Search Results (367)

To improve coating adhesion and tribological stability on aircraft-grade aluminum, this work utilizes periodic fiber-laser microtexts as a surface-engineering pre-treatment before applying an epoxy primer. AA2024-T3 panels were imprinted with rhombus, hexagon, and circular lattices (scale factors 100–250 µm; scan speeds 250–750 mm s⁻¹), then primed with an aerospace epoxy primer and evaluated within reciprocating sliding wear tests. Areal profilometry and sessile-drop goniometry measured topography and wettability, whereas friction–distance traces and scratch-track metrology resolved interfacial integrity. The textures expanded surface area and modified energy states in a geometry- and scale-dependent fashion, producing stable friction plateaus and smaller, less-lateral scratch scars compared to the untextured reference. Circular dimples reliably provided the best damage-tolerant behavior, a function of improved mechanical interlocking and debris/film management (reservoir and micro-trap effects), whereas polygonal lattices evidenced greater sensitivity to both scale and speed. Factorial analyses disclosed prevalent interaction effects amongst geometry, scale, and scan speed, reinforcing the notion that performance arises from co-optimized texture architecture rather than a single parameter. In systemic terms, laser-defined microtexts complemented with aerospace-standard primers represent a controllable pathway to vary friction, dampen wear, and improve coating–substrate adhesion. These results provide practical selection guides; and a broad selection prefers larger, well-spaced circular dimples for best-in-class performance and a transferable framework for designing texture-coating systems across aerospace and allied manufacturing contexts. Full article

Fretting wear significantly limits the service life of metal O-rings operating under harsh conditions. To address this limitation, this study investigates the wear behavior of metal O-rings under equivalent accelerated reciprocating motion and establishes an accelerated life prediction model based on similarity theory. Fretting wear experiments were conducted using Inconel 718 alloy and 304 stainless steel to replicate service conditions in a controlled laboratory environment. Wear morphology was characterized using laser scanning confocal microscopy, revealing a progressive transition from mild abrasive and adhesive wear to severe abrasive wear accompanied by material spalling. Based on the experimental results, regression analysis was performed to estimate the acceleration model coefficients, leading to the formulation of an equivalent acceleration equation capable of predicting seal wear life under practical service conditions. The resulting equivalent acceleration model can establish a quantitative connection between the acceleration test and the operating conditions. This model can shorten the testing time and can be used to predict parameters related to the surface morphology of static seals, providing a theoretical and experimental basis for reliable life assessment. This provides a practical basis for improving the reliability and safe operation of metal O-ring seals in critical applications, including nuclear energy and chemical processing systems. Full article

PEEK coatings have been applied to sliding bearings in marine machinery and equipment, but their low bonding force, poor thermal conductivity and weak oleophilicity result in insufficient anti-adhesive wear performance. To solve this problem, the textured surface of the substrate was fabricated using laser texturing technology to enhance the bonding force. The PEEK coatings were reinforced by introducing oleophilic-modified nano-SiO₂ and graphene. The tribological properties of the PEEK composite coatings were studied using the ball–disc reciprocating friction wear test and Abaqus wear simulation. The results show that the texturing treatment of the substrate surface improves the bonding force of the coating. The addition of nano-SiO₂ and graphene enhances the hardness, thermal conductivity and oleophilicity of the composite coating, which shifts the wear mechanism from adhesive to abrasive. Under dry friction conditions, the composite coating containing 5 wt% SiO₂ and 1 wt% graphene exhibits a low friction coefficient and the lowest wear rate. Under oil lubrication conditions, the composite coating containing 2 wt% graphene shows the lowest friction coefficient and wear rate. In summary, under the load-bearing capacity enhancement of nano-SiO₂ and the thermal conductivity enhancement of graphene, the composite coating exhibits excellent anti-adhesive wear performance. Full article

