Search Results (626)

Laser surface microtexturing has emerged as an effective approach for improving the performance of adhesive joints between dissimilar materials. In this study, the influence of laser-generated micrometric surface features on the mechanical behavior of hybrid adhesive joints was investigated for two material systems: structural steel bonded to polyamide (PA66) and structural steel bonded to technical ceramic (Al₂O₃). Single-lap joints were manufactured using a two-component epoxy adhesive with two nominal bond-line thicknesses (0.1 mm and 1.0 mm). Prior to bonding, selected surfaces were modified by ultrashort-pulse laser microtexturing, producing well-defined circular features with characteristic depths on the order of tens of micrometers. The resulting microstructures were characterized using optical and scanning electron microscopy, and their geometric parameters were quantified through profilometric measurements. Mechanical performance was evaluated under shear and bending loading conditions. The results demonstrate a substantial increase in joint strength for laser-microtextured surfaces compared with non-textured references for both material combinations. The effect of surface microtexturing was more pronounced than the influence of adhesive layer thickness within the investigated range. These findings confirm that laser-induced surface microtexturing is a versatile and application-oriented surface preparation method capable of enhancing the reliability of adhesive bonding in hybrid metal–polymer and metal–ceramic assemblies. 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

Laser surface texturing (LST) structures or laser-induced periodic surface structures (LIPSS) are typically created using laser pulses with durations ranging from femtoseconds to nanoseconds. However, nanosecond pulsed lasers, as cost-effective and more productive alternatives, can also be used to generate LST structures on stainless steel (SS) surfaces, making these structures more suitable for industrial applications. In this study, pulsed laser processing is employed to create LST structures on SS (AISI 304), with varying pulse and accumulated fluences, effective pulse counts, and scan parameters, such as pulse-to-pulse distance (pitch) and hatch spacing between scanning lines. A methodology for calculating oxidation density on processed AISI 304 surfaces is presented. Oxidation density, defined as the ratio of the oxidized area to the total processed area, is determined as a function of accumulated fluence, laser power, pulse-to-pulse distance, and hatch spacing. Optical images of the surfaces are analyzed, and oxidation regions are identified using machine learning techniques. The images are converted to grayscale, and machine learning algorithms are applied to classify the images into oxidation and non-oxidation regions based on pixel intensity values. This approach identifies the optimal threshold for separating the two regions by maximizing inter-class variance. Experimental modeling using response surface methodology is applied to experimentally generated data. Optimization algorithms are then employed to determine the process parameters that maximize pulsed laser irradiation performance while minimizing surface oxidation and processing time. This paper also presents a novel method for characterizing oxidation density using image segmentation and machine learning. The results provide a comprehensive understanding of the process and offer optimized models, contributing valuable insights for practical applications. Full article

The condition of technical surfaces strongly influences the functionality and lifetime of many components. In particular, the performance of aero-engines can be impaired by increased roughness of the turbine blade surfaces. In this work, an LED- and camera-based illumination sensor is presented for reflection-based characterisation of turbine blade surfaces, with a focus on rapid, wide-area assessment rather than direct roughness measurement. Traditional roughness measurements (e.g., profilometry, confocal microscopy) provide micrometre-scale height information but are limited in working distance and measurement volume, making complete surface coverage time-consuming. The proposed sensor acquires multi-illumination image data, from which an anisotropic BRDF (bidirectional reflectance distribution function) model is fitted on a per-pixel basis to obtain reflectance parameters. Independently, surface roughness parameters (Sa, Sq, Sz, Ssk, Sku) are measured using a confocal laser scanning microscope in accordance with ISO 25178 and used as reference data. Using two turbine blades with contrasting surface conditions (comparatively smooth vs. visibly rough), the study qualitatively investigates whether there are indications of relationships between BRDF model parameters and roughness characteristics. The results show weak relationships with height-based parameters (Sa, Sq, Sz), but clearer trends for distribution parameters (Ssk, Sku) and a good qualitative agreement between directional BRDF parameters and texture orientation. These findings indicate that the illumination sensor provides a complementary, reflectance-based approach for surface condition triage in MRO and QA contexts, highlighting regions that warrant more detailed roughness measurements. Extension of the approach to other component geometries and a comprehensive quantitative analysis of BRDF–roughness relationships are planned for follow-up studies. Full article

