Search Results (947)

Passive microvalves enable autonomous operation of microfluidic devices by allowing time-controlled fluid delivery without external actuation. Here, we report a simple, low-cost, single-use passive microvalve based on poly(vinyl alcohol) (PVA) for time-programmed fluid delivery. The valve operates through dissolution of a solidified PVA plug formed inside poly(methyl methacrylate) (PMMA) microchannels after evaporation of the solvent phase. The valve dissolves when exposed to an aqueous medium, enabling fluid flow. The valve opening time was experimentally characterized as a function of the injected liquid volume using three PVA formulations and three microchannel cross-sections fabricated in PMMA. Experimental results showed a non-linear dependence of the opening time on the injected volume, as well as the influence of PVA formulation, channel geometry, and temperature. In addition, a demonstrative multi-valve device showed sequential valve opening with delays up to 7 h. The proposed approach enables simple and autonomous timed fluid release using inexpensive materials and straightforward fabrication processes, representing a promising strategy for low-cost microfluidic applications. Full article

Pancreatic ductal adenocarcinoma is highly malignant with poor prognosis. Its dense tumor microenvironment severely limits the efficacy of conventional chemotherapy and causes severe side-effects. Herein, we adopt the established Schiff-base crosslinked thermoresponsive injectable self-healing poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate-co-aldehyde 2-hydroxyethyl methacrylate)/carboxymethyl chitosan (APMOH/CMCS) hydrogel as the delivery scaffold. By regulating monomer composition, the volume phase transition temperature (T_VPT) of the hydrogel was tuned to around 43 °C to match the therapeutic temperature requirement. Subsequently, copper–metal organic framework (Cu-MOF) nanoparticles co-loaded with 2,2′-azobis(2-methylimidazoline) dihydrochloride (AIPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cationic radicals (ABTS·⁺) (denoted as AB@Cu-MOF) were uniformly incorporated into the hydrogel network. Under near-infrared (NIR) irradiation, ABTS·⁺ acts as a photothermal agent to generate hyperthermia for tumor ablation; the elevated temperature further activates AIPH to produce alkyl radicals, which can oxidize inactivated ABTS back to ABTS·⁺ and construct a sustainable photothermal therapy–thermodynamic therapy (PTT-TDT) circulation. Meanwhile, Cu-MOF can consume intracellular glutathione (GSH) to protect active components from deactivation and initiate chemodynamic therapy (CDT) via Fenton-like reactions to produce toxic reactive oxygen species. Benefiting from the thermoresponsive characteristic, the hydrogel undergoes volume shrinkage upon heating, achieving NIR-triggered on-demand drug release with a cumulative release rate of 81.1%. In vitro and in vivo experiments verified that this integrated platform realizes remarkable triple synergistic efficacy of PTT, TDT, and CDT. The tumor volume of the treatment group was merely 13.3% of the control group, and the system also exhibited excellent biocompatibility. Collectively, it offers a feasible and promising intelligent platform for precise local treatment of pancreatic cancer. Full article

Maintaining wellbore stability in deep and ultra-deep formations demands plugging agents capable of sealing nano- to micro-scale pores under high-temperature conditions. A core–shell nano-plugging agent (CSP) was synthesized via emulsion polymerization using KH-570-modified nano-SiO₂ as the rigid core and a poly(styrene-co-butyl acrylate-co-methyl methacrylate) terpolymer as the deformable shell. CSP particles had a mean diameter of 196.5 nm (polydispersity index, PDI = 0.183) and an onset decomposition temperature of 342 °C. Compatibility tests at 180 °C confirmed that 3 wt% CSP caused no adverse changes in the rheology or emulsion stability of the oil-based drilling fluid (OBM). At 180 °C, CSP reduced the high-temperature high-pressure (HTHP) filtrate loss by 64.4% and the permeability plugging apparatus (PPA) filtrate loss by 66.1%. Sand-disk tests elevated the breakthrough pressure from 1.5 to 9.2 MPa. Core displacement on sandstone cores achieved a plugging rate of 98.30%, and pressure transmission tests on natural shale cores extended the 50% equalization time by 7.8-fold. Comparative evaluation confirmed that the core–shell architecture consistently outperformed nano-SiO₂ alone, polymer alone, and their physical blend. Low-temperature N₂ adsorption provided direct evidence of pore sealing, with the treated-shale Brunauer–Emmett–Teller (BET) surface area and total pore volume reduced by about 62% (12.6 to 4.8 m²/g and 0.0325 to 0.0121 cm³/g, respectively). Scanning electron microscopy of the shale surface before and after treatment further provided direct visual evidence of pore sealing, showing the open, porous matrix being converted into a dense, compacted filter cake. Filter-cake thickness measurements are consistent with a proposed three-stage plugging mechanism—bridging, deformation filling, and thermal compaction—driven by the complementary roles of the rigid core and the deformable shell. These findings indicate that CSP merits further evaluation as a high-temperature plugging agent for wellbore stabilization in deep shale formations. Full article

