BG113619A - METHOD AND DEVICE FOR MANUFACTURING POLYMER FIBERS BY ELECTROSPINNING WITH A DIELECTRIC BARRIER - Google Patents

Abstract

The invention relates to a method for the production of polymer fibers and a non-woven fibrous structure by electrospinning with a dielectric barrier and an alternating electric voltage, changing periodically in magnitude and/or direction, from an electrically conductive polymer-containing liquid solution, emulsion or melt, in which in the working air gap , a dielectric barrier with a thickness of 1 to 20 mm, relative dielectric permittivity of 2 to 10, specific electrical conductivity - over 1 (mu)S/m and dielectric strength - over 9 МV /m is introduced immediately next to the counter electrode. The dielectric barrier can be an insulating coating on the counter electrode or the counter electrode can be a metal coating on the dielectric barrier. The alternating electrical voltage can be a sinusoidal voltage or a half-periodic rectified voltage of industrial frequency or pulse voltage with a repetition rate of 10 to 1000 Hz and a duty cycle of 10% to 90%.

Description

METHOD AND DEVICE FOR MANUFACTURING PA POLYMER FIBERS BY DIELECTRIC BARRIER ELECTROSPINNING

Field of technique

The invention relates to a method of spinning in an electric field, or electrospinning (Anton Formhals, 1944: electrostatic spinning·, Darrell Reneker, 1966: electrospinning, E-spinning, ES), c dielectric barrier (dielectric barrier ES) and high alternating electric voltage , periodically changing in size and/or direction, for the production of polymer fibers - nanofibers with a diameter of less than 1 pm and microfibers with a diameter of less than 10 pm (less often, less than 50 pm), as well as for the production of non-woven fiber structures of them basis, which can find application in the field of: textiles; composite materials; filtration and separation (air and water); electronics and photopicaga - sensors, fuel cells, solar cells, supercopdspzagori; tissue engineering and regenerative medicine, enzyme immobilization, cancer diagnostics and treatment, the pharmaceutical industry - for the delivery of drugs, dressing materials, and others.

The invention can also be used in the technological implementation of similar technological processes, such as: (1) electrospraying, (2) near-field electrospinning, (3) electrospinning writing ·, and (4) Electrospinningprinting.

Prior art

A basic method of high constant voltage electrospinning is known (J. E. Cooley, W. J. Morton, 1902). the so-called needle or nozzle electrospinning (needle-, orifice-, nozzle-ES) is an electrically conductive liquid containing nolims with electrical conductivity above 1 pS/m. in the form of a polymer solution, emulsion or melt, which uses a characteristic unit for electrospinning - an electro-spinneret (electro-spinneret, spinneret, spinner), whose high-voltage electrode is a metal capillary tube, the liquid for electrospinning is filled, in which: (1) The liquid for electrocautery is forced under pressure, is a constant volumetric flow rate (or flow rate), through an outlet round hole at the end of the capillary tube, using a combination of a medical syringe and an infusion pump, where the medical syringe acts as a piston pump that forces the fluid in the capillary tube, while the infusion pump moves the plunger of the medical syringe at a constant speed, thereby determining a constant volumetric flow rate of the fiber-treated liquid through the capillary tube outlet; (2) The fibering liquid is placed under a high electrical potential, by applying a high direct current voltage (DCV) to ground - from 4 kV to 30 (100) kV, directly through the metal capillary tube, which is in continuous contact with the liquid and plays the role of a high-voltage electrode, or indirectly through an additional metal conductor (wire, rod) immersed in the liquid for slectrofibration; (3) The liquid for slectrofibration forms a "pendant drop" at the outlet opening (or at the end) of the capillary tube, under the action of: a) surface tension forces; b) adhesion to the walls of the capillary tube; (c) the weight of the liquid and (d) the pressure created by the movement of the piston; (4) The "hanging" drop acquires, under the action of electric forces, at a sufficiently high intensity of the electric field, a characteristic conical shape, called "cone of Taylor" (cone of Taylor, 1964); (5) From the tip of the Taylor cone, in the working air gap, in the direction and direction of the active electric field - towards the counter electrode, a micro-jet (micro-jet, jet) of the electrically charged liquid for electrospinning is ejected; (6) The jet maintains its straight line motion steadily, at a distance of 0.5 to 5.0 mm. in the so-called "near field" of electrospinning (near-field electrospinning), being continuously lengthened and thinned; (7) The jet enters the so-called "far-field electrospinning" area, where it loses its resistance and begins to move helically, with an ever-increasing diameter, forming a so-called conical helix, in which stretched, extended (splay) and whipped into long or short polymer fibers, with a diameter of up to 10 µm, while at the same time the solvent intensively evaporates, while the polymer melt ss hardens, - partially or completely, as ss produce polymer fibers and build a (non-woven) fibrous structure; (8) The polymer fibers ss deposit on the electrically active surface and the grounded anti-slip electrode (target) - a metal screen, plate or rotating ss drum, which stands from the hole of the hollow needle at a distance of 50 mm to 300 mm and plays the role of a stationary or moving collector for the produced polymer fibers; (9) Accumulating ss polymer fibers, randomly or ordered, depending on the spatial position and movement of the counter electrode (collector), produce a non-woven fibrous structure, representing a mat or mat of non-woven fibers (non-woven fiber mat), which also plays the role of "scaffold" (scaffold) in following applications, [1, 2, 3, 4|.

The metal capillary tube is a semi-finished product for the production of metal medical needles, ending with a round hole, or most often a "sunk" medical hollow needle (needle, blunt needle), the tip of which is cut across its axis. The needle is made of stainless steel (blunt stainless steel needle) and is characterized by its internal diameter (ID) - from 0.2 to 1.5 mm, or by its transverse size (gauge, G) - from G27 (ID 0.210 mm) to G15 (ID = 1.372mm).

The metal capillary tube performs two main functions in electrospinning: (1) Enables the property of capillarity (capillary effect, capillary movement) of the electrospinning liquid to be manifested by limiting the diameter of the column of liquid contained in the capillary tube, whereby at the outlet a bounded or "non-free" surface is created.

