Search Results (450)

Cutaneous leishmaniasis is a zoonotic disease caused by Leishmania parasites and leads to chronic, non-healing skin lesions. Although current drugs can control the disease, their use is limited by systemic side effects, low efficacy, and inadequate lesion penetration. Therefore, innovative local delivery systems are required to enhance drug penetration and reduce systemic toxicity. To address these challenges, silver nanoparticles (AgNPs) were synthesized using propolis extract through a green synthesis approach, and a tri-layer wound dressing composed of polyvinyl alcohol and gelatin containing synthesized AgNPs and Glucantime was fabricated by electrospinning. Characterization (SEM-EDX, FTIR, TGA) confirmed uniform morphology, chemical structure, and thermal stability; the wound dressing exhibited hydrophilicity, antioxidant activity, and biphasic release. Biological evaluations against Leishmania tropica demonstrated significant antiparasitic activity. Promastigote viability decreased from 76.3% in neat fibers to 31.6% in nanofibers containing AgNPs and 7.9% in tri-layer nanofibers containing both AgNPs and Glucantime. Similarly, the amastigote infection index dropped from 410 in controls to 250 in neat nanofibers, 204 in AgNPs-containing nanofibers, and 22 in tri-layer nanofibers containing AgNPs and Glucantime. The tri-layer nanofibers demonstrated enhanced antileishmanial activity over AgNPs-containing fibers, confirming synergistic efficacy. All nanofibers were biocompatible, supporting their use as a safe platform for cutaneous leishmaniasis treatment. Full article

Double-shell ZnO/Al₂O₃ submicron hollow fibers were successfully fabricated through a combined electrospinning and atomic layer deposition (ALD) approach. Polyvinyl alcohol (PVA) fibers were first produced by electrospinning and subsequently coated with a conformal Al₂O₃ barrier layer via low-temperature ALD employing trimethylaluminum (TMA) and deionized (DI) H₂O to preserve the integrity of the temperature-sensitive polymer core. The inner polymer was then removed using two different techniques—thermal annealing and water dissolution—to compare their effects on the fiber morphology. Finally, a functional ZnO layer was deposited by thermal ALD with diethylzinc (DEZ) and DI H₂O. It was found that the polymer removal method critically determined the final structural and morphological characteristics of the fibers. Thermal annealing resulted in smooth, shrunken fibers, while water dissolution led to diameter expansion and the formation of a highly rough, bubble-like surface structure due to swelling-induced micro-cracking. The selection of the polymer removal method offers a precise and controllable route for tailoring the fiber morphology. The resulting high-aspect-ratio (HAR) structures, particularly the rough and expanded fibers, exhibit enhanced specific surface area, making them highly promising for applications in sensing, catalysis, and filtration. Full article

This study focuses on the development of antibacterial polymer nanocomposites based on biologically synthesized silver nanoparticles (AgNPs) and polyvinyl alcohol (PVA) as the polymer matrix. Silver nanoparticles were produced using an aqueous extract from dried Lavandula angustifolia (lavender) leaves, which proved to be highly effective in reducing silver ions and stabilizing the resulting nanoparticles. The synthesized AgNPs were characterized by FTIR, UV-Vis, TEM, SEM, and DLS analyses. The nanoparticles were predominantly spherical, with more than 70% having diameters below 20 nm. Subsequently, AgNPs were incorporated into the PVA matrix via an ex situ approach to fabricate nanocomposite fibers and thin films. SEM analysis confirmed successful incorporation and uniform distribution of AgNPs within the polymer structures. The nanocomposites exhibited pronounced antibacterial activity against both Gram-positive (Staphylococcus aureus, Staphylococcus haemolyticus, Streptococcus uberis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, with nanofibers demonstrating superior performance compared to thin films. These findings highlight the potential of lavender-extract-mediated AgNPs as sustainable functional fillers for the fabrication of eco-friendly antibacterial materials applicable in biomedical and food packaging fields. Full article