This study investigates the process optimization and predictive modeling of femtosecond laser precision milling for commercial poly(methyl methacrylate) (PMMA) slices, with emphasis on surface roughness R_a and milling depth h. Three-dimensional surface morphology was measured using a laser confocal microscope, and the measurement methods for R_a and h were defined based on stable regions of interest and reference-plane correction. The effects of pulse energy, scanning line speed, scanning line spacing and pulse repetition frequency on milling quality were systematically analyzed. The results show that pulse energy and repetition frequency promoted material removal and increased milling depth, whereas scanning line speed and scanning line spacing reduced milling depth by decreasing the effective energy deposition per unit area. Surface roughness was influenced by both energy input and scanning uniformity, showing non-monotonic responses to scanning line speed and scanning line spacing. Quadratic response surface models were established using the Box–Behnken design. The ANOVA results indicate that both the R_a and h models were statistically significant, with R² values of 0.9970 and 0.9982, respectively. The validation results show that the average relative errors of the R_a and h models were 6.51% and 2.62%, respectively. These results demonstrate that the proposed models can effectively predict femtosecond laser milling quality and provide guidance for parameter selection and surface-quality control of commercial PMMA slices. Full article

A silk fibroin/cellulose inverse-opal photonic crystal composite with robust mechanical properties was fabricated by blending a silk fibroin solution with methylcellulose, utilizing a 3D poly(methyl methacrylate) (PMMA) photonic crystal array as a template, via sequential infiltration, curing, and etching processes. Leveraging the intrinsic water sensitivity of both silk fibroin and methylcellulose, the resulting composite exhibits exceptional moisture-sensing capabilities across gaseous, liquid, and solid phases. Specifically, for atmospheric humidity, the film delivers a distinct optical response to a relative humidity variation in merely 5%. In liquid systems, owing to the material’s excellent affinity for low-polarity organic solvents and the disruptive effect of highly polar solvents (e.g., water) on the photonic periodic structure, the structural color of the film can sensitively report trace water contents down to 0.025%. Furthermore, in solid matrices, the composite enables the precise detection of not only free water but also water of crystallization. Full article

Implant-Supported Fixed Prostheses (ISFPs) have become a common option for the rehabilitation of fully edentulous arches and have traditionally incorporated metallic substructures with ceramic or acrylic veneering. The rapid expansion of CAD/CAM technologies has introduced not only a range of polymer-based materials as alternatives to conventional metallic frameworks but also the possibility of the fabrication of monolithic rehabilitations. However, the evidence regarding the mechanical behavior of monolithic polymer-based full-arch rehabilitations remains limited. This study aimed to evaluate and compare the mechanical performance of monolithic polymer-based complete prostheses under static loading using Digital Image Correlation (DIC). A total of 12 specimens (3 per group) simulating an FP3 maxillary full-arch ISFP supported by four implants were milled from four materials: poly(ether ether ketone) (G1-PEEK), poly(ether ketone ketone) (G2-PEKK), poly(methyl methacrylate) (G3-PMMA), and fiber-reinforced composite (G4-FRC). All specimens were subjected to static loading up to 200 N at the incisors region, corresponding to the anterior unsupported span, and at the occlusal surface of the molars, corresponding to the most distal portion of the cantilever, using a universal testing machine. Full-field vertical displacement and strain distributions (principal tensile, compressive, and von Mises) were acquired through a stereo DIC system and analyzed using a Linear Mixed-Effects Model with Tukey’s HSD post hoc comparisons (α = 0.05). All prostheses withstood the applied load without macroscopic failure. G3-PMMA exhibited the highest vertical displacement, exceeding 1000 µm in the anterior span and 1500 µm in the cantilever region, along with the greatest strain concentrations, particularly at the interproximal embrasures distal to the terminal abutment. G1-PEEK provided the lowest displacement in the anterior span. G4-FRC presented displacements similar to G1-PEEK and G2-PEKK at the distal cantilever, but the lowest tensile strains and the most homogeneous strain dissipation in both loading at the anterior unsupported span and distal cantilever. This indicated that the biomechanical performance of full-arch ISFPs is highly influenced by the polymer used. PEEK, PEKK, and FRC appear as promising alternatives to PMMA for monolithic full-arch rehabilitations. Full article

