Nonwovens produced through electrospinning technique have been successfully used in various fi elds due to their unique properties. It is essential to investigate the impact of the parameters in the manufacturing process on the resulting properties of these materials. This research focuses on nonwovens made from fl uoroplast P(VDF-TFE) using a horizontal spraying system with a vertically positioned collector. The parameters studied include the interelectrode distance, the electric fi eld strength, and the viscosity of the molding solution. The study aims to determine the optimal parameters for producing nonwovens with specifi c characteristics, such as size, fi ber diameter, and surface wettability. The results indicate that the interelectrode distance between 15 and 25 centimeters yields the best results. In this study, we have investigated the change in viscosity of the solution during the electrospinning process and have found that it should not exceed 5–7%. Additionally, we have observed changes in the structure of the polymer macromolecules, which depended on the rate of solvent evaporation during the fi ber stretching process. The results obtained in this research can be used to optimize the technological processes for industrial production of nonwoven fabrics made from fl uoroplast P(VDF-TFE) with specifi c properties.

Vacuum electron devices operating at sub-THz frequencies require miniaturized high-frequency electromagnetic interaction structures manufactured using high-precision micromachining technologies. In this article, we present the results of microfabrication of 2-D planar microstrip periodic slow wave structures (SWSs) on dielectric substrate using magnetron sputtering and laser micromachining. A multistage optimized process that allows a substantial improvement of the fabrication accuracy is presented and discussed in detail. A batch of V-band meander-line SWS circuits is fabricated. Characterization of the fabricated structures by optical microscopy and scanning electron microscopy (SEM) demonstrates dimensional deviation less than 5 mu m. Experimental investigation of cold-test electromagnetic parameters shows good transmission and reflection characteristics.

A theoretical model is proposed that allows us to describe the processes of formation of the sputtered atom flow, transport of this flow in the target-substrate space and deposition of the substance onto the substrate during magnetron sputtering. The main difference between the presented model and the existing ones is the combined consideration of the spatial distribution of sputtered atoms and the temperature gradient in the working chamber during magnetron sputtering at high power. To verify the model, real technological parameters of deposition of metal films by magnetron sputtering were used, optimized to achieve a high film growth rate. The agreement between the calculated film thicknesses obtained as a result of modeling and the experimental data was no worse than 5% at discharge powers in the range of 100 – 700 W. Comparison of the experimental data with the simulation results showed that the model adequately describes the sputtering processes at high discharge powers and low pressures, in contrast to approaches that do not take into account the temperature gradient in the working space.

This paper presents the results of the study of silicon crystallization on flexible polyimide substrates. Crystallization was carried out by the method of metal-induced laser-stimulated crystallization. A feature of this work is the use of refractory metals such as molybdenum and tungsten as an absorbing layer. An infrared pulsed laser is used for crystallization. To determine the quality of crystallization, the structure of silicon was studied by Raman scattering.

The work is devoted to the formation of polycrystalline silicon coatings on electrospinned nonwoven polyacrylonitrile mats using a metal layer absorbing laser radiation. The results of experimental studies confirming the presence of crystallized silicon structures on non-woven polymer substrates are presented. The efficiency of tin films with different thicknesses is compared when using them as upper laser-absorbing layers during laser-stimulated metal-induced crystallization of silicon. It was found out that during laser processing, the metal does not ablate completely and the remaining part of it is collected into particles, the size of which depends on the initial thickness of the metal film. It has also been established that during the laser annealing process expansion or glass transition of fibers can occur.

Nowadays, additive manufacturing appears to be very promising for rapid, straightforward, and cost-effective fabrication of various novel circuits and components for millimeter- and THz-band electron devices. This paper presents the results of microfabrication of millimeter-band components by digital light processing (DLP) 3-D printing and magnetron sputtering. The cold-test electromagnetic measurements show good transmission and reflection properties of the fabricated structures.

Femtosecond laser irradiation of amorphous silicon films makes it possible to fabricate the laser-induced periodic surface structures which provide noticeable dichroism and birefringence of the films in the infrared range.

The effect of the ratio of CdS and PbS components on the surface morphology, optical and photoelectric characteristics of films obtained by hydrochemical deposition has been studied. It is shown that, depending on the predominance of CdS or PbS in the film, the surface morphology changes significantly, which correlates with changes in the optical and photoelectric characteristics. An increase in the stability of photoelectric characteristics is demonstrated only by samples with a predominance of CdS. When PbS predominates, photoquenching and slow relaxation of the dark current after illumination are observed.