11o its nature, the electrospinning liquid is a solution of high-molecular compounds with a large molar mass, i.e. the solution can be considered as a colloidal system, in which the interaction between the metallic capillary tube and the electrically conductive liquid is determined by the formation of a near-wall electric double layer ( electric double layer, EDL). According to the model of Bockris, Devanathan, Muller (1963), the movement of a column of liquid in a capillary tube occurs along: a) a cylindrical surface located inside the so-called diffuse (stern) layer, or b) a cylindrical surface that includes the diffuse layer and is located at the boundary between the diffuse and the adsorption (Helmholtz) layer, which in turn is immovably connected to the inner side of the capillary tube. As a result, the produced liquid microjet acquires an electric charge, which determines the subsequent behavior of its movement in the working air space. It is also known that electrically non-conductive liquid - below 1 pS/m and especially below 10 nS/m, is not subject to electrofibration; (2) It provides a large "concentration" of the electric field, i.e., a maximally high intensity of the electric field at the outlet of the metal capillary tube. Thus, at relatively low DC voltages, the critical electrical intensity is reached to form the Taylor cone and to eject an electrically charged microjet from the electrospinning liquid into the working air space. The electric field concentration depends on the outer diameter (OD) of the capillary tube, which varies from 0.413 mm (G27) to 1.829 mm (G15).

It is also known that the length of the metal capillary tube significantly affects the concentration of the electric field at the exit - the long length of the metal hollow needle reduces the intensity of the electric field, therefore the use of shorter needles is recommended [Kang et al. 2013 ]. External electrical insulation of the metal hollow needle to reduce its electrically active length is known and widely used. Kumar et al., 2010].

There is a known method of electrofibration with high constant voltage (DCV), which instead of a metal hollow needle uses a (capillary) metal nozzle (nozzle, orifice), which, due to its short length, concentrates the electric field more effectively in the exit hole. The forces of capillary action and adhesion to the walls of the capillary tube are overcome by the forces of the electric field to produce the microjet necessary for electrofibration. In both cases, the microjet is charged electrically by the metal hollow needle or the metal nozzle.

A known method of high constant voltage electrospinning (DCV) or electrospinning from the opening is located on the tip of a glass or polymer pipette, with or without a tip (pipette tip-ES), as the main element of the slsctrospinner. The orifice size of the capillary, glass pipette, or polymer pipette tip corresponds to the orifice size of the metal hollow needles and nozzles. The difference is that the electrospinning liquid is placed under a high constant electric potential by means of an additional metal electrode conductor, wire, wire immersed inside the liquid.

In this way, the maximum concentration of the electric field is achieved only in the exit opening, the tip of the pipette. In fact, the electrically charged column of liquid is electrically isolated from the tips of the pipette, as a result of which the electric current through the pipette decreases sharply due to a reduction in the active surface of the high-voltage electrode. Moreover, there is no longer the possibility of a partial electric discharge from the tip (edge) of the hollow needle or nozzle accompanying the production of microjets for electrospinning.

A known method of electrospinning with high constant voltage (DC E) is electrospinning with an insulated metallic capillary tube, which uses the electrically insulated hollow needle or nozzle (insulated-needle ES', insulated-nozzle ES), in which the high electric potential is transmitted to the liquid from an electrode further immersed in it. The behavior of the electrically insulated hollow needle completely overlaps with the behavior of the glass pipette. An insulated hollow needle, however, is preferred in industrial applications of electrospun.

A known method of electrospinning with high constant voltage (DCV) is the electrospinning of a single air (or gas) bubble that appears and is continuously maintained at the top of a metal tube (single-bubble electrospinning) [Varabhas et al., 2009; Ren, 2010; Pringle, 2011). The liquid from the top of the air bubble concentrates the electric field, due to its large curvature, at which the critical electric intensity of microslug ejection in the direction of the counter electrode is reached. The formation of a microjet from the surface of an air bubble is similar to that from the surface of a single "hanging" drop. Depending on the size (diameter) of the gas bubble, conditions are judged for the formation of more than one Taylor cone and for the simultaneous ejection of more than one jet from one air bubble. Understandably, in this case, the size of the polymer fibers produced is significantly smaller, due to the smaller diameter of the Taylor cone.

The described high direct voltage (DCV) electrospinning methods from the "hanging" drop from a metal hollow needle or metal nozzle, a dielectric pipette and an insulated metal hollow needle or nozzle, or from a single gas bubble on a metal hollow needle, together form the group of single capillary and single-jet electrospinning methods (single-jet ES). They are characterized by the fact that from the electrically conductive liquid "confined" by the walls of the hole, falling in the form of a hanging drop or gas bubble, a single Taylor cone is formed and produces a single jet for electrospinning, [1, 2, 3 , 4, 5 and 6].

The single-capillary and single-jet method of high constant electric voltage electrospinning thus described is carried out in four forming (spinning) stages, which correspond to four clearly defined spatial areas in the working air space, [1, 6]: (1) Main area { base region), or the spinneret region, which covers the output hole of the high-voltage electrode, together with the Taylor cone formed under the action of the applied electric field, where this region is the source of an electrically charged microjet for electrofibration, which begins its movement in the working air gap;

(2) Region of the stable straight jet region (straight jet region), or near-field region of the working air gap (near-field region), in which the microjet moves towards the counter electrode, along the direction and direction of the electric field, continuously lengthening and decreasing its transverse size, but retains its direction and direction of movement; (3) Region of the unstable whipping jet region, or far-field region of the working air gap, which is characterized by: first, instability and movement of the microjet in a spiral of increasing diameter, in which produces a copic helix, secondly, stretching, elongation and breaking up of the polymer microjet and thirdly, transition from liquid to solid state of the polymer and production of multiple long or short fibers; (4) Collector region, in which the produced polymer nano- and microfibers are randomly or orderly deposited on the surface of the collector, forming a non-woven fibrous structure.

