Modification Of Surface Roughness Research Articles

Temperature-responsive grafted polymer brushes obtained from renewable sources with potential application as substrates for tissue engineering

The novel temperature-responsive poly(cholesteryl methacylate) (PChMa) coatings derived from renewable sources were synthesized and characterized. Temperature induced changes in wettability were accompanied by surface roughness modifications, traced with AFM. Topographies recorded for temperatures increasing from 5 to 25°C showed a slight but noticeable increase of calculated root mean square (RMS) roughness by a factor of 1.5, suggesting a horizontal rearrangement in the structure of PChMa coatings. Another structural reordering was observed in the 55–85°C temperature range. The recorded topography changed noticeably from smooth at 55°C to very structured and rough at 60°C and returned eventually to relatively smooth at 85°C. In addition, temperature transitions of PChMa molecules were revealed by DSC measurements. The biocompatibility of the PChMa-grafted coatings was shown for cultures of granulosa cells and a non malignant bladder cancer cell (HCV29 line) culture.

The Influence of New Hydrophobic Silica Nanoparticles on the Surface Properties of the Films Obtained from Bilayer Hybrids.

Ultra-hydrophobic bilayer coatings on a glass surface were fabricated by sol–gel process using hexadecyltrimethoxysilane (C16TMS) and tetramethoxysilane (TMOS) (1:4 molar ratio) as precursors. After coating, silica nanoparticles (SiO2 NPs) functionalized with different mono-alkoxy derivatives (methoxytrimethylsilane, TMeMS; ethoxydimethylvinylsilane, DMeVES; ethoxydimethylphenylsilane, DMePhES; and methoxydimethyloctylsilane, DMeC8MS) were added, assuring the microscale roughness on the glass surface. Influences of the functionalized SiO2 NPs and surface morphology on the hydrophobicity of the hybrid films were discussed. The successful functionalization of SiO2 NPs with hydrophobic alkyl groups were confirmed by Fourier transform infrared spectroscopy (FTIR). The thermal stability of hydrophobic SiO2 NPs showed that the degradation of the alkyl groups takes place in the 200–400 °C range. Bilayer coating with C16TMS/TMOS and SiO2 NPs modified with alkoxysilane substituted with C8 alkyl chain (SiO2 NP-C8) has micro/nano structure. Hydrophobicity of functionalized SiO2 NPs-C8 and its higher degree of nanometer-scale roughness gave rise to ultra-hydrophobicity performance for bilayer coating C16TMS/TMOS + SiO2 NPs-C8 (145°), compared to other similar hybrid structures. Our synthesis method for the functionalization of SiO2 NPs is useful for the modification of surface polarity and roughness.

Suppressing breakers with polar oil films: Using an epic sea rescue to model wave energy budgets

AbstractOil has been used to still stormy seas for centuries, but the mechanisms are poorly understood. Here we examine the processes by using quantitative information from a remarkable 1883 sea rescue where oil was used to reduce large breakers during a storm. Modeling of the oil film's extent and waves under the film suggests that large breakers were suppressed by a reduction of wind energy input. Modification of surface roughness by the film is hypothesized to alter the wind profile above the sea and the energy flow. The results are central to understanding air‐sea momentum exchange, including its role in such processes as cyclone growth and storm surge, although they address only one aspect of the complex problem of wind interaction with the ocean surface.

As-built surface layer characterization and fatigue behavior of DMLS Ti6Al4V

Direct Metal Laser Sintering (DMLS) is a powder bed fusion technology used in the fabrication layer-by-layer of metallic parts directly from a CAD file. Since the fatigue behavior of DMLS Ti6Al4V is strongly influenced by the surface roughness of the as-built surface, fatigue tests were performed on smooth specimens produced with different orientations with respect to build using an EOS M 290 system. A SEM investigation and roughness measurements of the test surfaces were used to interpret the surface roughness as the contribution of i) roughness induced due to solidification of the melt pool (primary roughness); ii) roughness induced by partly melted powder particles (secondary roughness). Surface roughness modification from the as-built state by manual grinding was also investigated in fatigue and found to give a limited improvement. On the other hand, surface machining improves considerably the fatigue strength with respect to both the as-built condition and the manually ground condition.