Trends concerning the acceleration of the development of novel millimeter and terahertz-band vacuum microelectronic devices highly demand rapid and cost-effective techniques that allow microfabrication of the proof-of-concept physical models. The additive manufacturing can meet the abovementioned requirements. Nowadays, vat photopolymerization is one of the most flexible and precise additive technologies that allows fabrication of microsized elements with tolerance down to tens of microns. We proposed an approach based on the liquid crystal display vat photopolymerization and vacuum magnetron sputtering for rapid and low-cost microfabrication of the key sub-terahertz-band electromagnetic components. To validate the proposed approach, several samples of single grating slow-wave structure for a W-band (75-110 GHz) vacuum-tube device were successfully microfabricated for the first time. The structure with total length of 60 mm consisted of a 20-pitch uniform section and two 11-pitch tapered sections at both ends in order to reduce the reflections. Magnetron sputtering was used to deposit the thin copper film onto the inner surface of the fabricated samples. The surface roughness was measured before and after metallization using profilometry. Morphological and profilometric analyses have shown a decrease in the surface roughness up to 30% after 1-mu m-thick metallization and up to 50% after 3-mu m-thick metallization. Results indicate that a 3-mu m-thick metallization layer sufficiently meets requirements for suitable reflection and transmission losses in the W-band. Reflection and transmission losses in the W-band of the fabricated slow-wave structure were measured using a vector network analyzer and compared with the results of numerical simulation using 3D finite-difference time-domain code. Comparison with the numerical simulation results shows good qualitative and quantitative agreement. The measured reflections were below - 20 dB in the 88-105 GHz frequency range. The specific transmission attenuation was measured to be 0.08 dB per pitch. This study underscores the promise of the proposed method for swiftly prototyping complex electromagnetic structures, leading to significant time savings in proof-of-concept research endeavors.

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool and an up-to-date method of analytical chemistry due to its high sensitivity and fingerprint recognition capabilities. Nowadays SERS due to its label-free detection capabilities is being actively developed in medical fields, for example in the analysis of biologically important substances in different matrixes, for potential on-site detection of toxic substances, food safety, and so on. To get the SERS signal, it is necessary the presence of plasmonic nanostructures in the SERS substrates. Electrospun nanofibers have been an attractive alternative to SERS-platforms due to the diversity of advantages, including ease of preparation, structure flexibility, and others. In this review, we summarized the methods of plasmonic nanostructures incorporating substrate based on electrospun nanofibers. Also, the analytical application of SERS-active electrospun nanofibers with embedded nanostructures focused on biologically significant molecules is observed in detail. Finally, the future outlook in the application of these substrates in bioanalysis as the most promising area in analytical chemistry is presented.

The technology for fabrication of miniaturized slow-wave structures (SWS) for upper-millimeter-band vacuum microelectronic devices is presented. Nanosecond-pulse laser ablation technique was used to fabricate such micro-dimensional structures. Planar microstrip SWSs on dielectric substrates and all-metal ladder-type planar SWSs are fabricated for operation in V-band (40-75 GHz) and in W-band (75-110 GHz). The results of a morphological study and cold-test measurement of electromagnetic parameters are also presented.

Development of upper-millimeter or sub-THz radiation sources is of great importance for numerous applications in communications, radar, spectroscopy, etc. For fabrication of miniaturized electromagnetic components, novel precise, rapid, and cost-effective technologies are required. In this paper, we present the results of microfabrication of millimeter-band electromagnetic structures using digital-light-processing (DLP) 3-D printing and subsequent metallization by magnetron sputtering. V-band and W-band rectangular waveguides were fabricated, as well as more complicated periodic grating slow-wave structures. Characterization of the fabricated structures was performed by using surface morphology studies and scanning electron microscopy. Cold-test electromagnetic measurements reveal good transmission properties of the fabricated structures.

The effect of an extremely low frequency alternating magnetic field (ELF AMF) at frequencies of 17, 48, and 95 Hz at 100 mT on free and internalized 4T1 breast cancer cell submicron magnetic mineral carriers with an anticancer drug, mitoxantrone, was shown. The alternating magnetic field (100 mT; 17, 48, 95 Hz; time of treatment—10.5 min with a 30 s delay) does not lead to the significant destruction of carrier shells and release of mitoxantrone or bovine serum albumin from them according to the data of spectrophotometry, or the heating of carriers in the process of exposure to magnetic fields. The most optimal set of factors that would lead to the suppression of proliferation and survival of cells with anticancer drug carriers on the third day (in comparison with the control and first day) is exposure to an alternating magnetic field of 100 mT in a pulsed mode with a frequency of 95 Hz. The presence of magnetic nanocarriers in cell lines was carried out by a direct label-free method, space-resolved Brillouin light scattering (BLS) spectrometry, which was realized for the first time. The analysis of the series of integrated BLS spectra showed an increase in the magnetic phase in cells with a growth in the number of particles per cell (from 10 to 100) after their internalization. The safety of magnetic carriers in the release of their constituent ions has been evaluated using atomic absorption spectrometry.

