Surface Microroughness Research Articles

Comparison of different types of phacoemulsification tips. III. Morphological changes induced after multiple uses in an ex vivo model

To assess the ultrastructural morphologic changes in the surface's micro-roughness for single-use and multiple-use phaco tips after multiple phacoemulsification cycles in an exvivo animal model. John A. Moran Eye Center and Utah Nanofab, College of Engineering, University of Utah, Salt Lake City, Utah, USA. Experimental study. Eight types of phaco tips were studied using an identical experimental protocol. Two tips of each type were used to emulsify porcine cataractous lenses of moderate hardness for 2minutes. This cycle was then repeated 5 consecutive times for each phaco tip. Scanning electron microscopy and white-light interferometry were used to analyze each tip for potential ultrastructural damage. No significant structural damage was noted on either single- or multiple-use tips after 5 cycles of experimental use. There was a trend toward increased surface micro-roughness at the tip opening after multiple procedures. Most tips had salt crystals on their surface and deposits of organic material composed of carbon and oxygen, which were consistent with porcine tissue that had not been cleaned from the tip surface. No significant ultrastructural damage was detected after repeated experimental use of phaco tips in a porcine cataract model. There was no significant difference when phaco tips labeled for single use or multiple uses were compared.

Simulation algorithm to model the visible tunable filter for the Daniel K. Inouye Solar Telescope

The visible tunable filter is an imaging spectropolarimeter for solar observations in visible light. The instrument consists of several Fabry–Perot interferometers (FPIs), a polarization modulator, and a prefilter. It will be one of the first light instruments for the Daniel K. Inouye Solar Telescope (DKIST) on Haleakalaa, Maui, Hawaii. We have developed simulation algorithms to describe the instrument and its impact on scientific observations. Our aim is to study the expected measurement accuracy and to test calibration algorithms. A well-known problem is the surface quality of the glass plates for each FPI. We developed algorithms to describe the influence of a surface microroughness, reflectivity, and figure errors of the individual FPI plates, and the expected total photon flux for scientific data acquisition. This tool is used to derive the limits for manufacturing processes to achieve the measurement accuracy required for science observations with DKIST.

Influence of sputtering pressure on the nanostructure and the X-ray reflectivity of iridium coatings

Reflective mirror coatings made of iridium are used in X-ray telescopes of the Chandra X-ray Observatory (CXO) launched in 1999 by the National Aeronautics and Space Administration (NASA) to investigate astronomical sources at photon energies below 10keV. These coatings were produced in a DC magnetron sputtering process and have so far proven their suitability for space-based applications. We are considering in the present paper the processing of thin iridium films for lightweight telescopes using the radio frequency magnetron sputtering technique with an oblique angle deposition. The coating development presented here is focused on the influence of total sputtering pressure on film properties as well as on its impact on the mirror's performance. Characterisation methods such as X-ray diffractometry, X-ray reflectometry, atomic force microscopy and transmission electron microscopy have been used. Correlations between morphology, density, surface micro-roughness, crystal structure of the iridium layer and the expected reflectivity of the X-ray mirror are described and discussed.

Quantifying the changes of soil surface microroughness due to rainfall impact on a smooth surface

Abstract. This study examines the rainfall-induced change in soil microroughness of a bare smooth soil surface in an agricultural field. The majority of soil microroughness studies have focused on surface roughness on the order of ∼ 5–50 mm and have reported a decay of soil surface roughness with rainfall. However, there is quantitative evidence from a few studies suggesting that surfaces with microroughness less than 5 mm may undergo an increase in roughness when subject to rainfall action. The focus herein is on initial microroughness length scales on the order of 2 mm, a low roughness condition observed seasonally in some landscapes under bare conditions and chosen to systematically examine the increasing roughness phenomenon. Three rainfall intensities of 30, 60, and 75 mm h−1 are applied to a smoothened bed surface in a field plot via a rainfall simulator. Soil surface microroughness is recorded via a surface-profile laser scanner. Several indices are utilized to quantify the soil surface microroughness, namely the random roughness (RR) index, the crossover length, the variance scale from the Markov–Gaussian model, and the limiting difference. Findings show a consistent increase in roughness under the action of rainfall, with an overall agreement between all indices in terms of trend and magnitude. Although this study is limited to a narrow range of rainfall and soil conditions, the results suggest that the outcome of the interaction between rainfall and a soil surface can be different for smooth and rough surfaces and thus warrant the need for a better understanding of this interaction.

