Search Results (207)

Hybrid nanofluids combining thermally conductive nanoparticles with latent heat-storing nanocapsules have attracted growing interest for near-ambient liquid-based thermal management, yet direct comparisons between mono and hybrid phase-change-material-containing systems on a common experimental basis remain scarce. In this work, water-based mono Al₂O₃, mono polyurethane-nanoencapsulated n-nonadecane (PU-NEPCM), and Al₂O₃/PU-NEPCM hybrid nanofluids were prepared under identical surfactant, sonication, and dispersion conditions, and their thermal conductivity, dynamic viscosity, and Day-1 colloidal stability were characterized over 298–313 K at total volume fractions of 0.1, 0.3, and 0.5 vol.%, with the hybrids prepared at a 50:50 volumetric ratio. At 0.5 vol.% and 313 K, the hybrid (NFH3) exhibited the highest thermal conductivity enhancement (+8.27%), exceeding the corresponding mono Al₂O₃ and mono PU-NEPCM nanofluids by 4.6 and 5.2 percentage points, respectively, while maintaining a moderate viscosity penalty. The hybrid formulations also achieved |ζ| = 32–37 mV, exceeding the conventional electrostatic-stabilization threshold and outperforming both mono families. A two-factor analysis of variance (ANOVA) identified particle concentration as the dominant factor governing both properties (p < 0.001), with temperature becoming statistically significant only for the hybrid viscosity (p = 0.043). The synergy index varied between 0.85 and 1.43 across the tested conditions—reaching values of 1.20–1.43 for the lowest-loaded hybrid (NFH1)—while the performance index remained close to unity (0.97–1.01). These results identify low-loaded Al₂O₃/PU-NEPCM hybrid nanofluids as a balanced and stable candidate for near-ambient liquid-based thermal management applications. Full article

The self-formed rust layer is significant for weathering steels because their corrosion resistance in a marine atmospheric environment mainly relies on the stability, uniformity and compactness of the rust layer. However, the initial stage of rust formation is vulnerable and prone to being disturbed by the external environment, compromising the protectiveness of the rust layer at a later stage. Therefore, weathering steel often requires the application of rust stabilization techniques. This study has developed a waterborne polyurethane (WPU)-based coating incorporated with mesoporous/hollow SiO₂ nanoparticles, acting as the primary components for the construction of pathways for gaseous H₂O and O₂, as well as for Cl⁻ dissolved in moisture, while blocking liquid water. Salt spray was applied to accelerate the rust formation process, and rust can form beneath the coating, which provides shelter for rust formation against the external environment. Hexamethyldisilazane (HMDS) was applied to further hydrophobize the nanoparticles, and a hydrophobic surface with self-cleaning properties was achieved. The hydrophobized and non-hydrophobized coatings with different thicknesses (10–80 µm) were systematically compared: the morphology of the rust layer and coating surface after salt spray was investigated, the ability of the rust layer to inhibit chloride ingress was compared, and the electrochemical behaviors were analyzed. This study presents a new strategy for weathering steel rust stabilization that features maneuverability, environmental friendliness and low cost. Full article

The rapid advancement of flexible electronics technology has endowed flexible sensors with significant application potential in fields such as wearable sensors, bionic skin, and human–machine interaction, owing to their excellent conformability, stretchability, and comfort. However, as application scenarios continue to expand and deepen, higher requirements are imposed on sensor performance in terms of sensitivity, stability, biocompatibility, environmental friendliness, and multifunctional integration. Polyurethane composites, leveraging their intrinsic characteristics, including tunable molecular structure, superior flexibility, and good biocompatibility, can effectively impart properties such as electrical conductivity, self-healing capability, and high sensitivity through compositing with various functional materials, thereby precisely aligning with the diverse demands of next-generation flexible sensors. This article systematically reviews the synthesis strategies of polyurethane composites; provides a detailed analysis of the roles of fillers—including carbon-based materials, polymers, and metal nanoparticles/nanowires—in enhancing the mechanical, electrical, and functional properties of the composites; and further summarizes the research progress of polyurethane composite-based flexible sensors in cutting-edge areas such as eco-friendly sensing, human motion monitoring, health monitoring, and bionic electronic skin. Future development trends are also discussed, aiming to provide insights for the design and development of high-performance flexible sensors. Full article

