Search Results (137)

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

Wollastonite is a natural meta-silicate mineral material with fibrous characteristics. In this paper, wollastonite with different aspect ratios obtained after grinding was used as a mineral admixture to replace cement for preparing ultra-high-toughness cement-based composites (UHTCCs). The effects of wollastonite on the fluidity, compressive strength, flexural strength, and tensile properties of UHTCCs were investigated, and the crack morphology and micro-topography of the tensile specimens after fracture were observed. The experimental results show that when the wollastonite replacement ratio exceeds 4%, it exerts a negative effect on the fluidity of UHTCCs, and wollastonite with a larger aspect ratio has a more significant negative impact. Relying on the bridging effect, replacing cement with wollastonite can significantly improve the flexural strength and compressive strength of UHTCCs. However, when the replacement ratio exceeds 6%, the strength enhancement effect of wollastonite with a larger aspect ratio begins to decrease. When the cement replacement ratio of wollastonite is up to 6%, it can increase the initial cracking strength, tensile strength and tensile strain of UHTCCs. At the same replacement ratio, wollastonite with a larger aspect ratio shows a better reinforcing effect. According to the observation of post-fracture crack morphology, the cracks of UHTCCs change from the original smooth cracks to tortuous ones after cement is partially replaced by wollastonite. Replacing a part of cement with wollastonite optimizes the performance relationship among PE fibers, the matrix, and the PE fiber–matrix interface, and it enhances their synergistic effect. This not only raises the initial tensile cracking strength of UHTCCs but also improves its tensile strain. In particular, wollastonite with a larger aspect ratio exhibits a more pronounced reinforcing effect. Full article

The shift toward lightweight powertrain architectures necessitates a detailed characterization of polymer gears to verify their efficiency and durability. This study investigated the effectiveness of non-contact structured-light 3D scanning for evaluating the surface topography and dimensional tolerance quality of polymer gears produced via distinct manufacturing technologies. A structured-light 3D scanner was used to capture dense point clouds (exceeding 6 million points) of gears produced by three methods: conventional hobbing (POM-C), Material Extrusion (MEX) with carbon fiber reinforcement, and Selective Laser Sintering (SLS). The manufactured parts were compared against the nominal Computer Aided Design (CAD) models to evaluate their geometrical deviations in accordance with DIN 3961 and surface roughness parameters per ISO 25178. The experimental results revealed a consistent ranking of manufacturing quality. The conventionally hobbed POM-C gear exhibited superior precision, achieving DIN quality grades of Q9–Q10 and the smoothest surface finish (S_a = 5.0 µm). Among additive manufacturing techniques, SLS-printed PA 12 showed intermediate quality (Q11, S_a = 12 µm), whereas MEX-printed PPS-CF exhibited significant deviations (exceeding Q12) and the highest surface irregularity (S_a = 25 µm) due to stair-stepping effects. These findings indicate that while additive manufacturing offers geometric flexibility, conventional hobbing retains a decisive advantage in dimensional precision. The optical scanning methodology demonstrated here constitutes an efficient metrological framework for gear quality control, with potential applications extending to the quality assurance of additively manufactured adaptive fixtures and assembly tooling, including automotive assembly operations. Full article

The increasing demand for sustainable materials has accelerated the development of environmentally friendly filaments for fused deposition modeling (FDM). In this study, the surface roughness and thermal degradation behavior of sustainable PLA-based filaments, including PLA, recycled PLA (Re–PLA), and wood-filled PLA (Wood–PLA), were systematically investigated under different FDM printing conditions. A full factorial experimental design was employed to identify the dominant processing parameters and optimize surface quality. Surface roughness was evaluated using values Ra, Rz, and Rq parameters measured on three different surface orientations (top surface at 0°, top surface at 45°, and side surface). Scanning electron microscopy (SEM) was used to examine the relationship between roughness measurements and surface morphology, while thermogravimetric analysis (TGA) was performed to evaluate the thermal degradation behavior of the filaments in relation to printing temperature. The results have shown that filament material is the most important parameter affecting surface roughness. While Wood–PLA exhibited the highest roughness due to fiber-induced surface heterogeneity, recycled Re–PLA showed moderate surface irregularities resulting from degradation compared to pure PLA. Despite a rougher filament surface prior to production, recycled PLA exhibited a surface morphology similar to that of pure PLA after printing, influenced by the processing parameters. Furthermore, SEM findings indicated that the Ra parameter predominantly reflects macro-scale surface topography, while local microstructural heterogeneity can be better characterized by complementary roughness parameters such as Rz. These findings support optimizing printing conditions to improve surface quality and more widespread use of sustainable FDM filaments in applications where surface roughness is critical. Full article