A method for electrospinning with high constant voltage (DCV) and electrically conductive polymer-containing liquid is known, which uses multiple-jet electrospinning systems (multiple-jet nozzle ES, multiple-jet needle ES) and covers three technological implementations, [3, 4, 5 and 6] :

(1) Multijet electrofibration from the outlet of a single capillary, in which multiple microjets are generated. as a result of: (1.1) The combination of a high electric field intensity at the exit of the metal hollow needle with a low concentration of the polymer solution; (1.2) The combination of a large size of the metal hollow needle (capillary), with a high intensity of the electric field, [Kong et al., 20091; (1.3) The high intensity of the electric field in the region of the collector also induces the appearance of multiple microjets, \Varesano et al., 2009]; (1.4) The addition of an additional axial component of the electric field at the output of the metal hollow needle - through additional focusing electrodes that have the electric polarity of the hollow needle, [Stankus et al., 2004; Kim et al., 2006, Kim et al., 2007]; (1.5) The use of curvilinear counter electrodes (collectors) that redistribute the electric field at the exit of the metal capillary, [ Vaseashta, 2007]; (1.6) The use of a grooved hole profile, at the end of the metal capillary, with many tips, which are concentrators of the electric field {single needle with a grooved tip electrospinning)·, (1.7) The use of a longitudinally grooved hydrophobic core of PTFE, mounted inside the metal hollow needle, which sharply reduces the area of the hole and produces multiple microjets, [Kang et al.. 2020]; (1.8) The use of a capillary tube with a ball (ball) placed in it, as in writing pens, in which the liquid is ejected through the gap between the ball and the wall of the capillary tube, in the form of multiple microjets, - the productivity increases from 10 to 12 times, [Zhang et al., 2018].

(2) Multiple-nozzle, multiple-pipetie or multiple-needle electrospinning, with a single jet from each capillary, in which two or more metal capillaries are spatially arranged in a certain manner, in one or more planes, [Chu et al.. 2009; Cabello et al.. 2017] taking into account: (a) the mutual electrical influence (repulsion) between the produced adjacent microjets .which affects the quality of the produced polymer fibers. (b) the distribution of the electric field between the individual capillaries, which turns out to be a factor that significantly limits the number of capillaries used significant advantage over the triangular and rectangular linear distribution configuration, [Zhu et al., 2018].

(3) Multijet electrospinning with multiple jets from each capillary - this is electrospinning from multiple capillaries under the conditions of producing multiple jets from the opening of each capillary.

The use of tubular or flat porous electrofibers (porous-tube ES', porous-flat ES) made of insulating material, with multiple capillary holes, instead of metal needles and nozzles, minimizes the interaction between the produced microjets, |Theo et al.. 2005 ; Zhou et al.. 2009]. These electrospinning methods are seen as a natural development of pipette electrospinning by multiplying the capillary openings. Instead of a pipette, a capillary orifice is used. The multiplication of the number of capillary openings reaches its natural limit in open-pore rotating dielectric porous cylinder electrospinning, [Dosunmu et al., 2006; Varabhas et al., 20081, resulting in a significant increase in electrospinning productivity from 0.3 g/h to 0.5 g/h. This important advantage, however, becomes a serious disadvantage when uncontrollably and irreversibly individual pores begin to clog. Instead of capillary holes, capillary slits are also used. which allow the electrospinning productivity to be substantially increased to 1.68 g/h. [2].

Needle hollow electrodes as well as ninstites. are subjected to a much greater extent to the influence of air currents acting in the working air gap, compared to Duzovits electrodes, due to their great length. This disadvantage, however, is turned into an advantage in electrospinning (yarn-ES', thread-ES) by means of an air stream which is directed, for example, longitudinally of the in-line capillary hollow needles to entrain the produced multitude of long fibers, [Eormhals, 19441. However, the production of yarn (yarn·, thread) by slsktroirsdsns. however, it has no relation to the production of non-woven fibrous structures (mat. scaffold, scaffold).

A high DCE (DCE) electrospinning method is known. the so-called gas- or air-jet assisted electrofibration (electrohlowing, air/gas assisted ES, air/gas enhanced ES, air/gas jet ES), in which a gas nozzle covers the capillary tube - the metal nozzle or the hollow needle). so that the air stream or jet helps to eject a microjet of the electrospinning fluid into the working air space, [1, 2]. The air flow exerts a force on the column of liquid, at the beginning of its formation, by tightening it and pulling it in the direction of the acting electric forces, thus supporting the formation of a thin microjet for electrospinning, [Lin et al.. 2009].

Air-jet electrospinning dramatically increases productivity - from 42.5 g/h to 56.7 g/h, [Soli et al., 2015 ], actively supports the formation of a microjet from the liquid, maintains the integrity and stability of the produced microjet, directs it actively to the collector and significantly accelerates the deposition of polymer fibers on the surface of the collector. It is successfully applied to multi-capillary electrofibers, [1, 2, 6].

One development of the air-jet electrospinning method involves the use of additional swirling of the air jet around the capillary nozzle, which increases productivity and improves the quality of polymer fibers. This is the so-called air-vortex electrospinning (air vortex ES), [Tian et al.. 2020]. The use of hot air jet electrospinning allows even more intense solvent evaporation, where the fibers are deposited "dry" on the collector, significantly reduces the viscosity of the polymer solution and allows the production of long and smooth fibers, [Ahmad et al., 2012] . The air jet, combined with the use of high values of the electric voltage, allows the efficient withdrawal of the microjet from the liquid, without the formation of defects characteristic of polymer fibers - a string of beads along the length of the fiber, [Um et al., 2004; Peng et al., 20081.

A method of electrospinning with high constant electric voltage (DCV) is also known - the so-called centrifugal (or inertial) electrospinning (nozzle-based high speed rolary ES\ centrifugal ES), in which the action of the electric forces is amplified by the directionally applied centrifugal (inertial) forces, [Liu et al.. 2013]. They help to form, stabilize and direct the produced microjets to the collector and improve the quality of the produced polymer fibers. The capillary tubes are directed spatially along the line of action of the centrifugal force. Centrifugal electrospinning not only increases productivity - up to 240 g/h, | Pass et al.. 2019], but allows to achieve a high degree of fineness of the produced polymer fibers, \Dabirian et al., 2011; Edmondson et al., 2012; Liu et al., 20131.

The advantages of multi-jet electrospinning with high constant electric voltage consist in: (1) The simplicity of realization and management of the technological process; (2) The use of relatively low DC voltages; (3) Good quality management of manufactured fibers and nonwoven fiber structures; (4) The production of composite (multicomponent) fibers, hollow fibers, core-shell fibers, and specific fiber structures.

