Modification Of Topography Research Articles

Modification of the Surface Topography of Additive Materials under Ar+ Ion Irradiation

Additive manufacturing (AM) is a modern developing group of technologies based not on the removal of material, but on the layer-by-layer growth and synthesis of an object according to a CAD (Computer-Aided Design) model. The main disadvantages of objects manufactured using AM technologies are a high degree of porosity and surface roughness. This work examines the possibility of modifying the surface of additive materials Ti6Al4V and AlSi10Mg using irradiation with Ar+ ions with energies in the range from 2 to 9 keV. Using SEM, the surface topography was obtained before and after irradiation and mechanical polishing. A reduction in surface porosity and roughness was demonstrated, as well as the influence of beam energy on the final surface topography.

Endothelium-Mimicking Materials: A "Rising Star" for Antithrombosis.

The advancement of antithrombotic materials has significantly mitigated the thrombosis issue in clinical applications involving various medical implants. Extensive research has been dedicated over the past few decades to developing blood-contacting materials with complete resistance to thrombosis. However, despite these advancements, the risk of thrombosis and other complications persists when these materials are implanted in the human body. Consequently, the modification and enhancement of antithrombotic materials remain pivotal in 21st-century hemocompatibility studies. Previous research indicates that the healthy endothelial cells (ECs) layer is uniquely compatible with blood. Inspired by bionics, scientists have initiated the development of materials that emulate the hemocompatible properties of ECs by replicating their diverse antithrombotic mechanisms. This review elucidates the antithrombotic mechanisms of ECs and examines the endothelium-mimicking materials developed through single, dual-functional and multifunctional strategies, focusing on nitric oxide release, fibrinolytic function, glycosaminoglycan modification, and surface topography modification. These materials have demonstrated outstanding antithrombotic performance. Finally, the review outlines potential future research directions in this dynamic field, aiming to advance the development of antithrombotic materials.

Cleaning of laser-induced periodic surface structures on copper by gentle wet chemical processing

Laser-induced periodic surface structures (LIPSS) attract considerable attention due to the manifold applications enabled by these self-organised structures ranging from optical colouring to bio-mimicking or wetting effects. The mechanism of LIPSS-formation at metal surfaces includes laser-ablation processes that results in phase transitions, explosive material removal and partial redeposition of the ablation products in the form of nanoscopic debris or even sub-micrometre-sized spherical particles in case of melt ejection. For some applications, these particulates, debris, and microscopic features on top of the periodic surface structures are disadvantageous. We studied wet-chemical cleaning approaches to remove redeposited material from LIPSS to enhance their applicability. LIPSS on copper with a lateral periodicity of ∼ 365 nm, that were fabricated by ultrashort pulse laser exposure(λ: 515 nm, tp: 260 fs), were cleaned with different liquids ranging from solvents to microemulsions. The surface morphologies were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy(TEM) to study the surface topography, the size and density of surface particulates as well as other surface contaminations before and after wet cleaning. The LIPSS surface composition was analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Energy-dispersive x-ray spectroscopy (EDX) at the FIB-cross sections. The different cleaning approaches are classified with respect to their capability to remove particles and contaminations as well as to their influence on the morphology and shape of LIPSS pattern, whereby substantial differences are found. At least two wet-chemical solutions enable the removal of nanoparticles with only minor modification of the LIPSS topography. The main effect of wet cleaning is the detachment of particulates including sub-micrometre-sized spheres due to a gentle and selective etching of the interface region between the LIPSS and the redeposited material that comprise of modified copper and copper oxides.

Modification of the Surface Topography of Additive Materials under Ar$${}^{\mathbf{+}}$$ Ion Irradiation

Modification of the Surface Topography of Additive Materials under Ar$${}^{\mathbf{+}}$$ Ion Irradiation

Interface-Mediated Neurogenic Signaling: The Impact of Surface Geometry and Chemistry on Neural Cell Behavior for Regenerative and Brain-Machine Interfacing Applications.

