environment near large industrial enterprises. This paper shows how the application of materials with extreme wettability and a specific surface topography in spray separators can significantly increase the efficiency of water collection.

Extreme-Wettability Textured Materials for Water Collection from Aerosols

Creation of methods for complete and cost-effective collection of water droplets from an aerosols arising as a by-product of the low-potential heat uptake from industrial equipment is one of the key tasks of rational use of water resources contributing to the improvement of the environment near large industrial enterprises. This paper shows how the application of materials with extreme wettability and a specific surface topography in spray separators can significantly increase the water collection efficiency.

Decoration of Porous Silicon with Gold Nanoparticles via Layer-by-Layer Nanoassembly for Interferometric and Hybrid Photonic/Plasmonic (Bio)sensing.

Gold nanoparticle layers (AuNPLs) enable the coupling of morphological, optical, and electrical properties of gold nanoparticles (AuNPs) with tailored and specific surface topography, making them exploitable in many bioapplications (e.g., biosensing, drug delivery, and photothermal therapy). Herein, we report the formation of AuNPLs on porous silicon (PSi) interferometers and distributed Bragg reflectors (DBRs) for (bio)sensing applications via layer-by-layer (LbL) nanoassembling of a positively charged polyelectrolyte, namely, poly(allylamine hydrochloride) (PAH), and negatively charged citrate-capped AuNPs. Decoration of PSi interferometers with AuNPLs enhances the Fabry-Pérot fringe contrast due to increased surface reflectivity, resulting in an augmented sensitivity for both bulk and surface refractive index sensing, namely, about 4.5-fold using NaCl aqueous solutions to infiltrate the pores and 2.6-fold for unspecific bovine serum albumin (BSA) adsorption on the pore surface, respectively. Sensitivity enhancing, about 2.5-fold, is also confirmed for affinity and selective biosensing of streptavidin using a biotinylated polymer, namely, negatively charged poly(methacrylic acid) (b-PMAA). Further, decoration of PSi DBR with AuNPLs envisages building up a hybrid photonic/plasmonic optical sensing platform. Both photonic (DBR stop-band) and plasmonic (localized surface plasmon resonance, LSPR) peaks of the hybrid structure are sensitive to changes of bulk (using glucose aqueous solutions) and surface (due to BSA unspecific adsorption) refractive index. To the best of our knowledge, this is the first report about the formation of AuNPLs via LbL nanoassembly on PSi for (i) the enhancing of the interferometric performance in (bio)sensing applications and (ii) the building up of hybrid photonic/plasmonic platforms for sensing and perspective biosensing applications.

Investigation the influence of surface topography on scattering ability of aluminium reflectors from infrared quartz heater

Infrared (IR) heaters are used in many industries where heat treatment is required as well as in household appliances. One of the main problems with this type of equipment is non-uniform temperature field in the heating area, which results in a different degree of heating of the heated objects. In order to achieve greater uniformity of the temperature, some approaches are explored in practice, such as using embossed reflectors, mounting two or more heaters side-by-side, using emitter lamps with power controller devices, formation of gold or silver coatings, etc. The drawbacks of these approaches are complicating the design of the IR heaters, reducing the dimensions of heating area, increasing energy consumption, etc. Among the above-mentioned methods, the creation of a specific reflector surface topography is easily attainable and inexpensive technological approach. The main task of the present study is to investigate experimentally the influence of the specific patterns, obtained by ball burnishing process on scattering ability of the aluminium reflectors from infrared quartz heater.

Biomimetic polyetheretherketone microcarriers with specific surface topography and self-secreted extracellular matrix for large-scale cell expansion.