The main disadvantages of the known multi-strand electrospinning methods are high constant electric voltage determined by: (1) Clogging of the capillary openings, most often at a low boiling point of the solvent, which turns out to be a "bottleneck" during industrialization; (2) The electrical interaction (repulsion) of the adjacent microjets, in the working air space, which slows down the electrospinning process and deteriorates the quality of the produced polymer fibers; (3) The relatively small productivity - from 0.005 g/h to 0.010 (0.030) g/h per capillary, which greatly limits its industrial application. The total surface area of fiber formation is limited by the number of capillaries and their internal size. The internal size of the hollow needle or nozzle limits the maximum size of the Taylor cone, as well as the ability to generate more than one Taylor cone; (4) The need for a relatively high intensity of the constant electric field at the exit from the capillary hole, which requires the application of relatively large high value constant voltages up to 30 (100)kV); (5) The existence of a health and environmental risk determined by the nature of the solvents used, which evaporate partially or completely during the production of polymer fibers itself; (6) The risk of an electrical discharge or short circuit between the two electrodes, which is primarily determined by the threat of fire (or explosion) in the existing solvent vapor environment.

Electrospinning methods with a high constant electric voltage (DCV) are known, is an unlimited or free surface {free surface ES), or as they are also called nozzleless (or needleless) electrospinning methods (needleless ES', nozzleless ES), which use a thin layer of electrically conductive polymer solution for the simultaneous production of multiple Taylor cones of different base size and multiple microjets of different sizes for electrospinning, et al., 1979]. Moreover, the ejected electrically charged microjets are repelled, and this determines the limitation and presence of self-organization of the overall electrospinning process. Naturally, this in turn determines the greater size dispersion and lower quality of the fibers produced, [Vahtrus et al., 2015]. However, the high productivity of this method determines its increasingly wide industrial application, 11, 2, 3, 4, 5 and 6].

The following high DC free surface electrospinning methods are known, which use a thin layer of electrically conductive liquid on: (1) Flat surface ES, \Roman et al., 2013]; (2) The cylindrical surface of a slowly rotating semi-submerged drum or roller (rotating-cylinder ES; drum ES), (Ilaitao et al.. 2009; Jirsak et al., 2009; Niu et al.. 2012 ]; (3 ) 1 the surface of a rotating semi-immersed toroid, \Haitao et al., 2009]; (4) The spherical surface of a rotating ball or set of balls (spherical ball ES), \Miloh et al., 2009; et al.. 2009; Niu et al., 2012]. In the latter case, the much larger surface of the sphere is used compared to the cylinder, and the productivity of one rotating race reaches 1.92 g/h, [Willemse , 2013]; (5) A wire (string, wire) stretched horizontally, which is periodically wetted by the fiberization fluid (Yalcinkaya et al., 2016); (6) A pair of twisted wires , placed vertically along which the electrospinning liquid flows (vertical twisted-wire ES), \IIolopainen et al., 20151; (7) Slowly rotating in the conducting liquid, a cylindrical spiral of wire (rotating-spiral ES), \Niu et al.. 2012; Wang et al.. 2012]; (8) A slowly rotating semi-immersed in the conducting liquid cylinder of cotton strings arranged parallel to the axis of rotation (rotating wire ES), \Sambaer et al., 2011]; (9) Slow-rotating, semi-iotope in the liquid for

L ovlakpyavaps. rotating ring-coil ES) (10) A cylinder with u-shaped or u-shaped tslss profiles attached to a slowly rotating cylinder so that the long part of the profile is parallel to the axis of rotation, [ McCarty et al., 2019|; (P) Conical wire coil, placed vertically, tip down, whose wire is continuously wetted by a liquid flowing from above (conical wire coil ES), [Wang et al., 2009]; (12) A rotating ss rectangular blind frame that is periodically ss immersed in the electrospinning liquid {wire frame ES), [Forward et al., 2012; Forward et al., 2013, Bhattacharyya et al., 2016].

High constant voltage free surface electrospinning methods are known which use a thin layer of electrospinning liquid on surfaces of very high curvature - sharp edges and/or blades which concentrate the electric field by locating it on an edge or blade which increases substantially its intensity.

Stationary edge or blade electrospinning methods use: (1) Spikes projecting above the surface of the electrospinning fluid bath, [Yann et al., 20041; (2) Row-like metal electrodes parallel to each other, protruding above the liquid surface, [Lukas et al., 20081; (3) A metal bowl with a pointed peripheral rim filled to the brim with the liquid, [Thoppey et al., 2011]; (4) Metal chute with pointed longitudinal edges, filled to the brim with the liquid, [Wei et al., 2019]; (5) A metal bowl with pointed edges and a circular lid that repeats the profile of the bowl so that it forms a slotted (capillary) cap that leads to the pointed edge. while at the same time the lid prevents the rapid evaporation of the solvent, [Xiong et al., 20211; (6) An inclined metal plate ending in a sharp edge, on the upper surface of which the electrospinning liquid flows by gravity in a thin layer, {single-plate edge ES), [Thoppey et al., 2010|; (6) Cascading inclined planes, ending with a sharp edge, which are continuously wetted by the flowing SS liquid {waterfall geometry ES), [Thoppey et al., 2010]; (7) A horizontally arranged toroidal tube with multiple openings from which the electrospinning fluid flows, wets the tube and collects in an annular bath below, | Wei et al., 2019]; (8) A stepped copic pyramid formed by the superimposition, one after the other, of truncated cones of increasing diameter, each conical course being filled with the electrospinning fluid. and the circularly arranged one-to-one sharp edges simultaneously form multiple microjets {steppedpyramid ES), [Jiang et al.. 2013; Jiang et al.. 2014].

Rotary sharp-edge electrospinning methods use: (1) Centrifugal sharp-edge circular ES. from which a power of microjets for electrospinning is formed; (2) The circularly shaped sharp edge of a rotating hollow cone (hollow cone ES), [Lu et al., 2010]; (3) The circularly shaped sharp edge of a rotating horizontal disk (centrifugal-disk ES).