Nanomaterial advancements have driven progress in central and peripheral nervous system applications such as tissue regeneration and brain-machine interfacing. Ideally, neural interfaces with native tissue shall seamlessly integrate, a process that is often mediated by the interfacial material properties. Surface topography and material chemistry are significant extracellular stimuli that can influence neural cell behavior to facilitate tissue integration and augment therapeutic outcomes. This review characterizes topographical modifications, including micropillars, microchannels, surface roughness, and porosity, implemented on regenerative scaffolding and brain-machine interfaces. Their impact on neural cell response is summarized through neurogenic outcome and mechanistic analysis. The effects of surface chemistry on neural cell signaling with common interfacing compounds like carbon-based nanomaterials, conductive polymers, and biologically inspired matrices are also reviewed. Finally, the impact of these extracellular mediated neural cues on intracellular signaling cascades is discussed to provide perspective on the manipulation of neuron and neuroglia cell microenvironments to drive therapeutic outcomes.

The effects of submicron-textured surface topography on antibiotic efficacy against biofilms.

Submicron-textured surfaces have been a promising approach to mitigate biofilm development and control microbial infection. However, the use of the single surface texturing approach is still far from ideal for achieving complete control of microbial infections on implanted biomedical devices. The use of a surface topographic modification that might improve the utility of standard antibiotic therapy could alleviate the complications of biofilms on devices. In this study, we characterized the biofilms of Staphylococcus aureus and Pseudomonas aeruginosa on smooth and submicron-textured polyurethane surfaces after 1, 2, 3, and 7 days, and measured the efficacy of common antibiotics against these biofilms. Results show that the submicron-textured surfaces significantly reduced biofilm formation and growth, and that the efficacy of antibiotics against biofilms grown on textured surfaces was improved compared with smooth surfaces. The antibiotic efficacy appears to be related to the degree of biofilm development. At early time points in biofilm formation, antibiotic treatment reveals reasonably good antibiotic efficacy against biofilms on both smooth and textured surfaces, but as biofilms mature, the efficacy of antibiotics drops dramatically on smooth surfaces, with lesser decreases seen for the textured surfaces. The results demonstrate that surface texturing with submicron patterns is able to improve the use of standard antibiotic therapy to treat device-centered biofilms by slowing the development of the biofilm, thereby offering less resistance to antibiotic delivery to the bacteria within the biofilm community.

Topographic modification of the extracellular matrix precedes the onset of bladder cancer

BackgroundNon-muscle invasive bladder cancer (NMIBC) patients are affected by a high risk of recurrence. The topography of collagen fibers represents a hallmark of the neoplastic extracellular microenvironment. ObjectiveAssess the topographic change associated with different stages of bladder cancer (from neoplastic lesions to bona fide tumor) and whether those changes favour the development of NMIBC. Design, Setting, and ParticipantsSeventy-one clinical samples of urothelial carcinoma at different stages were used. Topographic changes preceding tumor onset and progression were evaluated in the rat bladder cancer model induced by nitrosamine (BBN), a bladder-specific carcinogen. The preclinical model of actinic cystitis was also used in combination with BBN. Validated hematoxylin-eosin sections were used to assess the topography of collagen fibrils associated with pre-tumoral steps, NMIBC, and MIBC. FindingsLinearization of collagen fibers was higher in Cis and Ta vs. dysplastic urothelium, further increased in T1 and greatest in T2 tumors. In the BBN preclinical model, an increase in the linearization of collagen fibers was established since the beginning of inflammation, such as the onset of atypia of a non-univocal nature and dysplasia, and further increased in the presence of the tumor. Linearization of collagen fibers in the model of actinic cystitis was associated with earlier onset of BBN-induced tumor. ConclusionsThe topographic modification of the extracellular microenvironment occurs during the inflammatory processes preceding and favoring the onset of bladder cancer. The topographic reconfiguration of the stroma could represent a marker for identifying and treating the non-neoplastic tissue susceptible to tumor recurrence.

