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This study aims to analyze the nano-grinding behavior of silicon wafer workpieces with nanoscale roughness by molecular dynamics simulations. The nano-grinding process of silicon wafer workpieces with varying root-mean-square roughness under different grinding depths is simulated, considering synchronous rotation and translation of the diamond abrasive. The material removal mechanism, thermodynamic properties and mechanical responses are revealed. The findings demonstrate that the material removal in the nano-grinding process can be influenced by surface roughness and grinding depth, leading to its classification into compression, ploughing and cutting regimes. Moreover, reducing the grinding depth and surface roughness also reduces temperature, von Mises stress and grinding force, thus mitigating surface damage to silicon wafer workpieces. However, a minimal initial root-mean-square roughness may result in reduced surface smoothness of silicon wafer workpieces after a single grinding. [ABSTRACT FROM AUTHOR]

This work attempts to investigate contact between two self-affine fractal surfaces with one being of a rigid solid and other of a FCC deformable body. A normal contact model between two self-affine fractal surfaces at the nanoscale is established. Effects of surface morphology on contact force, atomic structure, dislocation with normal displacement are investigated by simulating the contact process of self-affine surfaces. Results show that the normal force for rougher surfaces at initial contact yields the larger negative extremum due to effects of surface morphology on interatomic repulsion and attraction. Furthermore, the atomic structure change proportion varies monotonically with normal displacement whereas effects of surface morphology can be approximately ignored. However, the phase transition generated by too large atomic slip leads to a non-monotonic variation between total dislocation lines length and normal displacement. Differences in contact ratio-separation dependence between the classical micro-asperity model and the established model are compared. [ABSTRACT FROM AUTHOR]

Inducing roughness to achieve superhydrophobic surfaces through nanoparticlesʹ inclusion is a well-known concept; however, the consistency and secondary pollutants are challenges to be addressed. As a potential solution, we proposed a superhydrophobic nanofibrous membrane through the electrospinning of polyacrylonitrile and hydrophobic polydimethylsiloxane (PAN/H-PDMS) blended solution and post-heat treatment process. During carbonization, a drastic differential shrinkage between PAN and H-PDMS induces a hierarchically nanorough surface of the electrospun nanofiber. Thanks to the synergistic combination of micro-nano scale hierarchical roughness, a significant improvement in superhydrophobicity was observed with the water contact angle (WCA) of 163.48° and sliding angle (SA) of 4.2°. The proposed composite superhydrophobic nanofibrous membrane (CSN-M) exhibited excellent robustness against the tape peel, abrasion, and bending cycles by maintaining WCA higher than 158° and SA less than 6.5°. The outstanding self-healing feature recovered the WCA to 162.25° and lowered the SA to 5.0° after heat treatment at 60 °C. In addition, the CSN-M revealed a tensile modulus of 12.11 Mpa, a hydrostatic pressure of 39.18 cmH2O, and excellent breathability. The developed CSN-M is strong, with high permeability and outstanding mechano-chemical durability, making it a suitable choice for water/oil separation and self-cleaning applications.

Hypothesis: In recent years, some modern techniques such as plasma, ultraviolet irradiation and ozone treatment have been used in surface modification of polymers. Surface modification of polymeric fibers is aimed to improve dying and to achieve desirable physical properties like high moisture absorption and lower anti-static. In this study in an attempt to modify the surface of polyester fibers, a new complex method through ultraviolet/ozone treatment in two wet and dry forms has been applied. Methods: Surface modification of polyester fibers was performed by ultraviolet/ozone treatment on dry samples, as well as on samples impregnated with water, hydrogen peroxide and hydrogen peroxide/sodium silicate solutions. In order to study and compare the functional groups and morphology of the polyester fibers with those of control sample, Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used. Also, the moisture absorption and static electricity of the samples were studied.Findings: The results of FTIR spectra revealed that by ultraviolet/ozone treatment the number of oxygen-containing functional groups has increased considerably. Also, nanoscale surface roughness of the treated samples was revealed by SEM images. Additionally, the results indicated that moisture absorption of the treated polyester fibers has risen and consequently their static electricity has decreased. According to the results, the impregnation of polyester fibers can remarkably enhance surface oxidation process.