Surface nanostructuring of Ti-6Al-4V alloy through ultrasonic shot peening

Solution treated samples of titanium alloy Ti-6Al-4V were subjected to ultrasonic shot peening (USSP) for different durations of 5, 15, and 30 minutes with hard steel balls of 3 mm diameter and examined for modification of microstructure, surface roughness and hardness profile. Based on microhardness profile a nanostructured layer of approximately 100 µm thickness resulted from the USSP. The shot peened surfaces were examined also by XRD for phase transformation, if any, resulting from USSP. Grain refinement was observed to nano scale due to USSP without any phase transformation. However, surface cracking was observed in the sample subjected to longer duration of 30 minutes and surface roughness was increased with duration of USSP. Microhardness of the 30 minutes shot peened surface was increased by ∼34%, however, the increased hardness level was reduced by ∼14%, following stress relieving treatment (400°C−1 h). The results are discussed in terms of the processes of grain refinement through USSP.

Evaluation of enamel surface after orthodontic debonding and cleanup using different procedures: An in vitro study

Objectives: The purpose of this in vitro study was to evaluate and compare the efficiency of four protocols of adhesive remnant removal and polishing after bracket debonding on enamel surfaces using scanning electron microscope (SEM) and to compare the time spent to remove resin remnants. Materials and Methods: The present study was a comparative study, in which brackets were bonded on forty freshly extracted human premolar teeth. They were debonded after 24 h and removal of remnant adhesive to as close as possible to the original condition using tungsten carbide burs (TCBs) (30 flutted) with low-speed contra-angle handpiece, Super Snap ® discs (course, medium, fine, and superfine), TCB + Brownie and Greenie (BG) polishers, and TCB + Super Snap ® discs. The surfaces were evaluated under SEM and graded according to the modified surface roughness index. Time taken to remove the residual adhesive was recorded using a stopwatch. Results were subjected to statistical analysis. Results: Super Snap ® discs showed a smooth surface with minimal scratches. TCB resulted in an irregular enamel surface in SEM evaluation, showing horizontal scars with a consistent pattern and left remnants on the enamel surfaces. TCB followed by Super Snap ® discs produced some scratches on the enamel surface. The mean time was significantly higher in Group I than the other three groups (P = 0.000). The mean time was significantly lower in Group II than the other three groups (P = 0.000). TCB took the least amount of time followed by TCB + stainless steel and TCB + BG polishers. Conclusion: Enamel surface was restored as close to the original using the Super Snap ® discs. TCB produced a very rough surface, but it is an efficient and least time-consuming procedure. The resultant enamel surface with enamel scars needs to be finished by other polishing techniques after bulk removal using TCB as the sequential use of Super Snap ® discs and polishers is less aggressive in removing residual bonding resin and results in apparently better surface finish causing less damage to the enamel.

Understanding Acoustic Cavitation Initiation by Porous Nanoparticles: Toward Nanoscale Agents for Ultrasound Imaging and Therapy.