The design of multifunctional biomaterials that offer both structural support and biochemical cues is essential for enhancing tissue regeneration. In this study, hybrid nanofibrous scaffolds composed of poly(L-lactide-co-ε-caprolactone) (PLCL) and bioactive factors secreted by Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) were fabricated via co-electrospinning. Nanofibers were produced in aligned and random configurations following an optimized protocol developed at the Institute for Bioengineering of Catalonia (IBEC). Their morphology and topography were characterized by light microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM), and fiber orientation was quantified via Fast Fourier Transform (FFT) analysis. The scaffolds showed fiber diameters of 542.9 ± 62.3 nm, with aligned fibers predominantly oriented within 20° of the principal axis. Human AD-MSCs were used to assess biocompatibility and cell–material interactions. Aligned and random nanofiber architectures elicited distinct cellular responses. AD-MSCs on aligned fibers exhibited smaller spreading areas (~320 μm²) vs. on random nanofibers (~500 μm²) and substantially higher proliferation, resulting in a shorter cell-doubling time (~25 h) than those on random nanofibers (~130 h) or control substrates (~70 h). In addition, aligned nanofibers promoted markedly faster migration, reaching rates of ~5000 μm²/h surface coverage, compared with random nanofibers (~770 μm²/h) and controls (~1800 μm²/h). Together, the results show that nanofiber alignment and biochemical functionalization jointly influence MSC behavior and improve regeneration, highlighting the potential of these PLCL-based hybrid secretome/PLCL nanofibers for advanced wound healing. Full article

The existing scientific literature indicates that flowable short fiber-reinforced composites (SFRCs) can be used for direct restoration due to their favorable mechanical properties. However, there is a lack of data on the mechanical properties of SFRCs designed specifically for indirect CAD/CAM restorations. This study aims to fabricate a novel experimental SFRC CAD/CAM block and evaluate its fracture toughness and polishability as an indirect restoration in comparison with different conventional resin-based CAD/CAM blocks with different compositions. Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the chemical structure of the Experimental SFRC group, while the microstructure of specimens from each group was examined using scanning electron microscopy (SEM). Then, this study divided the specimens into three groups—Group 1 (Grandio blocks), Group 2 (Cerasmart 270), and Group 3 (Experimental SFRC)—with 30 specimens in each group. Each group was then subdivided into sub-groups for the fracture toughness test, which evaluated resistance to crack propagation, and the surface roughness test, which assessed surface topography. FTIR analysis showed that the experimental SFRC exhibited distinct spectral changes after polymerization, confirming successful chemical reactions and network formation. SEM analysis showed that the Experimental SFRC block had a polymeric matrix with randomly oriented, well-dispersed short fibers. Grandio blocs exhibited a dense nanohybrid structure with irregular fillers, while Cerasmart 270 displayed a more uniform microstructure with evenly dispersed nano-sized spherical fillers. The Experimental SFRC showed the highest fracture toughness (2.758 MPa·√m), surpassing the other groups (p < 0.05) and highlighting its superior resistance to crack propagation. Regarding surface roughness Ra, the novel Experimental SFRC group (0.182) presented a significant difference compared to other groups (p < 0.05) but within clinical acceptance, and they can be well polished for clinical use after milling. The Cerasmart 270 block showed the lowest surface roughness Ra (0.135) among the groups, which is attributed to its filler size, geometry, and composition, resulting in a smoother surface. The higher fracture toughness of the Experimental SFRC among the groups suggests superior resistance to crack propagation, attributed to the incorporation of short fibers that enhance energy absorption and reduce brittleness, thereby supporting its suitability for high-stress-bearing clinical applications. Full article

