Search Results (2,067)

Polydopamine (PDA) is a promising biomimetic material, but its structural complexity hinders rational control over its light absorption properties. The purpose of this study was to develop a simple post-synthetic method to tune the absorption spectrum of PDA using Bobbit’s salt (4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium salt) as a mild oxidant. Conventional PDA nanoparticles were treated with Bobbit’s salt either in pure water or in a 1:1 methanol–water mixture to obtain two modified samples. Structural analysis conducted using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and mass spectrometry demonstrated that Bobbit’s salt selectively oxidized catechol units to ortho-benzoquinone moieties, with the C–O/C=O ratio decreasing from 71:29 in the untreated PDA to 51:49 in the water-treated sample, while nitrogen functionalities remained unchanged. Consequently, the sample prepared in pure water showed generally lower absorbance across the visible–near-infrared range, whereas the sample prepared in the methanol–water mixture exhibited enhanced ultraviolet absorption but reduced near-infrared absorption. When coated onto polyvinylidene fluoride membranes, the water-treated PDA produced a brighter and more reddish-yellow appearance. On transparent poly(methyl methacrylate) substrates, the same coating also enhanced ultraviolet blocking and reduced visible transmittance. These findings conclude that Bobbit’s salt is an effective and selective reagent for tailoring the optical properties of PDA, with potential applications in protective coatings and light-modulating materials. Full article

Modern scanning microscopes and robotic scanning systems increasingly use visual recognition and machine learning technologies to extract complex data from acquired images. This study examined sensor data fusion in optical imaging to detect and control the deviation of the position of the tool during various micro-manipulations for biologic and microscale engineering. The sensor data fusion study was performed using a scanning micro-robotic system with an integrated optical microscope and a vision sensor providing an image of the object’s bottom. The bottom vision sensor is a typical complementary metal–oxide–semiconductor sensor that is used to observe micrometer-sized semi-transparent objects. The challenge for sensor fusion in such a study is not only data fusion, but also the trajectory deviation inherent in directing the manipulator in the X and Y directions according to the selected trajectory. The data fusion method was applied to estimate deviations from the given trajectory of the scanning microscope. The unique novelty of this work is that an additional vision sensor is used to increase the accuracy of positioning determination of a scanning micro-robotic system, placed under the semi-transparent object, using the fusion of the obtained data, thus additionally controlling the objective deviations. By testing several known data fusion methods, a unique solution was achieved. The proposed sensor fusion method achieved a positioning accuracy of less than 0.5 μm at speeds up to 5 mm/s. Experimental results demonstrate that the system maintains high stability. This quantitative performance proves the system’s suitability for high-precision biological micro-manipulation, where mechanical drift was previously a limiting factor. Full article

Nanoimprint lithography (NIL) is highly dependent on imprinted film as a pattern-transfer medium. This paper systematically reviews the research progress of imprint film materials for NIL. Firstly, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polyvinyl alcohol (PVA) and other single-polymer films are discussed, and their respective advantages (such as low surface energy, high optical transparency, water solubility) and inherent limitations (elastic deformation, demolding difficulties, humidity sensitivity)) are summarized. In order to overcome the above contradiction, researchers developed a composite imprint film structure, including an elastomer–rigid bilayer template and sandwich structure film, which achieved high resolution, conformal contact and facile demolding characteristics through mechanical function decoupling. At the same time, the emerging polymer/transparent electrode composite system (such as AgNWs/PVA, AgNWs/PDMS) gives the film active functions such as self-heating and antistatic ones, which effectively solves the key challenges in thermal management and electrostatic control. This paper comprehensively presents the evolution path from single-material to multi-functional composites, and provides guidance for the design of advanced imprint film for high precision, high reliability and large-scale NIL applications. Full article