Sharp-edge electrospinning methods are high constant electric voltage that use the surface of slowly rotating cylinders (drums) semi-immersed in the electrospinning fluid: (1) A metal cylinder with serrated caps with sharp edges, for example a cut-threaded cylinder, cylindrical or worm gear; (2) A metal cylinder with multiple blades on the surface, [Tehrani et al., 2018]; (3) A metal disk or set of disks with pointed edges on the periphery, [Niu et al.. 2009J.

Sharp edge electrospinning methods with high DC voltage also include the well-known slot-ES methods [Yan et al.. 2017]; clefts (cleft-surface ES), \Lucas et al.. 2008]; and slits (slit-ES), [Sharma et al., 2012; Yan et al., 2012; Ucar et al.. 2013]. located on the surface of the electrode, through which the liquid is forced out under the action of applied pressure. The additional effect of centrifugal forces is also used, which support the formation of a plurality of electrospinning microjets under the action of the applied electric field.

A group of high DC voltage electrospinning methods is known which uses temporary disruption of the surface (ES) of the electrically conductive liquid to concentrate the electric field and produce a plurality of jets for spinning. It is difficult to induce electrofibration from a flat and quiescent surface, even at very high electric field intensities. However, if ultrasound is used, which forms ripples propagating concentrically from the center to the periphery, multiple microjets can already be produced from this surface and the so-called ultrasonic agitation ES (ultrasonic agitation ES) can be induced [Nieminen and et al., 2018].

Another method of electrospinning from a free surface is significantly more widespread - it is high constant and alternating electric voltage - this is slsktrofibration, which is dissolving (bursting, opening) gas bubbles (bubble-surface disruption ES', multiple-jet blown bubble ES, air -jet assisted bubble ES). in which air (or gas) is passed through a layer of the electrically conductive liquid to form a multitude of bursting gas bubbles on its surface, [Liu and Ne, 2007; L-Niap et al., 2008; Varabhas et al., 2009; Higham et al., 2014; Kocis et al.. 2018].

A method of electrospinning with high constant electric voltage is known, which uses moving drops of the fiberizing liquid, which, passing through an electric field, are electrically charged, stretched and acquire a thread-like shape (droplets ES). There are many methods for producing the drops themselves, for example, an air jet that draws drops from the tip of one or more capillary needles has been successfully used [Filatov et al.. 2007]. Rotating head, in the form of a disc with a sharp edge. it also forms a multitude of drops that are continuously separated from the periphery of the disk and, once caught in the electric field, give rise to a multitude of electrospinning microjets, \Angammana et al., 2012]. A rather more complex rotating head, a profile that includes inclined surfaces forming a cascade of sharp edges, is also used in droplet electrospinning [Beran et al., 2017]. The main disadvantage of the droplet electrospinning method is determined by the fact that the drops produce only short polymer fibers.

The advantages of electrospinning methods from a free surface is a high constant electric voltage are the following: (1) Easy implementation and management; (2) The absence of plugging holes proves that the use of a capillary hole is not mandatory for electro-fibers, - an opportunity for rapid industrialization opens up; (3) High productivity; (4) Self-organization of the produced electrospinning jets.

Disadvantages of high DC voltage free surface electrospinning methods are as follows: (1) 110-large diameter dispersion of the produced polymer fibers compared to capillary hole methods; (2) Difficult to maintain constant values of the concentration and viscosity of the polymer solution; (3) Very high values of the critical electric voltage of electrospinning, since a higher viscosity of the polymer solution is used, therefore a higher electric field intensity is also required to produce the necessary microjets for fiberization. It even reaches voltage values where partial corona discharge occurs. The applied voltage cannot be increased indefinitely because sparks and arcing can occur between the high-voltage electrode and the counter electrode (collector), [McCarthy et al., 2019].

L

High direct current (DCV) electrospinning methods are known, which allow the production of a non-woven ordered fiber structure on the collector, under the following conditions, 11, 51:

(1) Method for producing ordered fiber structures by electrospinning with a rotating electrically conductive cylindrical collector cylinder, drum or shaft (rotating cylinder collector ES. drum- or mandrel-collector ES), which receives the polymer fibers moving towards it and mechanically forms an ordered fibrous structure. At the same time, the cylinder plays the role of an anti-slip electrode, which removes and neutralizes the electrical charge of the polymer fibers. The critical speed of arrangement (alignment speed) of the fibers is reached when the linear speed of the surface of the rotating CC cylinder reaches the deposition speed of the fibers. Gas speed is critical, because exceeding it leads to mechanical tearing of the polymer fibers, which is more pronounced with a small diameter of the fibers. The strength of the fibers, when they meet the collector, has a strong influence on this process, which is why ss requires the use of solvents with a lower boiling point to deposit so-called "dry" fibers. The sustained microjet produced also improves fiber alignment on the cylinder, [Zhou et al.. 2013].

(2) A method of producing ordered fiber structures by electrospinning. which uses a continuously moving conductive belt (belt collector ES) as a collector. with metal plates fixed on it. The ss tape moves continuously on guide rollers and plays the role of the metal counter electrode.

(3) Method for producing ordered fiber structures by electrospinning. which uses a rotating thin disk with a flat (rotating thin disk ES) or knife-edge of rotating thin disk ES (knife-edge of rotating thin disk ES) as a collector. which concentrates the electric field, exerts a force and arranges the fibers produced. [Theron et al., 2001].

(4) A method of producing ordered fiber structures by electrospinning that uses a stationary collector composed of two parallel (flat) strip electrodes (parallel conducting collector ES). Each of the two strip electrodes is equidistant from the high voltage electrode. The strip electrodes are grounded, or placed at a high negative potential, each individually. It is known that the electric field in the gap between the ss electrodes distorts very strongly, which in turn stretches and arranges the produced fibers [Li et al., 2003]. A collector representing a grid of parallel strip electrodes is also used [Li et al., 2004].

(5) A method of producing ordered fiber structures by electrospinning that uses a stationary collector composed of two parallel knife-edge electrodes, tapered at the top, \Secasanu et al. 20091. This collector allows the production of thicker ordered fibrous structures.