In this study, the effects of the surface structure of electrospun polyvinylidene fluoride (PVDF) nanoweb on surface wettability were analyzed. The conditions of the surface structure representing the lotus and petal effects were derived, and the difference in the dynamic behavior of the water droplets on the surfaces was investigated. To this end, a PVDF nanoweb was fabricated by electrospinning various concentrations of PVDF solutions. The nanoscale roughness was adjusted by varying the CF4 plasma etching time. It was seen that when the concentration of the electrospun PVDF solution was 15 or 20 wt%, a hierarchical structure of microbeads and nanofibers was formed. In the 20 wt% nanoweb, droplets formed an apparent contact angle of 149.5 ± 2.2°, and the petal effect was observed in which the droplets were pinned on the surface and did not roll off even when the nanoweb was tilted by 180°. As a result of introducing fine nanostructures with CF4 plasma etching on the 20 wt% nanoweb, the apparent contact angle increased to 162.8–164.4°, and the shedding angle decreased to 5.3–8.1°, showing a wetting transition to the lotus effect, regardless of the plasma etching time. In addition, the lotus effect was observed when 15 wt% nanoweb was treated with CF4 plasma etching for more than 10 min. We confirmed that the lotus effect was exhibited when the three-phase contact line of the PVDF nanoweb/water/air was discontinuous, and the contact area between the surface and the water droplets was reduced with increased air pockets at this interface, which led to a decrease in the adhesive force and the impact of negative pressure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoscale roughness was fabricated by using lithography to study the particle adhesion. • Fabricated rough surface was characterized by AFM, FE-SEM, and EDX. • Contact area between the AFM probes and surfaces depends on the type of probes and fraction of roughness on surfaces. • Increasing the contact area reduced the adhesion force and improved the repulsive force. Despite substantial theoretical approaches explaining the effect of nanoscale roughness (NR) on particle deposition, experiments are rarely performed. Fabricating the sophisticated rough surfaces and obtaining the experimental data for interaction between the colloids and surfaces are crucial to understand colloidal adsorption onto the rough surfaces. We investigated the adhesion of different particle types of atomic force microscope (AFM) probes (different shapes, i.e., sphere and plateau; diameters, i.e., 2 μm–15 μm) onto smooth and rough fabricated surfaces. We successfully fabricated well-organized rough surfaces on Silicon (Si) using colloidal lithography and metal-assisted chemical etching using a cylindrical shape of constant nanoscale height and diameter. The properties of roughness (i.e., height, diameter, and fraction) were quantitatively analyzed, and the corresponding. The force-distance curves measured with the AFM revealed that, for the four types of probes, contact area varied with the surface roughness, and their adhesion forces differed accordingly. Expanding the contact area tended to increase the repulsive force possibly because of the hydration force. This study effectively devised a simplified experimental system that explains the influence of NR on particle deposition using previous theoretical data. The findings should be considered in designing NR for subsequent colloidal deposition. [ABSTRACT FROM AUTHOR]

In this work, we present a novel methodology for incorporating the effect of fibre surface morphology on liquid water transport in polymer electrolyte membrane fuel cell gas diffusion layers (GDLs). Roughness features presented on the surface of the fibre are analysed using atomic force microscopy and are found to significantly impact the capillary pressure of liquid water pathways propagating through the GDL. A threshold capillary pressure was defined as the largest capillary pressure exhibited by the liquid water phase during the invasion of the throat. The threshold capillary pressures observed in the presence of roughness features are significantly greater than those in the absence of roughness features. Two-dimensional circumferential roughness models in cylindrical and converging-diverging throats are established, and an interfacial meniscus advancing algorithm is presented to determine the resulting threshold capillary pressures required for liquid water penetration. Revised Young-Laplace equations, which are particularly useful for pore network modeling, are suggested for calculating threshold capillary pressures that account for the effect of the roughness of throats with intrinsic contact angles greater than 90∘. [ABSTRACT FROM AUTHOR]