Integrating semi-transparent photovoltaics (STPVs) into greenhouses offers a dual-use solution for land efficiency, although matching electricity generation with crop spectral needs remains a challenge. To address this, this study assesses the optical and microclimatic impact of Cadmium Telluride (CdTe, 50% transparency) and amorphous Silicon (a-Si, 20%) technologies compared to a conventional control in a semi-arid Mediterranean climate. Spectral analysis revealed that CdTe aligned with chlorophyll absorption peaks, preserving a transparency window that yielded a 66% relative gain in biologically useful radiation over the blue-blocking a-Si. Furthermore, while both technologies significantly reduced Photosynthetically Active Radiation (PAR), this shading served as a protective filter against supra-optimal irradiance, stabilizing the internal microclimate. In the control prototype, extreme vapour pressure deficits (VPDs approaching 9.0 kPa) drove maximum reference evapotranspiration (ET₀) above 4.6 mm/day. In contrast, the STPV systems effectively capped ET₀ at approximately 3.09 mm/day (CdTe) and 1.64 mm/day (a-Si) through their radiative attenuation, despite internal VPDs still reaching 6.5–7.0 kPa during peak summer. This decoupling resulted in drastic average ET₀ reductions of 31.4% and 61.3%, respectively, while mitigating soil overheating by up to 17.8%. These findings demonstrate that specific STPV technologies transcend mere shading to function as passive climate resilience tools, naturally enforcing water conservation and physically disarming atmospheric aridity in high-radiation environments. Full article

Co²⁺-doped CsPbI₃ nanocrystals (NCs) (CsPbI₃:xCo, x = 0, 5, and 10 mol%) were synthesized in situ within a borosilicate glass matrix by the fusion method followed by controlled thermal treatment at 500 °C for 6–24 h. Transmission electron microscopy images showed quasi-spherical NCs with mean diameters of 4.9–7.1 nm. Energy-dispersive X-ray spectroscopy suggested cobalt incorporation within the nanocrystalline regions. X-ray diffraction patterns confirmed the exclusive stabilization of the cubic α-phase across all compositions, with systematic lattice contraction from a = 6.321 Å to a = 6.301 Å with increasing Co content, consistent with preferential B-site substitution of Pb²⁺ by Co²⁺. Transmittance measurements confirmed macroscopic optical transparency of all glass-NC composites after thermal treatment. The crystal field theory and Tanabe–Sugano analysis for d⁷ ions in tetrahedral (Td) symmetry yielded Δ = 5032 cm⁻¹ and B = 725 cm⁻¹ in the as-prepared state, evolving to Δ = 4428 cm⁻¹ and B = 805 cm⁻¹ after thermal treatment, confirming Td Co²⁺ coordination and significant metal–iodide covalency. CIE 1931 chromaticity analysis revealed tunable emission from deep-red coordinates to near-white-light regions, demonstrating potential for LED and single-material WLED phosphor applications. Long-term photoluminescence measurements demonstrated full preservation of α-phase excitonic emission after approximately 365 days under ambient conditions, establishing the robust phase stability of CsPbI₃:xCo NCs embedded in borosilicate glass. Full article

Quantitative characterization of internal stress fields in fracture-dominated geological materials remains a significant challenge due to the limitations of conventional measurement techniques. This study presents the first quantitative full-field stress analysis of slightly sandy dolomite (Level I sandification) using an enhanced CT-3D printing–photoelasticity workflow. Five transparent physical models were fabricated from CT-scanned dolomite specimens to replicate the natural fracture-matrix structure and tested under diametrical compression (800 N) using ten-step phase-shifting digital photoelasticity. To overcome the severe optical noise generated by dense fracture networks, a robust phase unwrapping procedure (CPULSI) was incorporated into the data processing pipeline, enabling continuous stress parameter retrieval where conventional unwrapping methods fail. The recovered full-field principal stress-difference maps reveal that the internal stress field is dominated by meso-scale fracture geometry: Stress concentrations localize at fracture tips and narrow intact matrix bridges, reaching 3–5 times the far-field stress, while the macro-scale loading pattern becomes progressively obscured as fracture complexity increases across the five models. Quantitative validation against CT-based finite element simulations (RFPA-3D) demonstrates good agreement in intact matrix regions, with mean relative errors of 9–18%. These results provide new experimental evidence for the meso-scale stress distribution mechanisms governing the mechanical behavior of sandy dolomite—a geomaterial of significant engineering relevance in Southwest China—and establish a validated experimental pathway for investigating stress fields in other fracture-dominated geomaterials. Full article