Aerospace canopies require both high impact resistance and optical transparency for pilot safety and aerodynamic shielding. While polycarbonate (PC) and poly(methyl methacrylate) (PMMA) are widely utilized, their vulnerability to strain-rate-dependent failure during high-velocity bird strikes necessitates advanced reinforcement strategies. This study presents a multiscale computational framework for nanoparticle-reinforced PC nanocomposites. To circumvent the prohibitive computational costs of atomistic simulations, a novel Strain-Rate Dependent Micromechanics (SRDM) framework is proposed for silica-, alumina-, and zirconia-reinforced PC systems, integrating the Goldberg constitutive model with Halpin–Tsai micromechanics to generate rate-dependent stress–strain responses and calibrate Johnson–Cook (J-C) parameters for impact-scale simulations. Unlike conventional approaches relying on atomistic simulations or empirical fitting, the proposed framework directly links micromechanical nanocomposite modeling with finite element bird-strike simulations. Bird-strike analyses were performed in LS-DYNA on a generic fighter canopy model. The framework further incorporates literature-based optical transparency criteria considering nanoparticle size and refractive-index compatibility. Among the investigated nanofillers, silica-reinforced PC provided the most favorable response. At the most critical impact location, the maximum canopy deformation decreased from 118.6 mm for neat PC to 61.9 mm, corresponding to an approximately 48% reduction. Although the reinforced canopy exhibited a reduction in peak internal energy absorption from approximately 10 kJ to 5 kJ due to its increased stiffness and reduced plastic deformation, it provided improved deformation resistance and structural stability under impact loading. Overall, this work provides a computationally efficient framework for designing bird-strike-resistant transparent nanocomposite canopy structures using nanofiller systems previously reported in the literature to preserve optical transparency. Full article

Semiconducting metal oxides are gaining attention in thermoelectric applications, where performance is evaluated by the figure of merit (ZT), which depends on the power factor (S²σ) and thermal conductivity (κ). However, achieving high ZT values in these materials remains challenging. This study introduces a distinct strategy to enhance thermoelectric performance by infiltrating aluminum-doped zinc oxide (AZO) into poly(methyl methacrylate) (PMMA) films using the vapor-phase infiltration (VPI) technique. The resulting AZO/PMMA hybrid films exhibit a unique composite structure with AZO nanocrystals embedded within an amorphous PMMA matrix. This structure facilitates energy-dependent carrier scattering (the energy filtering effect) at the AZO/PMMA interfaces, thereby enhancing the Seebeck coefficient, while phonon scattering at the interfaces reduces thermal conductivity. By precisely controlling VPI parameters, we achieved a uniform dispersion of AZO nanocrystals within the PMMA matrix. The optimized AZO/PMMA hybrid film demonstrated a power factor of 1306 μW m⁻¹ K⁻² and a thermal conductivity of 1.02 W m⁻¹ K⁻¹, resulting in a ZT value of approximately 0.384 at 300 K, which is one of the highest reported for metal oxide thermoelectric materials near room temperature. The successful integration of AZO into the PMMA matrix via VPI opens new pathways for developing high-performance, flexible thermoelectric materials. Full article