(6) Method for producing ordered fiber structures by electrospinning. which combines the effect of the rotating cylindrical collector with the effect of the two parallel strip conductors: (a) A rotating cylindrical collector composed of wires (strings) £ located on the periphery of the cylinder, oriented parallel to the axis of rotation (rotating wire drum collector E.S ), [Katta et al.. 2004]; (b) Rotating cylindrical collector, composed of metal fins located longitudinally but the periphery of the cylinder, oriented along its radius (rotating fin collector ES), [Afifi et al.. 20091; (c) Rotating disk, whose periphery includes evenly spaced conductive sectors (points) (rotating disk with evenly spaced conductive points ES), [Afifi et al.. 2009]; (d) Rings of wire spaced equidistant from each other on the surface of a rotating ring-coil collector, (f) A spirally wound conductor (wire) on the surface of a dielectric cylinder, with a pitch equal to of the gap between the two adjacent conductors, (rotating spiral collector ES)·, (f) A rotating collector composed of a plurality of disks spaced from each other at a distance equal to the distance between the two strip conductors;

(7) A method of producing ordered fiber structures by electrospinning, which uses so-called indicating electrodes in the form of: (7.1) Knife-like bladed high-voltage electrode and counter electrode. which comprise a diagonally rotating cylindrical collector, [Teo et al.. 2005]; (7.2) Grounded blade-counter electrode. located inside a rotating hollow cylindrical collector, which creates a focus of deposition and shifts it along the length of the cylinder (rotating drum with sharp pin inside collector ES), [Lee et al., 20091; (7.3) A grounded system of parallel knife-edge electrodes, used as a counter electrode, falling under a rotating dielectric cylindrical collector (rotating tube-collector with knife-edge electrodes ES), [Teo et al., 20051.

A known method for the production of polymer fibers by electrospinning is high alternating voltage (ACE), |7, 8|. which, in addition to all other noted advantages, reports a significant reduction in the so-called time of relaxation. The relaxation time is the time interval that elapses from the moment of application of the electrical voltage until the appearance of one or more microjets for electro-fibration. It characterizes the process of self-organization. flowing in the fluid under the action of the applied external electric field. Large relaxation times are characteristic of DC electrospinning from milliseconds to minutes, [ 81. A significant reduction in relaxation time has been observed in AC electrospinning with an electrically active collector.

It is known that AC electrospinning methods are frequency sensitive because the mobility of the ions in the conductive electrospinning fluid is limited - they can follow the change in the direction of the electric field, which turns out to be a determinant of the electric charge. of the produced electrospinning jets. Each polymer solution has its own critical frequency, \Sarkar et al.. 2007 ]. and at a frequency lower than the critical one, the produced microjet has the same polarity along its entire length, while at a frequency higher than the critical one, the jet acquires periodically alternating segments with a positive and a negative charge.

The segments with opposite polarity, however, attract, which is why a fiber plume is formed at a certain distance from the electrofiber, which slowly moves towards the collector, under the action of the so-called ionic wind between the electrodes. In this case, the loop of polymer fibers is almost electrically neutral, which also determines the neutral role of the collector. In practice, this collector does not determine the behavior of the fiber loop, which allows to work even without an anti-collector, i.e. in this case, the collector no longer needs to be part of the electrical circuit, |8, 9, 11 , and 12].

Collectorless electrospinning methods (collectorless ES) with high alternating electric voltage, from a free surface, are known: (1) A rotating vertical cylinder with serrated ends on the periphery and a closing lid that produces a plume of fibers in the form of a sleeve (corona alternating current ES), [9]; (2) Cylinder c diameter 10 mm (alternating current rodES), which produces a sleeve (plume) of fibers, [10]; (3) A rotating vertically profiled rod with a central opening and a nozzle at the tip (rod-shaped spinningelectrode alternating current ES), which produces a fiber sleeve (envelope) that is freely used in subsequent spinning processes, [11]; (4) Electrofiber with dissolving (bursting) ss bubbles (alternating current bubble ES), \Reneker et al.. 2010; Erben et al., 2020], [12].

A method of collectorless electrospinning with high alternating electric voltage with a trapezoidal variation profile and industrial frequency and free surface multijet electrospinning is known. The electric locomotive is a rotating double-conical disk with a pointed periphery. It is noted that the shape (profile) of the alternating voltage significantly affects the efficiency of the process - the trapezoidal shape provides a longer duration of fiber formation for each half-cycle of the voltage and a relatively smaller diameter of the produced fibers compared to the alternating sinusoidal psaprszhnis at the same frequency . Increasing the frequency to 150 Hz also resulted in a higher performance of the trapezoidal stress profile, 6.15 g/h versus 4.46 g/h, 18].

These methods of collectorless electrospinning with high alternating electrical voltage provide high productivity and produce a blank - a tow or sleeve of fibers that can then be used in various spinning processes. The production of yarns and threads by the methods of collectorless electrospinning with high alternating electric voltage, however, goes beyond the subject of electrospinning is the formation of a nonwoven fibrous structure.

A method of electrofibration with an active electrically conductive collector and alternating sinusoidal electrical voltage at industrial frequency is known, which uses a capillary hollow needle (II) = 0.9 mm) for a high-voltage electrode and an aluminum flat circular collector for a non-rotative electrode. spaced at a distance of 150 mm. This method is compared with a method of electrofibration with a pulse voltage with a rectangular shape of the pulses (pulse voltage ES) - unipolar pulses, the amplitude of which varies between two levels - 8 and 15 kVpeak, with a constant duration of 5 ms and a repetition frequency of 20 .50 and 100 Hz. The applicability of the pulsed electrospinning method has been proven when comparing it with electrospinning at a constant voltage, at a constant volume flow rate of the liquid 0.9 mL/h, [14].

The technological parameters of electrofibration with high alternating electric voltage, in the general case, include the following process parameters: the amplitude, the frequency, the character of change in time or the voltage profile, harmonic (sinusoidal) voltage, non-harmonic voltage with a different profile - triangular.

rectangular, trapezoidal. The parameters of electrofibration is pulse voltage (VS) are: symmetry or asymmetry of the pulses, relative to the time axis, the shape of the pulse, the frequency or period of repetition of the pulses, the duration of the pulse, the duration of the pause, etc.