Hydrocarbon polymer films (ppCH) enriched with various concentrations of titanium were deposited on microscopic glass slides by magnetron sputtering from a Ti target. The maximum concentration of Ti (about 20 at.%) was achieved in a pure argon atmosphere. The concentration of Ti decreased rapidly after n -hexane vapors were introduced into the plasma discharge, and reached zero values at n -hexane flow of 0.66 sccm. The decrease in Ti concentration was associated with decreasing oxygen and titanium carbide concentration in the films, decreasing wettability (the water drop contact angle increased from 20° to 91°) and decreasing root-mean-square roughness (from 3.3 nm to 1.0 nm). The human osteoblast-like MG-63 cells cultured on pure ppCH films and on films with 20 at.% of Ti showed relatively high concentrations of ICAM-1, a marker of cell immune activation. Lower concentrations of Ti (mainly 5 at.%) improved cell adhesion and osteogenic differentiation, as revealed by higher concentrations of talin, vinculin and osteocalcin. Higher Ti concentrations (15 at.%) supported cell growth, as indicated by the highest final cell population densities on day 7 after seeding. Thus, enrichment of ppCH films with appropriate concentrations of Ti makes these films more suitable for potential coatings of bone implants. [ABSTRACT FROM AUTHOR]

We present the evidence of a direct relationship between surface properties and platelet attachment for rapid activation using polydimethylsiloxane (PDMS). Three different surfaces of one uncoated glass slide and two spin-coated glass slides with two different ratios of PDMS (5:1 and 10:1) were prepared and tested. Prior to the platelet attachment test, nanoscale surface roughness and softness of PDMS, according to the degree of crosslinking, were measured using a compression tester and atomic force microscopy. The surface that encouraged the attachment and activation of platelets was 10:1 PDMS with Young's modulus of 2.58±0.27 MPa and roughness of 0.477nm. These data show that platelet attachment and activation can be triggered and enhanced through the control of nanoscale surface roughness and softness of PDMS, which is promising for biomedical applications using PDMS. [ABSTRACT FROM AUTHOR]

We present the first experimental study for enhancement of PtSi Schottky detectors using photonic crystal (PC) structures. PCs can be used for simultaneous reduction of reflection and increase of absorption. The 2-D PCs are fabricated by interference lithography and reactive ion etching. In PC with 4.2-μm depth, the average responsivity is enhanced by a factor of ~7 with respect to regular detectors. We show that the light absorption enhancement is not sufficient to explain efficiency enhancement. The extra enhancement may be due to nanoscale roughness on the PC walls that affect the carrier collection efficiency and cutoff wavelength. [ABSTRACT FROM PUBLISHER]

In this work the weathering phenomenon of building stones has been studied on the nanoscale. Red Quipar limestone samples have been exposed to ultraviolet (UV) radiation and acid attack and have been analysed by Scanning Force Microscopy (SFM) as well as optical measurements. The morphology of the samples along each step of the process has been characterised using the Root Mean Square (RMS) roughness and the Power Spectral Density of surface roughness (PSD). The results show that sulphuric acid produces an important increase of the micro and nanoscale surface roughness while essentially no variations are observed when the samples are irradiated with UV light. SFM results are compared to the optical appearance using conventional photographic images. The increase of nanoscale surface roughness is directly related to the loss of brightness and the apparent colour variation observed in the optical images. Loss of brightness and colour variations in Red Quipar stones are explained by the increase of the surface roughness suffered from the acid attack. The SFM topographic images can be used to monitor at the nanoscale the evolution of the morphology of samples during different processes such as those used in these experiments. Finally, this work proposes a general scheme combining SFM with traditional optical measurements as a powerful tool to better understand the effect of physical properties (in particular surface roughness) with the perceived optical appearance. [ABSTRACT FROM AUTHOR]