Ultrasound is widely applied in medical diagnosis and therapy due to its safety, high penetration depth, and low cost. In order to improve the contrast of sonographs and efficiency of the ultrasound therapy, echogenic gas bodies or droplets (with diameters from 200 nm to 10 µm) are often used, which are not very stable in the bloodstream and unable to penetrate into target tissues. Recently, it was demonstrated that nanobubbles stabilized by nanoparticles can nucleate ultrasound responsive microbubbles under reduced acoustic pressures, which is very promising for the development of nanoscale (<100 nm) ultrasound agents. However, there is still very little understanding about the effects of nanoparticle properties on the stabilization of nanobubbles and nucleation of acoustic cavitation by these nanobubbles. Here, a series of mesoporous silica nanoparticles with sizes around 100 nm but with different morphologies were synthesized to understand the effects of nanoparticle porosity, surface roughness, hydrophobicity, and hydrophilic surface modification on acoustic cavitation inception by porous nanoparticles. The chemical analyses of the nanoparticles showed that, while the nanoparticles were prepared using the same silica precursor (TEOS) and surfactant (CTAB), they revealed varying amounts of carbon impurities, hydroxyl content, and degrees of silica crosslinking. Carbon impurities or hydrophobic modification with methyl groups is found to be essential for nanobubble stabilization by mesoporous silica nanoparticles. The acoustic cavitation experiments in the presence of ethanol and/or bovine serum albumin (BSA) demonstrated that acoustic cavitation is predominantly nucleated by the nanobubbles stabilized at the nanoparticle surface not inside the mesopores. Finally, acoustic cavitation experiments with rough and smooth nanoparticles were suggested that a rough nanoparticle surface is needed to largely preserve surface nanobubbles after coating the surface with hydrophilic macromolecules, which is required for in vivo applications of nanoparticles.

Drivers of ASCAT C band backscatter variability in the dry snow zone of Antarctica

ABSTRACTC band backscatter parameters contain information about the upper snowpack/firn in the dry snow zone. The wide incidence angle diversity of the Advanced Scatterometer (ASCAT) gives unprecedented characterisation of backscatter anisotropy, revealing the backscatter response to climatic forcing. TheA(isotropic component) andM2(bi-sinusoidal azimuth anisotropy) parameters are investigated here, in conjunction with data from atmospheric and snowpack models, to identify the backscatter response to surface forcing parameters (wind speed and persistence, precipitation, surface temperature, density and grain size). The long-term meanAparameter is successfully recreated with a regression using these drivers, indicating strong links between theAparameter and precipitation on long timescales. While the ASCAT time series is too short to determine which factors drive observed trends, factors influencing the seasonal and short timescale variability are revealed. On these timescales,Astrongly responds to the propagation of surface temperature cycles/anomalies downward through the firn, via direct modulation of the dielectric constant. The influence of precipitation onAis small at shorter timescales. TheM2parameter is controlled by wind speed and persistence, through modification of monodirectionally-aligned surface roughness. This variability indicates that throughout much of coastal Antarctica, a microwave ‘snapshot’ is generally not representative of longer-term conditions.

Understanding the contribution of surface roughness and hydrophobic modification of silica nanoparticles to enhanced therapeutic protein delivery.

Intracellular protein delivery holds great promise for cancer therapy. In this work, the individual and combined contribution of the surface roughness and hydrophobic modification (octadecyl-group) of silica nanoparticles has been studied in a number of events for cellular delivery of therapeutic proteins, including loading capacity, release behaviour, cellular uptake and endo/lysosomal escape. Both surface roughening and hydrophobic modification enhance the protein adsorption capacity and sustained release, while the contribution from the surface roughness is higher for loading capacity and hydrophobic modification is more effective for sustained protein release. Both structural parameters improve the cellular uptake performance; however the difference in the contribution is cell type-dependent. Only the hydrophobic modification shows a contribution to endo/lysosomal escape, independent of the surface topography. Octadecyl-functionalized rough silica nanoparticles thus show the best performance in therapeutic protein (RNase A) delivery, causing significant cell viability inhibition in different cancer cells among all groups under study.

A Numerical Analysis of Wind Flow within and above Idealised Modified Terraced House Canyon in Malaysia

This study examines the effects of surface roughness (modifications to existing structures) on wind flow. Idealised modified terraced house arrays were used in the study to represent the typical Malaysian terraced house urban-residential neighbourhood. The wind flow characteristics within and above an idealised modified terraced house canyon were investigated, with the idealised arrangement in a square and staggered layout, and the modifications installed 0.5h from the ground. The results indicate that the modifications affected the wind flow because of the smaller canyon width and the sheltering effect of the new obstacle.

