Modification Of Surface Topography Research Articles

Harnessing ion beam erosion engineering for controlled self-assembly and tunable magnetic anisotropy in epitaxial films

The engineering of the surface morphology and the structure of the thin film is one of the essential technological assets for regulating the physical properties and functionalities of thin film-based devices. This study presents an easy and handy approach to tailor the surface structure of epitaxial thin films utilizing low-energy ion beam. Here, we investigate the evolution of the surface structure and magnetic anisotropy (MA) in epitaxial Fe/MgO (001) model systems subjected to multiple cycles of ion beam erosion (IBE) after thin film growth. The growth of Fe film occurs in the form of three–dimensional islands and exhibits intrinsic biaxial MA. Following a few cycles of IBE, an induced uniaxial magnetic anisotropy leads to a split in the hysteresis loop, and the film displays almost uniaxial magnetic switching behavior. More distinctly, we present a clear and conclusive evidence of (2 × 2) reconstruction of the Fe surface due to the atomic rearrangement by IBE. Furthermore, 57Fe isotope sensitive nuclear resonance scattering measurement provides insight into the depth-resolved magnetic information due to the modified surface topography. We also demonstrate that thermal annealing can reversibly tune the surface reconstruction and induced UMA. The feasibility of the IBE technique by adequately selecting IBE parameters for surface structure modification has been highlighted apart from conventional tailoring of the morphology for the tuning of UMA and introduces a new dimension to our understanding of self-assembled surface morphology evolution by IBE.

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.

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.

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.

Composite bone graft of CaO-MgO-SiO2 glass-ceramics and CaSO4 ceramics for boosting bone formation rate.

This study develops a composite bone graft of CaO-MgO-SiO2 glass-ceramic and CaSO4 [abbreviated as (CMS)3-x(CS)x] via the sponge replication technique with weight fractions of x = 0, 1, 1.5, 2, and 3. The (CMS)1.5(CS)1.5 composite displays a superior degradability and, a suitable compressive strength of ∼3 MPa, and excellent cell proliferation and differentiation. The in vivo rat femur test in the hybrid-pore (CMS)1.5(CS)1.5 composite granules achieves a higher rate of bone formation, which is ∼2.7 times better than that of the commercial HAP/β-TCP at 12 weeks. Improved expressions of osteocyte and mature osteocyte marker genes, namely (Spp1, Dmp1, and Fgf23), were observed in the (CMS)1.5(CS)1.5 group, indicating a faster differentiation into mature bone tissue. The ions release of (CMS)1.5(CS)1.5 through the ERK1/2 signaling pathway promotes osteogenic differentiation. The high bone generation rate can be attributed to faster active ions release and modified surface topography. This work highlights an excellent bone graft candidate for clinical applications in orthopedic surgery.

Investigating double-scan strategies for reducing heat-affected zone in laser surface melting

Laser surface melting (LSM) is a technique for modifying surface topography without adding or removing material. LSM may result in large heat-affected zones (HAZs) that may be undesirable in several applications. The current work aims to investigate double-scan strategies to reduce HAZ. This strategy used two laser scans, each at half the line energy density used for a single scan. A numerical model is developed for LSM to predict the MZ and HAZ and is validated against experimental results using Ti6Al4V. In addition, the effect of the double-scan strategy on the surface roughness, hardness and residual stresses is evaluated. The experimental results show the HAZ depth decreased by 26%, the surface hardness was improved, and the resultant residual stresses were preserved for the double scan strategy compared to the single scan. However, it resulted in a relatively rougher surface finish.

