DNA nanopatterning with self-organization by using nanoimprint

The paper presents the results of a study of the freezing point of polyvinyl alcohol (PVA) solutions dissolved in dimethyl sulfoxide (DMSO) and water. The influence of the nature of the solvent and glycerin additives on the freezing temperature of the PVA solution was determined. Elastic and thermophysical properties of cryogels based on PVA solutions were studied. It was found that PVA cryogels formed in DMSO have a lower elastic modulus and melting point than cryogels formed from aqueous PVA solutions. Since DMSO is a thermodynamically better solvent for PVA than water, i.e. the affinity of the polymer for DMSO is higher, this reduces the efficiency of gelation due to competition between polymer-solvent and polymer-polymer interactions. When cooling PVA solutions, the supercooling temperature of the system in water and DMSO was observed. For a 10% aqueous solution of PVA, the supercooling temperature of the system is minus 5 °C, before freezing begins, which occurs at a temperature of minus 1.5 °C. The supercooling temperature of a PVA solution in DMSO is minus 20 °C, and the freezing temperature is minus 0.8 °C. The introduction of glycerol into an aqueous PVA solution leads to a significant decrease in the freezing temperature of the three-component solution (PVA, glycerol and water). It is noted that with an increase in the concentration of glycerol in an aqueous PVA solution, the elastic modulus increases, and the melting temperature decreases, compared to cryogels based on a two-component cryogel. The results of the studies can expand the scope of use of PVA cryogels as composite materials intended for use in northern regions, including in oil production and transportation technologies. For citation: Fufaeva M.S., Manzhai V.N. Effect of dimethyl sulfoxide and glycerol on the properties of cryogels. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 8. P. 6-11. DOI: 10.6060/ivkkt.20256808.8t.

Wire electrodes for needleless electrospinning consist of stainless steel wires in place of cylinder electrodes. The effects of different numbers of constituent stainless steel wires on the morphology and diameter of polyvinyl alcohol (PVA) fibers are examined. With 1, 2, 3, or 4 stainless steel wires being twisted as wire electrodes, an 8, 10, or 12 wt.% polyvinyl alcohol (PVA) solution is electrospun into PVA nanofibers by using a needleless electrospinning machine. The morphology and diameter of PVA nanofibers is observed by scanning electron microscopy. The combination of the number of stainless steel wires (two), PVA solution (10 wt.%), and the collecting distance (10 cm) results in the finest diameter and an evenly formed fiber morphology. In addition, the nanofibers exhibit a wide range of diameters when electrospun with an electrode consisting of more than two stainless steel wires. Compared with the cylinder electrode, the use of a wire electrode can form nanofibers, which results in a more even morphology.

We have developed a series of block co-polymerized polyimides for KrF lithography and EB lithography. Block co-polymerization is a synthesis method to control molecular structures. We have developed solvent soluble polyimides in powdered form. We can use these polyimides for dielectric materials in devices, and also can use as a dry etching mask in semiconductor processes. Here we report the details of dry etching properties for the block co-polymerized polyimides by reactive-ion-etching (RIE) using fluoride and chloride gases, typically used for Si etching and GaAs etching, respectively. Etching rates for EB exposed polyimide, photosensitive polyimide, novolac standard photoresist and Si at the condition of 80 W RF power and 60 sccm SF₆ gas flow, were measured as < 1 nm/min, 1.7 nm/min, 34 nm/min and 31 nm/min, respectively. We also checked the etching rate for EB exposed polyimide, photosensitive polyimide, novolac standard photoresist and GaAs at the condition of 50 W RF power and 3 sccm Cl₂ gas flow in the inductive coupled plasma (ICP) RIE, were measured as < 1 nm/min, 50 nm/min, 120 nm/min and 500 nm/min, respectively. Dry etching selectivity of EB exposed polyimide to Si is more than 31, and dry etching selectivity to GaAs is more than 500. These values are much higher compared to novolac standard photoresist. The high resolution EB exposed polyimide is promising for nano-patterning as stable dry etching mask. RIE resistance for polyimide photoresist is 20 times more than novolac standard photoresist for SF₆ etching gas, and more than twice for Cl₂ etching gas.