In-vitro fretting tribocorrosion and biocompatibility aspects of laser shock peened Ti-6Al-4V surfaces

Laser shock peening without coating (LSPwC), a prospective surface modification technique for improving the mechanical aspects of Ti-6Al-4V alloy for automotive/aerospace sector, is also expected to dictate the efficiency of this material class for implant application. Here we unravel the impact of LSPwC on Ti-6Al-4V material surface characteristics, in-vitro tribocorrosion and biocompatibility. Micrography shows the presence of nano and sub-micron sized pores after LSPwC process. The role of nano and sub-micron sized pores along with topography modification induced by LSPwC to serve as cues for controlling gene expressions, cell adhesion and activities offer novel insights in this research direction. A detailed X-ray photoelectron spectroscopy analysis detected local chemical non-stoichiometry with reduced number of oxygen diffusion channels. A crucial outcome of this oxide layer modification is the negative skewness (−0.55 ± 0.11) and reduced kurtosis (3.49 ± 0.14) of the surface, along with localized plastic deformation. These factors are correlated with the shift in potential during fretting tribo-corrosion from −800 to −250 mV after LSPwC, accompanied by a lower coefficient of friction of 0.4. Furthermore, the presence of well-spread cells and the up-regulation of beneficial genetic markers (Ki67) on LSPwC surfaces have the potential to form a better bone-material interface. The findings open new frontiers of the LSPwC-treated Ti-6Al-4V surface to synergistically modulate the tribocorrosion and biocompatibility aspects, with exciting possibilities for biomedical implants.

Titanium alloys for orthopedic applications: A review on the osteointegration induced by physicomechanical stimuli

Titanium (Ti) alloys have been widely applied clinically due to their good biocompatibility, corrosion resistance and mechanical stability. However, how to improve the weak osteointegration caused by their intrinsic bio-inertness has been a long-standing puzzle. Osteogenic-related cells, endothelial cells (ECs) and macrophages are the main cells involved in osteointegration. In recent years, surface topography based on Ti alloys, which mimics the topographical cues of the extracellular matrix (ECM), has been confirmed to precisely regulate these cells' fate to improve osteointegration. More importantly, while serving as a physicomechanical stimuli, topographic surface modification is considered more biosafe and stable than biochemical cues. Nevertheless, how different topographic modifications affect cell behavior and the specific mechanisms involved remain elusive. In this review, we highlight the regulation of surface topography based on Ti alloys on the behaviors of bone repair-related cells, such as osteogenic-related cells, ECs and macrophages, and summarize the activated intracellular mechanotransduction pathways, which aims to provide basis and support for further research on osteointegration of Ti alloys.

Photo‐Arbuzov Reactions as a Broadly Applicable Surface Modification Strategy

AbstractChemical vapor deposition (CVD) polymerization is a commonly used approach in surface chemistry, providing a substrate‐independent platform for bioactive surface functionalization strategies. This work investigates the Arbuzov reaction of halogenated polymer coatings readily available via CVD polymerization, using poly(4‐chloro‐para‐xylylene) (Parylene C) as a model substance. Postpolymerization modification of these coatings via catalyst‐free and UV‐induced Arbuzov reaction using phosphites results in phosphonate‐functionalized polymers. The combination of infrared reflection‐absorption spectroscopy (IRRAS), X‐ray photoelectron spectroscopy (XPS), and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) provides detailed insights into the reaction progress. Time‐dependent studies suggest that the non‐polar phosphites penetrate deep into the CVD films and react with the polymer film. In addition, ToF‐SIMS, scanning electron microscopy (SEM), and atomic force microscopy (AFM) confirm spatial control of the reaction, resulting in localized chemical and topographical surface modification, recognizable by changes in interference color, fluorescence, and wettability. Preliminary 3D fluorescence spectroscopy investigations indicate tunable near‐infrared emission of these polymer films. This work is the first step toward generating multifunctional polymer coatings based on chemically modifiable, CVD polymers with potential applications in biomaterials, sensors, or optoelectronics.

