Poly (ε-caprolactone)/Poly (lactic acid) fibers produced by rotary jet spinning for skin dressing with antimicrobial activity

The rotary jet spinning technique permits the production of biomaterials that can be used as devices that come into contact with biological systems (including biological fluids) for diagnostic or surgical applications. These materials are composed of synthetic or natural compounds and allow the incorporation of drugs for therapeutic purposes. Two solutions containing 50% poly(lactic acid) (PLA) and 50% poly(ε-caprolactone) (PCL) diluted in three different solvents were prepared for rotary jet spinning (RJS) process. Vancomycin, an antibiotic indicated for the treatment of severe staphylococcal infections in patients with penicillin allergy, was added in the polymer solutions, to obtain drug-loaded fibrous mats. Morphological surface characterization by scanning electron microscopy revealed heterogeneous pores in the microfibers. Vancomycin loading interfered with the morphology of all samples in terms of fiber size, leading to smaller diameter fibers. Attenuated total reflectance/Fourier transform infrared spectroscopy was used for identification of the samples. The vibrational characteristics of PCL/PLA and vancomycin were consistent with expectations. Vero cell culture assays by the extract dilution and direct contact methods revealed the absence of cytotoxicity, except for the sample prepared with 50% of PCL and of a 9/2 (V/V) vancomycin content, with the growth of confluent and evenly spread cells on the fibrous mats surface. Microbiological analysis, performed on Staphylococcus aureus by the halo inhibition test and by the broth dilution method, showed that the antibacterial activity of vancomycin was maintained by the loading process in the polymer fibers. The results showed that rotary jet spinning produces satisfactory amounts of Vancomycin-loaded fibers, as potential web dressing for wound repair

Towards Electron-Beam-Driven Soft / Polymer Fiber Microrobotics for Vacuum Conditions

The possibility of creating vacuum robotics based on the polymer structures irradiated by an electron beam, in particular, polymer fibers, which provide high functional flexibility and a variety of states, is discussed. The possibility of using polymer fibers as different types of MEMS-like electromechanical elements is demonstrated - from elastic cantilevers to springs that change their state under the electron beam. Experimentally proved the presence of different functional types of fibers, correlating with their thickness, as well as the phenomenon of the fiber break. A number of exotic forms of dynamics have been demonstrated and a method for their detection has been developed using 2D Fourier spectra, integral spatial characteristics, time resolved correlograms and wavelet transforms (visualized as the scaleograms / scalograms). Access barcodes for the full video records of the corresponding experiments are provided.

Analysis of additional armor protection for lightly armored vehicles of the Armed Forces of Ukraine and foreign states

World military conflicts show that the armor protection of most light armored vehicles does not meet modern requirements. The constant development and improvement of fire weapons makes it necessary to search for new constructive solutions in this area. Increasing the level of armor protection by increasing the thickness of the armor is a hopeless path, since it will lead to an increase in the mass of the vehicle, and this, in turn, will negatively affect the power plant and chassis. One of the ways to increase the level of protection is the use of new booking schemes using modern armored materials. This article analyzes publications devoted to modern scientific research related to the development and improvement of armor protection for light armored vehicles, as well as an analysis and assessment of options for the use of modern armored materials and various structures to protect vehicle crews and increase the level of tactical and technical characteristics. It is shown that at present, in connection with traditional approaches in the design of armored vehicles, the advantage is given to armored steels, aluminum and titanium alloys. However, there is a trend towards the use of lighter ballistic materials such as ceramics and composites with polymer fibers. The basis for the creation of reliable armor protection for lightly armored vehicles has been determined – the development of new promising structures for combined protection using new armor materials and their various options. Variants of additional armor protection systems of both foreign manufacturers and domestic developments are presented. The new systems include several special materials that differ from each other in a wide range of physical and mechanical properties. The use of such protection, together with the main armor, can reduce the mass performance of the vehicle. It has been determined that the creation of new designs of armored elements using the most modern technologies will lead to a significant increase in the protective characteristics of the armor of light armored vehicles.