Corrosion fatigue is an accelerated failure mechanism in metallic components and coated systems, where the effectiveness of the polymer coating is determined by the structural integrity and adhesion at the coating/substrate interface. This study investigated the corrosion fatigue interaction in AISI 410 steel with and without a poly(3-hexylthiophene)/poly (methyl methacrylate) (P3HT/PMMA) coating exposed to a 3 wt.% NaCl solution under four stress levels $\left(∆\sigma \right)$ at room temperature. Electrochemical noise (EN) was recorded during the test, the surface and interface were characterized using scanning electron microscopy (SEM), and the mechanical behavior was quantified using $da/dN$ vs. $∆K$ and $\sigma$ vs. N curves. The coated samples exhibited a wider potential range ($\approx \pm$400 mV) than the uncoated steel ($\approx \pm$200 mV), indicating localized electrochemical activity under the coating. SEM observations revealed microblisters at low stress levels and coating cracking at high stress levels, with localized substrate exposure, slip bands, and microcracks. Overall, the results showed that the corrosion fatigue is governed by electrochemical activity under the coating and cathodic delamination, which reduces adhesion, locally exposes the steel, and causes the initiation and propagation of cracks. Full article

Amphiphilic statistical copolymers are valuable synthetic macromolecules for the formation of small, well-defined nanoassemblies able to be utilized as nanocarriers for drug and/or gene delivery applications. In this work, the synthesis of amphiphilic linear statistical copolymers of the poly(benzyl methacrylate-co-dimethylaminoethyl methacrylate) [P(BzMA-co-DMAEMA)] type is described in three different comonomer compositions. Their synthesis was realized through a one-pot reversible addition-fragmentation chain transfer (RAFT) solution polymerization scheme. Further quaternization of the amine groups of DMAEMA with methyl iodide (CH₃I) resulted in cationic amphiphilic statistical copolymers. Macromolecular characterization was performed using size exclusion chromatography (SEC) and spectroscopic techniques (¹H-NMR and ATR-FTIR). The aggregation properties of the copolymers in aqueous media were studied via dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Bimodal size distributions were determined in some cases. The BzMA to DMAEMA ratio determined aggregate size, with the copolymer of lower hydrophobic BzMA content producing smaller nanoparticles. Cryogenic transmission electron microscopy (cryo-TEM) showed the presence of spherical assemblies resulting from aggregation of primary micelles in the case of higher BzMA content. The copolymer aggregates experience dissociation at high salt concentration, and the pH-responsiveness of the amine precursors results in the formation of multifunctional potential nanocarriers. Full article

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

This experimental study systematically explores the impact of particle size variation in Layered Double Hydroxide (LDH) composites on the thermomechanical and optical properties of poly(methyl methacrylate) (PMMA) nanocomposites. Utilizing a co-precipitation method, LDHs modified with cocamidopropyl betaine (CPB) were synthesized in three distinct sizes (small 80 nm, medium 130 nm, and large 280 nm) and then incorporated into a PMMA matrix through bulk polymerization using Benzoyl Peroxide as the initiator. Morphological analysis via electron microscopy confirmed the exfoliation of LDHs layers within the PMMA matrix, indicating effective dispersion. The medium-sized LDH/PMMA nanocomposite exhibited enhanced interlayer interactions, facilitating polymerization and increasing the thermal degradation onset temperature by 21.2 °C compared to pristine PMMA. In contrast, the small-sized LDH/PMMA nanocomposite demonstrated a significant improvement in mechanical performance, with a 62% increase in storage modulus, attributed to its higher aspect ratio and improved stress transfer. Additionally, the optical transmittance of the nanocomposites across a visible range of 550 nm exceeded 88%, suggesting a minimal impact on optical clarity despite varied particle sizes. Overall, the incorporation of size-specific LDHs modifications led to notable enhancements in both the thermal stability and mechanical performance of the PMMA nanocomposites, underlining the potential of tailored nanoparticle modifications in advanced polymer matrices. Full article