The fabrication process of polydimethylsiloxane (PDMS) nanostructured films with antimicrobial properties against methicillin-resistant staphylococcus aureus (MRSA)

Physical topography modification is an approach to fabricate nanostructures surfaces with antimicrobial properties. Lithography-based technologies offer an effective technique to develop the desired sizes and geometry. The replica molding technique was employed to fabricate the PDMS nanostructures using the PMMA imaging layer and characterized using a FESEM and AFM. The cell viability of gram-positive bacteria on structural diminished by almost 80% and the cells were deformed and ruptured once attached to the structured surface. Thus, the PDMS structured surface enhanced the bactericidal properties of the film, which effectively inhibit bacterial attachment.

Ecological restoration of coastal wetlands in China: Current status and suggestions

Globally, coastal wetlands have experienced extensive loss and degradation over the past half-century. Ecological restoration is widely recognized as essential for maintaining ecosystem services. China has increased restoration efforts over the past twenty years, but there has been limited understanding of restoration's effectiveness. Through a review of 86 coastal wetland restoration projects in China, we analyzed restoration objectives, restoration measures, funding sources, and restoration effectiveness. We found that quantitative restoration objectives were unavailable from 90.7 % of those projects; active restoration was the primary measure (94.2 %), with vegetation management (40.6 %), topography modification (28.6 %), and hydrological regulation (24.8 %) being the main techniques. Restoration funding came mainly from governments (94.7 %), and the restoration costs per unit area decreased as the restoration area increased. Unrestored wetlands were mainly (75.6 %) used as references for restoration effectiveness evaluation, generally using species diversity (54.7 %) and physicochemical traits (48.8 %) as indicators. Most restorations were deemed as effective (89.5 %). We propose the following for future coastal wetland restorations: setting quantitative restoration targets focusing on protecting threatened species and enhancing ecological services; combining active with passive restoration measures that employ ecosystems' self-healing capabilities; expanding funding sources through diversified stakeholder collaborations; and establishing a comprehensive evaluation system for restoration effectiveness that includes ecosystem functions. This study provides a reference for the design, implementation, and adaptive management of future coastal wetland restoration in China and other coastal countries.

The use of biomimetic surfaces to reduce single- and dual-species biofilms of Escherichia coli and Pseudomonas putida

The ability of bacteria to adhere to and form biofilms on food contact surfaces poses serious challenges, as these may lead to the cross-contamination of food products. Biomimetic topographic surface modifications have been explored to enhance the antifouling performance of materials. In this study, the topography of two plant leaves, Brassica oleracea var. botrytis (cauliflower, CF) and Brassica oleracea capitate (white cabbage, WC), was replicated through wax moulding, and their antibiofilm potential was tested against single- and dual-species biofilms of Escherichia coli and Pseudomonas putida. Biomimetic surfaces exhibited higher roughness values (SaWC = 4.0 ± 1.0 μm and SaCF = 3.3 ± 1.0 μm) than the flat control (SaF = 0.6 ± 0.2 μm), whilst the CF surface demonstrated a lower interfacial free energy (ΔGiwi) than the WC surface (−100.08 mJ m−2 and −71.98 mJ m−2, respectively). The CF and WC surfaces had similar antibiofilm effects against single-species biofilms, achieving cell reductions of approximately 50% and 60% for E. coli and P. putida, respectively, compared to the control. Additionally, the biomimetic surfaces led to reductions of up to 60% in biovolume, 45% in thickness, and 60% in the surface coverage of single-species biofilms. For dual-species biofilms, only the E. coli strain growing on the WC surface exhibited a significant decrease in the cell count. However, confocal microscopy analysis revealed a 60% reduction in the total biovolume and surface coverage of mixed biofilms developed on both biomimetic surfaces. Furthermore, dual-species biofilms were mainly composed of P. putida, which reduced E. coli growth. Altogether, these results demonstrate that the surface properties of CF and WC biomimetic surfaces have the potential for reducing biofilm formation.

Antifouling strategies for electrochemical sensing in complex biological media.