To address the drag reduction requirements of superhydrophobic surface coatings for underwater vehicle hulls, this study designed a synthesis method based on resin substrate modification and filler modification according to superhydrophobic coating synthesis techniques. Three types of superhydrophobic microstructured surface coatings were prepared: polyurethane resin, silicone resin, and fluororesin. The coatings were fabricated by incorporating fluorine-modified SiO₂ nanoparticles into the modified resin matrices to construct hierarchical micro/nanostructures. The main components and synthesis processes for each coating were determined. Performance tests were conducted to evaluate mechanical properties (thickness, hardness, adhesion, wear resistance), functional characteristics (surface morphology, static/dynamic hydrophobic angles), and environmental resistance (seawater immersion, salt spray stability, thermal stability). Five surface coating test plans for underwater vehicle hull models were proposed, and drag reduction experiments were carried out to compare total drag, drag coefficient, and drag reduction rate across coating plans. Experimental results indicated that the silicone resin superhydrophobic coating with F660 + 8% SiO₂ exhibited the best comprehensive performance, while the PU + 6% SiO₂ superhydrophobic coating achieved optimal drag reduction at speeds below 9 m/s, meeting the performance criteria for underwater vehicle hull applications. Full article

The rapid detection of organophosphorus (OP) compounds is crucial for safeguarding human health and ensuring food safety. This study presents a novel wearable electrochemical biosensor that integrates miniaturized screen-printed electrodes with wearable devices to achieve real-time, on-site OP detection. The biosensor was fabricated by constructing a screen-printed carbon electrode (SPCE) on a thermoplastic polyurethane (TPU) substrate, sequentially modified with graphene (GR), gold nanoparticles (AuNPs), and organophosphorus hydrolase (OPH), and finally encapsulated with Nafion. This SPCE/GR/AuNPs/OPH/Nafion configuration yields a highly flexible and portable device. The detection principle relies on the enzymatic hydrolysis of methyl paraoxon (MPOX) by OPH, generating p-nitrophenol (PNP), which is quantitatively measured via square wave voltammetry (SWV). The sensor exhibits a broad linear detection range (30–400 μM) with a strong linear correlation (R² = 0.995) and a low detection limit (0.321 μM). It demonstrates excellent selectivity against common interfering substances, including urea, sucrose, and various metal ions. Application to real-world samples such as cabbage and tap water yielded high recoveries (107.2% for cabbage and 101.2% for tap water), with relative standard deviations (RSDs) below 8%. Furthermore, the biosensor maintains robust flexibility and mechanical resilience, with less than 5% signal loss after 100 bending cycles, confirming its suitability for wearable applications and reliable operation under mechanical stress. This innovative, flexible electrochemical biosensor provides a powerful and reliable platform for rapid OP detection, particularly in complex testing environments. Full article

In this study, Paliperidone Palmitate (PP), a second-generation antipsychotic, commonly used for the treatment of schizophrenia, was encapsulated in bio-based non-isocyanate polyurethane (NIPU) nanoemulsions. NIPU was synthesized via an isocyanate-free polyaddition route, addressing safety and environmental concerns associated with conventional polyurethanes. The drug-loaded nanoparticles were produced utilizing oil-in-water (O/W) emulsions followed by solvent evaporation and lyophilization. NIPU concentrations of 0.3% and 0.5% w/v, as well as 0.5% w/v PVA were employed, while PP was incorporated at 0.2%, 0.5% and 1% w/v. The formulations were characterized by FTIR, DSC and XRD analyses, and the mechanical strength of neat sponges was evaluated. The nanoparticle formation and size were assessed by DLS and SEM analyses. The water contact angle, porosity measurements and aquatic and enzymatic hydrolysis were additionally performed. The resulting nanocarriers exhibited controlled particle size, increased drug-loading values, structural stability and biodegradability. Lastly, the in vitro dissolution studies revealed a system-specific burst release behavior, and a controlled and sustained overall drug-release profile for majority of the formulations, thereby indicating the potential of NIPU nanocarriers for drug delivery applications, particularly where sustained therapeutic effects are required. Full article