Multi-Scale Structuring of CoCrMo and AZ91D Magnesium Alloys Using Direct Laser Interference Patterning

In this work, the technique of Direct Laser Interference Patterning (DLIP) was used to fabricate micrometric structures at the surface of Cobalt-Chromium-Molybdenum and AZ91D magnesium alloys. Line-like patterns with spatial periods of 5 μm were textured using an ultra-short pulsed laser (10 ps pulse duration and 1064 nm wavelength) with a two-beam interference setup. The surface topography, morphology, and chemical modifications were analysed using Confocal Microscopy, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS), respectively. Laser fluence and pulse overlap were varied to evaluate their influence on the final structure. Homogeneous structures were achieved for the CoCrMo alloy for every condition tested, with deeper structures (up to 0.85 μm) being achieved for higher energy levels (higher overlap and/or fluence). For high energy, sub-micrometric secondary structures, so-called LIPSS, could also be observed on the CoCrMo. The EDS analysis showed some oxidation after the laser texturing. Regarding the AZ91D alloy, deeper structures could be achieved (up to 2.5 μm), but more melting and oxidation was observed, forming spherical oxide particles. Nonetheless, these results bring new perspectives on the fabrication of microtextures on the surface of CoCrMo and AZ91D using DLIP.

Constructing superwetting membranes by sodium lignosulfonate-modified carbon nanotube for highly efficient crude oil-in-water emulsions separations

For the past few years, superwetting materials had been developed to enhance the treatment process of oily wastewater. Membranes are improved through the combination of surface topography and chemical modifications to achieve superwetting properties for treating oily wastewater effectively. In this work, we prepared an eco-friendly membrane by depositing sodium lignosulfonate (SLS)-modified carbon nanotube (CNT) on a cellulose acetate membrane via vacuum filtration without employing any organic solvents. The SLS@CNT membrane shows superhydrophilicity and underwater superoleophobicity with high stability. Furthermore, the SLS@CNT membrane exhibits outstanding antifouling and self-cleaning properties against crude oil of high viscosity. Most importantly, our SLS@CNT membrane exhibits outstanding oil-in-water emulsions separation performances including crude oil-in-water emulsions. For the surfactant-free and surfactant-stabilized emulsions, fluxes were revealed to reach up to 27,800 L m−2 h−1 bar−1 and 13,800 L m−2 h−1 bar−1, respectively, with very high separation efficiency (>99.97 % and 99.79 %, respectively). The distinguished performance of our SLS@CNT membrane, and its eco-friendly, low-energy consumption, and cost-effective preparation, demonstrate practical applicability.

Improving perovskite/P3HT interface without an interlayer: Impact of perovskite surface topography on photovoltaic performance of P3HT-based perovskite solar cells

The photovoltaic performance of poly(3-hexylthiophene) (P3HT)-based perovskite solar cells is inferior due to the improper perovskite/P3HT interface caused by a surface energy mismatch. The most promising method to improve the interface is the introduction of interlayers between perovskite and P3HT layers; however, this increases fabrication complexity and irreproducibility. Here, we show how the surface topography of the perovskite layer can improve the interface without an interlayer. To explore this, we varied surface topography by altering the crystal size of the methylammonium lead iodide through its deposition temperature namely, 10 0C and 30 0C. The solar cells based on the perovskite layers formed at 10 0C outperform the cells fabricated from perovskite layers deposited at 30 0C. Our studies reveal that the surface topography of the perovskite layer influences the surface energy that impacts the interface between perovskite and P3HT layers, consequently enhancing recombination resistance, short-circuit current, and open-circuit voltage, ultimately improving photovoltaic performance. Modification of surface topography is a simple approach to improve the perovskite/P3HT interface without an interlayer and can lead to better performance in P3HT-based perovskite solar cells.

