Modification Of Topography Research Articles

Multi-scale characterization of topographic modifications on metallic biomaterials induced by nanosecond Nd:YVO4 laser structuring

Laser surface structuring of biometals allows to achieve complex surface geometries at several scales since a rough surface is preferred to induce an optimal cellular response. A lack of standard measurement techniques to characterize implant surfaces was detected. This paper presents a comprehensive, multi-scale characterization of the topography of laser textured biometals with the ISO standard profile method; which allows to separate the contribution of the superimposed textures of the profile, the low frequency component (waviness) and the high frequency component (roughness), and to calculate the respective height parameters according to the standard definitions. Furthermore, the characterization was completed by the calculation of the spatial parameters obtained by FFT calculation in order to assess the horizontal characteristics of the surface. We focused on two common biometals, stainless steel 316L and titanium alloy Ti6Al4V, structured with an array of parallel grooves obtained by using a nanosecond Nd:YVO4 laser. Regarding waviness, some differences in symmetry and sharpness were found according to the metal. Conversely, the roughness of the topography revealed that the average height of the micro-structures developed inside the grooves is similar in both metals. The spatial periodicity of the micro-structures showed that the aspect ratio resulted higher in AISI 316L than in Ti6Al4V. The analytical approach presented in this paper allows to establish an elementary comparison of the results obtained in the scientific community, contributing to a better understanding of in vitro/vivo cellular growing on textured surfaces.

Pulsed laser remelting of A384 aluminum, part II: Modeling of surface homogenization and topographical effects

A simulation model is developed for pulsed laser remelting that captures the homogenization of surface chemical composition and height variations that occur due to silicon (Si) precipitates in a hypereutectic aluminum-silicon (Al-Si) casting alloy. The model simulates remelting pulse-by-pulse with two sequential and repeated steps: it first predicts surface homogenization by areal averaging within a laser spot and then generates and adds a surface feature, due to thermocapillary flow, whose size depends on the concentration of Si within the homogenized spot. Compositional data of remelted lines was collected with energy-dispersive x-ray spectroscopy and used to verify the homogenization step of the simulation model. It was found that Si precipitates get redistributed by the laser with the peak in Si concentration occurring in the direction opposite that of beam travel. Height data from remelted lines were measured using white light interferometry to verify the accuracy of the remelting model in simulating surface topographical modifications. It was found that variations of approximately ± 1 μm are induced in the Al-Si alloy during pulsed laser remelting due to the Si proeutectic precipitates. This is attributed to differences in laser absorption of Si and Al. Because the Si precipitates absorb more energy from the laser, they experience higher temperatures and temperature gradients, which cause larger thermocapillary flow. The results provide insights into approaches to model surface compositional homogenization that occurs during laser remelting and provides an understanding of surface microstructural and topographical features often seen in laser polished Al-Si casting alloys.

Ultrasound-enhanced electrospinning

Electrospinning is commonly used to produce polymeric nanofibers. Potential applications for such fibers include novel drug delivery systems, tissue engineering scaffolds, and filters. Electrospinning, however, has shortcomings such as needle clogging and limited ability to control the fiber-properties in a non-chemical manner. This study reports on an orifice-less technique that employs high-intensity focused ultrasound, i.e. ultrasound-enhanced electrospinning. Ultrasound bursts were used to generate a liquid protrusion with a Taylor cone from the surface of a polymer solution of polyethylene oxide. When the polymer was charged with a high negative voltage, nanofibers jetted off from the tip of the protrusion landed on an electrically grounded target held at a constant distance from the tip. Controlling the ultrasound characteristics permitted physical modification of the nanofiber topography at will without using supplemental chemical intervention. Possible applications of tailor-made fibers generated by ultrasound-enhanced electrospinning include pharmaceutical controlled-release applications and biomedical scaffolds with spatial gradients in fiber thickness and mechanical properties.

Effect of Ultrasonic Vibration Assisted Grinding Process on Surface Topography and Properties of C/SiC Composite

This paper study on the influence of ultrasonic vibration assisted grinding (UAG) process on surface topography and properties of C/SiC composites. Through the surface quality experiments of common grinding (CG) and UAG, the height distribution parameters and function parameters are obtained and used to analyze the characteristics of the material surface topography. The relationship between grinding process and the composites surface quality is pointed out by experimental research. The orthogonal design is employed to optimize ultrasonic parameters and grinding parameters. The optimized condition is carried out to modify the surface quality. The results show that ultrasonic vibration has a great influence on height and surface bearing properties; the surface roughness is improved by the small vibration amplitude and low frequency. The grinding depth is the key factor on surface topography modification and the feed rate is the second. According to the research, an important technical support is carried out to improve the surface performance of C/SiC composites.