Metal substrates were preprocessed via picosecond laser surface texturing (PLST, 532 nm) to fabricate interfacial microgrooves for tribological performance optimization prior to deposition of a magnesium silicate hydroxide (MSH)/graphite/MoS₂–PI solid lubricant coating. By tuning the PLST parameters (average laser power: 0.2–0.5 W, scan passes: 3–5, hatch spacing: 0.005–0.1 mm), three representative texture geometries (linear, circular, and square) were produced, and the resulting coating performance was compared with conventional mechanical polishing and sandblasting pretreatments. Among the three laser textures, the linear texture exhibited the most excellent tribological performance and interfacial adhesion, outperforming the circular and square counterparts. Ball-on-disk tests in a kerosene-contaminated environment (10 N, 800 rpm) showed that the linear-textured sample reached the lowest steady-state friction coefficient (0.038), lower than polished (0.048) and sandblasted (0.052) controls, together with reduced wear scar dimensions. Progressive-load scratch tests indicated a pronounced adhesion enhancement, with the critical failure load increasing from 7.05 N (polished) to 26.05 N for the linear-textured interface, which is higher than 21.21 N (circular) and 23.78 N (square) textures. Cross-sectional microscopy and EDS mapping reveal that the laser-defined microgrooves (~15 μm depth, ~120 μm width, ~500 μm spacing) act as a parameter-controlled interfacial architecture that promotes mechanical interlocking and provides lubricant-rich reservoirs. This laser-enabled interfacial design suppresses delamination, supports transfer film stability, and ultimately enhances the coating’s tribological performance by reducing friction and wear. Full article

In a previous study, we demonstrated that a novel surface treatment applied to laser-melted Ti6Al4V substrates supports osteoblast-like cell adhesion, proliferation, and the activation of early osteogenic pathways. Building on these preliminary findings, the present work aimed to further investigate the ability of the same surface to promote extracellular matrix (ECM) deposition, organization, and osteogenic maturation, which are critical events for the establishment of a stable bone–implant interface in subperiosteal dental implants. Human osteoblast-like MG-63 cells were cultured on Ti6Al4V discs subjected to different surface treatments, including a proprietary surface modification (ATcs) specifically designed for subperiosteal applications. ECM formation and maturation were evaluated through scanning electron microscopy coupled with energy-dispersive spectroscopy, immunofluorescence, and semiquantitative analyses of osteogenic markers type I collagen (COL1A1), secreted protein acidic and rich in cysteine (SPARC), and dentin matrix protein 1 (DMP1) through Western blotting. The results showed that, while all tested surfaces supported cell adhesion, the ATcs surface promoted a distinct osteogenic profile characterized by enhanced DMP1 expression, organized collagen deposition, and the formation of calcium–phosphate–rich mineralized structures. Compared to surfaces that primarily stimulated cell proliferation or early matrix production, ATcs appeared to favour progression toward late-stage osteogenic maturation and matrix mineralization. Taken together, these findings extend our previous observations and indicate that this novel surface treatment not only supports osteoblast viability and early differentiation but also promotes extracellular matrix maturation, a key prerequisite for effective osseointegration. Although further in vivo studies are required, the present data provide additional biological rationale for the use of ATcs-treated Ti6Al4V surfaces in next-generation custom-made subperiosteal implant designs. Full article

This study presents a low-cost, small-scale single-chamber microbial fuel cell (MFC) toxicity biosensor fabricated on a printed circuit board (PCB) and a 3D-printed chamber with a volume of 120 μL. The anode consists of a screen-printed carbon electrode on the PCB, while the air cathode is a carbon paper electrode. To address poor adhesion of microorganisms to the smooth anode surface, femtosecond laser processing was used to fabricate a micropore array with 40 μm pores on the electrode. This method can create micropores on the anode surface without damaging the screen-printed electrodes, the PCB substrate, or the pads. These micropores increase the anode’s surface area and hydrophilicity, allowing more microbial coatings to firmly adhere to its surface. In this study, the MFC utilised Rhizobium rosettiformans W3, extracted from activated sludge at a wastewater treatment plant, as the anode microorganism. Its aerobic nature simplifies the design of MFCs, enabling a single-chamber structure and miniaturisation. Using formaldehyde solution as a toxicity sample to test the biosensor’s performance, a 0.1% concentration significantly reduced the sensor’s output power. Full article