Imaging analysis of the interface between osteoblasts and microrough surfaces of laser-sintered titanium alloy constructs.

Previous work using focused ion beam (FIB) analysis of osteoblasts on smooth and microrough Ti surfaces showed that the average cell aspect ratio and distance from the surface are greater on the rough surface. In order to better interrogate the relationship between individual cells and their substrate using multiple imaging modalities, we developed a method that tracks the same cell across confocal laser scanning microscopy (CLSM) to correlate surface microroughness with cell morphology and cytoskeleton; scanning electron microscopy (SEM) to provide higher resolution for observation of nanoroughness as well as chemical mapping via energy dispersive X-ray spectroscopy; and transmission electron microscopy (TEM) for high-resolution imaging. FIB was used to prepare thin sections of the cell-material interface for TEM, or for three-dimensional electron tomography. Cells were cultured on laser-sintered Ti-6Al-4V substrates with polished or etched surfaces. Direct cell to surface attachments were observed across surfaces, though bridging across macroscale surface features occurred on rough substrates. Our results show that surface roughness, cell cytoskeleton and gross morphology can be correlated with the cell-material cross-sectional interface at the single cell level across multiple high-resolution imaging modalities. This work provides a platform method for further investigating mechanisms of the cell-material interface.

Surface characteristics and corrosion resistance of spangle on hot-dip galvanized coating

This work investigated spangle on Zn-0.05Al-0.2Sb galvanized coating with shiny, feathery and dull morphology. The main goal was to determine the influence of surface characteristics on the anti-corrosion performance of the produced spangle. Experimental results showed that spangle displays an increasing electrochemically active trend from shiny, feathery to dull spangle, which is attributed to the combined factors of surface micro-roughness, surface texture, and surface segregation of spangle. In addition, the Sb3Zn4 particles precipitated on the coating surface play an important role in the corrosion resistance of spangle. Difference in morphology of spangle leads to difference of surface micro-roughness, surface texture, surface segregation, and finally leads to difference of corrosion resistance of spangle, which is discussed by a proposed spangle growth model.

Experimental power spectral density analysis for mid- to high-spatial frequency surface error control.

The control of surface errors as a function of spatial frequency is critical during the fabrication of modern optical systems. A large-scale surface figure error is controlled by a guided removal process, such as computer-controlled optical surfacing. Smaller-scale surface errors are controlled by polishing process parameters. Surface errors of only a few millimeters may degrade the performance of an optical system, causing background noise from scattered light and reducing imaging contrast for large optical systems. Conventionally, the microsurface roughness is often given by the root mean square at a high spatial frequency range, with errors within a 0.5×0.5 mm local surface map with 500×500 pixels. This surface specification is not adequate to fully describe the characteristics for advanced optical systems. The process for controlling and minimizing mid- to high-spatial frequency surface errors with periods of up to ∼2-3 mm was investigated for many optical fabrication conditions using the measured surface power spectral density (PSD) of a finished Zerodur optical surface. Then, the surface PSD was systematically related to various fabrication process parameters, such as the grinding methods, polishing interface materials, and polishing compounds. The retraceable experimental polishing conditions and processes used to produce an optimal optical surface PSD are presented.