On-Site Surface Functionalization for Titanium Dental Implant with Nanotopography: Review and Outlook

Titanium (Ti) has been the first choice of material for dental implant due to bonding ability to natural bone and great biocompatibility. Various types of surface roughness modification in nanoscale have been made as promising strategy for accelerating osseointegration of Ti dental implant. To have synergetic effect with nanotopography oriented favors in cell attachment, on-site surface functionalization with reproducibility of nanotopography is introduced as next strategy to further enhance cellular bioactivity. Extensive research has been conducted to investigate the potential of nanotopography preserved on-site surface functionalization for Ti dental implant. This review will discuss nonthermal atmospheric pressure plasma, ultraviolet, and low level of laser therapy on Ti dental implant with nanotopography as next generation of surface functionalization due to its abilities to induce superhydrophilicity or biofunctionality without change of nanotopography.

Application of orthogonal array technique and particle swarm optimization approach in surface roughness modification when face milling AISI1045 steel parts

Face milling is an important and common machining operation because of its versatility and capability to produce various surfaces. Face milling is a machining process of removing material by the relative motion between a work piece and rotating cutter with multiple cutting edges. It is an interrupted cutting operation in which the teeth of the milling cutter enter and exit the work piece during each revolution. This paper is concerned with the experimental and numerical study of face milling of AISI1045. The proposed approach is based on statistical analysis on the experimental data gathered using Taguchi design matrix. Surface roughness is the most important performance characteristics of the face milling process. In this study the effect of input face milling process parameters on surface roughness of AISI1045 steel milled parts have been studied. The input parameters are cutting speed (v), feed rate (f z ) and depth of cut (a p ). The experimental data are gathered using Taguchi L9 design matrix. In order to establish the relations between the input and the output parameters, various regression functions have been fitted on the data based on output characteristics. The significance of the process parameters on the quality characteristics of the process was also evaluated quantitatively using the analysis of variance method. Then, statistical analysis and validation experiments have been carried out to compare and select the best and most fitted models. In the last section of this research, mathematical model has been developed for surface roughness prediction using particle swarm optimization (PSO) on the basis of experimental results. The model developed for optimization has been validated by confirmation experiments. It has been found that the predicted roughness using PSO is in good agreement with the actual surface roughness.

An in situ approach to robust superhydrophobic carbon‐based film

In this communication, the novel carbon‐based films have been obtained by a facile in situ deposition method controlling the deposition time, which exhibit a significant increase in the surface hydrophobicity. The detailed cause of this phenomenon has been well probed. The results reveal that the increase of the surface roughness and microstructure modification resulting from the etching effect of F ions could be in charge of the increase of the hydrophobicity. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Superior switching behavior of liquid crystals on surface-modified compound oxide films

We demonstrate high-performance liquid crystal (LC) devices using alignment layers formed of solution-processed HfYO films that were subjected to ion-beam (IB) irradiation. IB irradiation entails the increment of the surface roughness and chemical modification of the surface. Our X-ray photoelectron spectroscopy (XPS) analysis revealed that IB irradiation also breaks oxygen bonds, and thereby creates oxygen vacancies with lattice displacement of the metal atoms. This variation stabilizes the homogeneous LC alignment. The LC cells formed using the IB-irradiated HfYO films with an intensity of 2200eV yielded a rapid response time of 6.579ms. Therefore, our fast switching application based on IB-irradiated HfYO films has great potential for application of display devices.

Experimental Study on Material Removal Capability with Vibration-Assisted WEDM

Wire Electrical Discharge Machining (WEDM) is a thermal process that involves melting and vaporisation of work material by a wire electrode in order to obtain the required size. The present work covers a study to improve the material removal rate (MRR) and to machining required slot size by varying frequency lateral vibration of wire while WEDM machining on AISI H13. The machining experiments were conducted by means of two electrode wire materials such as brass and zinc coated wires. The experiments mainly focused on surface integrity aspects like surface/sub surface microstructure, kerf width and surface roughness modification of surfaces machined with Wire Electrical Discharge Machining. The experimental results present the machinability of work material with WEDM process with varying frequency of vibration of wire electrode materials.