The use of conventional plastics represents a major environmental concern, as approximately 79% ultimately accumulate in landfills or natural ecosystems. Consequently, there is growing interest in the development and application of renewable materials for food packaging. Therefore, the aim of this study was to develop and characterise gelatine-based hydrogels through the incorporation of two amino acids, cysteine and glutamine, thereby contributing to the advancement of safe and environmentally responsible materials. The hydrogels were prepared using the casting method and characterised in terms of their physical and structural properties. The results indicated that the addition of cysteine and glutamine significantly modified the structural, optical, thermal and barrier properties of the gelatine films and hydrogels. Cysteine produced materials with increased opacity, brownish hues and a more hydrophobic surface, changes attributed to the formation of disulphide bonds and the redistribution of non-polar functional groups towards the surface. In contrast, glutamine yielded more transparent and homogeneous films with a more intact internal structure, owing to the development of a more effectively cross-linked and stable polymeric network. Structural (XRD, FTIR) and thermal (TGA, DSC) analyses confirmed that glutamine enhances thermal stability and molecular cohesion, whereas cysteine increases the more ordered structure and rigidity of the matrix. The selection of an appropriate amino acid thus enables the tailoring of functional properties in these biopolymers, representing an effective strategy for their adaptation to biodegradable packaging applications. Full article

Bilayer scattering films offer a practical route to independently controlling transmission and reflection in transparent optical systems, yet the separate roles of nanoparticle loading and stacking order remain underexplored. In this work, Al₂O₃/poly(methyl methacrylate) bilayer films with four concentration pairs (5/15, 15/5, 5/30, and 9/30 wt%) were fabricated by sequential spin-coating and characterized by wavelength-dependent transmittance, reflectance, integrating-sphere haze decomposition, and optical surface interferometry under both glass-side (G-incident) and scattering-layer-side (SL-incident) illumination. Two independent design parameters govern the optical response: (i) the maximum nanoparticle concentration sets the overall scattering regime, and (ii) the layer stacking order controls the partitioning between parallel transmittance (PT) and diffuse transmittance (DT). Bilayers with a maximum loading of 15 wt% maintained total transmittance (TT) ≈ 99% and moderate haze (25%–40%), while reciprocal 5/15 and 15/5 wt% pairs exhibited a ~15 percentage-point shift in PT despite identical total loading. Incorporation of a 30 wt% layer shifted films into a diffusion-dominant regime (DT > 68%, haze > 70%), and positioning this layer at the incident side under SL illumination suppressed visible reflectance below 1%. These results provide a practical composition–sequence design map for transparent optical coatings in display, privacy, and anti-glare applications. Full article

DNA methylation is a fundamental epigenetic modification that regulates gene expression, genome stability, and cell identity across vertebrate development. Disruption of DNA methylation homeostasis contributes to a wide spectrum of human diseases, including developmental disorders, neurological conditions, and cancer. Understanding how DNA methylation patterns are established, maintained, and dynamically remodeled during development is therefore essential for elucidating disease mechanisms and identifying therapeutic opportunities. The zebrafish (Danio rerio) has emerged as a powerful vertebrate model for investigating DNA methylation dynamics in vivo. Its external fertilization, optical transparency, rapid embryogenesis, and high fecundity enable direct observation and experimental manipulation of epigenetic processes at developmental stages that are difficult to access in mammalian systems. In addition, the core enzymatic machinery governing DNA methylation, including DNA methyltransferase (DNMT) and ten-eleven translocation (TET) protein families, is evolutionarily conserved between zebrafish and humans. In this review, we summarize current knowledge of the zebrafish methylome and the enzymatic regulators that control DNA methylation dynamics. We discuss how DNA methylation shapes early embryonic development, organogenesis, and cell fate decisions, and highlight insights gained from zebrafish models of human disease. Finally, we examine emerging technologies that are enabling increasingly precise interrogation of epigenetic regulation in vivo. Together, these advances position zebrafish as an important platform for bridging developmental epigenetics with human disease biology and therapeutic discovery. Full article