Nanocomposites based on self-assembly poly(hydroxypropyl methacrylate)-block-poly(N-phenylmaleimide) and Fe3O4-NPs. Thermal stability, morphological characterization and optical properties

The current work presents the synthesis, characterization and preparation of organic–inorganic hybrid polymer films that contain inorganic magnetic nanoparticles (NPs). The block copolymer, prepared by Atom-Transfer Radical Polymerization (ATRP), was used as a nanoreactor for iron oxide NPs. The NPs were embedded in poly(hydroxypropyl methacrylate)-block-poly(N-phenylmaleimide) matrix. The following topographical modifications of the surface of the film were specially analyzed: control of pore features and changes in surface roughness. Finally, the NPs functionality inside the polymer matrix and how it may affect the thermal and optical properties of the films were assessed.

Tunable surface roughness and wettability of a soft magnetoactive elastomer

ABSTRACTSurface topographical modifications of a soft magnetoactive elastomer (MAE) in response to variable applied magnetic field are investigated. The analysis is performed in situ and is based on optical microscopy, spread optical reflection and optical profilometry measurements. Optical profilometry analysis shows that the responsivity of magnetic field‐induced surface roughness with respect to external magnetic field is in the range of 1 µm/T. A significant hysteresis of surface modifications takes place for increasing and decreasing fields. Investigations of shape of sessile water droplets deposited on the MAE surface reveal that field‐induced topographical modifications affect the contact angle of water at the surface. This effect is reversible and the responsivity to magnetic field is in the range of 20°/T. Despite the increased surface roughness, the apparent contact angle decreases with increasing field, which is attributed to the field‐induced protrusion of hydrophilic microparticles from the surface layer. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46221.

Designing 3D Biological Surfaces via the Breath‐Figure Method

The fabrication of biointerfaces that mimic cellular physiological environments is critical to understanding cell behaviors in vitro and for the design of tissue engineering. Breath figure is a self-assemble method that uses water droplets condensed from moisture as template and ends up with a highly ordered hexagonal pore array; this approach is used to fabricate various biological substrates. This progress report provides an overview of strategies to achieve topographical modifications and chemical-patterned arrays, such as modulation of the pore size, shape and selective decoration of the honeycomb holes. Using recent results in the biological fields, potential future applications and developments of honeycomb structures are commented upon.

3D Plasma Nanotextured® Polymeric Surfaces for Protein or Antibody Arrays, and Biomolecule and Cell Patterning.

Plasma micro-nanotexturing is a generic technology for topographical and chemical modification of surfaces and their implementation in microfluidics and microarrays. Nanotextured surfaces with desirable chemical functionality (and wetting behavior) have shown excellent biomolecule immobilization and cell adhesion. Specifically, nanotextured hydrophilic areas show (a) strong binding of biomolecules and (b) strong adhesion of cells, while nanotextured superhydrophobic areas show null adsorption of (a) proteins and (b) cells. Here we describe the protocols for (a) biomolecule adsorption control on nanotextured surfaces for microarray fabrication and (b) cell adhesion on such surfaces. 3D plasma nanotextured® substrates are commercialized through Nanoplasmas private company, a spin-off of the National Centre for Scientific Research Demokritos.

Tribology of Silicon Surfaces: A review

Micro Electro Mechanical Systems (MEMS) is an emerging technique with an immense number of applications in aerospace and automobile industry. This innovation is advanced with the effective improvement in microelectronics. Sensors and actuators are the utilitarian components of MEMS; Sensor based MEMS are industrially accessible, while actuator based MEMS have a relative movement and thus not yet been marketed because of high friction (forces associated with Surface dominates the forces associated with volume) which prevents the smooth movement and reliability of the device. Additionally, the conventional material for MEMS devices is silicon (Si), which experiences poor tribological properties, and the tribology structures in the system are the main reason for the MEMS devices to fail. Hence tribology of MEMS devices requiring relative movement is of significance. In this situation, new microengineering approaches have been employed to decrease the occurrences of failures, numerous different techniques like thin film coatings, topographical and chemical modification, and application of dual-film coating have been evaluated to strengthen the device, relieve stiction, and thus reduce the friction and adhesion to the system structures. This paper presents an overview of above techniques to improve the performance of silicon surfaces in MEMS devices.

