02240nas a2200121   4500008004100000022001400041245011300055210006900168300001100237490000700248520179100255856007202046       2026                        eng d  a2468-233000aMicro-compression analysis of biopolymer-producing bacteria using Cupriavidus necator as the model bacterium0 aMicrocompression analysis of biopolymerproducing bacteria using   a1001710 v153 a<p>With the development of highly sensitive experimental techniques, the mechanical properties of bacterial cells have become an important research topic. However, existing models used to fit experimental data from micro-compression tests often lack accuracy. The aim of this study was to address this limitation by developing a new curve-fitting mathematical model for evaluating the mechanical properties of rod-shaped bacterial cells. The proposed model is based on a thin-shell approach and is specifically designed for the interpretation of single-cell micro-compression experiments. To verify the applicability of the model, single-cell micro-compression tests were performed using a flat-punch nanoindenter tip larger than the bacterial cells. Atomic force microscopy (AFM) was used to obtain detailed morphological information, including precise cell dimensions required for curve fitting. As a model organism, the polyhydroxyalkanoate-producing bacterium Cupriavidus necator H16 was selected due to its ability to accumulate intracellular polyhydroxybutyrate (PHB) granules. For comparison, a mutant strain, C. necator PHB−4, which lacks PHB production, was also analyzed. The results showed that C. necator H16 cells, with an average PHB content of 72% of dry cell weight, exhibited a Young's modulus approximately 16× higher than that of the PHB−4 mutant, indicating a substantial contribution of intracellular PHB granules to cell stiffness. AFM analysis further revealed that PHB-producing cells were, on average, larger in volume than the non-producing mutant. The combination of AFM and micro-compression testing enabled comprehensive characterization of bacterial cell mechanics and demonstrated a clear correlation between PHB content and mechanical behaviour.</p>  uhttps://www.sciencedirect.com/science/article/pii/S246823302600004601453nas a2200109   4500008004100000022001400041245014700055210006900202300001100271520098900282856007201271       2026                        eng d  a0169-433200aOxidation resistance of organosilicon layered nanostructures synthesized by nonthermal plasma and plasma silica as a source of oxidizing agent0 aOxidation resistance of organosilicon layered nanostructures syn  a1649723 a<p>Plasma polymer (1.2 g cm−3), compact silicon carbide (2.1 g cm−3) and plasma silica (2.2 g cm−3) were synthesized from pure tetravinylsilane vapor or its mixture with argon or oxygen by plasma-enhanced chemical vapor deposition. These materials in the form of nanolayers were combined into layered nanostructures deposited on silicon wafers. XPS depth profiling was used to analyze the chemical depth profiles across the layered nanostructures. The oxidation resistance of highly cross-linked silicon carbide and plasma silica was confirmed after 18 months of storage. However, the plasma polymer with low oxidation resistance must be protected by a 5-nm thick compact silicon carbide barrier to prevent its oxidation. Plasma silica was identified as the source of oxidizing agent for the adjacent plasma polymer in the silica/polymer nanostructure protected by a barrier against the surrounding environment. Oxygen penetrated the polymer by 37 nm in two years.</p>  uhttps://www.sciencedirect.com/science/article/pii/S016943322502688101902nas a2200121   4500008004100000022001400041245010000055210006900155300001100224490000800235520146500243856007201708       2025                        eng d  a0141-813000aMultiscale analysis of mechanical and structural properties of agarose–silk fibroin hydrogels0 aMultiscale analysis of mechanical and structural properties of a  a1481330 v3303 a<p>This study provides a comprehensive characterization of the agarose–silk fibroin hydrogels, using atomic force microscopy and scanning transmission electron microscopy to analyse their structure and assess the effect of composition on mechanical properties via nanoindentation and rheological analysis. These measurements enabled determination of mechanical properties, including the elastic and viscoelastic moduli at both the micro- and macroscale. The hydrogels exhibited a wide range of moduli depending on different degrees of network crosslinking, influenced by varying concentrations of agarose (1 or 2&nbsp;wt%) and the percentage of fibroin fibres (0–4.5&nbsp;wt%) as an interpenetrating component. The viscoelastic modulus (G') and the elastic modulus determined using a relaxation model (E), were 5–57&nbsp;kPa and 1.2–110&nbsp;kPa, respectively. The adhesion energy of these hydrogels was determined from nanoindentation curves and analysed using the JKR model, with values ranging from 0.031 to 0.066&nbsp;J&nbsp;m−2. These results provide insight into how the hydrogels' microstructure influences their mechanical and transport properties. Incorporating fibroin into these gels modifies biological and biochemical characteristics of the gels, suggesting that such composite hydrogels could be further explored for potential applications in controlled release systems, extracellular matrix models, or tissue engineering scaffolds.