This work systematically investigates the coupled effects of femtosecond laser parameters (wavelength: 515 nm, pulse width: 373 fs, laser fluence: 3.18–12.7 J/cm², repetition frequence: 100 kHz) and post-fabrication thermal treatment on the micro/nano-structure evolution and wettability of aluminum alloys. By varying the scanning spacing (20–80 μm) and laser fluence, diverse hierarchical surface morphologies were obtained. At a small scanning spacing of 20 μm, increasing laser fluence causes severe thermal accumulation and structural collapse, with the microstructure height decreasing from 42.68 μm to 20.30 μm and the water contact angle (WCA) dropping from 158.6° to 143.5°, indicating a degradation of the superhydrophobic state. In contrast, at larger spacings (60–80 μm), moderate fluence enhances microstructure depth and roughness, yielding peak WCAs of ~160°, while excessive fluence induces feature coarsening and partial loss of nanoscale textures, leading to reduced wettability. Nanoscale evolution shows that optimized laser conditions promote dense nanoparticle redeposition and stable ridge-like structures. These structures are accompanied by cotton-like features with pore diameters of 50–100 nm and coral-like porous features with pore diameters of 100–200 nm, whereas excessive laser etching damage these nano-structures. Among, a scanning spacing of 40 μm achieves this most robust hierarchical nano-structure, corresponding to a maximum WCA of 162.6°. These results clarify the role of femtosecond laser parameters in regulating micro/nano-structural formation and the subsequent modulation of wettability through thermal treatment, providing a reference for the fabrication of coating-free superhydrophobic aluminum alloy surfaces. Full article

Thin vapor chambers are attractive for compact electronics but become difficult to operate reliably as the vapor space approaches the millimeter scale, especially when classical wick structures are omitted. This work investigates how coupled evaporator and condenser wettability governs the performance of a 1 mm thick wick-free vapor chamber. Six configurations are evaluated by combining three condenser surface states (reference, superhydrophilic, superhydrophobic) with either a reference copper evaporator or a laser-textured superhydrophilic evaporator. Thermal performance is assessed from 10 to 40 W using the evaporator–condenser temperature difference and overall thermal resistance. The results show that the preferred condenser wettability depends on evaporator capability. With the reference evaporator, the lowest thermal resistance at 40 W is achieved with reference and superhydrophobic condensers (1.21 and 1.18 K/W). With the laser-textured evaporator, a superhydrophilic condenser provides the best performance, and the SHPI–SHPI configuration reaches 0.77 K/W at 40 W. These findings provide practical guidance for designing ultrathin wick-free vapor chambers through coordinated interface wettability selection. Full article

In mechanical engineering, interest in reliable and practicable technologies for nano- and microstructuring of tool surfaces is increasing. Femtosecond laser structuring offers a promising approach that combines high processing speeds with high precision. However, a knowledge gap remains regarding the optimal process parameters for achieving specific surface patterns on hot-work tool steel substrates. The current study aims to investigate the effects of laser scanning parameters on the formation of self-organized surface structures and the resulting topography and morphology. Therefore, samples were irradiated using a 300 fs laser with linearly polarized light (λ = 1030 nm). Scanning electron microscopy revealed four structure types: laser-induced periodic surface structures (LIPSSs), micrometric ripples, micro-crater structures, and pillared microstructures. The results for surface area and line roughness indicate that high laser pulse overlaps lower the strong ablation threshold more effectively than high scanning line overlaps, promoting the formation of pillared microstructures. For efficient ablation and increased surface roughness, higher pulse overlaps are therefore advantageous. In contrast, at low fluences, higher scanning line overlaps support a more homogeneous formation of nanostructures and reduce waviness. Full article

Externally applied electric fields are widely employed during thin-film deposition to improve film uniformity, texture and densification. Despite extensive experimental evidence, the physical mechanisms by which such fields influence nucleation, surface diffusion, island coalescence and interface stability remain theoretically fragmented. Classical thin-film growth models assume a field-free energetic landscape and therefore provide limited predictive guidance for field-assisted manufacturing strategies. In this work, we introduce the Field-Driven Growth Model (FDGM), a unified theoretical framework that incorporates field–matter interactions directly into the free-energy functional governing thin-film growth. By explicitly accounting for effective dipolar coupling arising from field-induced polarization of surface species, predominantly quadratic in the field amplitude and consistent with linear-response polarization, the model consistently modifies the fundamental processes of nucleation, surface diffusion and coalescence. At the continuum scale, the FDGM predicts a field-induced stabilization mechanism that suppresses long-wavelength roughening modes and defines a field-controlled morphological crossover wavelength (field-controlled cutoff). The FDGM demonstrates that field-assisted nucleation bias, anisotropic surface diffusion, field-biased coalescence pathways and morphological stabilization are not independent phenomena, but multiscale manifestations of a single energy-minimization principle acting on a field-modified energy landscape. By providing analytical stability criteria and explicit links between external field parameters and morphological outcomes, the model establishes a predictive foundation for the manufacturing of thin films with improved uniformity in advanced thin-film-based devices. The framework is broadly applicable to deposition techniques such as sputtering, pulsed-laser deposition, chemical vapor deposition and atomic layer deposition. Full article

