Search Results (660)

Structural colors, generated by the physical interaction of light with micro- and nanostructured architectures, have emerged as an important platform in nanophotonics owing to their high color saturation, exceptional photostability, and long-term color durability. This review provides a comprehensive overview of recent advances in structural colors and establishes a unified classification framework based on their macroscopic angular optical responses. The intrinsic angular characteristics of four fundamental color-generation mechanisms are first distinguished, providing the physical basis for classifying structural colors into iridescent and non-iridescent systems. Representative iridescent architectures, including thin films, one-dimensional (1D) to three-dimensional (3D) photonic crystals, and diffraction gratings, are systematically reviewed, together with non-iridescent strategies based on independent plasmonic and dielectric resonators, quasi-amorphous structures, and engineered metasurfaces. Strategies for enhancing structural color visibility and saturation through absorption management are further discussed, particularly for suppressing undesired broadband and multiple-scattering backgrounds. Additionally, this review systematically summarizes quantitative methodologies for evaluating structural colors, including spectral metrics, CIE 1931 and CIE1976 color spaces, CIEDE2000 color difference, quantitative angular-response metrics, spatial resolution and pixel limits, and structural-order characterization using orientation parameters and two-dimensional fast Fourier transform (2D FFT) analysis. Particular attention is given to the quantitative assessment of angular stability through wavelength shifts and perceptual color differences, while recognizing that a universally accepted numerical boundary between iridescent and non-iridescent coloration has not yet been established. Representative functional applications are also reviewed, including self-cleaning coatings, passive daytime radiative cooling, label-free chemical and gas sensing, reflectometric interference spectroscopy (RIfS), surface-enhanced Raman scattering (SERS), and anti-counterfeiting. By integrating color-generation mechanisms, angular optical responses, quantitative evaluation methods, and functional applications, this review provides a unified framework for objectively comparing structural color platforms and highlights key trade-offs among color quality, angular stability, structural precision, durability, scalability, and multifunctionality, thereby providing design guidance for next-generation optical materials and devices. Full article

To improve the antifouling and self-cleaning performance of 3003 aluminum alloy, a fluorine-free water-repellent surface was fabricated by combining nanosecond laser texturing with subsequent heat treatment. The effects of scanning speed, laser power, pulse frequency, and scanning interval on surface wettability were systematically investigated. Under the optimal conditions of 2700 mm/s, 6 W, 35 kHz, and 20 μm, the surface achieved a maximum static water contact angle of 154.3 ± 0.8°. Surface characterization showed that laser processing generated hierarchical micro-/nano-scale structures, while heat treatment promoted surface chemical evolution associated with enhanced hydrophobicity. The highly water-repellent behavior resulted from the synergistic effect of hierarchical roughness and heat-treatment-induced surface chemical changes. The fabricated surface exhibited effective self-cleaning performance, achieving a SiO₂ removal efficiency of 98.8% under the specified test conditions. In addition, relatively high water repellency was retained after repeated water-impact and tape-peeling tests. These results demonstrate that nanosecond laser texturing combined with heat treatment provides a simple and environmentally friendly strategy for fabricating water-repellent AA3003 surfaces for antifouling and surface-protection applications. Full article

Hydrophobic and superhydrophobic coatings have attracted considerable attention due to their ability to provide water repellency, self-cleaning, anti-corrosion, anti-icing, and anti-fouling properties, making them promising for a wide range of industrial applications. This review summarizes recent advances in the development of hydrophobic and superhydrophobic coatings, with particular emphasis on wetting mechanisms, material selection, coating formation approaches, durability issues, commercial implementation, and environmental aspects. The analysis examines the principal classes of materials used for coating fabrication, including polymeric materials, inorganic compounds, and composite systems. The mechanisms responsible for the formation of hydrophobic and superhydrophobic surfaces are discussed in terms of surface chemistry modification and hierarchical roughness generation. Attention is devoted to factors limiting long-term performance, such as mechanical wear, chemical degradation, ultraviolet exposure, climatic effects, hydrodynamic erosion, and adhesion-related failures, as well as to current strategies for improving durability. Commercially available technologies and their application areas are reviewed, and the environmental challenges associated with fluorinated compounds are considered. The analysis demonstrates that the combination of controlled surface morphology and reduced surface energy remains an effective approach for achieving durable hydrophobicity, with optimized coating systems reaching contact angles of 160–170° and retaining superhydrophobic properties for more than 500 h under demanding operating conditions. Future developments are expected to focus on environmentally friendly, multifunctional, and long-lasting coating systems. Full article