Capillary wicking effect of a Cr-sputtered superhydrophilic surface on enhancement of pool boiling critical heat flux

Thermal safety function of coating layers on the fuel cladding has been considered as well as improvement of material function for development of advanced accident-tolerant fuel (ATF) system. In surface coating, material function seeks organizing coating structures dense without micro-morphologies for adhesive property. In light of thermal safety function, however, critical heat flux (CHF) is difficult to enhance on densely-structured surfaces in nanoscale because its nano-morphologies potentially reduce rewetting into dry spots near CHF. Thus, our focus is on control of micro-roughness of thin film-fabricated surfaces for CHF enhancement. We controlled the surface roughness Ra from 0.1–0.25μm allowable for fuel claddings and its morphologies, in the form of micro-scratches. Among a few ATF candidates, pure chromium Cr was fabricated using DC magnetron sputtering technique because its particulate nanostructures exhibited outstanding superhydrophilicity. Under a saturated pool boiling condition, CHF of Cr-sputtered surfaces resulted in a significant enhancement ranging from 32–79% despite of low roughness values. The major reason for CHF enhancement is attributed to improved capillary wicking, which was confirmed by measuring liquid spreading behaviors. To predict a monotonic CHF trend, roughness factor-based and capillary wicking models have been introduced. After geometrical modification in accordance with grinded surface morphologies, the capillary wicking model showed better agreement with our CHF data than roughness factor-based models. The results emphasize the importance of dynamic wetting analysis in terms of liquid spreading rather than equilibrium contact angle.

Scatter studies for visible emission line coronagraph on board ADITYA-L1 mission

Visible emission line coronagraph (VELC) on board ADITYA-L1 mission is an internally occulted mirror coronagraph designed for solar coronal observations over a field of view (FOV) of 1.05 R o to 3 R o . To achieve the proposed science goals, instrument background should be less than 5 ppm over the FOV of VELC. Major contributor toward instrument background is scatter from surface microroughness and particulate contamination over the primary mirror (M1). Hence, a detailed study of scatter through simulations is carried out to arrive at the surface microroughness specifications and surface cleanliness level requirements of M1. Estimation of RMS microroughness correction factor due to finite band width of the profilometer is very important while specifying the RMS microroughness of M1. This paper discusses in detail about scatter simulations, results, and analysis. All simulations are carried out using Advanced System Analysis Program, developed by Breault Research Organization.

Study on the optical performance of thin-film light-emitting diodes using fractal micro-roughness surface model

Although LEDs have been widely studied using optical simulations, there is no optical model considering the effect of micro-roughness surface (MRS) on the optical performance for packaged LEDs. In this work, we employ the finite-difference time-domain method and the direction-sensitive bidirectional scattering distribution function to characterize the optical properties of the MRS upon the n-GaN layer. The MRS is generated by the Weierstrass–Mandelbrot fractal function. Furthermore, thin-film LEDs (TFLEDs), blue TFLED devices, and white TFLED devices considering the MRS are investigated using the ray-tracing (RT) method. The results show that the MRS has different optical properties when the light propagates out and in the n-GaN layer. In turn, the difference in the scattering ability of various MRS causes a significant effect on the optical performance of packaged TFLEDs, including radiant efficacy, luminous efficacy, intensity pattern and spectrum, as well as the correlated color temperature.

Permeability model of micro-metal foam with surface micro-roughness

We present an analytical model capable of predicting permeability for isotropic and fully saturated micro-open-cell metal foam with surface modified by micro-rods (30–50 μm). The analytical model is based on the pore-scale volume-averaging approach and the assumption of piece-wise plane Poiseuille flow with the reconstructed three-dimensional cubic unit cell having cylindrical micro-rods synthesized on the cell walls. Both of the metal foam structure and the randomly distributed micro-rods are assumed to be periodic. The proposed model includes both the macroscopic and microscopic parameters that characterize the metal foam as well as the micro-roughness. The effects of micro-rod radius, height and interval on permeability and tortuosity are examined. To validate the present analytical model, experimental results are employed and good agreement is found. Results demonstrate that the micro-rods synthesized on the cell walls significantly decrease the permeability of the micro-foam. The increase in micro-rod radius/height or decrease in rod interval makes the metal foam surface rougher and thus decreases the foam permeability.