Impact of surface topography and coating on osteogenesis and bacterial attachment on titanium implants

Titanium (Ti) plays a predominant role as the material of choice in orthopaedic and dental implants. Despite the majority of Ti implants having long-term success, premature failure due to unsuccessful osseointegration leading to aseptic loosening is still too common. Recently, surface topography modification and biological/non-biological coatings have been integrated into orthopaedic/dental implants in order to mimic the surrounding biological environment as well as reduce the inflammation/infection that may occur. In this review, we summarize the impact of various Ti coatings on cell behaviour both in vivo and in vitro. First, we focus on the Ti surface properties and their effects on osteogenesis and then on bacterial adhesion and viability. We conclude from the current literature that surface modification of Ti implants can be generated that offer both osteoinductive and antimicrobial properties.

Time dependence of the natural passivation process on AISI 304 in an alkaline medium: Atomic force microscopy and scanning Kelvin probe force microscopy as additional tools to electrochemical impedance spectroscopy

Thin surface films formed on AISI 304 samples in an alkaline solution of pH = 13 are studied by atomic force microscopy (AFM), scanning Kelvin probe force microscopy (SKPFM) and electrochemical impedance spectroscopy (EIS) as a function of immersion time. The results reveal that changes on EIS diagrams correspond to topographical modifications on the sample surface as shown by AFM. Both techniques are therefore complementary. The oxide layer is chemically homogenous as shown by SKPFM imaging and our ultra-thin passive layer is an efficient barrier against corrosion.

Semi-Automatic Detection of Indigenous Settlement Features on Hispaniola through Remote Sensing Data

Satellite imagery has had limited application in the analysis of pre-colonial settlement archaeology in the Caribbean; visible evidence of wooden structures perishes quickly in tropical climates. Only slight topographic modifications remain, typically associated with middens. Nonetheless, surface scatters, as well as the soil characteristics they produce, can serve as quantifiable indicators of an archaeological site, detectable by analyzing remote sensing imagery. A variety of pre-processed, very diverse data sets went through a process of image registration, with the intention to combine multispectral bands to feed two different semi-automatic direct detection algorithms: a posterior probability, and a frequentist approach. Two 5 × 5 km2 areas in the northwestern Dominican Republic with diverse environments, having sufficient imagery coverage, and a representative number of known indigenous site locations, served each for one approach. Buffers around the locations of known sites, as well as areas with no likely archaeological evidence were used as samples. The resulting maps offer quantifiable statistical outcomes of locations with similar pixel value combinations as the identified sites, indicating higher probability of archaeological evidence. These still very experimental and rather unvalidated trials, as they have not been subsequently groundtruthed, show variable potential of this method in diverse environments.

Atomic layer deposition of nano-TiO2 thin films with enhanced biocompatibility and antimicrobial activity for orthopedic implants.

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO2) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO2 coatings on Ti substrates. The effect of nano-TiO2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO2 coatings was shown to inhibit gram-positive bacteria (Staphylococcus aureus), gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO2-coated samples with a moderate surface energy at 38.79 mJ/m2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants.

Late Quaternary coastal evolution and aeolian sedimentation in the tectonically-active southern Atacama Desert, Chile

Analyses of aeolianites and associated dune, surficial carbonate and marine terrace sediments from north-central Chile (27° 54′ S) yield a record of environmental change for the coastal southern Atacama Desert spanning at least the last glacial-interglacial cycle. Optically stimulated luminescence dating indicates phases of aeolian dune construction at around 130, 111–98, 77–69 and 41–28ka. Thin-section and stable carbon and oxygen isotope analyses suggest a predominantly marine sediment source for the three oldest dune phases. Aeolianites appear to have accumulated mainly from tectonically-uplifted interglacial marine sediments that were deflated during windier and/or stormier intervals. Bedding orientations indicate that sand-transporting winds varied in direction from S-ESE during MIS 5e and WNW-ESE during MIS 5c-5a. Winds from the southeast quadrant are unusual today in this region of the Atacama, suggesting either major shifts in atmospheric circulation or topographic airflow modification. Thin-section evidence indicates that the aeolianites were cemented by two phases of vadose carbonate, tentatively linked to wetter periods around 70 and 45ka. Tectonic uplift in the area has proceeded at an average rate of 305–542mmkyr−1. The study illustrates the complexity of understanding onshore-offshore sediment fluxes in the context of Late Quaternary sea-level fluctuations for an area undergoing rapid tectonic uplift.