The increasing emission of harmful gases into the atmosphere represents a major environmental challenge, driving the need for efficient air purification materials. Poly(methyl methacrylate) (PMMA) has emerged as a promising candidate due to its favorable physicochemical properties and adsorption potential. In this study, the interactions between PMMA and selected sulfur-containing pollutants (CH₃SH, COS, CS₂, H₂S, and SO₂) were systematically investigated using a multiscale computational approach. Initial structural exploration was performed using extended tight-binding (xTB) methods, followed by refinement at the density functional theory (DFT) level, while molecular dynamics (MD) simulations were employed to capture the dynamic behavior of the systems. The results suggest that all investigated gases exhibit attractive interactions with PMMA, with interaction strength strongly dependent on molecular polarity and electronic structure. Among the studied systems, SO₂ shows the strongest binding, while CS₂ exhibits the weakest interaction. Energy decomposition based on symmetry-adapted perturbation theory (SAPT) and electronic structure analyses suggest that electrostatic and donor–acceptor interactions play a dominant role for strongly interacting systems, whereas weaker interactions are primarily governed by dispersion forces. Full article

Micro- and nano-container-based self-healing coatings have emerged as a promising strategy for the long-term conservation of cultural heritage artifacts, including metals, stone, organic matter, and construction materials. These coatings incorporate microcapsules or nanocapsules with tailored shell and core materials, enabling autonomous release of healing agents or corrosion inhibitors in response to damage. For metallic artifacts, benzotriazole@mesoporous silica nanoparticles (BTA@MSN) microcapsules achieve selective pH-responsive release, reaching 77% at pH 9.0 and 42% at pH 5.0, effectively mitigating localized corrosion. Temperature-adaptive poly(methyl methacrylate-co-methacrylic acid) (PMMA-MA)/MgO microcapsules exhibit controlled rupture rates, with a 75% reduction at elevated temperatures, enhancing crack repair efficiency by approximately 5%. Organic artifacts, such as wooden or paper manuscripts, benefit from clove oil nanocapsules, which increase tensile strength by 43.5% and fracture toughness by 101.9%, with only 2.91% weight loss over 7 days compared to 33.1% for unencapsulated oil. Advanced fabrication methods—including microfluidics, Pickering emulsions, and multi-core systems—enable high encapsulation efficiency (up to 73.5%), uniform particle size, and repeatable healing. Multi-stimuli responsiveness (pH, temperature, light, magnetic fields) and biobased, environmentally friendly materials further enhance adaptability and sustainability. In this review, “self-healing” is defined broadly to include both physical crack repair and autonomous restoration of protective functions. Overall, self-healing micro/nanocapsule coatings provide a highly controllable, efficient, and durable solution for active heritage protection, representing a shift from passive to intelligent conservation strategies. Furthermore, a systematic comparison of different capsule systems is provided to clarify their respective advantages and limitations. Overall, hybrid systems exhibit the most balanced performance, while inorganic nanocontainers offer superior stability and controlled release, and polymeric capsules enable rapid healing but limited reusability. Full article

This study develops a quantitative kinetic framework for graft copolymerization of methyl methacrylate (MMA) and styrene (ST) onto natural rubber latex (NRL), with emphasis on Redox initiation and Interfacial polymerization in a multiphase system. Experiments were conducted using a cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA) system. Core–shell particles, consisting of a soft NR core and a rigid poly(vinyl monomer) shell, were obtained at 40–60 °C with initiator concentrations of 0.0051–0.0205 mol L⁻¹ and monomer concentrations of 0.39–0.83 mol L⁻¹. Radical generation occurs predominantly at the aqueous rubber interface, where monomer partitioning takes place between phases. This leads to simultaneous homopolymerization in the aqueous phase, while grafting occurs on the rubber backbone. Overall conversion (x_p), graft conversion (x_g), and grafting efficiency were determined gravimetrically, while morphology was confirmed by FTIR and TEM. The conversion profiles show nonlinear behavior consistent with power-law kinetics, allowing formulation of rate expressions for overall polymerization rate (R_p) and grafting rate (R_g). Reaction order and Arrhenius analyses indicate fractional, heterogeneous behavior characteristic of multiphase reaction kinetics. Styrene shows lower activation energy, whereas MMA exhibits higher collision frequency. The model reproduces experimental trends well (R² up to 0.95) and provides insight into propagation–grafting competition in natural rubber latex systems. Full article