Modification Of Topography Research Articles

Versatile Self‐Cleaning Coating Production Through Sol–Gel Chemistry

The performance of optical devices is dependent on their optical transparency (OT). This is evident when such devices are exposed to environmental conditions that can reduce OT. The development of a robust, transparent and self‐cleaning coating is highly desirable, for applications likeoptical windows and solar panels. This work reports the design of such coatings based on a hydrophobic thin film fabricated using a sol‐gel process. Coating properties were optimised by modification of the surface topography of the coatings, achieved by the incorporation of silica nanoparticles(NPs). The coating was characterised by water contact angle(WCA), scanning electron microscopy(SEM) and white light interferometry (WLI). The efficacy and robustness of the coating foroptical application was assessed.

Transfer of Direct and Moiré Patterns by Reactive Ion Etching Through Ex Situ Fabricated Nanoporous Polymer Masks.

We present a conceptually simple approach to nanolithographic patterning utilizing ex situ fabricated nanoporous masks from block copolymers. The fabricated block copolymer (BC) masks show predictable morphology based on the correlation between BC composition and bulk properties, independent of substrates' surface properties. The masks are prepared by microtoming of prealigned nanoporous polymer monoliths of hexagonal morphology at controlled angles; they appear as 30-60 nm thick films of typical dimensions 100 μm × 200 μm. Masks cut perpendicular to the cylindrical axis show monocrystalline hexagonal packing of 10 nm pores with a principal period of 20 nm. We demonstrate the transfer of the hexagonal pattern onto silicon by means of reactive ion etching through the masks. In addition, patterns of elliptic and slit-like holes on silicon are obtained by utilizing masks cut at 45° relative to the cylinder axis. Finally, we demonstrate the first transfer of moiré patterns from block copolymer masks to substrate. The nanoporous masks prepared ex situ show outstanding long-range order and can be applied directly onto any flat substrate, eliminating the need for topographic and chemical surface modification, which are essential prerequisites for the conventional procedure of block copolymer directed self-assembly. The demonstrated elliptic and moiré pattern transfers prove that the proposed ex situ procedure allows us to realize nanolithographic patterns that are difficult to realize by the conventional approach alone.

Evaluation of Surface Microtopography Engineered by Direct Laser Interference for Bacterial Anti-Biofouling

Modification of the biomaterial surface topography is a promising strategy to prevent bacterial adhesion and biofilm formation. In this study, we use direct laser interference patterning (DLIP) to modify polystyrene surface topography at sub-micrometer scale. The results revealed that three-dimensional micrometer structures have a profound impact on bacterial adhesion. Thus, line- and pillar-like patterns enhanced S. aureus adhesion, whereas complex lamella microtopography reduced S. aureus adhesion in static and continuous flow culture conditions. Interestingly, lamella-like textured surfaces retained the capacity to inhibit S. aureus adhesion both when the surface is coated with human serum proteins and when the material is implanted subcutaneously in a foreign-body associated infection model.

Ferromagnetic resonance in a topographically modulated permalloy film

A major focus within the field of magnonics involves the manipulation and control of spin-wave modes. This is usually done by patterning continuous soft magnetic films. Here, we report on work in which we use topographic modifications of a continuous magnetic thin film, rather than lithographic patterning techniques, to modify the ferromagnetic resonance spectrum. To demonstrate this technique we have performed in-plane, broadband, ferromagnetic resonance studies on a 100-nm-thick permalloy film sputtered onto a colloidal crystal with individual sphere diameters of 200 nm. Effects resulting from the, ideally, sixfold-symmetric underlying colloidal crystal were studied as a function of the in-plane field angle through experiment and micromagnetic modeling. Experimentally, we find two primary modes; the ratio of the intensities of these two modes exhibits a sixfold dependence. Detailed micromagnetic modeling shows that both modes are quasiuniform and nodeless in the unit cell but that they reside in different demagnetized regions of the unit cell. Our results demonstrate that topographic modification of magnetic thin films opens additional directions for manipulating ferromagnetic resonant excitations.

Selective (bio)functionalization of solid-state nanopores.

We present a method to selectively (bio)functionalize nanoscale features with the same materials chemistry. It was successfully combined with nanosphere lithography to fabricate and functionalize solid-state nanopores with PEG-brushes, supported lipid membranes, and functional proteins over large areas. The method is inexpensive, can be performed without specialized equipment, and can be applied to both topographic and planar surface modification.