In this paper, a highly ductile polyvinyl alcohol fiber engineered cementitious composite (PVA-ECC) was developed by replacing quartz sand (QS) with tuff stone powder (TP) at different replacement ratios of 20%, 40%, 60%, 80%, and 100%. The resulting mechanical properties and drying shrinkage were determined for the developed ECC. Qualitative and quantitative analyses of hydration products, pore structure, and micro-morphology of ECC were conducted by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, pore size and porosity, and scanning electron microscopic imaging. The influencing mechanism of tuff stone powder content on ECC performance was also studied at a micro level. It was found that with the increase in the replacement ratio of tuff stone powder, the ultimate tensile strain and tensile peak stress of ECC all exhibited an increasing trend, which declined afterward. The variation in compressive and flexural strengths also showed a similar pattern. When the replacement ratio of tuff stone powder was 40%, the ultimate tensile strain, peak tensile stress, flexural strength, and compressive strength were higher than the control group by 15.1%, 4.7%, 16.3%, and 10.7%, respectively. When the content of tuff stone powder did not exceed 80%, it could fill the internal pores of the ECC matrix, which reduced harmful pores. With the increase in tuff stone powder content, calcite content increases gradually while the Ca(OH)₂ amount decreases. It can be seen that tuff stone powder can improve ECC hydration products. However, incorporating tuff stone powder does not produce new hydration products. Incorporating tuff stone powder increased the drying shrinkage of ECC, and the value of drying shrinkage increased with the increase in the replacement ratio of tuff stone powder. Full article

To develop a cost-effective shape memory alloy fiber-reinforced engineered cementitious composite (SMAF-ECC) with excellent mechanical properties, polypropylene (PP) fibers were used to partially replace polyvinyl alcohol (PVA) fibers to prepare the ECC matrix, and superelastic shape memory alloy fibers (SMAFs) were incorporated to fabricate a novel SMAF-ECC. Uniaxial tensile tests were systematically performed to characterize the tensile mechanical properties of the composites, focusing on the effects of SMAF volume content and diameter. The results indicate that the optimal base ECC mix proportion is 0.8 vol.% PP fibers and 1.2 vol.% PVA fibers, achieving an ultimate tensile strain of 4.88% (only a 4.69% reduction compared to pure PVA-ECC) while significantly reducing material cost without sacrificing superior ductility. SMAF volume content and diameter notably influence the tensile performance of SMAF-ECC, with the specimen containing 0.2 mm diameter SMAFs at 0.2 vol.% exhibiting the best performance: initial cracking stress, ultimate tensile stress, and ultimate tensile strain are enhanced by 16.79%, 20.85%, and 2.87%, respectively, compared to pure ECC. This study provides a theoretical basis and parametric guidance for the engineering popularization and application of cost-effective SMAF-ECCs. Full article

Mechanical damage and microbial contamination are major challenges in the postharvest logistics of perishable fruit. In this study, two types of functionally modified chitosan-based aerogel pads were developed to enhance cushioning and preservation of wax apples. A chitosan/polyvinyl alcohol (CP) aerogel was first optimized by adjusting solid content, CS:PVA ratio, and crosslinker concentration. The optimal formulation (2% solids, 1:1 CS: PVA, 3% glutaraldehyde) exhibited a uniform porous structure and improved compressive strength. A chitosan/montmorillonite (CM) aerogel with 5% montmorillonite (MMT) showed high porosity, low density, and excellent cyclic stability. Incorporating 10% copper nanoparticle-loaded antibacterial fibers (CuNPs-TNF) into CM aerogels yielded CM-Cu aerogels with enhanced cushioning and antimicrobial properties. Under simulated transport and cold storage conditions, all aerogel-packaged groups reduced mechanical damage and decay of wax apples. Compared to the control, the CM-Cu group showed 66% lower decay, 5% less weight loss, 6 N greater firmness, 7% less juice yield, and a 13% reduction in relative electrical conductivity. Additionally, it better preserved fruit color and total soluble solids, extending shelf life by 4 d at 20 °C. These results demonstrate the potential of chitosan-based aerogels as multifunctional packaging materials that combine mechanical protection with antimicrobial activity for perishable fruit preservation. Full article