Improved in vitro angiogenic behavior on anodized titanium dioxide nanotubes

BackgroundNeovascularization over dental implants is an imperative requisite to achieve successful osseointegration onto implanted materials. The aim of this study was to investigate the effects on in vitro angiogenesis of anodized 70 nm diameter TiO2 nanotubes (NTs) on Ti6Al4V alloy synthesized and disinfected by means of a novel, facile, antibacterial and cost-effective method using super oxidized water (SOW). We also evaluated the role of the surface roughness and chemical composition of materials of materials on angiogenesis.MethodsThe Ti6Al4V alloy and a commercially pure Ti were anodized using a solution constituted by SOW and fluoride as electrolyte. An acid-etched Ti6Al4V was evaluated to compare the effect of micro-surface roughness. Mirror-polished materials were used as control. Morphology, roughness, chemistry and wettability were assessed by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy (EDX) and using a professional digital camera. Bovine coronary artery endothelial cells (BCAECs) were seeded over the experimental surfaces for several incubation times. Cellular adhesion, proliferation and monolayer formation were evaluated by means of SEM. BCAEC viability, actin stress fibers and vinculin cellular organization, as well as the angiogenic receptors vascular endothelial growth factor 2 (VEGFR2) and endothelial nitric oxide synthase (eNOS) were measured using fluorescence microscopy.ResultsThe anodization process significantly increased the roughness, wettability and thickness of the oxidized coating. EDX analysis demonstrated an increased oxygen (O) and decreased carbon (C) content on the NTs of both materials. Endothelial behavior was solidly supported and improved by the NTs (without significant differences between Ti and alloy), showing that endothelial viability, adhesion, proliferation, actin arrangement with vinculin expression and monolayer development were evidently stimulated on the nanostructured surface, also leading to increased activation of VEGFR2 and eNOS on Ti6Al4V-NTs compared to the control Ti6Al4V alloy. Although the rougher alloy promoted BCAECs viability and proliferation, filopodia formation was poor.ConclusionThe in vitro results suggest that 70 nm diameter NTs manufactured by anodization and cleaned using SOW promotes in vitro endothelial activity, which may improve in vivo angiogenesis supporting a faster clinical osseointegration process.

Interaction of silicalite-1 film with human osteoblast-like Saos-2 cells: The role of micro-morphology

Interaction of human osteoblast-like Saos-2 cells with a, b oriented silicalite-1 film is affected by its surface micro-roughness, controlled by a number of a oriented crystals on its surface, which can be simply tuned by synthesis conditions. The density of Saos-2 cells on days 1 and 3 after seeding increases with the number and dimensions of a oriented crystals.

Bone Response to Two Dental Implants with Different Sandblasted/Acid-Etched Implant Surfaces: A Histological and Histomorphometrical Study in Rabbits.

Background Scientific evidence in the field of implant dentistry of the past 20 years established that titanium rough surfaces have shown improved osseointegration rates. In a majority of dental implants, the surface microroughness was obtained by grit blasting and/or acid etching. The aim of the study was to evaluate in vivo two different highly hydrophilic surfaces at different experimental times. Methods Calcium-modified (CA) and SLActive surfaces were evaluated and a total of 18 implants for each type of surface were positioned into the rabbit articular femoral knee-joint in a split model experiment, and they were evaluated histologically and histomorphometrically at 15, 30, and 60 days of healing. Results Bone-implant contact (BIC) at the two-implant surfaces was significantly different in favor of the CA surface at 15 days (p = 0.027), while SLActive displayed not significantly higher values at 30 (p = 0.51) and 60 days (p = 0.061). Conclusion Both implant surfaces show an intimate interaction with newly formed bone.