Background: Zebrafish (Danio rerio) embryos are transparent in early stages of embryonic development; however, pigment formation at later stages hinders internal organ visualization during imaging. Chemicals such as 1-phenyl-2-thiourea (PTU) and kojic acid, used to block pigmentation, pose significant toxicity risks to human health. Therefore, effective and risk-free depigmentation agents are needed. This study investigates the efficacy of Alchemilla vulgaris (Lady’s mantle) as a safe, natural alternative for zebrafish embryo depigmentation. Methods: A. vulgaris was extracted using four solvents of varying polarities and evaluated for depigmentation efficacy and toxicity. Gas chromatography–mass spectrometry (GC–MS) was used to identify major constituents of the extract. Results: Ethyl acetate extract was more effective at removing pigments than all other extracts, and exhibited the lowest toxicity compared to PTU and kojic acid. Ethyl acetate extract of A. vulgaris remained effective even when administered 48 h post fertilization (post-pigmentation), making it suitable for long-term experiments requiring optical clarity. GC-MS revealed that this extract was rich in linoleic acid, various fatty acid esters, and phenolics, which likely contributed to its depigmentation activity. Conclusions: Based on these findings, we propose that ethyl acetate extract of A. vulgaris is a safer, natural alternative to PTU and kojic acid for depigmenting zebrafish embryos, particularly in long-term imaging experiments. The extract exhibits high efficacy at low concentrations, accompanied by a favorable toxicity profile, demonstrating potential as a depigmentation agent during early zebrafish development. However, further studies are needed to elucidate its mechanism of action. Full article

This study presents unique polymeric materials applicable to plastic substrates for use in flexible-display devices that overcome the trade-off between low linear coefficients of thermal expansion (CTE) and low thickness-direction birefringence (Δn_th) while combining a very high T_g, sufficiently high thermal stability, excellent optical transparency, good solubility, and minimum-required ductility. Polyimide (PI) films obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) with 2,2′-bis(trifluoromethyl)benzidine (TFMB) under different conditions resulted in widely varying CTE values and provided a clear CTE–Δn_th correlation, which can be regarded as a virtual lower boundary in the CTE–Δn_th relationship for various PI systems. The pristine CBDA/TFMB and CpODA/TFMB (CpODA = norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride) systems were modified using numerous specifically designed monomers, i.e., a vertical-alignment-type liquid-crystalline diamine and cardo-type and spiro-type monomers. However, it was very challenging to overcome the trade-off between low CTE and low Δn_th, that is, to significantly exceed this lower boundary by modifying the pristine systems, while ensuring other target properties. One of the keys to achieving the present goal was compatibility with chemical imidization or one-pot polymerization processes (i.e., high solubility of the PIs), because these processes were more advantageous in reducing CTE and enhancing film transparency than the conventional two-step process. The modifications using phenyl-substituted xanthene-pendant 2,7-diaminofluorene and fluorene-pendant 2,3,6,7-xanthenetetracarboxylic dianhydride exhibited a prominent effect on overcoming the trade-off without the help of any fillers, while combining other excellent target properties. Polarized FT-IR difference spectra measured at varying incidence angles suggested that these side groups, which are connected perpendicularly to the PI main chains, align in the Z-direction, rationalizing the observed prominent effect. Thus, unique high-temperature transparent materials applicable to plastic substrates were successfully obtained in this study. Full article