Large-scale atmospheric forcing and topographic modification of precipitation rates over High Asia – a neural-network-based approach

Abstract. The heterogeneity of precipitation rates in high-mountain regions is not sufficiently captured by state-of-the-art climate reanalysis products due to their limited spatial resolution. Thus there exists a large gap between the available data sets and the demands of climate impact studies. The presented approach aims to generate spatially high resolution precipitation fields for a target area in central Asia, covering the Tibetan Plateau and the adjacent mountain ranges and lowlands. Based on the assumption that observed local-scale precipitation amounts are triggered by varying large-scale atmospheric situations and modified by local-scale topographic characteristics, the statistical downscaling approach estimates local-scale precipitation rates as a function of large-scale atmospheric conditions, derived from the ERA-Interim reanalysis and high-resolution terrain parameters. Since the relationships of the predictor variables with local-scale observations are rather unknown and highly nonlinear, an artificial neural network (ANN) was utilized for the development of adequate transfer functions. Different ANN architectures were evaluated with regard to their predictive performance. The final downscaling model was used for the cellwise estimation of monthly precipitation sums, the number of rainy days and the maximum daily precipitation amount with a spatial resolution of 1 km2. The model was found to sufficiently capture the temporal and spatial variations in precipitation rates in the highly structured target area and allows for a detailed analysis of the precipitation distribution. A concluding sensitivity analysis of the ANN model reveals the effect of the atmospheric and topographic predictor variables on the precipitation estimations in the climatically diverse subregions.

Programming cell fate on bio-functionalized silicon

Controlling the growth of cells on the surface of silicon without an additive layer or topographical modification is unexplored. This research article delineates the discovery of unique properties of a bio-functionalized silicon substrate, programmed to repel or control cells, generated by ultrafast femtosecond pulse interaction with silicon. Remarkably, bio-functionalization in any shape or size without change in topology or morphology is observed indicating only sub-surface phase transformations. Material characterization reveals the presence of a unique mixture of phases of SiO2 and Si. Consequently, these variations in phase alter the physicochemical characteristics on the surface of silicon resulting in its bio-functionalization. The culture of mouse embryonic fibroblasts shows unique adhesion characteristics on these bio-functionalized silicon surfaces that include cell controlling, cell trapping, and cell shaping. Furthermore, the directionality of fibroblasts is restrained parallel to bio-functionalized zones as evidenced by changes in cytoskeleton. The controlling of proliferation, migration and adhesion of cells is attributed to unique phase bio-functionalization. This method presents considerable promise in a myriad of applications such as tissue engineering, MEMS, and lab-on-a-chip devices.

Inhibition effect of butan-1-ol on the corrosion behavior of austenitic stainless steel (Type 304) in dilute sulfuric acid

The electrochemical behavior of austenitic stainless steel (Type 304) in 3M sulfuric acid with 3.5% recrystallized sodium chloride at specific concentrations of butan-1-ol was investigated with the aid of potentiodynamic polarization, open circuit measurement and weight loss technique. Butan-1-ol effectively inhibited the steel corrosion with a maximum inhibition efficiency of 78.7% from weight-loss analysis and 80.9% from potentiodynamic polarization test at highest concentration studied. Adsorption of the compound obeyed the Freundlich isotherm. Thermodynamic calculations reveal physiochemical interactions and spontaneous adsorption mechanism. Surface characterizations showed the absence of corrosion products and topographic modifications of the steel. Statistical analysis depicts the overwhelming influence and statistical significance of inhibitor concentration on the inhibition performance.

Closed-Loop Feedback Flank Errors Correction of Topographic Modification of Helical Gears Based on Form Grinding

To increase quality, reduce heavy-duty gear noise, and avoid edge contact in manufacturing helical gears, a closed-loop feedback correction method in topographic modification tooth flank is proposed based on the gear form grinding. Equations of grinding wheel profile and grinding wheel additional radial motion are derived according to tooth segmented profile modification and longitudinal modification. Combined with gear form grinding kinematics principles, the equations of motion for each axis of five-axis computer numerical control forming grinding machine are established. Such topographical modification is achieved in gear form grinding with on-machine measurement. Based on a sensitivity analysis of polynomial coefficients of axis motion and the topographic flank errors by on-machine measuring, the corrections are determined through an optimization process that targets minimization of the tooth flank errors. A numerical example of gear grinding, including on-machine measurement and closed-loop feedback correction completing process, is presented. The validity of this flank correction method is demonstrated for tooth flank errors that are reduced. The approach is useful to precision manufacturing of spiral bevel and hypoid gears, too.