Surface fouling poses a significant challenge that restricts the analytical performance of electrochemical sensors in both in vitro and in vivo applications. Biofouling resistance is paramount to guarantee the reliable operation of electrochemical sensors in complex biofluids (e.g., blood, serum, and urine). Seeking efficient strategies for surface fouling and establishing highly sensitive sensing platforms for applications in complex media have received increasing attention in the past. In this review, we provide a comprehensive overview of recent research efforts focused on antifouling electrochemical sensors. Initially, we present a detailed illustration of the concept about biofouling along with an exploration of four key antifouling mechanisms. Subsequently, we delve into the commonly employed antifouling strategies in the fabrication of electrochemical sensors. These encompass physical surface topography (micro/nanostructure coatings and filtration membranes) and chemical surface modifications (PEG and its derivatives, zwitterionic polymers, peptides, proteins, and various other antifouling materials). The progress in antifouling electrochemical sensors is proposed concerning the antifouling mechanisms as well as sensing capability assessments (e.g., sensitivity, stability, and practical application ability). Finally, we summarize the evolving trends in the field and highlight some key remaining limitations.

Effect of erosive conditions on different sealant materials used in paediatric dentistry.

To evaluate the effect of acidic challenge on erosion depth and topographic characteristics of different materials used as occlusal sealants. Two hundred specimens of five sealant materials (Fuji IX, Ketac Molar, Fuji II, Equia and Clinpro) and forty bovine teeth enamel samples (control) were prepared and exposed to acidic challenge. The specimens were immersed in four different solutions (orange juice, coke drink, citric acid or distilled water) under mildly shaken conditions for 3 days. The erosion depth profiles were measured using a profilometer and Scanning Electron Microscope (SEM). Two-way ANOVA with Tukey post-hoc test was performed to evaluate the interactions. Sealant material and acidic challenge had significant effects on erosion depth. Among the materials, Fuji II presented the highest mean of erosion depth after immersion in orange juice, coke drink, and citric acid. All materials groups presented higher erosion depth values after immersion in the citric acid solution, except Clinpro. Bovine enamel presented higher erosion depth values compared to all materials when submitted to erosive challenge. Sealant materials submitted to the acidic challenge presented different degrees of erosion and topographic modification; however, they are less susceptible to erosion than bovine teeth enamel.

Training reinforcement learning-based controller using performance simulation of the laser remelting process

Surface topography modification is a common post-processing step used to enhance surface quality or to add micro/nano surface structures for various functionalities. Laser remelting (LRM) is a new technology aimed to resolve some of the shortcomings of traditional post-processing technologies. In LRM, a high-energy laser beam melts the top surface and offers control of the molten material flow through the control of laser power, scanning speed, melt pool size, and scan trajectory. By controlling the molten material flow, surface polishing by laser remelting (SP-LRM) can be used to produce finishes characterized by areal arithmetical mean height - Sa < 0.1 µm as well as surface microstructures. LRM is faster than traditional methods, creates no harmful byproducts, and allows for polishing high aspect ratio freeform surfaces without harming surrounding areas. The primary limiting factor for wide-rage industrial use of the LRM is represented by thermodynamic process instabilities that are associated with rapid melting and solidification. For instance, deep trenches or grinding marks in the initial surface can cause small deviations of local surface absorptivity to lead to laser melt pool instabilities. The high-speed nature of the LRM process combined with the complex thermodynamic phenomena makes process instabilities difficult to model, detect, predict, and control. This study aimed to use reinforcement learning (RL) in order to build a ‘self-learning’ controller capable of adapting to any material and control instabilities on-line and in real-time. Along these lines, the study will detail a preliminary application of two RL implementations involving SP-LRM performance simulation to demonstrate the implementation of a double dueling deep Q-network (DDDQN) controller for melt pool temperature distribution control. The results obtained showed that the 3-action implementation achieved 48% less variance and 35% increase in the mean value of the total reward collected compared with the 31-action implementation.

Tailoring the Coefficient of Friction by Direct Laser Writing Surface Texturing.