Gem-quality garnets exhibit significant potential for U-Pb geochronological applications due to their advantageous characteristics, including high closure temperatures (750–850 °C), optical transparency, chemical homogeneity, and low inclusion content. This study focuses on the gem-quality yellow-green grossular garnet variety (commonly termed Mali garnet), a unique gemstone exclusively occurring in contact metamorphic deposits of Western Africa’s Republic of Mali. Despite its mineralogical significance, fundamental aspects, including precise age determination and chromophore mechanisms of Mali garnet, remain poorly constrained. Here, we conducted standard gemological characterization, spectroscopic analyses (UV–Vis, FTIR, and Raman), electron probe microanalysis (EPMA), micro-X-ray fluorescence (μ-XRF) elemental mapping, and in situ trace element and laser ablation U-Pb geochronological analysis on Mali garnets. The spectral data and chemical composition studies reveal that the coloration of Malian garnets is primarily attributed to the presence of iron and chromium. Our U-Pb geochronological results yield a crystallization age of 197 ± 3 Ma for the Mali garnet samples. The robustness of garnet U-Pb systems in preserving crystallization ages through multiple thermal events supports their application to Precambrian polymetamorphic terranes, where zircon systems are frequently reset. Full article

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (₀₀₂) orientation for all compositions, indicating the successful substitution of Mg²⁺ ions into the ZnO lattice. The crystallite size (D₀₀₂) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn_1−xMg_xO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices. Full article

In this study, electrospun poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) biopapers were produced by annealing electrospun fiber mats from two commercial grades (151C and X131A) and compared with films prepared by the conventional melt-mixing/compression molding method. To obtain continuous biopapers, the fiber mats were subjected to mild thermal post-processing at various temperatures. The selected annealing temperatures were 140 °C (151C) and 130 °C (X131A), where interfiber coalescence occurred within a short annealing time (10 s), yielding continuous fibrous films (biopapers). To elucidate the structural mechanisms underlying interfiber coalescence, time-resolved synchrotron SAXS/WAXS and temperature-dependent FTIR spectroscopy were performed. These analyses showed that coalescence occurred through an interplay between thermally induced local ordering at sub-melting temperatures and premelting/partial melting of thin, ill-defined lamellae, with grade-dependent contributions. The resulting biopapers were evaluated against compression-molded films for optical, mechanical, and barrier properties relevant to packaging. All samples showed similar transparency, although compression-molded films were slightly more opaque. The lower-rigidity grade (151C) exhibited more ductile and tougher behavior than X131A. Biopapers showed slightly lower water and oxygen barrier performance than compression-molded films, attributed to differences in material compactness. Overall, brief mild annealing after electrospinning enabled continuous PHBH biopapers with balanced properties, supporting their potential for sustainable PHBH-based food-packaging applications. Full article

The rapid expansion of wireless communication in urban environments requires antenna systems that balance high electromagnetic performance with stringent aesthetic and security constraints. This review examines recent advances in concealed antenna technologies integrated into building structures, with a focus on performance variation, material-induced attenuation, and emerging concealment strategies. Techniques such as transparent conductors on glass, structural embedding within walls, and camouflage-based designs are shown to significantly influence resonance behavior, radiation efficiency, and pattern characteristics compared to free-space operation. Despite these challenges, optimized solutions including transparent conductive oxide arrays, wideband embedded antenna geometries, and metasurface-enhanced window structures can partially recover performance while maintaining optical transparency above 70%. Material loading effects are found to induce resonant frequency shifts of approximately 10–44%, depending on dielectric properties and environmental conditions. Transparent antenna arrays achieve gains ranging from 0.34 to 13.2 dBi, while signal-transmissive wall systems demonstrate transmission improvements of up to 22 dB relative to untreated building materials. These technologies enable a wide range of applications, including 5G and beyond-5G cellular networks across sub-6 GHz and millimeter-wave bands, as well as Internet of Things systems and smart city infrastructure. However, key challenges remain, including the need for comprehensive characterization of building material electromagnetic properties, optimization of multilayer structural environments, and the development of standardized design and evaluation methodologies. This review provides a unified framework for understanding the tradeoffs associated with antenna concealment and identifies critical research directions for the development of building-integrated wireless systems in next-generation communication networks. Full article