Treatment of postsurgical osteosarcoma remains one of the major challenges in orthopedic clinics. Conventional implants often fail to address complex pathological issues, including irregular bone defects, residual tumor cells, and delayed bone regeneration. Herein, this study reports a multifunctional shape-memory polyurethane (SMPU)/manganese dioxide (MnO₂) composite that provides adaptive support, antitumor activity, and osteogenic bioactivity. SMPU was synthesized by introducing 1,4-butanediol (BDO) and dimethylolpropionic acid (DMPA) as chain extenders at a specific ratio. Commercial MnO₂ nanoparticles were incorporated as both a photothermal agent and a bioactive component to achieve multifunctionality. As designed, a coordination system was formed between the polymer chains and MnO₂ nanoparticles within the composites. The influence of MnO₂ content was systematically investigated. Although increasing MnO₂ amounts improved photothermal and mechanical performance, excessive incorporation adversely affected the molecular structure and compromised the composite’s biocompatibility. By adjusting the MnO₂ content, the composites were demonstrated to possess robust mechanical performance, good shape-memory behavior, and controllable Mn²⁺ release. Additionally, the composites exhibited tunable photothermal performance under near-infrared (NIR) irradiation. Furthermore, in vitro studies confirmed that the composites containing 4 wt% MnO₂ could eliminate tumor cells via photothermal effects and promote the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Overall, the SMPU/MnO₂ composites had superior multifunction for treating irregular bone defects following bone tumor surgery. Full article

Developing environmentally friendly, multifunctional waterproof and breathable membranes (WBMs) has attracted extensive attention and is of great significance but remains challenging. Herein, an environmentally friendly and multifunctional waterborne polyurethane WBM with self-healing and self-cleaning properties is developed in two steps. Firstly, by using polydimethylsiloxane (PDMS) as a hydrophobicity giver and tannic acid (TA) as a crosslinker, a dual-modified waterborne polyurethane (PTWPU) is prepared, which has high surface hydrophobicity due to the surface enrichment of siloxane segments and self-healing performance from the formation of a dynamic phenolic carbamate network. Secondly, by incorporating titanium dioxide (TiO₂) photocatalyst nanoparticles to increase internal porosity and establish hydrophilic pathways, a multifunctional waterborne polyurethane WBM (TPTWPU) is developed. This membrane features further enhanced surface hydrophobicity from generated micro-roughness and effective self-cleaning performance, because TA acts as an electron trap to promote the photocatalytic activity of TiO₂. The TPTWPU membrane shows good hydrophobicity (water contact angle of 115.3°) and satisfactory moisture permeability of 135.0 g/(m²·24 h), which is 61.2% higher than unmodified membranes. Furthermore, it exhibits efficient self-healing, with a recovery rate exceeding 80% within 2 h. This feasible strategy will provide guidance for materials design in multifunctional coatings for textiles and leather. Full article

Sponge-based preservative packaging is an emerging approach to mitigate mechanical damage to fruits and vegetables during transportation, storage, and retail. However, conventional polyurethane sponges generally lack durable antibacterial activity and are neither biodegradable nor readily recyclable. Herein, to address these limitations, silver nanoparticles immobilized on TEMPO-oxidized cellulose nanofibers (TCNF@AgNPs) were incorporated into a quaternized chitin matrix to construct a synergistic antibacterial composite sponge (QCH/TCNF@AgNPs) for fruit preservation. The composite sponge exhibited strong antibacterial efficacy against Escherichia coli and Staphylococcus aureus, together with a low cumulative release of silver species of 2.49% after 336 h. In addition, the sponge showed >50% mass loss after 36 days in lysozyme solution, indicating good enzymatic degradability. Cytocompatibility assays further confirmed favorable biocompatibility and biosafety. Notably, the composite sponge provided satisfactory preservation performance for fresh strawberries. Overall, this work demonstrates the potential of QCH/TCNF@AgNPs as a biodegradable antibacterial packaging sponge for fruit preservation. Full article