Bending-dominated lattice structures offer superior stability but suffer from low stiffness and natural frequencies, posing resonance risks in aerospace applications. To address this, a novel Membrane-Wrapped Lattice (MWL) encapsulated by a micrometer-scale metallic film is proposed. A theoretical framework based on the tension-compression asymmetry of the membrane is established to analyze the influence of membrane thickness on the neutral axis shift, ultimately deriving analytical formulations for flexural stiffness and natural frequencies. MWL specimens with varying membrane thicknesses (0–50 μm) were fabricated via selective laser melting and adhesive bonding, then subjected to three-point bending and vibration tests. Results demonstrate that wrapping with a 50 μm 316 L stainless steel membrane increases the flexural stiffness by 128% and the fundamental natural frequency by 85%. The experimental measurements align well with theoretical and numerical predictions, validating this lightweight, high-stiffness design strategy. Full article

To address the problems of high digging resistance, elevated energy consumption, and severe soil adhesion encountered during mechanized potato harvesting, a bionic potato digging shovel inspired by the corrugated dorsal structure of the white grub was developed. Based on reverse-engineered geometric curves, two longitudinally corrugated shovel models (L-S-1 and L-S-2) were constructed, and a coupled soil–potato–shovel model was established using the Discrete Element Method (DEM) to evaluate soil disturbance characteristics and digging resistance at a forward speed of 0.5 m/s and an entry angle of 35°. The simulation results indicated that the longitudinally corrugated shovel L-S-2 exhibited the best overall performance, reducing digging resistance by 13.87% and increasing the soil fragmentation rate by 20.67% compared with a conventional flat shovel (P-S). Using L-S-2 as the baseline design, additional DEM simulations were conducted at forward speeds ranging from 0.4 to 0.6 m/s to systematically investigate the influence of operating speed on digging performance. To further enhance anti-adhesion performance, a composite bionic shovel (H-L-S-2) was developed by embedding polytetrafluoroethylene (PTFE) hydrophobic material into the surface of L-S-2 and reinforcing the shovel tip using laser cladding. Soil-bin experiments were then performed under controlled conditions with forward speeds of 0.4–0.6 m/s and soil moisture contents of 15–20% at an entry angle of 35°, and the results showed an average resistance reduction rate of 17.46%, with a maximum reduction of 18.02%. Both DEM simulations and soil-bin tests confirmed the effectiveness of the composite bionic shovel in reducing soil adhesion, with the number of adhered soil particles decreasing by 41.2% in simulations and the mass of adhered soil reduced by 37.5% in physical tests. These results demonstrate that coupling a bionic corrugated structure with surface material modification can effectively reduce digging resistance, enhance soil fragmentation, and mitigate soil adhesion, providing a practical approach for optimizing the design of potato digging shovels. Full article

Laser powder bed fusion has attracted increasing attention for the production of metallic substrates intended for surface functionalization by advanced physical vapor deposition coatings. This study investigates the influence of the substrate manufacturing route on the performance of titanium–aluminum–silicon nitride-coated AISI 316L stainless steel, with particular emphasis on substrates produced by laser powder bed fusion. Conventionally manufactured and additively manufactured AISI 316L substrates were coated with a titanium–aluminum–silicon nitride layer using high-power impulse magnetron sputtering. The substrates were characterized by tensile testing and microhardness measurements, while coating thickness and uniformity were evaluated using the crater ball method. The mechanical integrity of the coating–substrate system was assessed by progressive load scratch testing. The additively manufactured substrate exhibited a significantly higher yield strength (411 MPa) compared to the conventionally manufactured material (257 MPa), together with increased microhardness. The titanium–aluminum–silicon nitride coating showed a uniform thickness of 4.47 µm and a well-defined coating–substrate interface. Scratch tests revealed a delayed onset of coating damage on additively manufactured substrates, with the transition to severe adhesive failure occurring at higher normal loads compared to the conventionally manufactured substrate. These results demonstrate that AISI 316L stainless steel produced by laser powder bed fusion provides a mechanically robust substrate for titanium–aluminum–silicon nitride coatings deposited by high-power impulse magnetron sputtering, with favorable coating response under progressive loading conditions. Full article