Study of the Polyvinyl Alcohol-Borate-Iodine Complex II. Test Papers

An investigation of influence of cryogenic treatment on extremely dilute aqueous solution of poly(vinyl alcohol) (PVA) was performed by viscometry. The solution was frozen in liquid nitrogen or in a freezer at −25°C, then thawed at ambient temperature and concentrated by evacuation. The viscosity of the solution was measured using the dilute method. The experimental results indicated that the viscosity of the solution is related to N, the times of the freezing and thawing cycle, and the temperature for freezing. Undergoing a treatment of freezing and thawing, the viscosity of the solution is decreased, while it can be recovered the value of before the treatment as the solution had been heated at a high temperature. Thus, a conclusion may be obtained; that is, for an extremely dilute aqueous solution of PVA, which concentration is below Cgel, threshold concentration for gelation, an intramolecular hydrogen bonding cohesional entanglement can be formed by freezing as N < 5. However, in the case of N > 5, it not only formed an intramolecular hydrogen bonding but also produced an intermolecular hydrogen bonding. At the same time, the abnormal behavior of reduced viscosity of the solution in extremely dilute concentration region has been explained. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2421–2427, 1997

Hardwood dissolving pulp was used as the raw material for the preparation of cellulose nanocrytals (CNC) by sulfuric acid hydrolysis. CNC was added into the solutions of Polyvinyl alcohol (PVA) to prepared PVA/CNC blend films. The miscibility of PVA/CNC films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The strong hydrogen bonding was formed between the CNC and PVA in the mixing process, and also produced cross-linking between molecular. When the concentration of CNC was 1.0%, tensile strength and breaking tensile strain of blend films reached the max, with the increasing amount of CNC, flocculation of CNC was aggravated, and the compatibility of PVA and CNC was deteriorated, the mechanical properties of blend films were reduced.

Study of the thermal resistance of alpha-phase aluminum oxide (α-Al2O3) films deposited on the paper substrate

本文以聚乙烯醇(PVA)溶液作为粘结剂，研究其对钙长石–氧化铝多孔隔热材料性能及显微结构的影响，并确定聚乙烯醇(PVA)溶液的适宜掺量。研究结果表明：随着PVA量的增加，钙长石–氧化铝多孔隔热材料的体积密度在1.52 g/cm3~1.54 g/cm3，线收缩率在2.25%~2.50%，显气孔率由66.55%下降到58.51%；由显微结构SEM观察可知，随着PVA量的增加，晶粒间粘结作用增强，聚集体相互间粘结的颈部增大，聚集体有增大趋势，气孔逐渐清晰且均匀，但是晶粒的大小和形状并未发生明显变化；由材料的热震分析可知，加入PVA后，由于材料温度梯度的减小而使抗热震性次数有所提高，材料的热震性能良好。 Polyvinyl alcohol (PVA) solution as binder, study the influence of the anorthite-alumina insulation material properties and microstructure, and to determine the appropriate content of polyvinyl alcohol (PVA) solution. The results show that: with the increase in the amount of binder PVA, anorthite-alumina insulation material bulk density of 1.52 g/cm3,1.54 g/cm3 linear shrinkage of 2.25% to 2.50%, the apparent porosity decreased from 66.55% to 58.51%; SEM observation shows that, with the increase in the amount of binder PVA, the enhanced role of the inter-granular bonding while enhancing the role of bonding between the aggregates and aggregates between the neck increases aggregates increases gradually clear pores and homogenization, but the grain size and shape has not changed; anorthite-alumina thermal shock analysis shows that the material with PVA have well thermal shock resistance, due to lower temperature gradient improving the thermal shock.