Current Trends in Modifying Surface Topography of Dental Implants - A Literature Review

Current Trends in Modifying Surface Topography of Dental Implants - A Literature Review

A Hybrid Approach to Surface Engineering Based on Laser Texturing and Coating

A hybrid approach based on laser texturing and surface coating for the combined modification of surface topography and chemistry has been proposed to provide a versatile approach for the development of functional surfaces. The experimental procedure comprised nanosecond pulsed laser texturing of AISI 304 stainless steel substrates followed by the deposition of thin (&lt;1 µm) coatings with two different technologies, sol–gel deposition and PE-CVD, with the aim of independently modifying the surface topography and chemical composition. Laser texturing with different scanning strategies achieved a variety of surface morphologies with an arithmetic mean height (Sa) in the range 0.2–6.4 µm. Coatings were then deposited on laser-textured substrates to quantify the deposition effectiveness and the influence of the coating type and parameters on the resulting surface topography and chemistry. Sol–gel deposition was found to be more effective with a polymeric interlayer, improving adhesion between the coating and the textured surface; however, this also led to an increase in Sa of approximately 0.5 µm. Conversely, PE-CVD was effective in modifying the surface chemistry while inducing no measurable differences in surface morphology, effectively decoupling the texturing and coating processes. Analysis of the surface chemistry showed a higher concentration of silicon for PE-CVD than sol–gel deposition and therefore a more pronounced effect on the surface chemical composition.

Molecular dynamics exploration of ion association mechanism of apatite controlled by a nanogrooved hydroxyapatite surface

Surface topography modification is a promising tissue engineering technology that provides an adjustable geometric microenvironment for the implant-tissue interface. Nanogrooves can affect the amount and arrangement of apatite deposition, which plays a crucial role in the formation of bionic bone tissue in the preferred direction. The effects of grooved topography on the ion association must be understood for designing and optimizing bone implant materials. We performed molecular dynamics and metadynamics simulations to explore the effect of grooves with different slope angles on the ion association of Ca2+ and PO43- ions. The ion deposition degree could be controlled by regulating the slope angle of the nanogrooves. The groove model with a 60° slope angle has the greatest biological activity for ion deposition. Ions were selectively adsorbed at the sharp corners of the groove. This phenomenon was attributed to relative differences in binding thermostability in different regions of the groove, which could partially explain why a grooved topography can improve the production of a well-organized apatite structure. Our results provide a molecular mechanism to understand the effects of the grooved topography on the ion association, which can aid in optimizing the biological activity of materials through topography-modified tissue engineering technology.

A Polymer Canvas with the Stiffness of the Bone Matrix to Study and Control Mesenchymal Stem Cell Response.

Reproducing in vitro the complex multiscale physical features of human tissues creates novel biomedical opportunities and fundamental understanding of cell-environment interfaces and interactions. While stiffness has been recognized as a key driver of cell behavior, systematic studies on the role of stiffness have been limited to values in the KPa-MPa range, significantly below the stiffness of bone. Here, a platform enabling the tuning of the stiffness of a biocompatible polymeric interface up to values characteristic of human boneisreported, which are in the GPa range, by using extremely thin polymer films on glass and cross-linking the films using ultraviolet (UV) light irradiation. Itisshown that a higher stiffness is related to better adhesion, proliferation, and osteogenic differentiation, and that it is possible to switch on/off cell attachment and growth by solely tuning the stiffness of the interface, without any surface chemistry or topography modification. Since the stiffness is tuned directly by UV irradiation, this platform is ideal for rapid and simple fabrication of stiffness patterns and gradients, thus representing an innovative tool for combinatorial studies of the synergistic effect of tissue environmental cues on cell behavior, and creates new opportunities for next-generation biosensors, single-cell patterning, and lab-on-a-chip devices.