Optical microfibers are fabricated by pulling classical silica fibers until reaching diameters of a few micrometers or less. These devices are significantly exploited in many science and engineering fields, ranging from fundamental research to practical applications. Despite their many attractive advantages, a major technological challenge remains: heating caused by laser absorption from surface defects and contaminants. In the present study, we propose, for the first time to our knowledge, a novel method to measure the temperature evolution of laser self-heated microfibers in air at a wavelength of 1.48 µm. This method, simple and fast, enables us to investigate the influence of the diameters and lengths of the microfibers. We found that the temperature of the microfibers increases linearly with the power and measured a rise of 70 °C for a 1 µm diameter and 20 mm length microfiber at a moderate power of 160 mW. A numerical model considering the microscale and the heat exchange with air is proposed and is adjusted with experimental data, providing values for the thermal transfer coefficient. By investigating power scaling, this work enables the prediction of temperature increases in self-heated microfibers in air, paving the way for new insights into the self-cleaning of microfiber-based devices and for optimized control of light propagation at high power levels. Full article

Self-supervised knowledge distillation is widely used to compress reusable encoders, but an untrusted distillation implementation can itself become an attack surface. We study an algorithm-level threat in which the teacher encoder and user-visible distillation dataset remain unchanged, while malicious code internally generates trigger-bearing views and optimizes an additional backdoor objective. To instantiate this threat, we propose soft gradient collaboration (SGC), which combines distribution-alignment-based distillation, target-representation-based backdoor design, and conflict-avoidance gradient collaboration to reduce interference with benign representation transfer while embedding a trigger-to-target association in the student encoder. Experiments on CIFAR-10 and STL-10 show that SGC maintains competitive downstream accuracy and effective non-target attack success. Quantitative CKA, feature-distribution, and class-structure analyses further indicate that SGC retains clean representations closer to benign distillation than fixed scalarization or removal of distribution alignment. Its no-defense attack success is not the highest among the compared attacks; instead, its main empirical advantage is stronger residual attack persistence after MIMIC, MKD, and SSLDefender. Under SSLDefender, SGC retains 9.12% non-target ASR on CIFAR-10 and 9.06% on STL-10, the highest residual values among the compared attacks. Additional experiments with a compact ResNet-18 student, multiple target classes and trigger configurations, and a supplemental CIFAR-100 setting broaden the empirical evaluation across student capacity, target semantics, trigger configurations, and label-space complexity. These results show that security assessment of self-supervised distillation should include executable training logic in addition to model weights and visible data. The concealment considered here is limited to dataset-only inspection and clean-output validation; SGC is not claimed to evade source-code auditing, runtime data-flow monitoring, or training-log inspection. Full article