Alkaline anion exchange membrane fuel cells (AEMFC) have gained interest due to their potential as electrochemically energy conversion devices and a competitive alternative to the more extensively studied commercialized proton exchange membrane fuel cells (PEMFCs). Nevertheless, their development impedes the limited ion conductivity, chemical and mechanical stability in an alkaline medium of anion exchange membranes (AEMs). The ionic conductivity of AEM is lower than that of a proton exchange membrane (PEM) because the mobility of hydroxide ions is inherently lower than that of protons [1]. Deep eutectic solvents (DESs) as green solvents can overcome this issue.The main idea of this research is to fabricate a deep eutectic solvent-supported polymer-based AEM for alkaline fuel cell application by electrospinning technique. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of AEM due to its water solubility, biodegradability, high fiber forming ability, non-toxicity, and high chemical and thermal stability [2]. This work aims to achieve high ionic conductivity, chemical and mechanical stability by two methods: swelling polyvinyl alcohol (PVA)-based nanofibers into DES and encapsulating DES inside the PVA-nanofibers together with optimizing fabrication methods.In this study, polymer electrolytes as potential AEMs were first prepared using the swelling method, where electrospun PVA nanofibers were fabricated via the electrospinning technique, followed by swelling in a series of DESs. To prepare the DES solutions, choline chloride (ChCl) and ethylene glycol (EG) were mixed at different molar ratios. The cross-linking of pure PVA fibers with glutaraldehyde in ethanol (see Figure 1B) and DES uptake and the presence of voids as channels for ion conduction (see Figure 1C) were successfully confirmed with a scanning electron microscopy (SEM, Crossbeam500, Zeiss). The ionic conductivity of swelled in DES PVA-based membranes were evaluated by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature and was equal to 0.336 mS/cm. The presence of DES in the membrane was confirmed with FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10): a slight C-N+ peak at 953 cm-1 from ChCl has proven interaction between PVA and DES with FTIR spectroscopy, meaning that DES is present in the fiber. In addition, the nitrogen content in the obtained membrane was determined by CHNS elemental analysis (Elemental Vario micro cube) as 3.32 wt.%.In order to overcome high weight loss in the swelling method, the encapsulation method was suggested as an alternative option, which is based on the encapsulation of DES into the PVA solution by mixing them, varying the amount of DES added, and then preparing fibers using electrospinning. Observing the morphology of DES-encapsulated PVA nanofibers with a scanning electron microscope (SEM, Crossbeam500, Zeiss), as the content of DES in the solution increased, there was an observed rise in the average diameter of the nanofibers (see Figure 1D). Encapsulation of DES in PVA nanofibers was primarily confirmed by transmission electron microscope (TEM, JEM -1400 Plus, JEOL): PVA appears lighter due to its decreased density, proving that DES is present inside the fibers. Also, the same tendency was observed with the results of FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10) as for the swelling method, meaning that DES is present in the fiber. According to CHNS elemental analysis (Elemental Vario micro cube), nitrogen content was lower than for the swelling method - 0.70 wt.%. The ionic conductivity was evaluated as 0.364 mS/cm by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature, which was almost the same as for the swelling method.As a result, very flexible and visually transparent electrospun DES-supported PVA-based AEMs were obtained via the swelling and encapsulation method.

Up until the late 1960s, chemical etching, also called wet solvent etching, was the key technology to integrated circuit manufacturing. Indeed, from the standpoint of manufacturing, wet etching provides low cost and often infinite selectivity. But, inherent limitations in wet etching preclude the use of this technique for micron and submicron pattern sizes. The most serious limitation is that of isotropic etching, which results in undercutting of the mask material and hence limits the minimum size of the pattern. To obtain high-density packing of microelectronic circuits, anisotropic etching is essential. By the early 1970s, CF /02 dry etching was widely adopted for patterning. It was widely recognized that dry etching offered the possibility of a vertical etch rate that greatly exceeded the horizontal etch rate (namely anisotropic etching). As a result, these dry etching techniques, which can generate anisotropic etch profiles, came into prominence. Dry etching soon began to appear in IC fabrication. However, these dry etching technologies, like wet processes, had their resolution limited by undercutting, and other, even more anisotropic etching techniques appeared. Among these were reactive ion etching (RIE). The RIE technique which has been widely adopted for IC fabrication until now provides moderate selectivity, etch rate and high anisotropy. In the mid-to-late 1970s, research began on a dry etch technique which would combine the positive features of RIE with directional bombardment of the surface by ions accelerated through electrostatic sheaths. Figure 1.1 shows how integrated circuits have evolved and how the number of individual components per circuit has increased with time. It is seen in the figure that the component density of IC circuits has doubled every year and this yearly doubling rate has been maintained from the first IC in 1960 until recently. At the same time, the design feature size has shrunk from 6 μm to 0.8 μm in the last 15 years, and the smallest dimensions are expected to decrease to 0.1 μmin the near future.