Multiphysics modeling of femtosecond laser–copper interaction: From electron dynamics to plasma eruption

The femtosecond laser ablation of metals is a complex and violent nonequilibrium process, and numerous studies have sought to reveal the evolution of a single physical phenomenon, such as laser-induced periodic surface micro-nanostructures or plasma eruptions. By considering the multiphysics scenarios of energy and heat transfer, structural mechanics, hydrodynamics, and nucleation dynamics, a femto-nanosecond and nano-micrometer multiscale framework combining electron–phonon-coupled heat transfer, lattice deformation, phase transition, and plasma eruption was constructed to describe the heat and mass transfer mechanism of femtosecond laser–copper interaction. A multiphysics model was proposed in this study to simulate the ablation process with different laser fluences. Ablation occurs at low near-threshold fluences primarily via a combination of the thermal phase transition process of melting and thermoplastic deformation coupled with the nonthermal phase transition process of hot electron explosion. Marangoni convection and non-uniform nucleation at the solid–liquid interface create micro-nano structures on the surface of the ablation crater. At a high laser fluence, plasma plumes are emitted via gasification and eruption, and as the material is heated to decrease its density, the surface is broken into a micro-column structure, and then the micro-columns fracture and erupt to form micro-nano structures and plasma plumes. Numerical results offer a better understanding of surface topography modifications and plasma plume evolution and promote the application of femtosecond laser precision fabrication in the fields of aviation, mechanics, electronics, and materials engineering.

Selective Topography Directed Cell Adhesion on Spider Silk Surfaces

AbstractFor tissue engineering applications, guided cell interaction with a biomaterial surface is one essential feature since, in natural tissue, cells constantly interact with their extracellular matrix, which provides different topographical, mechanical and biochemical stimuli. Therefore, the introduction of topographical surface features is one promising approach to direct material‐cell interactions. In this study, maskless lithography and soft lithographic methods are used to produce recombinant spider silk films with size gradient patterns, including grooves, circles, squares, triangles, and stars, to enhance specific cell attachment. The influence of surface features on cell behavior is analyzed using eight different cell lines. It can be shown that surface indentations provide cellular attachment sites and guiding structures for restructuring, aligning, and adopting cell morphology, with a relation of cell to feature size for some of the cell lines investigated. Therefore, specific topographical surface modifications can be used to guide selective cell adhesion, allowing the generation of tissue‐specifically modified implant surfaces in the future.

Surface Texturing and Combinatorial Approaches to Improve Biocompatibility of Implanted Biomaterials.

Biomaterial associated microbial infection and blood thrombosis are two of the barriers that inhibit the successful use of implantable medical devices in modern healthcare. Modification of surface topography is a promising approach to combat microbial infection and thrombosis without altering bulk material properties necessary for device function and without contributing to bacterial antibiotic resistance. Similarly, the use of other antimicrobial techniques such as grafting poly(ethylene glycol) (PEG) and nitric oxide (NO) release also improve the biocompatibility of biomaterials. In this review, we discuss the development of surface texturing techniques utilizing ordered submicron-size pillars for controlling bacterial adhesion and biofilm formation, and we present combinatorial approaches utilizing surface texturing in combination with poly(ethylene glycol) (PEG) grafting and NO release to improve the biocompatibility of biomaterials. The manuscript also discusses efforts towards understanding the molecular mechanisms of bacterial adhesion responses to the surface texturing and NO releasing biomaterials, focusing on experimental aspects of the approach.

Titanium Implant Surface Effects on Adherent Macrophage Phenotype: A Systematic Review.

Immunomodulatory biomaterials have the potential to stimulate an immune response able to promote constructive and functional tissue remodeling responses as opposed to persistent inflammation and scar tissue formation. As such, the controlled activation of macrophages and modulation of their phenotype through implant surface modification has emerged as a key therapeutic strategy. Methods: Online databases were searched for in vitro studies between January 1991 and June 2020 which examined the effect of titanium implant surface topography on the adherent macrophage phenotype at either the gene or protein level. Results: Thirty-nine studies were subsequently included for review. Although there was significant heterogeneity between studies, treatment of titanium surfaces increased the surface roughness or hydrophilicity, and hence increased macrophage attachment but decreased cell spreading. Physical coating of the titanium surface also tended to promote the formation of cell clusters. Titanium and titanium-zirconium alloy with a micro- or nano-scale rough topography combined with a hydrophilic surface chemistry were the most effective surfaces for inducing an anti-inflammatory phenotype in adherent macrophages, as indicated by significant changes in cytokine gene expression and or cytokine secretion profiles. Conclusions: The published data support the hypothesis that incorporation of specific topographical and physiochemical surface modifications to titanium can modulate the phenotypic response of adherent macrophages.