The escalating severity of microplastic pollution and oily wastewater discharge has intensified the demand for recyclable, multifunctional, and environmentally benign materials. In this study, we present a composite polyurethane (PU) sponge constructed through the synergistic integration of cuttlefish-ink nanoparticles (CINPs), Ti₃C₂T_X MXene, and polydimethylsiloxane (PDMS). The synergistic CINP@MXene framework imparts high photothermal conversion efficiency and structural stability, while the PDMS coating confers superhydrophobicity. The resulting sponge demonstrates efficient oil absorption and oil–water separation capabilities, alongside a stable photothermal response, achieving a temperature of 84.1 °C within 10 s under 1.5 Sun irradiation. Notably, the sponge absorbed approximately 0.05 g of crude oil within 10 s, the saturated absorption capacity of crude oil under 1.5 solar days was 24.52 g/g, and the adsorption rate of 5 g crude oil within 4 min was 91.4%. Furthermore, it exhibits remarkable adsorption performance toward common microplastics and nanoplastics. Overall, the CINPs@MXene/PU/PDMS sponge represents a versatile and scalable platform with significant potential for addressing challenges in oily wastewater treatment, solar-assisted oil recovery, and microplastic remediation, thereby contributing to sustainable environmental protection efforts. Full article

Developing sustainable, high-performance biomass composites is crucial for replacing non-renewable structural materials. In this study, a “bamboo steel” composite was fabricated using a multilevel modification strategy involving alkali pretreatment, toughened resin impregnation, and surface functionalization. Bamboo fibers were treated to remove hemicellulose and lignin, enhancing porosity and interfacial bonding. The bamboo scaffold was subsequently impregnated with a thermo-plastic polyurethane-modified epoxy resin to create a robust, interpenetrating network. The optimized composite (treated at 80 °C) exhibited a flexural strength of 443.97 MPa and a tensile strength of 324.14 MPa, demonstrating exceptional stiffness and toughness. Furthermore, a superhydrophobic coating incorporating silica nanoparticles was applied, achieving a water contact angle exceeding 150° and excellent self-cleaning properties. This work presents a scalable strategy for producing bio-based structural materials that balance mechanical strength with environmental durability. Full article

Background: Soft actuation relies on materials that are lightweight, flexible, and responsive to external stimuli. In biomedical applications, miniaturization and biocompatibility are key requirements for developing smart devices. Thermoplastic polyurethane (TPU) is particularly attractive due to its elasticity, processability, and biocompatibility; however, an improvement in its shape-recovery performance would significantly enhance its suitability for actuation systems. This study aims to develop TPU-based shape memory polymer (SMP) composites with improved functional behavior for biomedical applications. Methods: TPU was modified with aluminum nanoparticles (AlNPs) and multi-walled carbon nanotubes (MWCNTs), incorporated individually (1 wt.% and 3 wt.%) and in hybrid combinations (MWCNT:AlNP ratios of 2:1, 5:1, and 10:1). Samples were produced by compression molding and characterized through thermal, mechanical, electrical, and shape-recovery tests, supported by morphological analysis. Results: AlNPs moderately improved thermal conductivity, while MWCNTs significantly enhanced electrical conductivity and doubled the recovery force compared with neat TPU. Hybrid composites showed intermediate properties, with the 5:1 MWCNT:AlNP ratio offering the best balance between recovery force and activation speed. Conclusions: The synergistic combination of MWCNTs and AlNPs effectively enhances TPU’s multifunctional behavior, demonstrating strong potential for soft actuation in biomedical devices. Full article