The conservative single-layered wound dressing system is decomposed when mixed in polyvinyl alcohol (PVA) solution, which means it cannot be used with a temperature-sensitive drug. The goal of this investigation was to make an amniotic membrane extract (AME)-loaded double-layered wound dressing with an improved healing result compared to the conservative single-layered wound dressing systems. The double-layered wound dressing was developed with PVA/sodium alginate using a freeze–melting technique; one layer was PVA layer and the other was the drug-loaded sodium alginate layer. Its gel properties were assessed compared to single-layered wound dressings. Moreover, in vivo wound-healing effects and histopathology were calculated compared to commercial products. The double-layered wound dressing gave a similar gel fraction and Young’s module as single-layered wound bandages developed with only PVA, and a similar inflammation ability and WVTR as single-layered wound dressings developed with PVA and sodium alginate. Our data indicate that these double-layered wound bandages were just as swellable, but more elastic and stronger than single-layered wound dressings comprised of the same polymers and quantities, possibly giving an acceptable level of moisture and accumulation of exudates in the wound zone. Compared to the commercial product, the double-layered wound dressing comprising 6.7% PVA, 0.5% sodium alginate and 0.01% AME significantly enhanced the wound-healing effect in the wound-healing test. Histological investigations showed that superior full-thickness wound-healing effects compared to the commercial product. Therefore, the double-layered wound dressing would be an outstanding wound-dressing system with improved wound healing and good gel property.

Electron beam (EB) lithography using polymethylmethacrylate (PMMA) andoxygen gas reactive ion etching (RIE) were used to fabricate fine patterns in adiamond mould. To prevent charge-up during EB lithography, thin conductivepolymer was spin-coated over the PMMA resist, yielding dented line patterns 2μm wide and 270 nm deep. The diamond mould was pressed into PMMAon a silicon substrate heated to 130, 150 and 170ºC at 43.6, 65.4 and87.2 MPa. All transferred PMMA convex line patterns were 2 μ mwide. Imprinted pattern depth increased with rising temperature andpressure. PMMA patterns on diamond were transferred by the diamondmould at 150ºC and 65.4 MPa, yielding convex line patterns 2 μm wide and 200 nm high. Direct aluminium and copper patterns wereobtained using the diamond mould at room temperature and 130.8 MPa. Thediamond mould is thus useful for replicating patterns on PMMA and metals.

A planar quantum magnetic disk (QMD) with a magnetic storage density of 65 Gbit/in.2, over two orders of magnitude greater than the state-of-the-art magnetic storage density, has been fabricated. The planar QMD structure consists of single-domain nickel (magnetic) nanopillars uniformly embedded in a SiO2 (nonmagnetic) disk. Electron beam lithography was used to define the QMD bit’s size and location, and reactive ion etching was used to form an SiO2 template. Nickel electroplating was used to selectively deposit nickel into the template openings, and chemical mechanical polishing was used to planarize the surface. The resulting QMD consists of ultrahigh density arrays of single-domain magnetic pillars with a 50 nm diameter and 100 nm period uniformly embedded in 200-nm-thick SiO2 and with a surface roughness of 0.5 nm root mean square. Each single-domain structure has a quantized magnetic moment and acts as a single bit to store one bit of binary information. Furthermore, a method for mass production of QMDs, the nanoimprint technique, is discussed.

A Fresnel zone plate, a focusing element that operates using diffraction, is a promising candidate for x-ray optical elements since the index of refraction of all materials in this region is slightly less than unity. In this report, a new fabrication method for zone plates using electron beam lithography and reactive ion etching is described. By this method, it is possible to obtain a high resolution zone plate with a large aspect ratio. Focusing characteristics of fabricated zone plates are measured by synchrotron radiation. At the wavelength of 9 nm, the spot size of 2 μm is obtained at the focal point of 100 mm.

Silk fibroin (SF) and polyvinyl alcohol (PVA) solutions were prepared respectively by formic acid and deionized water as solvent, the solutions were then blended, and after that AgNO3 was added. The PVA/SF/AgNO3 solution was electrospun to form nanofibers. A number of particles were generated on the surface of nanofibers during electrospinning, which was confirmed by transmission electron microscopy (TEM). The diameter distribution of the nanofibers was narrow and the particles were nano-sized and well-dispersed. X-ray diffraction (XRD) patterns of the composite nanofibers indicated that the component of the nanoparticles was silver. By annealing the composite nanofibers at 155°C for 5 minutes, the silver nanoparticles possibly clustered into the larger size. The size of Ag nanoparticles was 2.25nm without post treatment, and this value increased to 3.76nm after the heat treatment. The antibacterial activity of the heat-treated PVA/SF composite nanofibers containing Ag nanoparticles was evaluated and the resultant nanofibers showed strong antimicrobial activity on Staphylococcus aureus and Escherichia coli. Moreover, the antibacterial PVA/SF composite nanofibers containing Ag nanoparticles have the possibility to be used in wound dressing due to the electrospun PVA nanofibers could preserve the web structure in water after the heat treatment.