Abstract: Doped polypyrrole coatings of varying degrees of wetting characteristics were prepared by a one-step anodic polymerization process and subsequently subjected to external applied potentials in an aqueous sodium benzenedodecylsulfonate solution. When an applied potential was increased from −0.9 to +0.9 at steps of 300mV for 300s at each step, static contact angles gradually increased from 64° to 122°. The surface morphology of as-deposited polypyrrole was observed to transform from being nodular to an increasingly rough surface composed of microscale islands with nanoscale roughness, forming a micro/nanoscale hierarchical structure. The average roughness of these microscale islands were measured to be 2.3nm at −0.8V, which increased to 14.6nm at +0.8V, compared to the average roughness of doped polypyrrole at 4.8nm. These microscale islands were oblong in shape, and their sizes increased as the applied potential increased. Changes in the average roughness resulted in a change in the surface wettability of polypyrrole—as-deposited polypyrrole showed a static contact angle of 90°, however, it lowered to 70° at −0.8V and irreversibly increased to 115° at +0.8V. [Copyright &y& Elsevier]

Surface morphologies of thin films of polypyrrole doped with two similar anions (with different ionic radii) viz. chloride and bromide were compared by means of fractal geometry. Scanning electron micrographs of the polymer surfaces showed a significant difference between the surface structures of two anion-doped polypyrrole films in microscale and particularly in nanoscale. Surprisingly, the bromide-doped polypyrrole had nanostructure: whereas. the chloride-doped polypyrrole sud~ace was smooth in nanoscale. An electrochemical method based on gold-masking approach was employed to reveal the tYactality of these polymer surfaces in microscale. Fractal geometry successfully discovered the effect of anion doping on microstructure of the conductive polymer by suggesting different fractal dimensions. In addition, SAXS analysis indicated significant difference in fractality of the polymer in nanoscale. [ABSTRACT FROM AUTHOR]

Atomic force microscopy is used as a vital tool in understanding the fundamental mechanisms of particulate processes in dry, humid and aqueous systems. Adhesion forces in both dry and humid systems were studied between surfaces of varying roughness, taking into account the capillary forces at high humidity conditions. Colloidal stability in aqueous systems due to non-DLVO forces and steric effects of surfactant aggregates formed on particle surfaces at varying pH and ionic strength conditions were investigated. The force–distance curves obtained by atomic force microscopy were used to determine the mechanical and thermodynamic properties of the self-assembled surfactant structures formed on the surface. Besides determining the repulsive force barrier provided by the surfactant aggregates in dispersion of slurries, the frictional interactions between surfactant adsorbed surfaces were measured using lateral force microscopy, providing valuable insights into the role of dispersants acting as lubricants. The range of interaction forces that can be explored using the Atomic Force Microscopy (AFM) can be utilized to predict, optimize and design a variety of industrially relevant processes such as chemical mechanical polishing (CMP), powder flow and handling and nano-dispersions, just to name a few. [ABSTRACT FROM AUTHOR]