The modification of the surface topography at the micro- and nanoscale is a widely established as one of the best ways to engineering the surface of materials, to improve the tribological performances of materials in terms of load capacity and friction. The present paper reviews the state of the art on laser surface texturing by exploiting the technique of direct laser writing for tailoring the coefficient of friction, highlighting the effect of the textures' arrangement on the lubricated conformal and non-conformal contact behavior.

Effect of oxygen plasma-treatment on surface functional groups, wettability, and nanotopography features of medically relevant polymers with various crystallinities

The surface properties of polymeric biomaterials play a crucial role in their biocompatibility and performance. This study explores the application of cold oxygen plasma treatment as a versatile technique for surface modification of polymeric materials with different degrees of crystallinity: crystalline high-density polyethylene (HDPE), crystalline-amorphous poly(chloro‑paraxylylene) (parylene C), and amorphous aromatic polyether-based polyurethane (PU). The investigations focus on the generation of surface functional groups and hydrophilicity, as well as nanotopography. X-ray photoelectron spectroscopy (XPS) analysis confirmed the generation of oxygen-containing functional groups, resulting in controlled wettability (water contact angle), while atomic force microscopy (AFM) showed topography modifications in the nanoscale. At the same time, it was revealed that oxygen plasma treatment did not affect the bulk properties (confirmed by TG and XRD). The effects of the same plasma treatment conditions varied significantly among the different polymers studied, depending on their crystallinity. This was discussed in terms of the preferential etching of amorphous regions in the polymeric structures. The findings emphasize the advantages of oxygen plasma treatment for tailoring the surface properties of polymeric biomaterials, highlighting its significance for biomedical applications.

Green‐Based Modifications of Polyethylene Surfaces Enhancing Antifouling Properties in Water‐Related Systems

AbstractThe effects of fouling in plastics, such as polyethylene (PE), can have a major economic impact due to tube clogging and other issues. Surface properties, both chemical and physical, can substantially influence biofilm formation, so developing antifouling materials through engineering these properties is very promising. In this work, two main approaches are evaluated for reducing the fouling on PE surfaces: chemical modification with green coating (polyethylene glycol (PEG) and different chitosan nanoparticles (CS NPs)) and physical modification with distinct micro‐topographies. First, the antibacterial adhesion is tested with Escherichia coli. The results reveal that CS NPs result in a considerable decrease in adhesion depending on which source of chitosan is used. PEG coating only reduced adhesion by 26%, while CS NPs with a high molecular weight (CS3) decreased adhesion by 88% in relation to non‐modified surfaces. Moreover, lozenges topographic modification (T2) has the highest effect on the bacteria adhesion within the physically‐modified PE surfaces. Finally, CS3 and T2 surfaces are tested in water samples in dynamic conditions for 27 days and results showed lower bacterial adhesion than unmodified surfaces. Overall, both strategies offer eco‐friendly and cost‐effective solutions for preventing fouling and extending the lifetime of polymeric surfaces for environmental applications.

Reconstruction of an Ancient Hill Used as an On-Site Quarry: Castrum Zerzevan (SE-Türkiye)

ABSTRACT The Roman period Castrum Zerzevan is on a hill 35 km south of Diyarbakır, Türkiye. Various field evidence (e.g. petrographic similarities, sudden changes of the topographic contours, the morphology of the nearby hills, and traces of the on-site quarry activities) suggests that the topography of the hilltop was artificially modified and used as a quarry. This study aims to introduce an approach that creates the ancient topography and calculates and verifies the volume of the on-site material required to build the fortification and associated structures by applying morphological analyses. The primary objective of the methodology is to reconstruct the site’s ancient topography and examine the difference between its former and present surfaces. The result indicates that approximately 36% of the extracted material was used in the enclosure. The overall findings and site investigations suggest quarrying and construction activities were carried out in a planned manner or concurrently at the site. In addition to the collected samples’ petrographic and geochemical similarities, the Castrum‘s topographical modifications and the suitability of the geological unit as a building material support our claim that the Romans were well aware of environmental conditions (including topography and morphology) and material performance.