Reusable microcarriers with appropriate surface topography, mechanical properties, as well as biological modification through decellularization facilitating repeated cell culture are crucial for tissue engineering applications. Herein, we report the preparation of topological polyetheretherketone (PEEK) microcarriers via gas-driven and solvent exchange method followed by hydrothermal treatment at high temperature and pressure. After hydrothermal treated for 8 h, the resulting topological PEEK microcarriers exhibit walnut-like surface topography and good sphericity as well as uniform size distribution of 350.24 ± 19.44 µm. And the average width between ravine-patterned surface of PEEK microcarriers is 780 ± 290 nm. After repeated steam sterilization by autoclaving for three times, topological PEEK microcarriers show nearly identical results compared with previous ones indicating strong tolerance to high temperature and pressure. This is a unique advantage for large-scale cell expansion and clinical applications. Moreover, PEEK microcarriers with special topography possess higher protein adsorption efficiency. In addition, the reutilization and biofunctionalization with repeated decellularization of topological PEEK microcarriers show highly beneficial for cell adhesion and proliferation. Therefore, our study is of great importance for new generation microcarriers with micro-and nano-scale surface feature for a broad application prospect in tissue engineering.

Study on Cell Behavior on Surfaces with Various Nanostructured Modifications

Several researchers have developed finite element analysis (FEA) models on dental implants; however, few have used it to investigate the effects of nanosurface treatment on the cell-implant interface. For cell proliferation and differentiation are believed related to the physical stimulations of modification surfaces. In the present study, the cell adhesion affected by mechanical stimulation from substrate was evaluated by culturing the MG-63 osteoblast-like cells on Ti materials with different chemical composition using computer-aided programs. Three types of surfaces were made by mechanically abraded, anodized and anodized following with hydrothermal treatment on Ti substrates. The cell adhesion behavior was promoted because the physical stimulation of specific surface topography provided cells mechanical external forces. The finite element analysis (FEA) was used to investigate the deformations stresses which cells were suffered on these 3 different modifications surfaces. Results indicated that cells in the HTT group were received larger stimulation of deformations and stresses than the control group (P > 0.01). This confirmed that the superior cell proliferation and differentiation resulted from the specific roughly surfaces of HYT surface for implants.

Effect of laser induced topography with moderate stiffness on human mesenchymal stem cell behavior

Though the effects of scaffold properties such as stiffness and topography on stem cell behavior was well known of, there were multiple theories that explain such behavior and there has been no common consensus thus far. This study deals with using polydimethylsiloxane (PDMS) to mimic a specific microenvironment that favors human mesenchymal stem cells (hMSCs) differentiation into myogenic lineages through the manipulation of specific surface topography and appropriate substrate stiffness. Femtosecond laser was applied to machine microchannels on PDMS substrates in this work. hMSCs were seeded and cultured on lasercut substrates, uncut substrates and controls. Quantitative and qualitative analyses of stem cell behavior were discussed herein with the use of Picogreen Assay for cell proliferation, staining of cytoskeleton for cell orientation, immunostaining of Myosin Heavy Chain for a myogenic biomarker, and quantitative real time polymerase chain reaction for gene expression analysis. It was found that both myogenic differentiation of hMSCs could be achieved by moderate stiffness or microchannels. And differentiation was further boosted by such PDMS substrates with additional microchannels.

The effect of different surface topographies of titanium implants on bacterial biofilm: a systematic review

To compare the different surface topographies of titanium implants used in dentistry against the formation of bacterial biofilm. To identify relevant studies, the electronic databases PubMed, Science Direct and Springer Link were searched from inception until January 2019. A total of 38 studies were selected for the systematic review (n = 38). The most commonly used titanium surfaces were machined titanium (16.3%), sandblasted, large-grit, acid-etched titanium (10.9%), untreated or pure titanium (10.9%), polished titanium (9.8%), physically textured titanium (9.8%), acid-etched titanium (8.7%) and anodized titanium (5.4%). The majority of the studies (78.9%) found that surface topographies (with varying degrees of roughness) had a beneficial effect on the ability to allow low bacterial biofilm on the surfaces. A low roughness value (Ra) of below 1 µm was found in 68% of these surfaces. Overall, no specific surface topography was found to be the ideal surface in allowing the least bacterial biofilm attachment. In this study, meta-analysis was not performed. This narrative systematic review provides a summary of the effects of surface topographies for future research and development of new dental implant surfaces and decontamination techniques.

