Photo-Healable Fabrics: Achieving Structural Control via Photochemical Solid-Liquid Transitions of Polystyrene/Azobenzene-Containing Polymer Blends.

While polymer fabrics are integral to a wide range of applications, their vulnerability to mechanical damage limits their sustainability and practicality. Addressing this challenge, our study introduces a versatile strategy to develop photohealable fabrics, utilizing a composite of polystyrene (PS) and an azobenzene-containing polymer (PAzo). This combination leverages the structural stability of PS to compensate for the mechanical weaknesses of PAzo, forming the fiber structures. Key to our approach is the reversible trans-cis photoisomerization of azobenzene groups within the PAzo under UV light exposure, enabling controlled morphological alterations in the PS/PAzo blend fibers. The transition of PAzo sections from a solid to a liquid state at a low glass transition temperature (Tg ∼ 13.7 °C) is followed by solidification under visible light, thus stabilizing the altered fiber structures. In this study, we explore various PS/PAzo blend ratios to optimize surface roughness and mechanical properties. Additionally, we demonstrate the capability of these fibers for photoinduced self-healing. When damaged fabrics are clamped and subjected to UV irradiation for 20 min and pressed for 24 h, the mobility of the cis-form PAzo sections facilitates healing while retaining the overall fabric structure. This innovative approach not only addresses the critical issue of durability in polymer fabrics but also offers a sustainable and practical solution, paving the way for its application in smart clothing and advanced fabric-based materials.

Hollow Hafnium Oxide (HfO2) Fibers: Using an Effective Combination of Sol-Gel, Electrospinning, and Thermal Degradation Pathway.

In recent years, hafnium oxide (HfO2) has gained increasing interest because of its high dielectric constant, excellent thermal stability, and high band gap. Although HfO2 bulk and film materials have been prepared and well-studied, HfO2 fibers, especially hollow fibers, have been less investigated. In this study, we present a facile preparation method for HfO2 hollow fibers through a unique integration of the sol-gel process and electrospinning technique. Initially, polystyrene (PS) fibers are fabricated by using electrospinning, followed by dipping in a HfO2 precursor solution, resulting in HfO2-coated PS fibers. Subsequent thermal treatment at 800 °C ensures the selective pyrolysis of the PS fibers and complete condensation of the HfO2 precursors, forming HfO2 hollow fibers. Scanning electron microscopy (SEM) characterizations reveal HfO2 hollow fibers with rough surfaces and diminished diameters, a transformation attributed to the removal of the PS fibers and the condensation of the HfO2 precursors. Our study also delves into the influence of precursor solution molar ratios, showcasing the ability to achieve smaller HfO2 fiber diameters with reduced precursor quantities. Validation of the material composition is achieved through thermogravimetric analysis (TGA) and energy-dispersive spectroscopy (EDS) mapping. Additionally, X-ray diffraction (XRD) analysis provides insights into the crystallinity of the HfO2 hollow fibers, highlighting a higher crystallinity in fibers annealed at 800 °C compared with those treated at 400 °C. Notably, the HfO2 hollow fibers demonstrate a water contact angle (WCA) of 38.70 ± 5.24°, underscoring the transformation from hydrophobic to hydrophilic properties after the removal of the PS fibers. Looking forward, this work paves the way for extensive research on the surface properties and potential applications of HfO2 hollow fibers in areas such as filtration, energy storage, and memory devices.

Smart Thermoresponsive Electrospun Nanofibers with On-Demand Release of Carbon Quantum Dots for Cellular Uptake.