Antimicrobial resistance is a critical global challenge that necessitates the development of durable, material-based strategies to limit pathogen survival and transmission. Conventional cleaning and disinfection methods only provide transient protection due to rapid surface re-contamination. This study investigates the fabrication of polyethylene terephthalate (PET) surfaces designed for antibacterial applications via femtosecond laser-induced micro- and nanostructuring. Surface texturing was performed using a Ti:sapphire femtosecond laser (wavelength λ = 800 nm, pulse duration τ = 70 fs) at peak laser fluences (F) of 2.04 J/cm² and 4.08 J/cm², generating hierarchical surface textures with controlled morphology, spacing, and geometry through ultrafast, non-contact laser processing while preserving the bulk properties of PET. The resulting patterns, including parallel and intersecting microchannels decorated with laser-induced nanostructures, enabled tunable surface roughness and wettability, with water contact angles ranging from 33.21° to 118.2°. Comprehensive surface characterization, including morphological, topographical, and wettability analyses, was performed to establish structure–property relationships associated with previously reported antibacterial surface design principles. However, direct antibacterial performance was not evaluated in the present study and will be the subject of future investigations. In addition, the durability of the laser-structured PET was evaluated under simulated real-life conditions, including thermal cycling, ultraviolet exposure, abrasion, chemical resistance, and dust contamination. The structured surfaces demonstrated high structural and functional stability following environmental testing. The results indicate that the laser-induced surface modifications remain stable under conditions representative of prolonged practical use, supporting their potential long-term applicability for antibacterial and self-cleaning PET surfaces. Full article

Accurate solar radiation forecasting is essential for photovoltaic energy generation, smart grid stability, and renewable energy management. This study proposes a lightweight hybrid deep learning framework that combines a transformer encoder and Gated Rrecurrent Uunit (GRU) network for short-term solar radiation forecasting in Makkah and Madinah, Saudi Arabia. Hourly meteorological data from the NASA POWER dataset (2020–2025) were utilized, including solar radiation intensity, temperature, humidity, wind speed, cloud amount, rainfall, surface pressure, and dew point temperature. A preprocessing pipeline consisting of missing value treatment, outlier removal, normalization, timestamp alignment, and data cleaning was applied to improve data quality. Feature engineering techniques were incorporated to capture temporal dependency, meteorological interactions, weather dynamics, and solar variability patterns. The transformer encoder was used to learn long-range temporal dependencies through multi-head self-attention, while the GRU layer modeled sequential temporal dynamics efficiently. Hyperparameter optimization was performed using Bayesian optimization with Optuna. The experimental results demonstrate that the proposed transformer GRU framework achieved a Mean Absolute Error (MAE) of 0.014, Root Mean Square Error (RMSE) of 0.0219, and a coefficient of determination (${\mathrm{R}}^2$) of 0.98. The proposed model outperformed ARIMA, LSTM, GRU, and XGBoost models while maintaining stable performance across varying weather conditions and forecasting horizons. Full article

A cascade impactor equipped with microparticle surface acoustic wave sensors along with a surface cleaning system is an innovative system developed by our team to measure particles and monitor air quality. The system has been proven to function properly under various particle concentrations. Nevertheless, long exposure times and heavily polluted media impose a limitation on cascade impactors, known as surface saturation. This problem affects the sensitivity of our sensors, which tends to degrade with particles fouling the surface. To overcome this issue, a surface cleaning system that uses a Rayleigh wave-actuated water droplet has been implemented and tested. Rayleigh waves were generated on an innovative SAW chip, thus exciting the droplet using Radio-Frequency power. NaCl solutions and SiC particles were considered. The optimal droplet size was determined along with the required Radio-Frequency power. Experiments showed that the SAW-driven droplet successfully displaced the collected particles outside of the sensing zone, irrespective of their nature, without affecting the sensor’s performance. The results found in this study provide further improvements to our particle measuring system, advancing it towards an autonomous self-regenerating prototype. Full article

Corner cleaning is a critical sub-stage of finishing and is used to remove residual material left by previous machining operations, thereby ensuring the designed dimensional precision and surface quality. Although essential in CNC machining, many current industrial CAM software like UG NX, PowerMill systems were largely developed based on early-stage theoretical frameworks. Meanwhile, the geometric shapes of machined workpieces are becoming increasingly complex, making such software gradually unable to meet the growing requirements for tool path quality. This paper establishes a rigorous mathematical framework to bridge the gap between industrial practice and theoretical modeling. Based on this framework, an enhanced Principal Component Analysis (PCA) method is proposed to generate an optimal drive curve by integrating geometric variance maximization with vector field guided directional optimization. Furthermore, a robust offset strategy is presented, incorporating self-intersection detection, critical-point trimming, and segment connection mechanisms to ensure path continuity and smoothness. Experimental results and real machining cases demonstrate that the proposed method outperforms the widely used commercial software in terms of robustness and path smoothness, validating its effectiveness and practical applicability. Full article