Structural properties of scaffolds: Crucial parameters towards stem cells differentiation.

Tissue engineering is a multidisciplinary field that applies the principles of engineering and life-sciences for regeneration of damaged tissues. Stem cells have attracted much interest in tissue engineering as a cell source due to their ability to proliferate in an undifferentiated state for prolonged time and capability of differentiating to different cell types after induction. Scaffolds play an important role in tissue engineering as a substrate that can mimic the native extracellular matrix and the properties of scaffolds have been shown to affect the cell behavior such as the cell attachment, proliferation and differentiation. Here, we focus on the recent reports that investigated the various aspects of scaffolds including the materials used for scaffold fabrication, surface modification of scaffolds, topography and mechanical properties of scaffolds towards stem cells differentiation effect. We will present a more detailed overview on the effect of mechanical properties of scaffolds on stem cells fate.

The Effect of Titanium Surface Modifications on Dental Implant Osseointegration.

The use of titanium dental implants has consistently changed the way of rehabilitating patients in modern dentistry and can count on high long-term survival and success rates. With respect to its introduction in the late 1960s, clinical indications for implant therapy have been significantly extended and optimal results have been achieved, even in clinical conditions formerly considered as unfavourable. Such evolution owes a lot to the significant progress made in the field of titanium surfaces. The topographical and chemical modification of traditional titanium surfaces has led to a real epochal shift in implant dentistry. Depending on the type and characteristics of the surface treatment applied, a wide range of implants has been produced, which have contributed to the success but also increased the risk of confusion in implant selection criteria for the clinician. This chapter, which provides an updated analysis of the relevant literature, the characteristics of modern implant surfaces, the biological principles underlying their role in promoting osseointegration and the scientific evidence about their clinical use are analyzed and presented.

Rice-fish Integration in Sub-Saharan Africa

In light of the logistical challenges for gearing production and conservation efforts to the scale of the smallholder, there is growing interest in promoting Integrated Irrigation-Aquaculture (IIA), such as rice-fish culture, which has strong potential in Sub-Saharan Africa. Available literature has stressed institutional shortcomings in providing necessary services, including extension, training, and creditlending; ways in which farmers could craft new water-management regimes if these services were available have not been well studied and are key to successful farming integration. In this paper, we analyzed the conditions for achieving integrated water governance, with reference to the available evidence relating to the rice-fish system environment, investment incentives, collective action, and property rights. Our analysis suggests that the system design should be adapted to existing farm conditions to minimize topographical and technical modifications and maximize successful adoption of rice-fish culture. Labor and capital requirements must remain within the bounds of investment capacity, which is limited and seasonal among African smallholders. Investments in IIA should promise an adequate profit margin to secure reinvestment. Since reinvestment is important for the advanced operation and maintenance of water facilities, sustainable rice-fish farming requires strong accountability in organizing water distribution, monitoring, and related rule enforcements. Therefore, a preliminary need is to understand farmers’ socioeconomic characteristics and interests that affect participation and free riding.

流れ山分布の地形学的特徴からみた古羊蹄火山の巨大山体崩壊

Hummocks are conically shaped mounds, which occur following catastrophic sector collapses, and are mainly observed around volcanoes. Empirical relationships of hummocks proposed by Yoshida et al. (2012) are basically applicable if hummocks now distributed on a debris avalanche depositional area do not have remarkable disturbances due to topographical barriers or modifications after deposition. Using these empirical relationships, the Old Yotei volcano, whose mega-collapse in the Late Pleistocene has not been clarified yet, is examined. The results show that the size-distance relationship of hummocks (N=297), distributed west of the volcano can be expressed by an exponential function as, A=α exp (−β D),where A is the average area of a hummock within a certain span and D is the average distance from the source. For the Old Yotei volcano, the values of coefficients α and β of the fitted curve are 170286.4 and 0.000429, respectively. Based on a geomorphological interpretation of both α and β values, it can be concluded that the collapse volume of the Old Yotei volcano is ca.1.3 km3, and the equivalent coefficient of friction of the debris avalanche is 0.129. The latter also reveals a high probability that the pre-collapse summit of the Old Yotei volcano reached 1700 m a.s.l. Thus, the image of the flank collapse of the Old Yotei volcano has been restored more decisively by the distribution of hummocks.