To investigate the fracture behavior of super-absorbent polymer (SAP) internally cured polyvinyl alcohol (PVA) fiber-reinforced concrete (SAP-PVAC), three-point bending tests were carried out. This study systematically examined the effects of (1) PVA fiber content and (2) initial crack-depth-to-beam-height ratios (a₀/D) on the failure modes, fracture toughness (K_IC), and residual flexural tensile strength (f_R,1) of SAP-PVAC beams. The test results demonstrate that SAP particles have a weakening effect on concrete strength (reduce about 6%). Still, the addition of PVA fibers can effectively improve the crack-resistance performance of SAP-PVAC and significantly increase the residual flexural tensile strength by 4.5–42%. The softening performance of the concrete is affected by the initial crack-height ratio. An increase in a₀/D leads to an obvious increase in the crack opening displacement but has little impact on the fracture toughness, while the fracture energy shows a downward trend. SEM microscopic analysis reveals that the synergistic effect of SAP and PVA fibers exhibits a positive promoting effect on the toughening and crack resistance of SAP-PVAC specimens. These results establish a theoretical framework for SAP-PVAC fracture assessment and provide actionable guidelines for its shrinkage-crack mitigation structure engineering applications. Full article

Electrospun polymeric nanofibers have emerged as promising materials for wound management owing to their high surface area, efficient exudate absorption and gas exchange, and extracellular-matrix-like architecture. This study investigates the fabrication of nanofiber dressings from poly(vinyl alcohol) (PVA) and hyaluronic acid (HA), prepared by fully aqueous electrospinning (without organic solvents) for potential wound-care applications. HA incorporation is expected to influence hydration and matrix interactions, properties that have been associated with modulation of wound healing in previous studies. However, the high solubility of PVA-based NFs in aqueous environments limits their use in biological applications. To address this issue, PVA/HA nanofibers were chemically crosslinked through a solid-state esterification process at 150 °C using biocompatible citric acid (CA). The electrospinning parameters were optimized to obtain PVA/HA fibers with diameters ranging from 130 to 200 nm, which were assembled to form mats with different porosity and intersection density. FTIR confirmed the formation of ester bonds, while DSC analysis showed an increase in Tg from 41 °C to about 55 °C and a slight decrease in Tm after crosslinking. Swelling and degradation analyses demonstrated a significant enhancement in hydrolytic stability, as the weight loss of the nanofiber mats decreased from ~90% in the non-crosslinked samples to less than 10% after 2 h of crosslinking. Dynamic mechanical analysis (DMA) showed an increase in Young’s modulus from ~70 MPa to 230 MPa after crosslinking. Overall, the results demonstrate the stabilizing effect of citric-acid crosslinking on PVA/HA nanofibers and support their potential use in wound dressings under physiological conditions. Full article

A polyvinyl alcohol (PVA)-coated optical fiber humidity sensor for respiratory monitoring is proposed. The humidity sensor forms a fiber Mach–Zehnder interferometer (MZI) by bending the single-mode fiber (SMF) coated with PVA. The refractive index of PVA coatings varies with changes in relative humidity (RH), causing phase changes in higher-order modes and resulting in shifts in the transmission spectrum. The sensor exhibits excellent dynamic humidity response performance (92.8 ms for response time and 63.6 ms for recovery time), realizing a humidity sensitivity of −1.927 nm/%RH within the humidity range of 86.1% to 92.2%. Compared to the balloon-shaped fiber optic sensor based on polydimethylsiloxane (PDMS) coating previously proposed by our research group, the PVA coating facilitates easier surface composite on the fiber, exhibits faster response speed, and its humidity response range is more suitable for respiratory monitoring. Ultimately, the sensor was encapsulated within a mask to enable human respiration monitoring functionality. Full article