A strategy combining imprinting with anode oxidation is proposed for preparing an aluminum template with a negative compound-eye array. Injection compression molding with the aluminum template mounted on the mold cavity surface is applied to fabricate polystyrene replicas with a biomimetic compound-eye array on their surfaces. It is demonstrated that orderly microlenses and dense nanopillars with average diameters of approximately 225 μm and 63 nm, respectively, are formed on the polystyrene replicas. The polystyrene replica surfaces with the compound-eye array exhibit both hydrophobicity, with a water contact angle of 151 ± 2° and a rolling angle of 4 ± 1°, and excellent antireflectivity, showing an average reflectance of approximately 4% across the 400–1000 nm wavelength range. The microlens and nanopillar structures on the PS replicas are therefore key to achieving both hydrophobicity and antireflectivity simultaneously. The proposed fast mass-replication approach, which combines imprinting, anode oxidation, and injection compression molding, offers an efficient route for producing bioinspired compound-eye arrays. This strategy shows potential for applications in optoelectronics, photovoltaics, and self-cleaning optical surfaces. Full article

This review systematically summarizes recent advances in the field of surface finishing for wood products, with a focus on three cutting-edge directions: functionalization, intelligence, and sustainability. The article first outlines the fundamental theories and the evolution and modernization of traditional surface-finishing techniques, then delves into the construction mechanisms and performance characteristics of advanced functional surfaces such as superhydrophobic, self-cleaning, and smart-responsive coatings. Surface finishing of wood products is transitioning from conventional passive protection and aesthetic enhancement toward active functional empowerment and intelligent interaction. Functionalization, intelligence, and sustainability have become mainstream trends in technological development, supported by the deep integration of materials science, digital technologies, and design disciplines. Finally, the paper identifies current research challenges and prospects for key future research directions, aiming to provide a systematic knowledge framework and developmental guidance for academic studies in wood-product surface finishing. Full article

Waterproofing is crucial for maintaining the structural integrity and extending the longevity of buildings. However, traditional waterproofing materials possess limitations, including restricted durability, complex installation procedures, and environmental pollution, making them insufficient to meet the advanced waterproofing demands of modern buildings under complex conditions. Superhydrophobic materials, characterized by a water contact angle greater than 150° and a water sliding angle less than 10°, exhibit low surface energy, self-cleaning properties, and corrosion resistance due to their distinctive micro–nano structure and chemical composition, thereby serving as an innovative high-performance solution for building waterproofing and helping address some limitations of traditional waterproofing technologies. This review systematically elucidates the fundamental wetting theory and formation mechanisms of superhydrophobic materials, categorizes superhydrophobic materials used in building waterproofing mainly according to substrate type, discusses their modification strategies and key functional components, and conducts a detailed analysis of their application scenarios, performance advantages, and engineering test data in the waterproofing of concrete structures, steel structures, and building envelope materials (wood, stone, building coatings). Furthermore, this review analyzes the technical bottlenecks, performance limitations, and industrialization challenges associated with the current practical application of superhydrophobic building waterproofing materials, and outlines future development trends and engineering application strategies from the perspectives of material performance optimization, cost control, construction technology enhancement, and standardization. Full article