Filled-polymer coatings enable functional surfaces for selective metallisation, wetting control and local conductivity, but pulsed-laser texturing is often limited by process non-uniformity caused by scan kinematics and plume shielding. Here, we develop a three-tier numerical workflow for nanosecond pulsed-laser surface treatment of a thermoplastic coating containing glass microspheres (baseline case: PLA matrix with V_f = 0.20; spheres represented via an effective optical transport model). Tier 1 predicts spatially resolved ablation depth under raster scanning, using an incubation law and regime switching (no-removal/melt-limited/logarithmic ablation/blow-off) coupled to a dynamic shielding factor. Tier 2 computes the 1D transient (pulse-averaged) temperature field and the thickness of the thermally softened layer. Tier 3 models post-pulse capillary redistribution of the softened layer to estimate groove reshaping. The simulations show that scan overlap and shielding dynamics dominate groove homogeneity more strongly than average power alone: under identical average power, variations in local pulse count and shielding lead to significant changes in depth statistics and regime fractions. The workflow produces quantitative maps and summary metrics (mean depth, P5–P95 range, uniformity index and regime fractions) and demonstrates how controlled reflow can smooth peaks while preserving groove depth. These results provide a predictive tool for laser parameter selection and process optimisation prior to experimental trials. Full article

Facial aging is not a singular phenomenon but a cascade of anatomical and biological transformations unfolding across the skeleton, fat, ligaments, muscles, dermis, and epidermis. Its clinical expression-volume loss, sagging, wrinkling, and surface irregularities-cannot be adequately explained by simplistic metaphors of “filling” or “lifting.” This article is a narrative review synthesizing current anatomical, physiological, and clinical evidence relevant to multimodal facial rejuvenation. Traditional monotherapies, while sometimes effective in isolation, are increasingly inadequate for contemporary patients who demand outcomes that are natural, harmonious, and durable. Modern esthetic practice has therefore shifted toward multimodal approaches that address aging across multiple planes. Hyaluronic acid (HA) fillers provide volumetric scaffolding and hydration; collagen stimulators such as poly-L-lactic acid (PLLA) and calcium hydroxylapatite (CaHA) induce neocollagenesis and long-term dermal remodeling; botulinum toxin restores balance to muscular vectors and improves expression dynamics; while energy-based devices (EBDs), including fractional lasers, radiofrequency microneedling, and high-intensity focused ultrasound (HIFU), enhance skin texture, tone, and elasticity. When applied in a sequenced and evidence-based manner, these modalities act synergistically to deliver results unattainable by any single intervention. In addition to established modalities, the field has recently witnessed aggressive promotion of “regenerative” therapies-growth factors, exosomes, platelet-rich plasma (PRP), and platelet-rich fibrin (PRF). While biologically plausible, their efficacy and safety remain uncertain due to the absence of robust, randomized clinical trials and the heterogeneity of current data. This raises a critical question: is aesthetic medicine advancing through science, or being driven by novelty and marketing? This review synthesizes current anatomical and physiological knowledge of aging, evaluates the mechanisms, clinical applications, and safety considerations of major treatment modalities, and proposes practical sequencing strategies. It also emphasizes the ethical imperative that aesthetic medicine, while innovative and fast-evolving, must remain anchored in scientific evidence and patient safety—because aesthetic medicine is, fundamentally, still medicine. Full article

This study investigates the influence of surface texturing on temperature distribution in lubricated sliding contacts using infrared thermography. The work addresses the broader challenge of understanding thermal effects in conformal hydrodynamic contacts, where localized heating and viscosity variations can significantly affect tribological performance. A pin-on-disc configuration was employed, featuring steel pins with laser-etched micro-dimples that slid against a sapphire disc, allowing for thermal imaging of the contact zone. A dual-bandpass filter infrared thermography technique was developed and rigorously calibrated to distinguish between the temperatures of the steel surface and the lubricant film. Friction measurements and laser-induced fluorescence were used in parallel to assess contact conditions and the behavior of the lubricant film. The results show that surface textures can alter local frictional heating and contribute to non-uniform temperature distributions, particularly in parallel contact geometries. Lubricant temperature was consistently higher than the surface temperature, highlighting the role of shear heating within the fluid film. However, within the tested parameter range, no unambiguous viscosity-wedge signature was identified beyond the dominant temperature-driven viscosity reduction captured by the in situ correction. The method provides a novel means of experimentally resolving temperature fields in sliding textured contacts, offering a valuable foundation for validating thermo-hydrodynamic models in lubricated tribological systems. Full article