Engineering surfaces operating in harsh environments frequently require simultaneous resistance to abrasive wear and the minimization of interfacial adhesion. Achieving this dual functionality through a single surface modification strategy remains challenging. This study presents a novel hybrid approach combining bionic laser surface texturing with a polytetrafluoroethylene/polydimethylsiloxane/TiO₂ nanocomposite coating to synergistically enhance both wear resistance and hydrophobicity of 65Mn steel. Crescent-shaped micro-dimples, inspired by the exoskeleton of Procambarus clarkii, were fabricated via a femtosecond laser. A composite coating containing hydrophobically modified TiO₂ nanoparticles was subsequently deposited. Single-factor experiments identified effective parameter ranges. A four-factor, five-level central composite rotatable design combined with response surface methodology was employed to systematically optimize texture depth, texture spacing, TiO₂ mass fraction, and coating thickness. The results demonstrate that textures with a depth of less than 100 μm and spacing less than 400 μm effectively homogenize surface stress distribution. RSM analysis revealed that TiO₂ content and texture depth predominantly influence hydrophobicity, while texture spacing overwhelmingly controls wear mass loss. Significant interactions between coating and texture parameters were identified. The optimal parameter combination was determined as: 6% TiO₂, 40 μm coating thickness, 50 μm texture depth, and 250 μm texture spacing. Under these conditions, the surface achieved a superhydrophobic contact angle of 152.1° and a low-wear mass loss of 8.9 mg. Validation tests yielded values of 150.8° and 9.3 mg, respectively, confirming model reliability. The synergistic mechanism involves textures acting as debris reservoirs and stress distributors, while the coating provides a low-surface-energy, hardened top layer that minimizes adhesion and facilitates a rolling–sliding contact mode. This work provides a robust, optimized framework for designing multifunctional surfaces for demanding tribological applications. Full article

Background/Objectives: The purpose of this study was to investigate the laser removal of implant-supported ceramic single crowns, focusing on their efficiency and the potential reusability of the removed restorations. Methods: Sixty single crowns made of lithium disilicate were adhesively bonded to prefabricated titanium abutments in a total of six test series (n = 10). The test series were divided according to the different spacer settings of the crowns (90 µm, 120 µm, 150 µm) and the taper of the abutments (4°, 6°). After seven days of storage in distilled water, the single crowns were removed using an erbium-doped yttrium aluminium garnet (Er:YAG) laser. The number of laser pulses needed and the time required to remove the crowns were recorded. This was followed by a micro- and macroscopic score evaluation of the crowns using a fluorescent penetration method. Results: Laser removal of all sixty crowns was successfully performed. Using a taper of 6° and a spacer of 150 µm, the crowns were removed with significantly fewer pulses (61.40 (±36.78)). The taper and spacer had a significant effect on both the microscopic (p = 0.040) and macroscopic (p = 0.035) fracture patterns. Based on the final score of the fracture analysis, 44 of the 60 crowns could be classified as potentially reusable. The remaining 16 crowns failed due to purely macroscopic (7), purely microscopic (6), and combined microscopic and macroscopic (3) fracture behavior. Conclusions: Based on the results of this study, increasing the size of the taper and spacer has proven beneficial for laser removal in terms of time efficiency and non-destructive removal of crowns. Full article

In view of the potential fretting wear issues of Laser Metal Deposition (LMD) In718 in engineering applications, this paper investigates the fretting wear behavior of LMD In718 alloy subjected to two different heat treatment processes: homogenized Solution-Treated and Aged (STA) and direct-aged only. This was conducted utilizing a newly designed fretting wear apparatus to enable real-time dynamic monitoring of the contact interface and maintain uniform normal force distribution. Furthermore, to provide a more comprehensive understanding of how different heat treatments influence the fretting wear performance of LMD In718, this study systematically evaluates their distinct tribological responses and underlying wear mechanisms. The wear resistance of the material was predicted by analyzing the proportion of the main strengthening phase γ″ in samples with different heat treatments using microstructural characterization methods. Wear resistance tests were conducted under ambient conditions. The results show that the homogenized STA sample has a specific wear rate of 1.375 × 10⁻⁷ mm³/(N∙m), while the direct-aged sample has a wear rate of 1.550 × 10⁻⁷ mm³/(N∙m). The direct-aged sample exhibited severe fatigue spalling accompanied by adhesive and abrasive wear, with numerous subsurface cracks. The homogenized STA sample demonstrated a combined mechanism of oxidative wear and localized abrasive wear. Full article