Evaluation of nano surface modification on CPTi dental implant using chemical method: mechanical and histological evaluation

The application of nanotechnology to biomedical surfaces is explained by the ability of cells to interact with nanometric features. The aim of this study was to consider the role of nanoscale topographic modification of CPTi dental implant using chemical etching method for the purpose of improving osseointegration. Materials and methods: Commercial pure titanium rod was machined into 20 dental implants. Each implant was machined in diameter about 3mm, length of 8mm (5mm was threaded part and 3mm was flat part). Implants were prepared and divided into 2 groups according to the types of surface modification method used: 1st group (10 implant) remained without nano surface modification (control), 2nd group include (10 implant) etched with 15N H2SO4 and 30% H 2 O 2, Surfaces were characterized by scanning electron microscope (SEM), Xray diffraction (XRD), atomic force microscope (AFM), thickness measurement for the invitro experiments. While for invivo part tibia of 5 white new Zealand rabbits were chosen as implantation sites. The tibia of each rabbit received two screws. Biomechanical test was performed to understand the bone-implant interface, after two weeks healing periods. Implants from 4animals were tested for the torque required to remove the implant from the bone and the other one animal was prepared for histological examination. Results and Conclusion: For in vitro results, scanning electron microscope showed that the chemical etching of Ti substrate becomes highly porous and has surface consisting of nanosized pits. Removal torque means value after 2 weeks of implantation mentioned that, there was a gradual increase in the removal torque mean values as a follow (M±SD): 12.625(N.cm) ± 0.517, 30.500(N.cm) ± 4.071for machined surface(X), nano chemically etched (X1) respectively. In addition, the histological analysis showed improved quality of bone in response to the nano modified screws, that the chemically treated implants shows trabeculated thread.

Laser and chemical surface modifications of titanium grade 2 for medical application

The article presents combined, chemical and physical approach to titanium surface functionalization designed for biomedical applications. The topography modification has been obtained by employing the double laser beam interference technique and chemical etching. In the outcome, clean and smooth Ti surface as well as periodic striated topography with the roughness range from nano- to micrometers were created. The obtained structures were characterized in terms of shape, roughness, chemical composition, mechanical properties and microstructures. In order to achieve all information, numerous of research methods have been used: scanning electron microscopy, atomic force microscopy, optical profilometry and microhardness measurements. Demonstrated methodology can be used as an effective tool for manufacturing controlled surface structures improving the bone–implants interactions.

Sub-10 nm resistless nanolithography for directed self-assembly of block copolymers.

The creation of highly efficient guiding patterns for the directed self-assembly of block copolymers by resistless nanolithography using atomic force microscopy (AFM) is demonstrated. It is shown that chemical patterns consisting of arrays of lines defined on a brush layer by AFM allow the alignment of the blocks of lamella-forming polymers. The main advantage of this method relies on the capability to create high-resolution (sub-10 nm line-width) guiding patterns and the reduction of the number of process steps compared to the state-of-the-art methods for creating guiding patterns by chemical surface modification. It is found that the guiding patterns induce the block alignment very efficiently, allowing the achievement of a density multiplication factor of 7 for block copolymers of 14 nm half-pitch, which is attributed to the combined effect of topographical and chemical modification.

Stability of weakly alkaline barrier slurry with the high selectivity

In order to improve the CMP performance, many methods have been devoted to the development of barrier slurry. H2O2 as an oxidizer and benzotriazole (BTA) as an inhibitor is considered to be an effective method in barrier CMP. In this paper, the high-stability weakly alkaline barrier slurry is presented. Major components include complexing agents, silica, nonionic surfactant and pH-modifier but free of oxidizers and inhibitors. We studied the stability of the slurry using the material removal rate of Cu, Ta and TEOS blanket wafers, particle size, PH-value, viscosity and zeta potential tests as a function of aging time during one month. A 300mm copper pattern wafer was polished by the barrier slurry after one-month time to examine performance of the slurry. The results indicate that as the aging time is increased, the mean particle size, PH-value, viscosity and zeta potential of the slurries fluctuated slightly in time. The polishing results of Cu, Ta and TEOS blanket wafers show that the slurry has high selectivity of Ta and TEOS to Cu even after one-month time. The aging time has little impact on removal rate selection. The dishing values and roughness of Cu wiring after 300mm pattern wafer polishing suggest that the slurry has an effective performance in topography modification. By experiment research, the barrier slurry exhibits a stability having a shelf life of at least 30days.

