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Glycerol-Enhanced Gum Karaya Hydrogel Films with a Sandwich-like Structure Enriched with Octenidine for Antibacterial Action against Multidrug-Resistant Bacteria
(2025-07-02) Černá, Eva; Neděla, Vilém; Tihlaříková, Eva; Brtníková, Jana; Fohlerová, Zdenka; Lipový, Břetislav; Vacek, Lukáš; Růžička, Filip; Matulová, Jana; Vojtová, Lucy
This study explores the innovative approach in the development of freeze-dried hydrogel films, leveraging the unique properties of gum Karaya (GK), poly(vinyl alcohol) (PVA), poly(ethylene glycol) (PEG), and glycerol with a coating of octenidine dihydrochloride (OCT). These innovative hydrogel films exhibit at a certain glycerol concentration a sandwich-like structure, achieved through a tailored freeze-drying process, which enhances transparency and mechanical stability. OCT provides superior antibacterial performance, effectively combating multidrug-resistant bacteria with a controlled and gradual release mechanism, surpassing conventional OCT solutions that require frequent reapplication for infected wound treatment without the creation of bacterial resistance. Advanced environmental scanning electron microscopy (A-ESEM) reveals the complex microstructure of the hydrogel, highlighting the dense surface layer and interconnected porous bulk. Variations in glycerol concentrations proved to significantly impact hydrogels' properties. Increasing the glycerol concentration decreases the pore size (around 4.5 mu m) while enhancing the polymer network density and flexibility. However, low concentration increases the pore size (7.8-15.6 mu m), impacting enhanced swelling behavior and hydrolytic stability. OCT's rapid antibacterial action, releasing over 30% within the first hour and maintaining prolonged activity for up to 2 weeks, emphasizes the material's potential for diverse applications. Hydrogels' remarkable transparency, porosity, structural stability, and antibacterial efficacy against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli strains suggest promising uses as transparent dressings, biomedical devices, and infection-resistant surfaces.
Nanostructures for Achieving Selective Properties of a Thermophotovoltaic Emitter
(MDPI, 2021-08-19) Šimonová, Lucie; Matějka, Milan; Knápek, Alexandr; Králík, Tomáš; Pokorná, Zuzana; Mika, Filip; Fořt, Tomáš; Man, Ondřej; Škarvada, Pavel; Otáhal, Alexandr; Čudek, Pavel
This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter.
Study of micro structural material changes after WEDM based on TEM lamella analysis
(MDPI, 2020-06-07) Mouralová, Kateřina; Zahradníček, Radim; Beneš, Libor; Prokeš, Tomáš; Hrdý, Radim; Fries, Jiří
Wire electrical discharge machining is an unconventional machining technology that is crucial in many industries. The surface quality of the machined parts is carefully monitored, but the condition of the subsurface layer also plays a crucial role, especially in case of defects occurrence such as cracks or burnt cavities. The subsurface layer of individual materials is affected differently due to wire electrical discharge machining. For this reason, this study was carried out focusing on a detailed analysis of transmission electron microscope (TEM) lamellae made of Ti-6Al-4V titanium alloy, AlZn6Mg2Cu aluminium alloy, pure molybdenum, Creusabro 4800 steel, and Hardox 400 steel. The attention was first of all paid to the concentration and distribution of individual elements in the recast layer and also in the base material, which was often affected by Wire electrical discharge machining. Further, a diffraction analysis was performed for each TEM lamella in the adhesive area and in the area of the base material. In order to assess the macro-effects on the machined material, the analysis of the topography of the machined surfaces and the morphology analysis were performed using electron microscopy.
Chemical Separation on Silver Nanorods Surface Monitored by TOF-SIMS
(Hindawi, 2017-06-01) Petruš, Ondrej; Oriňák, Andrej; Oriňáková, Renáta; Christian, Muhmann; Macko, Ján; Hrdý, Radim; Hubálek, Jaromír; Erdelei, Branislav; Arlinghaus, Heinrich F.
The article introduces a possible chemical separation of a mixture of two compounds on the metal nanorods surface. A silver nanorods surface has been prepared by controlled electrochemical deposition in anodic alumina oxide (AAO) template. Rhodamine 6G and 4-aminothiophenol have been directly applied to the sampling point on a silver nanorods surface in an aliquot mixture. The position of the resolved compounds was analysed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) which measured the fragments and the molecular ions of the two compounds separated on the silver nanorods surface. Rhodamine 6G has been preconcentrated as 1.5 mm radial from the sampling point while 4-aminothiophenol formed a continuous self-assembled monolayer on the silver nanorods surface with a maximum molecular ion intensity at a distance of 0.5 mm from the sampling point. The separation of the single chemical components from the two-component mixture over the examined silver nanostructured films could clearly be shown. A fast separation on the mentioned nanotextured films was observed (within 50 s). This procedure can be easily integrated into the micro/nanofluidic systems or chips and different detection systems can be applied.
0.3-V Nanopower Biopotential Low-Pass Filter
(IEEE, 2020-06-29) Kulej, Tomasz; Khateb, Fabian; Kumngern, Montree
This paper presents a compact power-efficient CMOS fourth-order low-pass filter suitable for electrocardiogram (ECG) acquisition systems. The CMOS structure of the proposed filter utilize the bulkdriven technique and operates in subthreshold region to achieve extremely low-voltage supply (0.3V) and nanopower consumption (0.676 nW) for cut-off frequency of 100 Hz. The filter was designed and simulated using 0.18 mu m CMOS TSMC technology. The total input referred noise of the filter is 87 mu Vrms and the dynamic range is 58.1 dB. The filter offers the best figure of merit of 2.91 x 10(-14) J, the lowest power consumption and voltage supply, compared with the previous state-of-the-art nanowatt filter designs.

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