Encapsulation of Recrystallized Inorganic Perovskite Quantum Dots in Nonwoven Fluoropolymer Fibers

Since emerging Metal Halide Perovskites were attracting elevated attention from scientific and industrial communities. Although, we still yet to see commercial products based on perovskite materials a significant body of work has been already done. Here we present our own method of Metal Halide Perovskites integration into possible industrial applications. Our way of Perovskite Quantum Dots encapsulation in polymer fibers provides exceptional water and ambient stability as well as optimal photoluminescence.

Spinning conditions affect structure and properties of Nephila spider silk

Raman spectroscopy is used to elucidate the effect of spinning conditions upon the structure and mechanical properties of silk spun by Nephila spiders from the major ampullate gland. Silk fibers produced under natural spinning conditions with spinning rates between 2 and 20 mm s−1 differed in microstructure and mechanical properties from fibers produced either more slowly or more rapidly. The data support the “uniform strain” hypothesis that the reinforcing units in spider silk fibers are subjected to the same strain as the fiber, to optimize the toughness. In contrast, in the case of synthetic high-performance polymer fibers, the both units and the fiber experience uniform stress, which maximizes stiffness. The comparison of Nephila major and minor ampullate silks opens an intriguing window into dragline silk evolution and the first evidence of significant differences between the two silks providing possibilities for further testing of hypotheses concerning the uniform strain versus uniform stress models. Impact statement It is well established that the microstructure and mechanical properties of engineering materials are controlled by the conditions employed to both synthesize and process them. Herein, we demonstrate that the situation is similar for a natural material, namely spider silk. We show that for a spider that normally produces silk at a reeling speed of between 2 and 20 mm s−1, silk produced at speeds outside this natural processing window has a different microstructure that leads to inferior tensile properties. Moreover, we also show that the silk has a generic microstructure that is optimized to respond mechanically to deformation such that the crystals in the fibers are deformed under conditions of uniform strain. This is different from high-performance synthetic polymer fibers where the microstructure is optimized such that crystals within the fibers are subjected to uniform stress. Graphic abstract

Effect of Cold Plasma Treatment of Polymer Fibers on the Mechanical Behavior of Fiber-Reinforced Cementitious Composites

Fiber-reinforced cementitious composites (FRCC) are a class of materials made by adding randomly distributed fibers to a cementitious matrix, providing better material toughness through the crack bridging behavior of the fibers. One of the primary concerns with FRCCs is the behavior of the fiber when a crack is formed. The fibers provide a stress-bridging mechanism, which is largely determined by the bond that exists between the concrete and the fiber’s outer surface. While many studies have determined the properties of FRCCs and potential benefits of using specific fiber types, the effects of low temperature or cold plasma treatment of polymer fibers on the mechanical behavior of the composite material are limited. Polymer fibers are notable for their low density, ductility, ease of manufacture, and cost-effectiveness. Despite these advantages, the surface properties of polymers do not enable the bonding potential given by steel or glass fibers when used in untreated FRCC, resulting in pull-out failures before the full displacement capacity of the fiber is utilized. For this reason, modification of the surface characteristics of polymer fibers can aid in higher bonding potential. Plasma treatment is a process wherein surfaces are modified through the kinetics of electrically charged and reactive species in a gaseous discharge environment. This paper is a preliminary study on the use of atmospheric pressure plasma generated at approximately room temperature. This atmospheric, cold plasma treatment is a method for improving the mechanical properties of FRCC using polymeric fibers. In this study, polypropylene and polyvinyl-alcohol fibers were cold plasma treated for 0, 30, 60, and 120 s before being used in cementitious mortar mixtures. Compression and flexure tests were performed using a displacement-based loading protocol to examine the impact of plasma treatment time on the corresponding mechanical performance of the fiber-reinforced cementitious composite. The experimental results obtained from this study indicate that there is a positive correlation between fiber treatment time and post-peak load-carrying capacity, especially for specimens subjected to flexural loading.