Macromolecular Materials and Engineering最新文献

Tailored ribbing structures are obtained by large-scale rolling in polymer PDMS thin-films by adding carbon nanotubes (CNT) inclusions, which significantly improved the mechanical behavior of systems subjected to dynamic compressive strain rates. A nonlinear explicit dynamic three-dimensional finite-element (FE) scheme is used to understand and predict the thermomechanical response of the manufactured ribbed thin-film structures subjected to dynamic in-plane compressive loading. Representative volume element (RVE) FE models of the ribbed thin-films are subjected to strain rates as high as 10⁴ s⁻¹ in both the transverse and parallel ribbing directions. Latin Hypercube Sampling of the microstructural parameters, as informed from experimental observations, provide the microstructurally based RVEs. An interior-point optimization routine is also employed on a regression model trained from the FE predictions that can be used to design ribbed materials for multifunctional applications. The model verifies that damage can be mitigated in CNT-PDMS systems subjected to dynamic compressive loading conditions by controlling the ribbing microstructural characteristics, such as the film thickness and the ribbing amplitude and wavelength. This approach provides a framework for designing materials that can be utilized for applications that require high strain rate damage tolerance, drag reduction, antifouling, and superhydrophobicity.

This study fabricates multiscale glass fiber/epoxy composites by incorporating graphene nanoparticles (GNPs) and zinc oxide nanoparticles (ZnO NPs) to investigate the influences of NPs on the mechanical properties of composites. The composites are manufactured using the compression molding technique with different GNP contents (i.e., 0, 0.5, 1, and 1.5 wt.%), whereas the contents of glass fibers and ZnO NPs remained the same at 40 and 4 wt.%, respectively. Their mechanical properties, chemical compositions, and fracture morphologies are then evaluated. It is found that the mechanical properties of composites improve significantly at a lower content (i.e., 0.5 wt.%) of GNPs and tend to decrease at higher contents (i.e., 1 and 1.5 wt.%). The composite is composed of 0.5 wt.% GNPs exhibit maximum tensile modulus and strength of 6.74 GPa and 230.25 MPa, and flexural modulus and strength of 16.43 GPa and 831.79 MPa, respectively, impact strength of 47.25 kJ m⁻², and maximum hardness (97.96 Shore D), among all nanocomposites. Moreover, fracture morphologies reveal that composite failure is predominately caused by fiber breakage, fiber-matrix debonding, voids, and GNP agglomeration. The outcomes of this study provide some insights to promote the application of manufactured multiscale composites in the aerospace, automotive, and marine industries.

Here, the use of cellulose films (CFs) produced from low-quality cotton is reported as a template for in situ synthesis of well-known conductive polymers, e.g., polyaniline (PANI) and polypyrrole (PPY) via oxidative polymerization. Three successive monomer loading/polymerization cycles of aniline (ANI) and pyrrole (PY) within CFs as PANI@CF or PPY@CF are carried out to increase the amount of conductive polymer content. The contact angle (CA) for three times ANI and PPY loaded and polymerized CFs as 3PANI@CF and 3PPY@CF are determined as 26.3±2.8 and 42.3±0.6 degrees, respectively. As the electrical conductivity is increased with increased number of conductive polymer synthesis within CF, the higher conductivity values, 3×10⁻⁴±8.1×10⁻⁵ S.cm⁻¹ and 2.1×10⁻³±5.8×10⁻⁴ S.cm⁻¹, respectively are measured for 3PANI@CF and 3PPY@CF composites. It is found that PANI@CF composites are hemolytic, whereas PPY@CF composites are not at 1 mg mL⁻¹ concentrations. All PPY@CF composites exhibit better biocompatibility than PANI@CF composites on L929 fibroblast cells with more than 70±8% viability at 1 mg of CF-based conductive polymer composites. Moreover, MIC and MBC values of 3PPY@CF composites for Escherichia coli (ATCC8739) and Staphylococcus aureus (ATCC6538) are determined as 2.5 and 5.0 mg.mL⁻¹, whereas these values are estimated as 5 and 10 mg.mL⁻¹ for Candida albicans (ATCC10231).

Highly sensitive strain sensors have been widely used in human motion monitoring, medical treatment, soft robots, and human–computer interaction, and the recycling of functional materials is in a huge demand for eco-friendly and sustainable electronics. However, the manufacturing of recyclable strain sensors still remains challenging. Here, a semi-wrapped structure based on silver nanowires and polyvinyl alcohol is proposed to realize a recyclable and stable strain sensor. It has shown excellent sensitivity, fast response, high stretchability and good environmental stability, and is successfully applied for human motion monitoring. In addition, a simple strategy is developed to effectively recycle silver nanowires in an eco-friendly manner. The recyclable and stable strain sensor demonstrates potential applications in wearable and stretchable electronics, and the recycling strategy can be extended to other noble metal nanomaterials.