Background: Clear aligners have become a common alternative to fixed appliances for tooth movement, and thermoplastic retainers hold the outcome. The prolonged intraoral contact of these devices has made the materials a focus of biocompatibility research. Objectives: This paper aims to summarize laboratory evidence on the biocompatibility of clear aligners and thermoplastic retainers. Materials included thermoformed polyethylene terephthalate glycol-modified (PETG), multilayer polyurethane, and directly printed resins. Primary outcomes were cytotoxicity, endocrine activity, and chemical or particle release. Methods: We systematically searched PubMed, the Cochrane Library, and Google Scholar through 31 May 2025, and we followed the PRISMA 2020 statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We applied predefined eligibility criteria. Two reviewers screened records and extracted data in duplicate, including study design, extraction conditions, surface-area-to-volume ratio (SA/V), cell models, endpoints, and analytical sensitivity as the limit of detection (LOD) and limit of quantification (LOQ). We assessed the risk of bias across seven domains and graded certainty by outcome. We did not register a protocol prospectively. Results: Seventeen studies met the inclusion criteria. Materials spanned multilayer polyurethanes (SmartTrack, Clarity), PETG sheets (Essix ACE, Duran), and directly printed resins (Graphy TC-85DAC); a subset tested zinc-oxide (ZnO) nanoparticle coatings. Typical extractions immersed 0.1–1 g of material in cell-culture medium or artificial saliva at 37 °C for 24 h to 30 days. Cell viability usually remained ≥80%. Mild cytotoxicity (about 60–70% viability) appeared with harsher extractions, extended soaks, or an inadequate post-curing of printed parts. The estrogen-sensitive proliferation assay (E-Screen) returned negative results. In saliva-like media, bisphenol A (BPA) and related leachables were undetectable or in the low ng/mL range. In printed resins, urethane dimethacrylate (UDMA) sometimes appeared in water extracts, and amounts varied with curing quality. Evidence for chemical leaching and endocrine outcomes is sparse. We found no eligible in vitro study that quantified particle or microplastic release while also measuring a biological endpoint; we discuss particle findings from mechanical wear simulations only as the external context. Limitations: The evidence base is limited to in vitro studies. Many reports incompletely described extraction ratios and processing parameters. Risk of bias and certainty: Most studies used appropriate cell models and controls, but the reporting of surface-area-to-volume ratios, LOD/LOQ, and detailed post-processing parameters was often incomplete. Sample sizes were small, and dynamic wear or enzymatic conditions were uncommon. The overall risk of bias was moderate, and the certainty of evidence was low to moderate due to heterogeneity and in vitro indirectness. Conclusions: Under standard laboratory conditions, clear aligners and thermoplastic retainers show a favorable biocompatibility profile. For printed resins, outcomes depend mainly on processing quality, especially thorough washing and appropriate light-curing parameters. To improve comparability and support clinical translation, we recommend harmonized test protocols, transparent reporting, interlaboratory ring trials, and targeted clinical biomonitoring. Full article

Bone defect repair presents a significant clinical challenge, especially for critical-sized defects, due to the limitation of conventional 3D-printed scaffolds to provide simultaneous mechanical support and bioactivity. Herein, this study developed a bioactive composite scaffold through a low-temperature rapid prototyping (LT-RP) 3D printing technology. The scaffold comprises a polyurethane (PU) matrix enhanced with bioactive manganese dioxide (MnO₂) nanoparticles, combining structural integrity with versatile bioactivity for bone repair. By incorporating 2, 6-pyridinedimethanol (PDM) into the PU molecular network, a coordination system is formed, enabling homogeneous distribution and structural integration of MnO₂ nanoparticles. As designed, the bioactive scaffolds are fabricated through LT-RP 3D printing technology with a regular porous architecture for improving cell growth. With 10 wt% MnO₂, the scaffolds (PPM10) have optimal comprehensive properties, with a modulus of ~14.1 MPa, improved thermal stability, good cytocompatibility, and enhanced osteogenic differentiation. Furthermore, in vitro degradation tests revealed the responsive release of Mn²⁺ from the PPM10 scaffolds in a glutathione-rich microenvironment. This functionality indicates the potential of the scaffolds to modify the tumor microenvironment for ultimate bone regeneration after bone tumor surgery. 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