In this work, the influence of illumination on the adsorption of enzyme molecules from an aqueous solution on a single-crystal silicon substrate with a layer of amorphous silicon (a-Si) is shown by atomic force microscopy. It was shown that the effect of illumination during the formation of an enzyme layer depends both on the type of Si conductivity and on the presence of an a-Si layer on the surface. The 2-beam interference pattern on the surface of the n-Si/a-Si structure, fabricated by illumination with a wavelength of 491 nm before the adsorption process, made it possible to fabricate ordered rows of the precipitated enzyme. This pattern not observed for p-Si/a-Si structure or bare substrate of single-crystal Si without the amorphous silicon layer. The developed technique is promising for the fabrication of multienzyme coatings for multiplex analysis using silicon transducer.

In this paper, we present the results aimed at development of a miniaturized traveling-wave tube (TWT) amplifier with a microstrip meander-line (MML) slow-wave structure (SWS) operating at V band. The MML SWS on quartz substrate was designed and fabricated using the technology based on laser ablation and magnetron sputtering. Cold-test electromagnetic parameters of the SWS are measured and compared with the simulations. An electron gun with high compression of a low-voltage (5 kV) sheet electron beam is designed and beam transmission in a uniform magnetic field is studied. Hot-test operation of the TWT is simulated by a 3-D particle-in-cell (PIC) code. The simulations predict small-signal gain of 28 dB and nearly 14 W saturated power.

For vacuum microelectronic devices operating at sub- THz frequencies, tiny slow-wave structures must be produced using high-precision microfabrication technologies. Nowadays, a variety of high-tech technologies, including UV-LIGA, deep reactive ion etching, 3D printing, nano-CNC milling, and laser micromachining, are used to fabricate microsized electromagnetic structures with micron and sub-micron accuracy. In this paper, we present an enhancement of our previously developed method for microfabrication of the designed 2D planar microstrip slow-wave structures for V-band operation using magnetron sputtering and nanosecond laser micromachining. A detailed illustration of the improved laser-based micromachining approach is presented. We'll go into great depth about the outcomes of the morphological analyses of the microfabricated samples slow-wave structures.

We propose a technology based on the liquid crystal display (LCD) 3D printing and magnetron sputtering for rapid and low-cost fabrication of millimeter-band electromagnetic components. To verify the proposed approach, D- and H-band straight waveguide sections were fabricated. Magnetron sputtering was used to deposit a thin copper film onto the inner surface of the fabricated structures. Morphology and profilometry studies revealed that the fabrication tolerance corresponds to the pixel size of the LCD screen in the used 3D printer, while the surface roughness is less than 500 nm with a metallization layer thickness of 5 $\mu \mathrm{m}$ . For the D-band 3D-printed samples, measured reflection loss was not worse than 20 dB, while the transmission loss was around 1–2 dB/cm. The reflection loss for the H-band samples was found to be around 15 dB, while the transmission loss ranged from 3 to 5 dB/cm. Several ways to decrease the transmission loss will be discussed.

The absorption of light in the near-infrared region of the electromagnetic spectrum by Au-hyperdoped Si has been observed. While silicon photodetectors in this range are currently being produced, their efficiency is low. Here, using the nanosecond and picosecond laser hyperdoping of thin amorphous Si films, their compositional (energy-dispersion X-ray spectroscopy), chemical (X-ray photoelectron spectroscopy), structural (Raman spectroscopy) and IR spectroscopic characterization, we comparatively demonstrated a few promising regimes of laser-based silicon hyperdoping with gold. Our results indicate that the optimal efficiency of impurity-hyperdoped Si materials has yet to be achieved, and we discuss these opportunities in light of our results.

A method for preparation of luminescent silicon coatings applicable to both rigid glass substrates and flexible nonwoven polymeric electrospun mats is proposed. This technique allows for synthesis of nanosized silicon crystallites that fluoresce in visible and near-IR light. Proposed approach to preparation of nanostructured fluorescent fibrous materials seems promising for applications in biosensing.