Boiling-over dense pyroclastic density currents during the formation of the ~ 100 km3 Huichapan ignimbrite in Central Mexico: Stratigraphic and lithofacies analysis

A lithofacies analysis of the Huichapan ignimbrite has been undertaken to evaluate its depositional history from large pyroclastic density currents. The Huichapan ignimbrite is a massive ignimbrite sheet with a maximum runout of at least 55km and thickness variations between 6 and 80m. The lower portion of the Huichapan ignimbrite consists of a large plateau [~100km3; 69km3 as dense-rock equivalent (DRE)] of massive ignimbrites with welding variations from densely welded to partly welded, devitrification, and high-temperature vapor-phase alteration. The lower part grades laterally to moderately welded and non-devitrified ignimbrites. These variations are interpreted as the sedimentation of density-stratified pyroclastic density currents erupted as boiling-over pulses from the Huichapan-Donguinyó caldera complex at a continuous rate, supporting deposition by quasi-steady progressive aggradation of sustained and hot currents. To the north of the caldera, the lower portion of the ignimbrite consists of a small plateau (<10km3) in which the densely welded and devitrified lithofacies are absent. Our interpretation is that the pyroclastic density currents flowed late to the north of the caldera and formed a smaller ignimbrite plateau with respect to the western one. This northern ignimbrite plateau cooled faster than the western ignimbrite plateau. Deposition-induced topographic modifications suggest that topographic obstacles, such as remnants of older volcanoes, may have promoted the deviation of the density currents to the north. The upper portion of the ignimbrite is composed of extensive, massive, coarse clast-rich, non-devitrified, and non-welded ignimbrites with abundant fines-poor pipes. This upper part was deposited from largely sustained and rapidly aggrading high-concentration currents in a near end-member, fluid escape-dominated flow boundary zone. The absence of welding in the upper portion may record pyroclastic density currents cooling during the formation of a relatively high pyroclastic fountain at the vent. We have established a depositional model for the Huichapan ignimbrite that explains the differences between the western and northern plateaus. The Huichapan ignimbrite was formed during a large caldera-forming eruption with concentrated pyroclastic fountains. High mass-flow rate was maintained for long periods, promoting the mobility of the pyroclastic density currents.

Response of umbilical cord mesenchymal stromal cells to varying titanium topographical signals.

A wide variety of titanium implant modifications have been developed to improve tissue- or cell-material interactions including bone bonding, implant failure, and contact osteogenesis. Osteogenesis can be stimulated by mechanobiological signals such as topography though translation of in vivo reactions to in vitro bioactivity and stem cell culture data, and vice versa, is challenging. We hypothesized that a systematic in vitro approach comparing clinically well-accepted implant surface topographical modifications could shed light on potential cell biological mechanisms provoked by submicron-, micron- or macrostructured surfaces. In this study, we investigated the response of umbilical cord derived mesenchymal stromal cells (UC-MSCs) to anodized, particle blasted, and plasma sprayed highly porous Plasmapore surfaces, which is known to promote bony ingrowth in vivo. After 21 days, UC-MSCs undergo a morphological shift from a 2D to 3D behavior on micro- or macrostructures visualized by actin-vinculin fluorescence and are able to fill the porous surfaces completely. Cell viability after 7 days was significantly decreased on the micro- and macrostructured surfaces particle blasted and Plasmapore, compared to polished controls. The analysis of osteogenic differentiation under noninduced conditions revealed a significantly elevated ALP activity on Plasmapore, indicating a beneficial effect of this macrostructured surface toward osteogenic differentiation supported by late elevated gene expression of osteopontin evaluated by qPCR. Mineralization as well as in vitro bioactivity was pronounced on anodized surfaces. Our findings point to synergistic implant modification strategies allowing early contact osteogenesis and bone ingrowth for future implant designs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 180-191, 2018.

Application of Novel Polymeric Surface Remediation Technique Based on Flying Jet Plasma Torch

A flying jet plasma torch (FJPT) was applied to treat raw polymers before the end use process. Specimens of the raw polymers (polypropylene, polystyrene, and two grades of polyethylene) were treated for a few minutes. The examined specimens were analyzed by using scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray spectroscopy. The results indicated that FJPT effectively stimulated the topographical modifications and changed the chemical composition of the surface, which consequently affected the roughness of the surface. Machinability of the examined high-density polyethylene (HDPE) was investigated through measuring the melt mass flow rate index (MFI). The results showed that MFI increased around 30% after 5 min treatments. Longer treatment periods resulted in reductions of MFI attributed to thermal effects. Measured MFI for treated HDPE slightly decreased for 3 days after treatment. Hence, FJPT proved useful for treating polymer surface homogeneously and tailoring the sur...