Relative humidity (RH) and temperature are crucial parameters in environmental monitoring and have attracted significant attention. However, traditional commercial sensors typically suffer from inherent limitations such as structural complexity, bulkiness, and high manufacturing costs. To address these issues, this study proposes a novel tilted fiber Bragg grating (TFBG)-based optical fiber humidity sensor, coated with a composite film of polyvinyl alcohol (PVA) and graphene oxide (GO). First, the sensing mechanisms of the TFBG functionalized with nanofiber films were theoretically analyzed, and the transmission spectra of TFBG under varied structural parameters were simulated. These theoretical investigations laid a solid foundation for subsequent experimental validation. Subsequently, PVA/GO composite nanofiber films tailored for humidity sensing were fabricated by electrospinning technology, and the proposed TFBG sensor was experimentally implemented in accordance with the theoretical design. The experimental results indicate that the developed sensor exhibits a humidity sensitivity of −0.24 pm/%RH within the RH range of 35–85%. Furthermore, we calculated temperature and RH changes while discounting cross-sensitivity, thereby enabling simultaneous decoupling of temperature and RH measurements. Owing to its distinctive advantages of compact size, light weight, and cost-effectiveness, the proposed TFBG sensor holds great promise for practical applications in environmental monitoring. Full article

Building structures are inherently susceptible to damage from extreme dynamic loads, while conventional concrete exhibits inadequate tensile resistance. While hybrid fibers systems can surpass the limitations of single-fiber reinforcement through their synergistic action, their internal damage mechanisms under impact loading remain inadequately understood. This study investigates the dynamic splitting behavior of hybrid fibers-reinforced cementitious composites combining polyvinyl alcohol (PVA) with either steel (SF) or polyethylene (PE) fibers, using Split Hopkinson Pressure Bar (SHPB) tests at strain rates of 5–31 s⁻¹, along with industrial CT scanning for meso-scale damage analysis. Results indicate that the SF–PVA hybrid improved strength by up to 15.6% compared to mono-PVA, while the PE–PVA hybrid achieved an 11.1% increase. All hybrid systems exhibited improved energy dissipation (which rose 25–45% with strain rate) and displayed secondary stress peaks. Quantitative CT analysis revealed distinct damage patterns: the mono-PVA specimen developed extensive damage networks (porosity: 7.20%; crack ratio: 4.48%), the SF-PVA hybrid system displayed the lowest damage indices (porosity: 3.29%; crack ratio: 1.76%), whereas the PE-PVA hybrid system exhibited the most significant dispersed damage pattern (crack-to-pore ratio: 39.32%). The hybrid systems function via distinct mechanisms: SF–PVA offers multi-scale reinforcement and superior damage suppression, whereas PE–PVA enables sequential energy dissipation, effectively dispersing concentrated damage. These insights support tailored fiber hybridization for impact-resistant structural design. Full article

Traditional concrete materials have limitations in terms of load-bearing capacity and ductile failure. In contrast, Engineered Cementitious Composites (ECCs), with their superior strain-hardening behavior and multiple cracking characteristics, have attracted widespread attention in the field of high-performance materials. In this study, ECC specimens incorporating different types of fibers (polyethylene (PE) fibers, polyvinyl alcohol (PVA) fibers) at varying contents were tested to systematically analyze their influence on mechanical properties. Compressive, flexural, and uniaxial tensile strength tests were conducted to evaluate the mechanical performance of ECCs. In addition, scanning electron microscopy (SEM) was employed to examine the fracture surfaces of the fibers, providing deeper insights into the interfacial behavior and fracture morphology of the different fiber-reinforced systems. Fracture surface analysis reveals that the interfacial bonding characteristics between different fibers and the matrix significantly influence fracture behavior. Moreover, as the tensile performance of ECCs is influenced by the interaction of multiple factors, traditional constitutive models exhibit limitations in accurately predicting its complex nonlinear behavior. To address this limitation, an Artificial Neural Network (ANN) approach was adopted to develop a predictive model based on bilinear stress–strain relationships. The model was constructed using ten key input parameters, including matrix composition and fiber properties, and was able to accurately predict the first cracking strain, first cracking stress, ultimate strain, and ultimate stress of ECCs. Sensitivity analysis revealed that fiber tensile strength and fiber content were the most significant factors influencing the tensile behavior. The predicted tensile curves showed strong consistency with the experimental results, thereby confirming the reliability and applicability of the proposed ANN-based model. Full article