Evaporation and boiling crisis of droplets alcohol solution

Evaporation and boiling crisis of droplets ethanol aqueous solution were studied experimentally. The evaporation intensity depends on the nucleate boiling, solution diffusion, a change in physical characteristics with time and droplet interfacial surface area. At nucleate boiling in a droplet, most evaporation relates to a growth in the droplet surface area and only 20 % relates to the diffusion effect and a variation in the thermophysical coefficients. At boiling crisis, experimental dependence for vapor layer height on overheating was observed. At Leidenfrost temperature, the height of the vapor layer was many times higher than the surface microroughness value of the wall. There are oscillates of liquid-vapor interface, and this increases the transitional temperature range associated with a boiling crisis of droplets.

Influence of facial types on sliding mechanics

Abstract Background/objectives/aims The present study considered the effect of orthodontic friction in an evaluation of the relationship of craniofacial pattern and surface micro-roughness of fixed appliances as determinants of treatment response and time. Methods Brachyfacial (BF; N = 17) and dolichofacial (DF; N = 18) patients treated by canine retraction using sliding mechanics, were identified. One archwire and one bracket per patient (those of the hemi-arch showing the fastest space closure of 4 mm) were subjected to confocal scanning microscopic analysis. Total treatment duration, sliding time, tooth movement rate, topographical surface average roughness (Ra), root mean square roughness (RMS), surface-kurtosis (SK), and surface-skewness (SS) were recorded and compared between groups using the Mann-Whitney U test. Correlations between final micro-roughness and treatment time were investigated using Pearson’s coefficient within each craniofacial type (a = 0.05). The post-treatment appliance surfaces were examined by SEM. Results BF patients recorded a significantly higher sliding time, lowest retraction rates, and greatest final Ra and RMS (p < 0.001). A comparison of total treatment time and final SK and SS values yielded no significant differences. Significant positive correlations between sliding time and final Ra were identified in both groups. Conclusions Compared with DF subjects, BF patients registered higher friction between the orthodontic components, required longer sliding time, and showed lower retraction rates.

Influence of surface roughness on a change in the growth mode from two-dimensional to three-dimensional for strained SiGe heterostructures

The influence of the surface microroughness on the critical thickness for the two-dimensional growth of strained SiGe structures on Si(001) and Ge(001) substrates is investigated. A decrease in the critical thickness for the two-dimensional growth of Ge films with increasing number of lattice periods or a decrease in the thickness of Si spacer layers is found for Ge/Si lattices grown on Si(001) substrates. This change is related to an increase in the surface roughness with the accumulation of elastic energy in compressed structures. A comparative study of the growth of SiGe structures on Si(001) and Ge(001) substrates shows that the critical thickness for the two-dimensional growth of tensile-strained layers is much larger than for compressed layers in a wide range of SiGe-layer compositions at an identical (in magnitude) lattice mismatch between the film and substrate.

Acidic magnetorheological finishing of infrared polycrystalline materials.

Chemical-vapor-deposited (CVD) ZnS is an example of a polycrystalline material that is difficult to polish smoothly via the magnetorheological finishing (MRF) technique. When MRF-polished, the internal infrastructure of the material tends to manifest on the surface as millimeter-sized "pebbles," and the surface roughness observed is considerably high. The fluid's parameters important to developing a magnetorheological (MR) fluid that is capable of polishing CVD ZnS smoothly were previously discussed and presented. These parameters were acidic pH (∼4.5) and low viscosity (∼47 cP). MRF with such a unique MR fluid was shown to reduce surface artifacts in the form of pebbles; however, surface microroughness was still relatively high because of the absence of a polishing abrasive in the formulation. In this study, we examine the effect of two polishing abrasives-alumina and nanodiamond-on the surface finish of several CVD ZnS substrates, and on other important IR polycrystalline materials that were finished with acidic MR fluids containing these two polishing abrasives. Surface microroughness results obtained were as low as ∼28 nm peak-to-valley and ∼6-nm root mean square.

