Rapidly growing 3D printing of hydrogels requires network materials which combine enhanced mechanical properties and printability. One of the most promising approaches to strengthen the hydrogels consists of the incorporation of inorganic fillers. In this paper, the rheological properties important for 3D printability were studied for nanocomposite hydrogels based on a rigid network of percolating halloysite nanotubes embedded in a soft alginate network cross-linked by calcium ions. Particular attention was paid to the effect of polymer cross-linking on these properties. It was revealed that the system possessed a pronounced shear-thinning behavior accompanied by a viscosity drop of 4–5 orders of magnitude. The polymer cross-links enhanced the shear-thinning properties and accelerated the viscosity recovery at rest so that the system could regain 96% of viscosity in only 18 s. Increasing the cross-linking of the soft network also enhanced the storage modulus of the nanocomposite system by up to 2 kPa. Through SAXS data, it was shown that at cross-linking, the junction zones consisting of fragments of two laterally aligned polymer chains were formed, which should have provided additional strength to the hydrogel. At the same time, the cross-linking of the soft network only slightly affected the yield stress, which seemed to be mainly determined by the rigid percolation network of nanotubes and reached 327 Pa. These properties make the alginate/halloysite hydrogels very promising for 3D printing, in particular, for biomedical purposes taking into account the natural origin, low toxicity, and good biocompatibility of both components.

A transition between the volatile and non-volatile resistive switching regimes is demonstrated in nanocomposite parylene-MoO_x crossbar memristors and used for the development of a homogeneous reservoir computing system.

Reliable parylene–PbTe memristors controlled via electrical and optical stimuli replicate key synaptic functions and are applicable in neuromorphic computing systems.

The results of the microbial synthesis of extracellular silver nanoparticles (Ag NPs) in a liquid medium using the metal-reducing Shewanella oneidensis MR-1 strain and silver-nitrate salts are presented. The shape of the Ag NPs is determined by scanning transmission electron microscopy as close to spherical; more than 50% of Ag NPs have dimensions from 10 to 15 nm. The spectra of energy-dispersive X-ray microanalysis show the presence of Ag peaks in all samples of biogenic Ag NPs. The interplanar distances in the crystals of Ag NPs are 2.71 Å. Fourier-transform infrared (IR) spectroscopy confirms the presence of nitrogen-containing organic compounds of protein nature on the surface of the nanomaterial. The values of the hydrodynamic diameter, zeta-potential, and optical parameters of Ag NPs are determined by dynamic light scattering and spectrofluorimetry. It is shown that a large amount of Ag NPs is present on the surface of S. oneidensis MR-1 cells during biosynthesis. A technological approach is proposed to increase the yield of nanomaterial using the ultrasound treatment of cells, followed by the isolation of Ag NPs. It is shown that the compositions of the protein corona in Ag NPs obtained by the standard method and isolated from the cell surface after ultrasound treatment, as well as the size of Ag NPs, have some differences. A technological method for producing powdered preparations of nanomaterial by lyophilization (freeze drying) of aqueous suspensions of Ag NPs and cellular biomass containing Ag NPs is developed. The possibility of restoring preparations in the form of aqueous suspensions without the agglomeration and sedimentation of nanoparticles is shown. A high biocidal activity of all forms of the nanomaterial as antimicrobial agents of a wide spectrum of activity against gram-positive and gram-negative bacteria and microscopic fungi, including yeasts and phytopathogenic mold fungi, is established, which can be used to create polymer nanocomposites of varying nature with antibacterial properties.

The fiber formation process via the uniaxial stretching jet of concentrated polyacrylonitrile solutions in dimethyl sulfoxide has been investigated. Data on viscoelastic properties obtained by oscillatory shear rheometry have been compared with the evolution of jet thinning during stretching. It was found that at a fixed temperature and moderate air humidity (20%), the jet thinning process involves an initial rapid viscous thinning followed by phase separation and the formation of solid fibers coated with solvent droplets. Changes in morphology as the solution transforms into solid fiber were analyzed using cryo-microscopy. It was demonstrated that at the final thinning stages there exists an increase in a solvent concentration in the near-surface layers of the jet/fiber. Finally, the role of air humidity was analyzed. Two possible scenarios of fiber formation were considered: predominantly due to uniaxial deformation or through coagulation of solution with moisture from the air humidity. Comparative morphological analysis of prepared fiber cross sections showed that monolithic fibers with homogeneous transverse morphology are obtained in the case of strain-induced formation. In contrast, fibers obtained due to phase separation induced by air humidity have gradient porosity. The mechanisms underlying the observed behavior are discussed.

This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope’s drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3–30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.