Effect of surface topography and bioactive properties on early adhesion and growth behavior of mouse preosteoblast MC3T3-E1 cells.

The effects of bioactive properties and surface topography of biomaterials on the adhesion and spreading properties of mouse preosteoblast MC3T3-E1 cells was investigated by preparation of different surfaces. Poly lactic-co-glycolic acid (PLGA) electrospun fibers (ES) were produced as a porous rough surface. In our study, coverslips were used as a substrate for the immobilization of 3,4-dihydroxyphenylalanine (DOPA) and collagen type I (COL I) in the preparation of bioactive surfaces. In addition, COL I was immobilized onto porous electrospun fibers surfaces (E-COL) to investigate the combined effects of bioactive molecules and topography. Untreated coverslips were used as controls. Early adhesion and growth behavior of MC3T3-E1 cells cultured on the different surfaces were studied at 6, 12, and 24 h. Evaluation of cell adhesion and morphological changes showed that the all the surfaces were favorable for promoting the adhesion and spreading of cells. CCK-8 assays and flow cytometry revealed that both topography and bioactive properties were favorable for cell growth. Analysis of β1, α1, α2, α5, α10 and α11 integrin expression levels by immunofluorescence, real-time RT-PCR, and Western blot and indicated that surface topography plays an important role in the early stage of cell adhesion. However, the influence of topography and bioactive properties of surfaces on integrins is variable. Compared with any of the topographic or bioactive properties in isolation, the combined effect of both types of properties provided an advantage for the growth and spreading of MC3T3-E1 cells. This study provides a new insight into the functions and effects of topographic and bioactive modifications of surfaces at the interface between cells and biomaterials for tissue engineering.

Parylene C surface functionalization and patterning with pH-responsive microgels.

Parylene C is a polymer well-known for its inertness and chemical resistance, thus ideal for covering and sealing 3D substrates and structures by conformal coating. In the present study, the Parylene C surface is modified by functionalization with pH-responsive poly(methacrylic acid) microgels either over the whole surface, or in a pattern through a poly(dimethylsiloxane) stamp. The surface functionalization consists of two phases: first, an oxygen plasma treatment is used to make the surface superhydrophilic, inducing the formation of polar functional groups and surface topography modifications; then, the plasma-treated samples are functionalized by drop casting a solution of pH-responsive microgels, or in a pattern via microcontact printing of the same solution. While both techniques, namely, drop casting and microcontact printing, are easy to use, fast, and cheap, the microcontact printing was found to provide a more homogeneous functionalization and to be applicable to any shape of substrate. The functionalization effectiveness was tested by the repeated uptake and release of a fluorescent labeled monoclonal CD4 antibody at different pH values, thus suggesting a new sensing approach.

Integration of a 2-D Periodic Nanopattern Into Thin-Film Polycrystalline Silicon Solar Cells by Nanoimprint Lithography

The integration of two-dimensional (2D) periodic nanopattern defined by nanoimprint lithography and dry etching into aluminum induced crystallization (AIC) based polycrystalline silicon (Poly-Si) thin film solar cells is investigated experimentally. Compared to the unpatterned cell an increase of 6% in the light absorption has been achieved thanks to the nanopattern which, in turn, increased the short circuit current from 20.6 mA/cm2 to 23.8 mA/cm2. The efficiency, on the other hand, has limitedly increased from 6.4% to 6.7%. We show using the transfer length method (TLM) that the surface topography modification caused by the nanopattern has increased the sheet resistance of the antireflection coating (ARC) layer as well as the contact resistance between the ARC layer and the emitter front contacts. This, in turn, resulted in increased series resistance of the nanopatterned cell which has translated into a decreased fill factor, explaining the limited increase in efficiency.