Organic/polymeric antibiofilm coatings for surface modification of medical devices

Infections arising from implanted medical devices cause considerable challenges for medicinal specialists and patients. These infections usually arise from the accumulation of biofilm on the device, which is difficult to eliminate and typically needs antibiotic treatment and removal of the device. In this regard, efforts have been made to design the devices or functional polymer coatings that have anti-fouling or antimicrobial properties to limit the formation of biofilm and following infection by preventing or killing bacteria near the device surface or by restricting the initial binding of proteins and bacteria. Herein, the extent of device-related infections, the biofilm formation mechanism, the role of biofilm construction in human pathogenesis, and the key strategies for the progress of antibiofilm coatings are discussed. The most promising antibiofilm coating approaches, comprising the surface topography modifications as well as the PEG, hydrogel, polyzwitterion, Benign bacterial biofilm, enzyme, cationic polymer, PTFE, and smart coatings, etc., were also summarized to avoid the biofilm formation and bacteria proliferation via controlling the antibiofilm mechanisms.

Altering the surface morphology and wettability of chitosan/graphene coatings by femtosecond and nanosecond laser processing

A major drawback of the currently used orthopedic implants is the formation of a bacterial biofilm on their surface after implantation. A potential strategy for overcoming this problem is developing micro- and nano-structured motifs on the implant’s surface to prevent bacterial attachment. Additionally, the use of materials with inherent antimicrobial properties could further stall the aggregation of bacteria. This paper demonstrates an approach to obtaining a modified surface topography on chitosan-graphene 2D films via femtosecond and nanosecond laser treatment. Atomic force microscopy (AFM) revealed that laser irradiation leads to a strong surface roughness increase due to formation of non-ordered topography features with peak-to-valley distance ranging between 200 nm and 1 μm. Interestingly, sharp single protrusions (∼200 nm) were observed on the untreated samples. Transmission electron microscopy analysis confirmed the presence of graphene monolayers within the composite films. Wettability tests showed that nanosecond laser ablation of the samples resulted in super hydrophilic surface properties, which repel bacteria per se. Based on our findings, we hypothesized that the topography motifs of both laser treated and untreated samples could potentially impede bacterial attachment via different mechanisms – reduction of contact points for adhesion or restriction of motility.

Submicron topography design for controlling staphylococcal bacterial adhesion and biofilm formation.

Surface topography modification with nano- or micro-textured structures has been an efficient approach to inhibit microbial adhesion and biofilm formation and thereby to prevent biomaterial-associated infection without modification of surface chemistry/bulk properties of materials and without causing antibiotic resistance. This manuscript focuses on submicron-textured patterns with ordered arrays of pillars on polyurethane (PU) biomaterial surfaces in an effort to understand the effects of surface pillar features and surface properties on adhesion and colonization responses of two staphylococcal strains. Five submicron patterns with a variety of pillar dimensions were designed and fabricated on PU film surfaces and bacterial adhesion and biofilm formation of Staphylococcal strains (Staphylococcus epidermidis RP62A and Staphylococcus aureus Newman D2C) were characterized. Results show that all submicron textured surface significantly reduced bacterial adhesion and inhibited biofilm formation, and bacterial adhesion linearly decreased with the reduction in top surface area fraction. Surface wettability did not show a linear correlation with bacterial adhesion, suggesting that surface contact area dominates bacterial adhesion. From this, it appears that the design of textured patterns should minimize surface area fraction to reduce the bacterial interaction with surfaces but in a way that ensures the mechanical strength of pillars in order to avoid collapse. These findings may provide a rationale for design of polymer surfaces for antifouling medical devices.