In this work, we demonstrate precise control over laser-induced periodic surface structures (LIPSS) on stainless steel (SS) using femtosecond (fs) laser processing to suppress bacterial adhesion. We systematically compare the antifouling behavior of laser-textured surfaces with distinct pattern directionalities—linear and circular. Fs laser irradiation with linear polarization produces directional and anisotropic LIPSS, which progressively evolve into more complex hierarchical surface textures as processing conditions vary. In contrast, fs laser irradiation with circular polarization yields isotropic surface morphologies. Despite these morphological differences, the surface wettability remains nearly constant, with contact angles confined to a narrow range of 32.6–36.9°. Bacterial adhesion tests using Escherichia coli reveal that surfaces patterned with anisotropic features generated by linear polarization—particularly at an incident power of 30 mW—exhibit enhanced antifouling performance compared to isotropic counterparts. These results indicate that antifouling efficacy is governed not only by surface wettability but also by the spatial organization and anisotropy of the LIPSS. This study highlights the critical role of polarization-controlled fs laser processing in tailoring surface architectures and provides a rational strategy for designing bio-resistant metallic surfaces. Full article

This study evaluated the influence of various surface treatments on the bonding performance and mechanical behavior of zirconia, with particular emphasis on the effect of laser surface texturing (LST) compared with conventional 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and airborne particle abrasion (APA) methods. Two zirconia compositions, 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 5 mol% partially stabilized zirconia (5Y-PSZ), were subjected to four surface treatment protocols: as-milled, 10-MDP, APA, and LST (n = 12). Shear bond strength (SBS) to titanium and biaxial flexural strength (BFS) of zirconia were measured. Surface morphology, failure mode, and phase composition were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Data were analyzed with two-way ANOVA and Tukey’s post hoc test (α = 0.05), and the reliability of flexural strength was assessed using Weibull analysis. Surface treatment significantly affected SBS (p < 0.05). The LST groups exhibited the highest SBS values and a higher proportion of mixed failures, whereas other groups predominantly showed adhesive failures. However, LST-treated specimens, particularly 5Y-PSZ, showed reduced BFS. XRD confirmed phase stability, although localized microstructural changes were observed after LST. LST enhanced the zirconia–titanium interfacial bond strength and promoted mixed failure modes; however, this improvement was accompanied by a reduction in flexural strength, particularly in 5Y-PSZ. Full article

Surface finish plays a critical role in the tribological performance of additively manufactured engineering components. In exploring part characteristics in laser powder-bed fusion (L-PBF), this study investigates the effect of contouring strategies on the upskin surface of inclined specimens (30°, 45°, and 60°) made with L-PBF, using post- and pre-contouring strategies with various levels of process parameters. The surface data of fabricated inclined specimens were acquired by white-light interferometry, followed by a quantitative analysis using surface images. The results show that post-contouring leads to better surface finishes, with the lowest S_a of 8.68 µm attained at the highest laser power (195 W) and the slowest scan speed (500 mm/s) on 30°-inclined specimens, likely due to increased remelting and less step-edges. In contrast, pre-contouring produces distinct surface textures on the upskin of L-PBF specimens, resulting in a rougher surface morphology, with a maximum S_a of 33.39 µm also from 30°-inclined specimens at the lowest power (100 W) and the highest speed (2000 mm/s), suggesting an insufficient remelting of surface defects. In comparative analysis, in general, post-contouring yields smoother upskin surfaces, with a 17%–30% reduction in S_a, than those from equivalent pre-contouring conditions, highlighting the potential of scan sequences for optimizing L-PBF to improve the surface finish of inclined structures. Full article

Fiber laser surface texturing was applied to AA1050 aluminum to improve friction and wear performance of PTFE coatings. A Taguchi L16 design varied texture geometry (square, diamond, hexagon, circle), scanned area ratio (20% to 80%), and laser power (40 to 100 W) prior to primer plus PTFE topcoat deposition (25 to 35 µm). Dry reciprocating sliding against a 6 mm 100Cr6 ball was conducted at 20 N, 1 Hz, and 50 m, and wear track geometry was measured by non-contact profilometry. The non-textured reference exhibited an average COF of 0.143, whereas the lowest mean COF was achieved with diamond 60% and 40 W (0.095) and the highest with hexagon 60% and 100 W (0.156); hexagon 20% and 60 W matched the reference. ANOVA indicated scanned area ratio as the dominant contributor to COF (39.72%), followed by geometry (35.07%) and power (25.21%). Profilometry confirmed reduced coating penetration for optimized textures: the reference wear track was approximately 1240 µm wide and 82 µm deep, compared with 930 µm and 34 µm for square 80% and 40 W, 997 µm and 39 µm for diamond 60% and 40 W, and 965 µm and 36 µm for hexagon 40% and 40 W. Full article