Improvement of material removal rate of single-crystal diamond by polishing using H2O2 solution

In this study, we investigated the possibility of improving the material removal rate (MRR) of a single-crystal diamond (100) substrate by a polishing technique that utilizes a chemical reaction with H2O2 solution. To demonstrate the feasibility of improving the MRR of the diamond substrate, we investigated the polishing characteristics of the substrate when employing polishing plates of different materials, such as Fe, Cu, Ni, and SUS304, in H2O2 solution. We found that the MRR was highest (33.3nm/h) when using the Ni polishing plate. We also examined the removal characteristics of the diamond substrate in the case of polishing with and without feeding of H2O2 solution to the polishing plate under atmospheric conditions at room temperature. The results showed that polishing with feeding of H2O2 solution to the polishing plate dramatically improved the MRR to 216.7nm/h and also maintained a low surface microroughness of less than 1nm p-v and 0.1nm rms.

Pit Formation, Patterning and Flattening of Ge Surfaces in O2-Containing Water by Metal-Assisted Chemical Etching

Recently, metal-assisted chemical etching has attracted a great deal of attention because it is a simple and low-cost process for the fabrication of nanostructures on a semiconductor surface, mainly Si [1, 2]. This electroless etching is made possible by using noble metals, such as Pt and Ag, to catalyze the reduction of a chemical oxidant, such as H2O2, in the presence of HF. Namely, the reduction is accompanied by the selective oxidation around the loaded metals followed by the dissolution of oxide (SiO2) in HF solution. By controlling the etching conditions, a vast variety of nanostructures from porous structures to nanowire arrays can be fabricated in a chemical lab without the need for expensive equipment. Ge is regarded as a promising channel material in future electronics. It is necessary to develop and/or optimize wet processes, such as lithography, planarization and cleaning, for Ge. Ge oxide (GeO2) is soluble in water, unlike SiO2. Also, O2 molecules dissolved in water are oxidants. These chemical properties enable us to develop a novel process for a Ge surface using metal-assisted chemical etching in water. In this study, we immersed a Ge(100) surface loaded with Pt or Ag particles with the size of 10 nm order into O2-containing water and observed the formation of inverted pyramidal etch pits around the particles. This is caused by the catalytic effect of metals whereby O2 molecules in water are reduced, resulting in an enhanced oxidation of a Ge surface to form soluble GeO2. We confirmed that the O2 concentration in water is a key in etch rate [3, 4]. Then, we tested nanoscale patterning of a Ge surface by metal-assisted etching in O2-containing water. This was achieved by scanning a metal-coated cantilever on a Ge surface in the contact mode in an atomic force microscopy setup. We found that the Ge surface scanned by the cantilever was selectively removed, and the etched depths depended on experimental conditions such as the O2 concentration in water, the pressing force of the cantilever to the Ge surface, and the conduction type (n-type or p-type) of Ge. These findings indicate that the mechanism of inducing enhanced etching along the trajectory of the cantilever probe is a catalytic chemical effect rather than a mechanical one [4]. Finally, we used this metal-assisted chemical etching to improve the microroughness of a Ge surface. In this scheme, a thin film of noble metal (Pt) was deposited on a soft elastomer pad. This Pt surface was brought into contact with a Ge wafer surface by applying 0.01 MPa in O2-containing water. Both the pad coated with the metal and the Ge wafer were rotated independently in the same plane. Consequently, the Ge surface was flattened. The flattening mechanism is as follows. First, protrusions on the Ge surface have a higher probability of coming into contact with the metal surface than do grooves. These protrusions were selectively oxidized by the catalytic effect of the metallic film in water. After the oxidized protrusions were dissolved in water promptly, a flattened surface was created [5]. [1] X. Li et al., Appl. Phys. Lett. 77, 2572 (2000). [2] Z.P. Huang et al., Adv. Mater. 23, 285 (2011). [3] T. Kawase et al., J. Appl. Phys., 111, 126102 (2012). [4] T. Kawase et al., Nanoscale Res. Lett., 8, 151 (2013). [5] T. Kawase et al., ChemElectroChem, 2, 1656 (2015).