Artificial Tactile Sensor With Pin-type Module for Depth Profile and Surface Topography Detection

Haptic sensors based on piezoelectric sensor arrays with pin-type modules which have high responses and dynamic sensing capabilities are designed and studied for surface topography measurements. Unlike the human finger, most flexible tactile sensor designs do not detect the depth information of surfaces well, which change at the mm level despite the fact that they have a good sensitivity for pressure or force. To enhance the ability to detect depth information of the surfaces of objects, a piezoelectric sensor combining a pin-type module with excellent monitoring in the depth direction by spring is developed in this paper. Because spike types of piezoelectric signals do not match a specific surface topography directly, a signal processing method that reconstructs the surface topography is studied considering the piezoelectric working principle and spring dynamics. According to the sensor design, it can detect 3 mm depth changes with a two-dimensional plane structure at mm-level resolutions. The results show that the proposed sensor could measure various shapes and depth profiles precisely via a sliding motion, and the surface topography is reconstructed through highly accurate measurement results, similar to a human.

Effect of the specific surface topography on surface wettability of chromium-based coatings

ABSTRACTSurfaces featuring hydrophobic behaviour are generally prepared by a wide spectrum of technologies featuring different process complexity (anodic oxidation, lithography, electrodepositing, etc.). The aim of the work was to use a relatively simple method of magnetron sputtering to prepare metallic hydrophobic surface. Chromium coatings were selected due to their high adhesion to steel and corrosion resistance while conserving certain level of hardness and ductility. The tested coatings included pure Cr and pure Cr with CrN interlayer. The resulting contact angle value of up to 111° has confirmed hydrophobic behaviour. The resulting surface morphology is formed by almost perfectly developed crystals in the shape of hexagonal pyramids providing a suitable surface roughness conditions for hydrophobicity.

Modelling of the Influence of Tool Runout on Surface Generation in Micro Milling

Micro milling is a flexible and economical method to fabricate micro components with three-dimensional geometry features over a wide range of engineering materials. But the surface roughness and micro topography always limit the performance of the machined micro components. This paper presents a surface generation simulation in micro end milling considering both axial and radial tool runout. Firstly, a surface generation model is established based on the geometry of micro milling cutter. Secondly, the influence of the runout in axial and radial directions on the surface generation are investigated and the surface roughness prediction is realized. It is found that the axial runout has a significant influence on the surface topography generation. Furthermore, the influence of axial runout on the surface micro topography was studied quantitatively, and a critical axial runout is given for variable feed per tooth to generate specific surface topography. Finally, the proposed model is validated by means of experiments and a good correlation is obtained. The proposed surface generation model offers a basis for designing and optimizing surface parameters of functional machined surfaces.

Interrelationships among hydrogen permeation, physiochemical properties and early adsorption abilities of titanium.

This study aimed to investigate if the titanium samples with low hydrogen permeation which treated with a novel etching combination: phosphoric acid and sodium fluoride could influence the surface physiochemical properties and early adsorption ability. Titanium samples were treated with three different concentrations of the new formula, as groups A, B and C, and treated with the traditional etching formula, as group T. Zeta potential, contact angle, X-ray photoelectron spectroscopy (XPS) and fibronectin (FN)/vitronectin (VN) adsorption of Sprague-Dawley (SD) rat tibial osteotomies in the initial 30min and MG-63 adsorption in the initial 24 h were detected. Basing on the results of trails and pearson correlation analysis, the low hydrogen permeation into titanium didn't exert an impact on the surface morphology and surface stability. The adsorptions of F, P, S, acid hydroxyl and basic hydroxyl on the surfaces brought no bear on them as well. Surface concave depth and surface skewness showed highly positive correlation and moderate negative correlation with adsorption ability, respectively. Therefore, the surface morphology of titanium treated with the novel etching formula plays the only and primary role on the early adsorption. Because of its specific surface topography, group C showed the best performance which possessed slightly superiority than those of group B and group T, and with the lowest being group A. The low hydrogen permeation into titanium substrate was just benefit for improving the titanium mechanical properties, but not for the surface biochemical traits.