Giant Strain and Induced Ferroelectricity in Amorphous BaTiO₃ Films under Poling.

We report an effect of giant surface modification of a 5.6 nm thick BaTiO3 film grown on Si (100) substrate under poling by conductive tip of a scanning probe microscope (SPM). The surface can be locally elevated by about 9 nm under −20 V applied during scanning, resulting in the maximum strain of 160%. The threshold voltage for the surface modification is about 12 V. The modified topography is stable enough with time and slowly decays after poling with the rate ~0.02 nm/min. Strong vertical piezoresponse after poling is observed, too. Combined measurements by SPM and piezoresponse force microscopy (PFM) prove that the poled material develops high ferroelectric polarization that cannot be switched back even under an oppositely oriented electric field. The topography modification is hypothesized to be due to a strong Joule heating and concomitant interface reaction between underlying Si and BaTiO3. The top layer is supposed to become ferroelectric as a result of local crystallization of amorphous BaTiO3. This work opens up new possibilities to form nanoscale ferroelectric structures useful for various applications.

Combination of Functional Nanoengineering and Nanosecond Laser Texturing for Design of Superhydrophobic Aluminum Alloy with Exceptional Mechanical and Chemical Properties.

Industrial application of metallic materials is hindered by several shortcomings, such as proneness to corrosion, erosion under abrasive loads, damage due to poor cold resistance, or weak resistance to thermal shock stresses, etc. In this study, using the aluminum-magnesium alloy as an example of widely spread metallic materials, we show that a combination of functional nanoengineering and nanosecond laser texturing with the appropriate treatment regimes can be successfully used to transform a metal into a superhydrophobic material with exceptional mechanical and chemical properties. It is demonstrated that laser chemical processing of the surface may be simultaneously used to impart multimodal roughness and to modify the composition and physicochemical properties of a thick surface layer of the substrate itself. Such integration of topographical and physicochemical modification leads to specific surface nanostructures such as nanocavities filled with hydrophobic agent and hard oxynitride nanoinclusions. The combination of superhydrophobic state, nano- and micro features of the hierarchical surface, and the appropriate composition of the surface textured layer allowed us to provide the surface with the outstanding level of resistance of superhydrophobic coatings to external chemical and mechanical impacts. In particular, experimental data presented in this study indicate high resistance of the fabricated coatings to pitting corrosion, superheated water vapor, sand abrasive wear, and rapid temperature cycling from liquid nitrogen to room temperatures, without notable degradation of superhydrophobic performance.

Morphology of the Morasko crater field (western Poland): Influences of pre-impact topography, meteoroid impact processes, and post-impact alterations

Small impact craters (<1km) developed in unconsolidated sediments are expected to be relatively common on Earth; however, only a few tens of them have been documented thus far. Among the reasons for this small number of documented craters are the post-impact erosion and sedimentation processes that modify craters and the lack of universal identification criteria to allow the differentiation of impact structures from landforms of other origins. Here, we focus on the well-preserved impact craters on the Morasko Hill push moraine in western Poland. These craters were formed by iron meteoroid impacts in unconsolidated sediments of glacial and fluvial origins ca. 5000–6000years ago. We provide a new high-resolution topographic model of the crater field to identify the influences of the pre-impact topography, impact processes, and post-impact modifications on the final morphology of the craters. The topographic model obtained from airborne LiDAR data and total station surveying consists of DEMs related to the recent and reconstructed pre-impact topographies. Parameterization of recent topography in terms of slope gradients, slope curvatures, and roughness allowed us to delimit the boundaries of the craters and to calculate their Feret diameters, ellipticities, slope gradients, crater depths, and volumes. The novelty of our study lies in the estimation of the last two parameters based on the reconstructed pre-impact topography and modelled paraboloids related to each crater. The obtained results show that the studied craters are circular, bowl-shaped features displaying different cross-sectional asymmetries that resulted from the interplay between the trajectories of the bombarding projectiles and the topographies of the primary pre-impact glacial and post-glacial landforms. The oblique impacts likely influenced the asymmetric distribution of ejecta during the excavation of the craters and are considered as factors conditioning mass movements during the post-impact modification of the craters. The compilation of the existing data on terrestrial small-impact craters reveals that they are susceptible to post-impact geometry modification (shallowing and widening) and that many craters have depth/diameter ratios lower than are typical for simple impact craters.