Polyetheretherketone (PEEK) is a high-performance engineering plastic widely used in aerospace, automotive, and other industries due to its heat resistance and mechanical strength. However, its high friction coefficient and low thermal conductivity limit its use in heavy-load environments. Existing studies have extensively explored the individual effects of thermal processing or irradiation on PEEK. However, the synergistic mechanism between the initial microstructure formed by mold temperature and subsequent irradiation modification remains unclear. This paper investigates the coupled effects of injection molding temperature and electron beam irradiation on the tribology of carbon fiber-reinforced PEEK composites, with the aim of identifying process conditions that improve friction and wear performance under high load by controlling the crystal morphology and cross-linking network. Carbon fiber (CF) particles were mixed with PEEK particles at a 1:2 mass ratio, and specimens were prepared at injection molding temperatures of 150 °C, 175 °C, and 200 °C. Some specimens were irradiated with an electron beam dose of 200 kGy. The friction coefficient, wear rate, surface shape, and crystallinity of the material were obtained using friction and wear tests, white-light topography, SEM, and XRD. The results show that the injection molding temperature of the material influences the friction performance. Optimal performance is obtained at 175 °C with a friction coefficient of 0.12 and wear rate of 9.722 × 10⁻⁶ mm³/(N·m). After irradiation modification, the friction coefficient decreases to 0.10. This improvement is due to the moderate melt fluidity, adequate fiber infiltration, and dense crystallization at this temperature. In addition, cross-linking of chains occurs, and surface transfer films are created at this temperature. However, irradiation leads to a slight increase in wear rate to 1.013 × 10⁻⁵ mm³/(N·m), suggesting that chain segment fracture and embrittlement effects are enhanced at this dose. At 150 °C, there is weak interfacial bonding and microcrack development. At 200 °C, excessive thermal motion reduces crystallinity and adds residual stress, increasing wear sensitivity. Overall, while irradiation reduces the friction coefficient, the wear rate is affected by the initial microstructure at molding. At non-optimal temperatures, embrittlement tends to dominate the wear mode. This study uncovers the synergistic and competitive dynamics between the injection molding process and irradiation modification, offering an operational framework and a mechanistic foundation for applying CF/PEEK under heavy-load conditions. The present approach can be extended in future work to other reinforcement systems or variable-dose irradiation schemes to further optimize overall tribological performance. Full article

Background: This study aimed to evaluate the influence of scleral contact lens (SCL) wear on optical coherence tomography (OCT) scan quality and structural measurements in patients with keratoconus. Methods: This retrospective observational study included 28 eyes of 28 keratoconus patients. All participants underwent a comprehensive ophthalmologic evaluation, including corneal topography and spectral-domain OCT (Optopol REVO 60). Two OCT measurement sessions were performed on the same day: one without SCLs and one after a 30–75 min adaptation period with Mini Misa^® scleral lenses. Recorded parameters included corneal and epithelial thicknesses, ganglion cell–inner plexiform layer (GCIPL) thickness, retinal nerve fiber layer (RNFL) thickness, and device-reported quality index (QI). Correlation analyses between topographic values, age, and OCT parameters were also conducted. Results: The mean age of participants was 32.96 ± 13.72 years. SCL wear significantly decreased anterior segment QI (6.76 ± 1.73 vs. 5.57 ± 2.34, p = 0.019) but improved posterior segment QI in both the ganglion (2.52 ± 1.03 vs. 5.76 ± 2.17, p < 0.001) and disc (2.82 ± 0.94 vs. 4.39 ± 1.87, p < 0.001) modules. Central corneal thickness remained stable, while central epithelial thickness decreased slightly (50.53 ± 6.66 µm vs. 47.59 ± 7.20 µm, p = 0.007). RNFL and GCIPL thicknesses showed no significant changes, except for minor sectoral variations. Steeper keratometry values correlated with lower QI in both conditions. Conclusions: SCLs enhanced posterior OCT scan quality while reducing anterior segment image clarity. These findings suggest that SCLs not only provide visual rehabilitation but also facilitate more reliable posterior segment imaging in keratoconus patients, despite mild interference with anterior segment OCT metrics. Further prospective studies are warranted to validate these results. Full article