Developing a smart responsive surface for on-demand delivery of organic, inorganic, and biological cargo in vitro cellular uptake is always in constant demand. Herein, we present carbon quantum dot (CQD)-loaded (poly(N-isopropylacrylamide) (PNIPAAm)/poly(methyl methacrylate (PMMA)) blend nanofiber sheets having a thermoresponsive nature. As a model cargo, fluorescent CQDs are used for the demonstration of the on-demand delivery mechanism. In addition, a thermoresponsive nature is produced by the PNIPAAm polymer in the nanofiber matrix while the PMMA polymer provides extra stability and firmness to the nanofibers against the sudden dissolution of the nanofibers in aqueous media. The synthesis of CQDs and their loading into a blend nanofiber matrix are confirmed using fluorescence spectrophotometry, transmission electron microscopy, and fluorescence microscopy. The morphologies and diameters of the nanofibers are analyzed by scanning electron microscopy. Burst effect analysis proves that 30% (w/w) PNIPAAm-containing nanofibers possess the highest stability with the least dissolution in aqueous media. Thermoresponsiveness of the nanofibers is further confirmed through water contact angle measurements. Quantitative fluorescence results show that more than 80% of loaded CQDs can be released upon thermal stimulation. The fluorescence micrographs reveal that the blend nanofiber sheets can effectively improve the cellular uptake of CQDs by simply increasing the local concentrations via applying thermal stimulation as the released mechanism.

Effects of Integrative Neuromuscular Training Combined With Regular Tennis Training Program on Sprint and Change of Direction of Children.

OBJECTIVE: The aim of this study was to investigate the effects of integrative neuromuscular training (NMT) on sprint and the ability to change direction for children who are between the ages of 7 and 8 and beginning to play tennis. METHODS: Thirty-two participants were randomized into a training group (TG; n = 16) and a control group (CG; n = 16). All participants attended tennis classes twice a week for a continuous 8 weeks. In addition, the TG received NMT (e.g., 20-m sprints, running at four corners, rope ladder drills, etc.), which progressed in difficulty every 2 weeks. Pre-intervention and post-intervention measurements, including a 30-m sprint test, a 5-10-5 test, and a 3 × 10 m shuttle run test, were assessed by a Smartspeed laser timing gate system, while the spider agility test was evaluated with a stopwatch. RESULTS: Two-way repeated measures ANOVA found significant differences in the interaction between time and group among variables measured. Results were as follows: time in the 30 m sprint (F = 13.467, 95% CI = 7.163-7.506, p = 0.001, η 2 p = 0.310, Δ = 0.42 s); 5-10-5 test (F = 13.975, 95% CI = 8.696-9.017, p = 0.001, η 2 p = 0.318, Δ = 0.78 s); 3 × 10 m shuttle run (F = 7.605, 95% CI = 11.213-11.642, p = 0.01, η 2 p = 0.202, Δ = 0.77 s); and spider agility test (F = 34.555, 95% CI = 28.258-29.670, p < 0.001, η 2 p = 0.535, Δ = 3.96 s). The results demonstrated a greater decrease in sprint and change of direction (COD) time among the TG than the CG from pre-intervention to post-intervention. CONCLUSION: A regular tennis training combined with NMT program could produce greater improvement in a player's sprint and ability to change direction when introduced to childhood tennis beginners in a sensitive period, compared to tennis class intervention only.

Light-Induced Nanowetting: Erasable and Rewritable Polymer Nanoarrays via Solid-to-Liquid Transitions.

Template wetting methods have been widely applied in the preparation of one-dimensional (1D) polymer nanomaterials. The pattern control using the template wetting methods, however, still remains a great challenge, mainly due to the nonselectivity of the polymers toward the environmental triggering. In this work, we present a facile light-induced nanowetting (LIN) method to fabricate patterned nanoarrays using anodic aluminum oxide (AAO) templates. Photoresponsive azobenzene-containing polymers (azopolymers) that exhibit light-induced reversible solid-to-liquid transitions are used. Upon exposure to ultraviolet lights, the azopolymer chains can wet the nanopores of the AAO templates in a liquid state via capillary force. The azopolymer chains are then solidified by illuminating them with visible lights, resulting in the formation of azopolymer nanoarrays. Notably, using designed photomasks, the patterns of the nanoarrays can be ingeniously controlled with the characteristic of erasable and rewritable nanostructures.