The task of the invention consists in the creation of a method for the production of polymer fibers by electrospinning with a dielectric barrier, from an electrically conductive polymer-containing liquid - solution, emulsion or melt, with a highly variable electric field, changing periodically in magnitude and/or direction over time, created in the interelectrode space of one or more high-voltage electrodes belonging to the fiber optic and a counter electrode. called a collector, as in the working air space, in the immediate vicinity of the anti-slip electrode, there is a solid dielectric (insulating) barrier, with a high relative dielectric permeability and electrical strength - made of polymer, glass, ceramic or quartz, which: first, separates the working air space - between the tip of the high-voltage electrode and the dielectric barrier, secondly, it pushes the variable electric field into the working air space, concentrating it at the tip of the high-voltage electrode, thirdly, it takes the role of a collector for the produced polymer fibers, fourthly, it ensures the arrangement of the produced fibers in a plane non-woven fibrous structure.

The method of electrospinning with a dielectric barrier and alternating electric voltage must: (1) Be based on the use of the known types of electrospinning machines - single-jet and multi-jet, static and dynamic, performing rotational movement (centrifugal. inertial), with an air jet supporting the formation of micro jets for electrospinning; (2) To be based on the use of the known types of simple and compound metal (electrically conductive) counter electrodes; (3) To provide safe electrospinning of polymer solutions, emulsions and melts. without the occurrence of a corona electric discharge and a short circuit between the electrodes, which would create conditions for fire or explosion; (4) To ensure safe electrospinning in the plasma medium and dielectric barrier discharge in air, at normal atmospheric pressure and room temperature; (5) To ensure safe electrospinning of polymer solutions and melts with increased and high electrical conductivity; (6) To use an active counter electrode and avoid the formation of the polymer fiber plume characteristic of AC (no dielectric barrier) electrofibration.

Technical essence

The task of the invention is solved by a method for the production of polymer (nano micro) fibers and non-woven fiber structures on a base basis, from an (electro)conductive polymer-containing liquid - solution, emulsion or melt, by electrospinning with variable electric voltage, changing periodically amplitude and/or direction in time, in air at normal atmospheric pressure and room temperature, wherein between the high-voltage electrode of the electrical fiber, which is in electrical contact with the conductive liquid, and a grounded counter electrode located in the far region of the working air space , an electric field varying in magnitude and/or direction over time is applied, such as the slectrofiber. which can be single-jet or multi-jet, static or perform a rotary working motion, producing one or multiple jets directed in the direction of the electric field to the counter electrode. and the anti-slsktrode has a suitable spatial shape and structure, remains stationary or moves to form an unordered or ordered non-woven fibrous structure, characterized in that in the path of the electrofibration microjet produced by the high-voltage electrode, in the far region of the working air gap - above 50 mm, in the immediate vicinity of the counter electrode, a solid dielectric barrier is placed, with a thickness of 1 to 20 mm, a relative dielectric permittivity of 2 to 10. a specific electrical conductivity of more than 1 pS/m and a (di)electric strength of more than 9 MV/ m. which pushes the electric field into the working air gap and takes the role of a collector for the produced polymer fibers and the formed non-woven fibrous structure.

One variant of the electrospinning method is a dielectric barrier and an alternating electric voltage, characterized by the fact that the counter electrode has a shape and dimensions that concentrate the electric field. i.e. increase its intensity on the surface of the dielectric barrier.

Another variant, the electrofibrous lime with a dielectric barrier and variable electric voltage, is characterized by the fact that the counter electrode has the shape of a rotating metal cylinder, the axis of which is located transversely to the movement of the microstructures for electrofibration, and its linear speed of rotation does not exceed the critical fiber deposition rate on its surface.

L

A variant of the electrofibration method with a dielectric barrier and alternating electric voltage, characterized by the fact that the dielectric barrier is an insulating (functional) coating on the electrically active surface of the anti-slsktrode.

Another variant of the electrofibration method with a dielectric barrier and an alternating electric voltage is characterized by the fact that the anti-electrode is an electrically conductive (metallic) coating on the dielectric barrier and together with it forms an electrically isolated collector, on the dielectric surface of which the manufactured polymer fibers are deposited and builds the non-woven fibrous structure.

Another variant of the electrospinning method with a dielectric barrier and an alternating electric voltage is characterized by the fact that the produced polymer fibers are deposited on a stationary or moving substrate (tape) located before the dielectric barrier, which assumes the role of a collector for the produced polymer fibers and the constructed nonwoven fiber structure.

A variant of the dielectric barrier electrospinning method with an alternating electric voltage, characterized in that the high electric voltage is an alternating sinusoidal electric voltage that varies harmonically in time with an industrial frequency.

Another variant of the dielectric barrier electrospinning method and alternating electric voltage, characterized in that the high alternating electric voltage is a pulsating electric voltage that varies in time in the form of periodically repeating unipolar pulses, with a repetition rate of 10 to 1000 Hz and pulse duty cycle from 10% to 90%.

Another variant of the dielectric barrier electrospinning method with an alternating electric voltage is characterized in that the pulsating electric voltage is a single half-period rectified voltage of industrial frequency. A constant component of the output voltage appears with the value: Vdc = V _av = Vpeak/π, where V _pea k is the maximum value of the input ACV- voltage.

A variant of the dielectric barrier electrospinning method with alternating electric voltage, characterized in that the high-voltage electrode is placed under a high alternating voltage of industrial frequency with respect to ground, and the counter electrode is placed under a high direct voltage, also with respect to ground, such that the amplitude of the alternating (Vpeak) voltage is less than the constant voltage value (Ios): Vpeak < VDC, OR RATIO Vpeak IVDC < 1 .

Another variant of the method of electrospinning with a dielectric barrier and an alternating electric voltage, characterized by the fact that between the high-voltage electrode of the electrospinning pit and the counter electrode, a high sinusoidal alternating voltage is applied at an industrial frequency, the value of which exceeds the first critical ignition voltage of a dielectric barrier discharge, which burns in air, at atmospheric pressure and room temperature, so that the electrospinning is carried out in an oxygen- and ozone-containing nsrvvss cold plasma of the dielectric barrier discharge.