Bioinspired superhydrophobic surfaces (SHS) have been proven to afford high corrosion inhibition to the underlying metal. Targeting brass metal, this paper presents a biomimetic mineralization route for obtaining SHS. Calcium carbonate is first synthesized in an ethanol solution containing an organic curing agent through CO₂ gas introduction, resulting in colloidal material. Subsequent modification with stearic acid yields the SHS. Electrochemical impedance spectroscopy (EIS) experiments reveal that the biomimetic calcium carbonate cluster coating significantly improves the corrosion inhibition performance. After the coverage of the CaCO₃ SHS, the low-frequency impedance modulus value increases to 4.6 × 10⁵ Ω cm², which is enhanced compared with the bare brass with 3.2 × 10³ Ω cm². Meanwhile, the corrosion current density value decreases substantially from 2.31 × 10⁻⁶ mA/cm² for bare metal to 1.30 × 10⁻⁸ mA/cm² for the SHS surface. This demonstrates its high anti-corrosion properties. Acid-base corrosion tests further confirm the good resistance of the coating to an alkaline environment. Moreover, the coating exhibits anti-freezing adhesion and self-cleaning properties, surpassing the bare brass. The combined characteristics of the biomimetic calcium carbonate SHS coating highlight the promising potential in corrosion protection applications. Full article

Hydrophobic and superhydrophobic surfaces have emerged as key solutions for fluid transport, biofouling prevention, and energy efficiency, with market forecasts projecting a compound annual growth rate (CAGR) of over 15% through 2030 due to their broad range of applications. This review critically examines the principles of natural hydrophobicity, as exemplified by lotus leaves and shark skin, and their translation into engineered surfaces via micro/nanofabrication techniques, such as laser patterning, etching, and self-assembly. Recent advances in hybrid nanomaterials have demonstrated WCAs in the range of 140–160°, along with enhanced mechanical strength and chemical stability, enabling applications in self-cleaning, anti-corrosion, and oil–water separation technologies. Superhydrophobic coatings are particularly important for reducing ice adhesion by more than 80%, while drag reduction in pipelines can reach up to 30%, contributing to energy savings. Despite these advances, challenges remain in achieving long-term stability under harsh environmental conditions, minimizing environmental impact, and developing cost-effective, scalable fabrication techniques. Future directions focus on environmentally friendly, multifunctional nanocomposites with switchable wettability, including pH- and light-responsive coatings capable of reversibly transitioning between superhydrophilic (<5°) and superhydrophobic (>150°) states, paving the way for sustainable and adaptable surface technologies. Full article

Superhydrophobic materials offer promising prospects for utilization in energy, environmental, and related fields. However, their long-term stability in natural environments is constrained by factors such as mechanical wear and aging, which compromise their practical effectiveness and service life. While notable experimental results have been obtained worldwide, scalable application remains limited by the complexity of the requisite fabrication processes. In this study, a durable superhydrophobic coating was developed through a facile one-step process, utilizing a polyaspartic ester (PAE) matrix reinforced with a composite of self-synthesized fluorinated silica (F-SiO₂) and hexagonal boron nitride (h-BN) micro-/nano-structures. This strategy effectively enhanced filler dispersion within the resin matrix and promoted hydrophobicity, yielding a stable superhydrophobic surface. The resulting coating exhibits significant potential for scalable application. The optimized coating demonstrated a water contact angle of 161.2° and a roll-off angle of 7.6°, showing excellent repellency to water, corrosive liquids, and fluids across a wide pH range, along with remarkable self-cleaning performance. Benefiting from the synergistic enhancement of h-BN and F-SiO₂, the coating also exhibits superior mechanical durability, maintaining a contact angle of 144.4° after 1000 abrasion cycles. Furthermore, in low-temperature anti-icing tests, the coating significantly delayed ice formation on its surface. Notably, after 1000 h of UV aging tests, the F-SiO₂@BN/PAE coating retained its intact superhydrophobic structure, with the water contact angle only slightly decreasing from 159.6° to 152.8°, still within an excellent superhydrophobic state, demonstrating outstanding weather resistance. By integrating surface functionalization with mechanical reliability through a facile one-step fabrication process, this study provides significant insights for the large-scale application of hydrophobic materials in the energy and transportation sectors. Full article