The barrier membrane is a key component in guided bone regeneration (GBR); however, there is no current commercially available membrane universally suitable for all clinical situations. The semi-resorbable bioactive barrier membrane derived from a silk fiber sheet (SF), polyvinyl alcohol (PVA), and biphasic calcium phosphate (BCP) was fabricated to provide improved physical, mechanical, and bioactive properties. There were four experimental groups: PVA/SF, 1BCP/PVA/SF, 3BCP/PVA/SF, and 5BCP/PVA/SF. All fabricated membranes appeared white in color with a smooth texture; however, SEM images revealed a rougher top surface compared to the bottom surface. FTIR and DSC validated the presence of the SF and PVA with or without BCP. All membranes displayed high hydrophilicity, except the PVA/SF group, which remained hydrophobic on the bottom surface. The water uptake of all groups reached the plateau phase within 10 min. The degradation rate fell within the range of 5–20% over a three-month period. Both fibroblastic and osteoblastic cells attached and survived on the BCP-incorporated membranes, comparable to those observed in the commercially available ossifying collagen membrane. Among the fabricated membranes, the 3BCP/PVA/SF formulation demonstrated the most favorable physical, mechanical, and biological properties for GBR applications. Full article

This study presents a comprehensive investigation into the large-scale production of synthetic and hybrid (nanoparticle-loaded) nanofibers using needleless electrospinning. A diverse range of polymers, including polyamide 6 (PA6) and its other polymer combinations, recycled PA6, polyamide 11 (PA11), polyamide 12 (PA12), polyvinyl butyral (PVB), polycaprolactone (PCL), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyurethane (PU), polyvinyl alcohol (PVA), and cellulose acetate (CA), were utilized to fabricate nanofibers with tailored properties such as polymer solution concentrations and various solvent systems. Furthermore, an extensive variety of nano- and micro-particles, including TiO₂, ZnO, MgO, CuO, Ag, graphene oxide, CeO₂, Er₂O₃, WO₃, MnO₂, and hyperbranched polymers, were incorporated into the polymeric systems to engineer multifunctional nanofibers with enhanced structural characteristics. The study examines the impact of polymer–nano/micro-particle interactions, fiber morphology, and the feasibility of large-scale production via needleless electrospinning. The resulting nanofibers exhibited diameters starting from 80 nm, depending on the polymer and processing conditions. The incorporation of TiO₂, CeO₂, WO₃, Ag, and ZnO nanoparticles into 15% PA6 solutions yielded well-dispersed hybrid nanofibers. By providing insights into polymer selection, nano- and micro-particle integration, and large-scale production techniques, this work establishes a versatile platform for scalable hybrid nanofiber fabrication, paving the way for innovative applications in nanotechnology and materials science. Full article

Diabetic foot ulcers (DFUs) are complex to heal and can lead to amputations and high healthcare costs. To address this, a promising alternative is the creation of electrospun fiber scaffolds for wound dressings. This study fabricated these scaffolds using a blend of natural polymers—chitosan (CTS), polyvinyl alcohol (PVA), and hyaluronic acid (HA)—along with antibacterial silver (Ag) and zinc oxide (ZnO) nanoparticles. The researchers conducted comprehensive analyses, including physicochemical, morphological, and biological assessments. The Ag structures showed potential as microbicidal agent, while the ZnO nanoparticles demonstrated photoactivity and the ability to generate reactive oxygen species (ROS) for antibacterial action. The resulting PVA-CTS-HA-Ag-ZnO scaffolds were found to be both hemocompatible and non-hemolytic, meaning they are safe for use with blood. The cytotoxicity evaluation using the ISO 10993-5 standard showed that the incorporation of CTS and HA decreased cytotoxicity of pure PVA, obtaining non-cytotoxic scaffolds (viability > 70%). Electrospun scaffolds composed with Ag-ZnO NPs in 50-50 and 70-30 ratios also maintained this biocompatibility, while the 30-70 ratio (Ag-ZnO) showed a cytotoxic effect, suggesting a ZnO concentration-dependent effect. These findings confirm that these materials are suitable for supporting skin cell regeneration, having a high potential for use as interactive dressings for treating chronic wounds. Full article