• A thin film evaporation model is developed to account for the effect of nanoscale surface roughness. • The model shows that roughness enhances thin film evaporation when the effect of disjoining pressure is more pronounced. • Roughness inhibits thin film evaporation when the effect of flow permeability is more pronounced. • There exists a critical pitch for rough surface structures below which roughness inhibits thin film evaporation. Thin film evaporation yields high local heat fluxes that contributes significantly to the total heat transfer rate during various two-phase transport processes including pool boiling, flow boiling, and droplet evaporation, among others. Recent studies have shown a strong correlation between the roughness of a surface and its two-phase heat transfer characteristics, but the underlying role of nanoscale surface roughness in thin film evaporation is not fully understood. In the present work, a thin film evaporation model is developed that accounts for the role of the roughness-affected disjoining pressure and flow permeability in determining the film thickness profile and heat transfer rate. Nanoscale surface roughness leads to a flatter evaporating meniscus profile when the effect of disjoining pressure is more pronounced of the two and promotes evaporation, consistent with previous experimental observations. However, our results reveal that surface roughness may also inhibit evaporation and lead to a steeper evaporating meniscus profile when flow permeability has the more pronounced influence on thin film evaporation. It is important to identify the specific surface roughness characteristics that determine whether disjoining pressure or flow permeaiblity has the stronger influence. To this end, a parametric study is performed that analyzes thin film evaporation on V-grooved surfaces of different depths and pitches. While the heat transfer rate increases monotonically with groove depth, there exists an optimal groove pitch that leads to a maximized evaporation rate. Also, when the groove pitch is smaller than a critical value, surface roughness inhibits thin film evaporation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Cr sputtering process generated particulate nanostructures with various sizes. • Cr-coated layer showed a good wetting characteristics (superhydrophilic). • Nanoscale roughness increased after oxidation, different from microscale. • CHF enhancement could be predicted through spreading measurement and its analysis. • Cr-coated surfaces improved oxidation resistance and safety margin simultaneously. The oxidation of an accident-tolerant fuel (ATF) cladding alters the surface roughness, which, in turn, affects the capillary wicking characteristics and critical heat flux (CHF) during the boiling process. To evaluate the effect of oxidation on the boiling performance of ATF coating, this study fabricated Cr-coated surfaces by varying the substrate temperature, resulting in various sizes of deposited particulate nanostructures by using a direct-current magnetron sputtering technique. To consider the oxidation effect, sputtered test specimens were oxidized at 400 °C dry air for 20 days, forming a Cr 2 O 3 oxide layer with a thickness of approximately 0.1 μm. Pool boiling CHF experiments were conducted in deionized water under atmospheric pressure. The resultant CHF on the fresh and oxidized Cr-coated surfaces was enhanced by up to 36% and 48%, respectively. A higher CHF enhancement was achieved with a lower substrate temperature during sputtering, which resulted in a higher nanoscale surface roughness. The spreading velocities on each specimen were measured through the characterization experiments of liquid droplet spreading, which can be interpreted as the capillary wicking momentum. The pool boiling CHF was predicted with spreading velocity and roughness parameters. The predicted CHF showed a good agreement with the measured CHF. This study suggests that the oxidation of Cr-coated ATF specimens has a positive effect on the enhanced CHF, which can be confirmed through the altered surface roughness and capillary wicking momentum. [ABSTRACT FROM AUTHOR]

Implantable microelectrodes that can be remotely actuated via external fields are promising tools to interface with biological systems at a high degree of precision. Here, we report the development of flexible magnetic microelectrodes (FMμEs) that can be remotely actuated by magnetic fields. The FMμEs consist of flexible microelectrodes integrated with dielectrically encapsulated FeNi (iron-nickel) alloy microactuators. Both magnetic torque- and force-driven actuation of the FMμEs have been demonstrated. Nanoplatinum-coated FMμEs have been applied for in vivo recordings of neural activities from peripheral nerves and cerebral cortex of mice. Moreover, owing to their ultrasmall sizes and mechanical compliance with neural tissues, chronically implanted FMμEs elicited greatly reduced neuronal cell loss in mouse brain compared to conventional stiff probes. The FMμEs open up a variety of new opportunities for electrically interfacing with biological systems in a controlled and minimally invasive manner.

Surface roughness and energy significantly influence protein adsorption on to biomaterials, which, in turn, controls select cellular adhesion to determine the success and longevity of an implant. To understand these relationships at a fundamental level, a model was originally proposed by Khang et al to correlate nanoscale surface properties (specifically, nanoscale roughness and energy) to protein adsorption, which explained the greater cellular responses on nanostructured surfaces commonly reported in the literature today. To test this model for different surfaces from what was previously used to develop that model, in this study we synthesized highly ordered poly(lactic-co-glycolic acid) surfaces of identical chemistry but altered nanoscale surface roughness and energy using poly(dimethylsiloxane) molds of polystyrene beads. Fibronectin and collagen type IV adsorption studies showed a linear adsorption behavior as the surface nanoroughness increased. This supported the general trends observed by Khang et al. However, when fitting such data to the mathematical model established by Khang et al, a strong correlation did not result. Thus, this study demonstrated that the equation proposed by Khang et al to predict protein adsorption should be modified to accommodate for additional nanoscale surface property contributions (ie, surface charge) to make the model more accurate. In summary, results from this study provided an important step in developing future mathematical models that can correlate surface properties (such as nanoscale roughness and surface energy) to initial protein adsorption events important to promote select cellular adhesion. These criteria are critical for the fundamental understanding of the now well-documented increased tissue growth on nanoscale materials.