In this study, sludge retting was used as a pretreatment method for extracting banana pseudostem fibers. A Box–Behnken response surface design was employed to optimize the retting conditions. Three variables—Bacillus subtilis concentration, treatment time, and pH—were selected for analysis. Their effects on the mechanical properties of the fibers were systematically evaluated. Experimental data were analyzed using ANOVA in Design-Expert 13, and a regression model was established for parameter optimization. The optimal conditions were determined to be a Bacillus subtilis concentration of 1.18%, a treatment time of 20 days, and a pH of 7. Under these conditions, the tensile strength, elastic modulus, and elongation at break of the fibers reached 1161.63 MPa, 50.68 GPa, and 2.32%, respectively—representing improvements of 46.23%, 42.48%, and 34.1% compared to untreated samples. In addition, the fibers were analyzed using SEM, TGA-DTG, FTIR, and XRD to investigate changes in surface topography, thermal behavior, chemical bonding, and crystalline structure. Results showed that sludge retting effectively removed non-cellulosic components, enhanced thermal stability and crystallinity, and significantly improved the mechanical performance of the fibers. This study demonstrates that sludge retting is a green and sustainable pretreatment technique with strong potential for banana pseudostem fiber processing. Full article

CFRP is extensively utilized in the manufacturing of aerospace equipment owing to its distinctive properties, and hole-making processing continues to be the predominant processing method for this material. However, due to the anisotropy of CFRP, in its processing process, processing damage appears easily, such as stratification, fiber tearing, burrs, etc. These damages will seriously affect the performance of CFRP components in the service process. This work employs acoustic emission (AE) and infrared thermography (IT) techniques to analyze the characteristics of AE signals and temperature signals generated during the CFRP drilling process. Fast Fourier transform (FFT) and short-time Fourier transform (STFT) are used to process the collected AE signals. And in combination with the actual damage morphology, the material removal behavior during the drilling process and the AE signal characteristics corresponding to processing defects are studied. The results show that the time-frequency graph and root mean square (RMS) curve of the AE signal can accurately distinguish the different stages of the drilling process. Through the analysis of the frequency domain characteristics of the AE signal, the specific frequency range of the damage mode of the CFRP composite material during drilling is determined. This paper aims to demonstrate the feasibility of real-time monitoring of the drilling process. By analyzing the relationship between the RMS values of acoustic emission signals and hole surface topography under different drilling parameters, it provides a new approach for the research on online monitoring of CFRP drilling damage and improvement of CFRP machining quality. Full article

Purpose: Focal cortical dysplasia (FCD) is a common developmental malformation disease of the cerebral cortex. Although mounting evidence has suggested that FCD lesions have variable locations and topographies throughout the cortex, few studies have explored consistencies in structural connectivity among different lesion types. In this study, we analyzed microscopic structural changes via lesion analysis and explored structural changes in nonlesion regions across the brain. Methods: Diffusion tensor imaging (DTI) and magnetization transfer imaging were used to compare FCD lesions and contralateral normal appearing gray/white matter (cNAG/WM). Voxel-based morphometry was calculated for 28 children with FCD and 34 sex- and age-matched healthy participants. DTI indices of the FCD and healthy control groups were analyzed via the tract-based spatial statistic method to evaluate the microstructure abnormalities of WM fiber tracts in individuals with FCD. Results: In terms of FCD lesions, compared with those of the cNAG, the fractional anisotropy (FA) values were decreased, and the mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values were increased; the magnetization transfer ratios were also decreased. In terms of whole-brain changes due to FCD, compared with the healthy control group, the FCD group showed a decrease in the volume of the right hippocampus and left anterior cingulate cortex. FCD patients had lower FA values, higher MD values, lower AD values, and mainly increased RD values in relation to WM microstructure. Conclusions: Microstructural abnormalities outside lesion regions may be related to injury to the epileptic network, and the identification of such abnormalities may complement diagnoses of FCD in pediatric patients. Full article