Corneal alkali burns have become a frequent and urgent issue in ophthalmology, but current treatments are limited. To address this, a diclofenac-loaded thermogel with anti-inflammatory agents is developed to target inflammation and improve drug delivery for corneal alkali burns. Thermogels are prepared by dissolving methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) in phosphate-buffered saline (PBS), adding diclofenac (DF), and storing the solution at 4 °C. The thermogel's temperature-sensitive behavior and injectability at 35 °C are assessed. Freeze-dried thermogels are examined using scanning electron microscopy. Rheological properties, swelling behavior, and in vitro release studies are conducted. In vitro and in vivo biocompatibility tests are performed. A corneal alkali burn model is established in rats, and different treatments are administered for 7 days. Eyeballs are collected for histological and molecular analysis. The thermogel formulation formed a stable gel at 35 °C and continuously released DF for 7 days. In vitro and in vivo tests confirmed the thermogels' excellent biocompatibility. The released DF promotes the expression of the anti-inflammatory cytokine interleukin-10 (IL-10) and inhibits the expression of pro-inflammatory factors TNF-α and vascular endothelial growth factor (VEGF). This novel DF/thermogel offers an efficient, topical, and cost-effective approach with significant potential for treating corneal alkali burns.

Recent progress in additive manufacturing has enabled the application of stereolithography (SLA) in bioprinting to produce 3D biomimetic structures. Bioinks for SLA often require synthetic polymers as supplements to ensure the structural integrity of the printed cell-laden constructs. High molecular weight (MW) poly(ethylene-glycol)-diacrylate (PEGDA) (MW ≥ 3400 Da) is commonly used to enhance the mechanical property of crosslinked hydrogels. However, the production of bioink with high MW PEGDA requires in-house polymer synthesis or the acquisition of costly reagents, which may not be readily available in all laboratory settings. As an alternative to high MW PEGDA, this research investigated the use of poly(ethylene-glycol)-dimethacrylate (PEGDMA) (MW = 1000 Da) as a supplement of a bioink to enhance the mechanical properties of the SLA-printed constructs. The successful demonstration showcases 1) the fabrication of 3D constructs with overhang and complex architecture, and 2) the cytocompatibility, with high cell viability of 71–87% over 6 days of culture, of the GelMA-PEGDMA bioink to enable cell-laden bioprinting. This study suggests PEGDMA as a viable supplement in the formulation of SLA bioink. The accessibility to PEGDMA will facilitate the advance in 3D bioprinting to fabricate complex bioinspired structures and tissue surrogates for biomedical applications.

Recently, in vitro models emerge as valuable tools in biomedical research by enabling the investigation of complex physiological processes in a controlled environment, replicating some traits of interest of the biological tissues. This study focuses on the development of tubular polymeric scaffolds, made of electrospun fibers, aimed to generate three-dimensional (3D) in vitro intestinal models resembling the lumen of the gut. Polycaprolactone (PCL) and polyacrylonitrile (PAN) are used to produce tightly arranged ultrafine fiber meshes via electrospinning in the form of continuous tubular structures, mimicking the basement membrane on which the epithelial barrier is formed. Morphological, physical, mechanical, and piezoelectric properties of the PCL and PAN tubular scaffolds are investigated. They are cultured with Caco-2 cells using different biological coatings (i.e., collagen, gelatin, and fibrin) and their capability of promoting a compact epithelial layer is assessed. PCL and PAN scaffolds show 42% and 50% porosity, respectively, with pore diameters and size suitable to impede cell penetration, thus promoting an intestinal epithelial barrier formation. Even if both polymeric structures allow Caco-2 cell adhesion, PAN fiber meshes best suit many requirements needed by this model, including highest mechanical strength upon expansion, porosity and piezoelectric properties, along with the lowest pore size.

The memristors are expected to be fundamental devices for neuromorphic systems and switching applications. The device made of a sandwiched layer of poly(N- vinylcarbazole) and reduced graphene composite between asymmetric electrodes (ITO/PVK:rGO/Al) exhibits bistable resistive switching behavior. The performance of the memristor can be optimized by controlling the doped graphene oxide. To assess the device performance when it switches between ON and OFF states, optical characterization approaches are highly promising due to their non-destructive and remote nature. Here, speckle pattern (SP) analysis to this end is introduced. SPs include a huge amount of information about their generating mechanism, which is extracted through statistical elaboration. SPs of the PVK:rGO in different states in situ and examine the conduction mechanism is acquired. The variations in the statistical parameters are attributed to the resistance state of the PVK:rGO with regard to the physical switching mechanism. The resistance/conduction state, in turn, depends on the activity and properties of PVK:rGO memristors, as well as the additional non-uniformities induced through the variations of density of carriers. The present optical methodology can be potentially served as a bench-top device for characterization purposes of similar devices during their operating.

The utilization of biofiber in recent years has significantly increased due to its advantages like being environmentally friendly, availability, and low costs. This paper investigates the physicochemical, mechanical, and morphological properties of the yucca fiber extracted by three methods such as water-retting, traditional, and chemical methods. These analyses are designed to evaluate the extraction methodology and the hypothesis of the influence of harvesting location and growth conditions of the fiber. Various technologies are used, such as SEM, FTIR, XRD, and tensile tests. The fiber extracted by water retting is the strongest in the mechanical analysis with a strength of 690.48 MPa, followed by fiber extracted with the traditional method with 685.48 MPa, also 673.06, 657.94, 373.68 MPa for the fiber extracted by the chemical method using 3%, 5%, 10%NaOH respectively. The fiber obtained by the water retting method also has a higher chemical composition with 80.25% cellulose, 10.45% lignin, and 13.75% hemicellulose. The morphological characteristics are examined using Scanning Electron Microscopy. The crystallinity index ranged from 61.75% to 70.77%, and crystallite size from 1.73 to 2.04 nm is calculated from the XRD analysis. All these results confirm that yucca fiber can be a good sustainable choice for composite reinforcement.