Effect of Surface Property on Transfer-Print of Au Thin-Film to Micro-Structured Substrate

This present study describes a novel micro-fabrication technique using transfer-print of thin-film for micro-mechanical structure. Some thin-films of Au have been transferred from a stamp onto pre-structured micro-ridges of polymer substrate. These thin-films successfully form into an array of fixed micro-beams as a mechanical structure. The fabricated micro-beams typically have a thickness of less than 100 nm and a tens micro-meter long. This present paper also reports an investigation about effects of stamp surface properties. A modification of stamp surface wettability and roughness improves adhesive force (releasability) of thin-film to provide flat micro-beam without undesired deformations. Hydrophobic stamp with micro-roughness results in an increase of production yield of micro-beams to reach more than 90%. Simple mechanical test shows that the fabricated micro-beam is transversely tensioned by the supporting micro-ridges of substrate. It is clarified that the proposed process can be applied to fabricate micro/nano-mechanical elements.

Identification and analysis of power substrates degradations subjected to severe aging tests

Severe thermal cycles [−55°C/+245°C] have highlighted degradations in Active Metal Brazing Si3N4 power substrates with copper metallization, nickel-plated and gold finish. After 1000 thermal cycles, the metallization patterns of the top side were imprinted on the rear one due to microcracking of the rear surface metallization and the surface roughness modification. This phenomenon was not observed in less severe thermal cycles such as [-40°C/+150°C]. This study focuses on the causes of this degradation appearance and on issues to prevent such phenomenon. First, the power electronics context is presented to justify the severe stresses applied to high temperature power modules and then induced degradations were described and analyzed. The choice was to perform a protocol of aging process by finite element simulations in order to have a better understanding on the propagation of mechanical stresses in the substrate which is the origin of these degradations. Indeed, this phenomenon could be reproduced by thermomechanical simulations. To propose solutions for these metallization reconstructions, the effect of the copper metallization thickness, the coefficient of thermal expansion of this layer, the substrate warpage and the size of metallization bonding tracks were assessed. The objective is to offer technological choices in terms of geometry of metallization track bonding (minimal etching or traditional engraving) and choices of materials used in power substrates in order to avoid these degradations in extreme environment conditions.

Controlled synthesis of bifunctional PbWO4 dendrites via a facile solution method at room temperature: Photoluminescence and superhydrophobic property

PbWO4 dendrites have been synthesized successfully via the solution method in the absence of templates. The products were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results indicated that the PbWO4 dendrites had a tetragonal unit cell. It was observed that the pH value played an important role in the control of morphology of PbWO4. The products showed a strong photoluminescence peak at 484nm and superhydrophobic property. The water contact angle (CA) greater than 150° was observed, which was closely related to the surface roughness and chemical modification.