This study presents a U-Net-based automatic segmentation framework for quantitative analysis of surface morphology in a PEEK-based composite following tribological testing. Controlled Pin-on-Disc tests were conducted to characterize tribological performance, worn surfaces were captured by laser scanning microscopy to acquire optical images and height maps, and the model produced pixel-level segmentation masks distinguishing different regions, enabling high-throughput, objective analysis of worn surface morphology. Sixty-three manually annotated image sets—with labels for fiber, third-body patch, and matrix regions—formed the training corpus. A 70-layer U-Net architecture with four-channel input was developed and rigorously evaluated using five-fold cross-validation. To enhance performance on the challenging patch and fiber classes, the top five model instances were ensembled through Bayesian-optimized weighted voting, achieving significant improvements in class-specific F1 metrics. Segmentation outputs on unseen data confirmed the method’s robustness and generalizability across complex surface topographies. This approach establishes a scalable, accurate tool for automated morphological analysis, with potential extensions to real-time monitoring and other composite systems. Full article

The largest Eurasian rodent, the Eurasian beaver Castor fiber, is known for its amphibious lifestyle that allows it to adapt its environment to its needs. Due to its lifestyle and evolutionary history, the beaver is characterized by a distinct, unique parasitofauna. In this context, the occurrence of mites from the Demodecidae family in the Eurasian beaver was investigated. The topography of the Demodex castoris was analyzed: it was previously known from a single record from a single skin location of this host. The mite was found in large numbers in various locations in the hairy skin, including the head, trunk, and limbs. In addition, a new species associated with hairless skin, mainly around the mouth, was discovered and described: Demodex ovaportans sp. nov. The females of this species carry the egg on the dorsal side of the podosoma, which may be a form of care and a previously unknown reproductive strategy in Demodecidae. Our findings confirm that a host-specific demodecid mite species associated with the hairy skin of the entire body is a universal model in mammals. They also emphasize the uniqueness of the beaver parasitofauna, as evidenced by the host specificity and the different biology of the demodecids described in it. Full article

Electrospun fibers, possessing biomimetic characteristics similar to fibrous extracellular matrices, have attracted widespread attention as scaffold materials for skin tissue engineering. The topographical structure of electrospun fibers plays a critical role in determining cell behavior. However, the effects of fiber topography on human skin fibroblasts (HSFs) remain unclear. In this study, electrospinning technology was employed to investigate how parallel and crossed fiber architectures influence the spreading morphology, proliferation, and migration of HSFs. The results demonstrated that cells exhibited spindle-shaped elongation along single fibers; on closely spaced parallel fibers, cells formed cross-adhesions between adjacent fibers, with a fiber spacing of 30–60 μm serving as the threshold range for distinguishing individual cell behaviors. At fiber intersections, a characteristic spacing of 100 μm distinguished three distinct cellular responses: anchoring, turning, and bridging. The probability of a cell altering its preexisting migration path depended on its ability to extend laterally and reach adjacent fibers, which was constrained by the upper limit of the cell body’s minor axis. This study elucidated the unique role of the electrospun fiber topography in guiding cellular decision-making in complex microenvironments, provided important insights into topography-triggered cell migration, and highlighted the practical significance of material-guided strategies in tissue engineering. Full article

Noncorrosive concrete reinforcement, such as polymer fibers, is needed to overcome the current issues caused by corroded steel reinforcements. Fibers made of polypropylene show a low bonding behavior in concrete. Fillers can help to overcome this issue but often lead to reduced mechanical properties. Core-shell fibers, which split the mechanical properties and the bonding behavior between the core and the shell component, could be a solution. This study investigates mono-material and core-shell fibers produced with calcium carbonate and bentonite fillers and compares their behavior in tensile tests, density measurements, contact angle measurements, topography measurements, single fiber pull-out tests, reflected light microscopy, and thermogravimetric analysis. The fillers caused an increased drawability, resulting in higher mechanical properties. Further, in the core-shell fibers, the calcium carbonate increased the surface roughness, which led to a better anchoring of the fiber in concrete, which was also visible in the deformation during pull-out observed in reflected light microscopy pictures. The thermogravimetric analysis showed a delay in onset of degradation for fibers containing bentonite. Full article