</p>  uhttps://www.sciencedirect.com/science/article/pii/S014181302508690802416nas a2200121   4500008004100000022001400041245009200055210006900147300001100216490000800227520198700235856007202222       2023                        eng d  a0257-897200aStable a-CSi:H films with a wide range of modulus of elasticity and low internal stress0 aStable aCSiH films with a wide range of modulus of elasticity an  a1291470 v4593 a<p>Amorphous hydrogenated silicon carbide (a-CSi:H) thin films were deposited by plasma-enhanced chemical vapor deposition using tetravinylsilane as organosilicon precursor. The mechanical properties of the thin films, namely the modulus of elasticity, hardness, and elastic recovery parameter, were determined by nanoindentation, as well as the internal stresses by scanning electron microscopy and optical profilometry. It was found that the modulus of elasticity increased from 10 to 137&nbsp;GPa with increasing power (2–150&nbsp;W) delivered to plasma, while the hardness increased from 1.5 to 14.5&nbsp;GPa. This improvement in mechanical properties with increasing energy delivered to the plasma is related to greater fragmentation of the precursor which led to an increase in the crosslinking of the material network. The compressive internal stresses in the films reached low values of −0.04 to −0.2&nbsp;GPa with increasing power (2–75&nbsp;W) and an acceptable −0.5&nbsp;GPa for 150&nbsp;W. The elastic recovery parameter decreased with increasing power from 0.86 to 0.64, i.e., the thin films behaved more plasticity with increasing power. The modulus of elasticity and hardness were investigated in terms of the aging of the films for a period of 6&nbsp;years when samples were stored under ambient conditions. No significant changes in these properties were observed. However, minor changes were observed in the indentation curves obtained for the 2&nbsp;W and even less for the 10&nbsp;W samples. Small changes were then also observed for the elastic recovery parameter, whose value for these samples partially decreased which may be related to postdeposition oxidation. No changes in internal stress values over time were observed. The wide range of mechanical properties of stable a-CSi:H films with low internal stress increases their application potential and their wide use as materials with tailored properties from polymer-like to tough material.</p>  uhttps://www.sciencedirect.com/science/article/pii/S025789722201068401467nas a2200109   4500008004100000245008800041210006900129300001400198490000800212520109100220856004601311       2022                        eng d00aExperimental analysis of microhardness changes of subsurface areas affected by WEDM0 aExperimental analysis of microhardness changes of subsurface are  a1979-19910 v2363 a<p>The influence of the surface area by the impact of high temperatures after wire electric discharge machining (WEDM) is a known fact. However, the affected parameters also include a change in microhardness. In order to further investigate this statement, 5 different ferrous and non-ferrous materials were selected, from which three samples were always made with different settings of machine parameters (gap voltage, pulse on and off time, wire feed and discharge current). This examined not only the effect of the machining itself on the material but also whether the change in the microhardness of the material is affected by the setting of the machine parameters. In order to measure the microhardness of the subsurface layer, a metallographic preparation was made from each sample, which enabled accurate measurements always in the same area. Subsequent evaluation revealed that the microhardness may not be affected at all and everything depends only on the type of material being machined. The changes in microhardness affected by setting machine parameters are negligible.</p>  uhttps://doi.org/10.1177/0954408922107838302491nas a2200121   4500008004100000022001400041245005600055210005600111300001100167490000800178520211100186856007202297       2022                        eng d  a0040-609000aSurface topography affects the nanoindentation data0 aSurface topography affects the nanoindentation data  a1391050 v7453 a<p>The near-surface mechanical properties of thin films as well as bulk materials are amongst the key parameters important for their application, and instrumented nanoindentation is a standard technique for determining these mechanical properties. However, it is known that the surface topography of the characterized materials may affect the nanoindentation data when a sharp indenter for small penetration depths (displacements) is used. A thin film of hydrogenated amorphous silicon carbide with a thickness of 1.0&nbsp;μm was deposited on a silicon wafer by plasma-enhanced chemical vapour deposition. The cyclic nanoindentation was used to construct a depth profile of mechanical properties for the flat surface (0.5&nbsp;nm roughness) of the thin film, which made it possible to determine its modulus of elasticity of 83&nbsp;GPa and hardness of 8.6&nbsp;GPa unaffected by the silicon substrate. Grains with a spherical cap geometry with a typical radius of 0.5&nbsp;µm and a&nbsp;height of 60&nbsp;nm are distributed along the flat surface of the film. The grains have the same mechanical properties as the deposited film. Depth profiles of mechanical properties were determined for different types of contact between the Berkovich indenter with a radius of 50&nbsp;nm and the selected grain (grain top, grain foot, two or three grains); i.e. for these measurements the following applied - the radius of the tip curvature was less than grain radii (RBerkovich &lt; Rgrain). Residual imprints after nanoindentation measurements were carefully observed by atomic force microscopy and scanning electron microscopy. The near-surface mechanical properties were significantly affected by the surface topography, and the determined modulus of elasticity and hardness were crucially under- or overestimated in the range of 50% to 100% compared to the real values. The nature of these deviations was discussed. The solution is to use cyclic nanoindentation performed on the flat surfaces or on the top of grains, followed by extrapolation of the depth profiles to the zero-contact depth (film surface).</p>  uhttps://www.sciencedirect.com/science/article/pii/S0040609022000268