Electro-Polishing of Additive Manufactured Porous Titanium for Medical Implants

Advances in Additive Manufacturing (AM) allow for high resolution fabrication of complex three dimensional structures. This enables the construction of fully porous lattice materials with tailored micro-architecture to achieve variable graded properties. One promising application of this approach is the development of graded open cell lattices for orthopaedic bone implants [1]. The use of a graded lattice allows for the material properties of the structure, including stiffness, to match those of the local host bone. In addition, the morphological parameters (including porosity, pore size, and diffusivity) of the individual lattice unit cell can be optimized to achieve optimal bone ingrowth and fixation for long-term implant success. Because of its bio-inertness and high strength, TI6Al4V is an appealing monolithic material for constructing fully porous lattice orthopaedic devices [2]. However, from the process of Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM) processes, semi-melted beads appear to be attached to the individual struts of the lattice. The beads used here generally range from 10-45 microns for DMLS and from 45-106 microns for EBM. The strut diameter of the lattice typically ranges from 150-300 microns. Because the designed strut diameter and bead size are of similar length scale, the addition of semi-melted beads can lead to significant discrepancies between the designed and manufactured strut thickness. This is especially prevalent in struts with thin diameter,near the resolution limit of AM. This discrepancy may induce morphological mismatches that negatively impact the lattice performance. Electrochemical polishing provides an interesting approach to control the reduction of semi-melted beads. This helps to ensure that the manufactured part is identical to the designed structure, allowing for the optimal performance of the implant. Electrochemical polishing can also be used for the creation of micro and nano-roughness surface modifications on the individual struts of the lattice, an outcome that can increase in-vitro cell response and in-vivo bone response [3]. The addition of surface roughness modifications imparted by electrochemical polishing may serve to further improve the bone tissue response of fully porous lattice implants. In this electrochemical process, mass transport controlled dissolution results in surface smoothing. Multiple parts with complex geometry can concurrently be polished. Preliminary results show the potential to use pulse technology (with pulse width of 50µs – 500µs, and duty cycle < 50%) that eliminates surface asperities more effectively than direct current. Surface roughness for a titanium work-piece of around Ra= 4 nm could be obtained with a 4 hours treatment [4]. In the current study, electro-polishing was performed on a fully porous Ti6Al4V manufactured with EBM by applying cyclic voltammetry. The Ti6Al4V work-piece was employed as working electrode, and then immersed in a solution of ethylene glycol and 0.9 molar sodium chloride. The anodic polarization was applied by sweeping the voltage from 15V to 0V at a scan rate of 10 mV/s, using an Ag/AgCl reference electrode. The original average diameter of the beads is 50 µm. The semi-melted beads can clearly be observed in figure 1.A. Figure 1.B. shows the work-piece after the electro-polish treatment (3 cycles) in the solution. The semi-sintered beads are greatly reduced and a smooth surface is achieved. These preliminary results are promising and warrant further investigation. [1] S. A. Khanoki, D. Pasini, Journal of the mechanical behavior of biomedical materials, vol. 22, pp. 65-83, 2013. [2] H. J. Rack, J. I. Qazi, Materials Science and Engineering: C, vol. 26, pp. 1269-1277, 9, 2006. [3] G. Zhao, O. Zinger, Z. Schwartz, M. Wieland, D. Landolt, B. D. Boyan, Clinical Oral Implants Research, vol. 17, pp. 258-264, 2006. [4] A. F. Teixeira, Master of Applied Science - Thesis, Concordia University, March 2011. Figure 1

Surface roughness effects on the tribo-charging and mixing homogeneity of adhesive mixtures used in dry powder inhalers

For active pharmaceutical ingredients (APIs) delivered to the lung it is of main importance that they reach the deeper lung, in order to cause the intended therapeutic effect. To obtain inhalable powders that on the one hand are small enough to travel along the tiny airways finally reaching their target site and on the other hand show sufficient flowability, so-called adhesive mixtures are used. They consist of API particles in the size range of 0.5μm–5μm and carrier particles in the size range of 50μm–200μm, that, due to the size of the carrier, exhibit adequate flowability. However, when administered to the patient, the API has to separate from the carrier surface in order to be able to penetrate the deep lung. The performance of dry powder inhalers (DPIs) and adhesive mixtures is mainly governed by interparticle forces like Van der Waals and triboelectric forces. Carrier surface roughness modification is a new method to alter the contact area and thus the Van der Waals forces between API and carrier. Unfortunately the tribo-charging during handling, especially during the generation of the adhesive mixtures in a tumble blender, is strongly influenced by particle characteristics like particle surface roughness. Thus the mixing quality and stability and thereby the usability of the powder mixture might be additionally influenced by tribo-charging. Therefore the aim of the present work is to investigate whether tribo-charging during the mixing process is influenced by the carrier particle surface roughness. Further the influence of tribo-charging on mixing homogeneity is assessed. Net charge measurements are performed using a Faraday cup. As model API and carrier salbutamol sulfate and spray dried mannitol are used respectively. It is shown that the carrier particle characteristics impact tribo-charging of the pure carriers in a tumble blender. This influence is not observed for the adhesive mixtures of carrier and API. Nevertheless the homogeneity of the adhesive mixtures is still influenced by the charging of the carriers.