Soft-tissue management is critical for guided bone regeneration (GBR), yet conventional titanium meshes lack the ability to regionally regulate fibroblast behavior where opposite biological responses are needed. Here, we fabricated two femtosecond-laser patterned stripe topographies on titanium using a unidirectional scanning strategy with parameter tuning, generating LSFL with a periodicity of 820 ± 30 nm and micro-grooves with a periodicity of 4.7 ± 0.1 μm. Surface morphology and physicochemical properties were characterized by SEM/AFM, XPS, microhardness testing, and wettability measurements. Human gingival fibroblasts (HGF-1) were used to assess adhesion, cytoskeletal organization, spreading area, and proliferation (CCK-8). The submicron LSFL promoted robust fibroblast adhesion, aligned cytoskeletal organization, larger spreading areas, and higher proliferation, whereas the micro-groove surface markedly restricted spreading and was associated with poorer cytoskeletal organization and lower proliferation. Alternating patterned regions further demonstrated geometry-driven spatial selectivity, with preferential cell occupation on LSFL stripes. These findings support a fabrication-ready surface-engineering strategy to synchronize rapid soft-tissue sealing while restricting unwanted fibroblast advancement at defined regions, offering a promising route toward more predictable GBR outcomes. Full article

To investigate the effect of surface roughness on the fretting wear behavior of the Inconel 718 alloy, specimens fabricated by selective laser melting (SLM) were polished using SiC abrasive papers to obtain different surface roughness levels. Ball-on-flat tangential fretting tests were conducted under a normal load of 50 N, displacement amplitudes of 50 and 100 µm, and a total of 10⁴ cycles. The results reveal that all test conditions fall within the gross slip regime (GSR). The coefficient of friction was not significantly affected by surface roughness, while the energy dissipation per cycle exhibited a decreasing trend with decreasing roughness. The high-roughness surface (R_a = 0.80 µm) exhibited severe stress concentration, leading to asperity fracture and fatigue delamination. The medium-roughness specimen (R_a = 0.43 µm) developed a dense third-body layer, showing a synergistic mechanism of abrasive and fatigue wear. The low-roughness specimen (R_a = 0.07 µm) maintained a stable contact interface with sufficient debris evacuation, dominated by adhesive and abrasive wear. At a displacement amplitude of D = 100 µm, the wear depth reached −6 µm, indicating the largest material removal and the most severe damage. Full article

Adhesive bonding has emerged as a promising technology for joining carbon fiber reinforced polymer (CFRP) structures in aircraft, offering advantages over traditional mechanical fastening such as weight reduction and uniform stress distribution. This study evaluates the effectiveness of innovative laser ablation and electrospinning surface treatments compared to the conventional peel-ply method for secondary bonding. Surface features and wetting behavior were characterized using scanning electron microscopy (SEM) and contact angle measurements, while mechanical performance was assessed via single lap shear tests. Results demonstrate that laser ablation (30 W power, 10 m/s speed) achieved the highest bond strength at 20.68 MPa, followed by electrospinning (18.20 MPa) using 10 wt% PA-66 nanofibers. Both advanced techniques significantly outperformed the peel-ply method, which yielded the lowest shear strength of 15.18 MPa. SEM analysis confirmed that laser treatment facilitated direct fiber exposure with minimal damage, while nanofibers provided enhanced physical interlocking. In conclusion, laser ablation proved to be the most effective technique for enhancing interfacial bonding in aerospace-grade CFRP structures, followed by electrospinning, offering a superior alternative to traditional surface preparation. Full article