Another variant of the electrospinning method is a dielectric barrier and alternating electric voltage, characterized by the fact that between the high-voltage electrode of the electrospinning pit and the counter electrode, a high sinusoidal alternating voltage is applied, an industrial frequency, the value of which exceeds the second critical ignition voltage of a dielectric barrier discharge, in air, at atmospheric pressure and room temperature, so that the slsctrofibration is carried out in the non-equilibrium cold plasma of a dielectric barrier discharge containing nitrogen oxides (NOx).

A device for the production of polymer fibers by electrospinning with a dielectric barrier and high alternating electric voltage, which consists of a source of alternating electric voltage and two electrodes, the first being a high-voltage electrode, which is the main component of the electrospinning machine and is a capillary metal tube, a hollow needle of stainless steel, through which the liquid in the form of a microjet enters the working air gap, and the slectrofibrator also includes a medical syringe, which is a cylinder with a solid piston moving inside it, filled with the liquid for electrofibration. to which the hollow needle is attached, and an infusion pump driving the plunger of the syringe at a constant linear velocity, which determines a constant flow of fluid through the cylindrical opening at the end of the hollow needle, and the second is a grounded cylindrical counter electrode. which is located transverse to the axis of the hollow needle, characterized in that in the interelectrode space, transverse to the axis of the hollow needle, a solid dielectric barrier is located immediately on the active surface of the counter electrode, which plays the role of a stationary or moving collector for the produced polymer fibers and the nonwoven fiber structure.

L

A device for producing polymeric fibers by electrospinning with a dielectric barrier and a high alternating electric voltage of an electrically conductive fluid, characterized in that the electrically conductive electrospinning fluid inside the medical syringe is electrically isolated from the grounded housing of the infusion pump by placed inside a larger medical syringe so that the hollow needle of the small syringe protrudes through the front opening of the large syringe and the plunger of the large syringe directly drives the plunger of the small syringe.

The described method for the production of polymer fibers and non-woven fiber structures based on them, by electrospinning with a dielectric barrier and alternating electric voltage, is characterized by improved technology, applicability, universality, reliability and safety. This method of electrospinning can be applied both laboratory and industrial, regardless of: (1) The type of electrospinning machine with one or many jets; (2) The type of technological approaches used to focus and deflect the jets in the interelectrode space - slsktroovlaknitsl with an air jet or centrifugal electrofibrator, additional electrodes focusing, directing or withdrawing, of different shape, location and power source; (3) The type of technological approaches used to arrange the fibers on the collector is a rotating CC cylinder, moving CC endless belt, concentrating the electric field between two parallel electrodes, or using guiding and pulling electrodes.

The method for the production of polymer fibers and fiber structures based on them, by electrospinning is a dielectric barrier and alternating electric voltage, allows: (1) Electrospinning to be safe — not to pass into a corona electric discharge mode, with a risk of fire or a blast. This allows polymer solutions with increased electrical conductivity and melts of electrically conductive polymers to be fiberized; (2) To carry out electrospinning with plasma-chemical modification on the surface of the produced fibers, by safely switching to electrospinning mode with dielectric barrier discharge. (3) The dielectric barrier to maintain its level of insulation, even with complete electrical breakdown of the air gap. (4) Yes ss works with significantly lower voltages, since the maximum high intensity of the field, in the region of the capillary opening or at the free surface of the liquid, ss obtains safely, at lower values of the applied voltage.

The dielectric barrier redistributes the intensity of the electric field in the working air gap, inversely proportional to the relative dielectric permittivity, for example, for polypropylene (PP) insulation: e _r .air « £ _g .pp'· 1.00059 «2.1; for alkaline glass: Er.air « Рг.пр'. 1.00059 « |6: 8], so hs the dielectric barrier is electrically discharged, and the air is maximally charged. At a relatively low operating voltage, the intensity in the working area of the electrofiber increases very rapidly, for two reasons first, the strong non-uniformity of the field at the exit of the hollow needle (nozzle); and secondly, introducing a dielectric barrier into the interelectrode space. At the same time, a significant unloading of the dielectric barrier takes place, the intensity of the electric ball remains far from the (di)electric strength of the insulating material, for example for polytetrafluorostyrene (PTFE) insulation: Ed.pTFE (60 173) MV/m >> Ed,air 3.17 MV/m. This means that the dielectric barrier maintains its level of insulation, even with a complete electrical breakdown of the air gap. The electrospinning process can be successfully and safely carried out even in dielectric barrier discharge plasma.

Thus, the proposed method of surface modification carries out plasma chemical treatment of the surface of the newly produced polymer fibers in the plasma of a barrier uneven discharge, in air or active gas at room temperature and atmospheric pressure, and allows to manifest new positive qualities of the produced fiber structures: increased capillary activity of the porous fibrous materials produced; increased chemical activity of sadadenits on the surface of the fibers chemically active centers; improvement of physical and mechanical properties, and others.

Description of attached figures

An exemplary embodiment of the method and apparatus for producing polymer fibers by dielectric barrier electrospinning and alternating voltage, from an electrically conductive polymer solution, emulsion or melt, is presented with the aid of the accompanying figures, wherein:

Fig. 1 shows an embodiment of the electrospinning method with a dielectric barrier and an alternating electric voltage for the production of polymer fibers by co-jet single-nozzle electrospinning with a "flooded" medical hollow needle and syringe actuated by an infusion pump, with the dielectric barrier located immediately in front of the counter electrode . concentrates the electric field at the tip of the needle and plays the role of a collector for the produced polymer fibers and the constructed fibrous structure;

Fig. 2 presents an embodiment of the method of FIG. 1, is the difference that a composite collector shape is used to produce two electrospinning jets from the orifice of a single-Edipate hollow needle. i.e. to carry out multi-jet electrospinning;

Fig. 3 presents another embodiment of the method of electrospinning is a dielectric barrier and an alternating electric voltage, for the production of polymer fibers by multi-jet multi-needle electrospinning is "submerged" medical hollow needles and syringes, actuated by a single infusion pump and a solid dielectric barrier , located in front of the rotating electrode. which acts as a collector for the produced fibers and the non-woven fibrous structure;

Fig. 4 presents another embodiment of the electrospinning method is a dielectric barrier and an alternating electric voltage, for the production of polymer fibers by multi-jet electrospinning from the "free" surface of a slowly rotating drum, semi-immersed in the electrospinning liquid, and a dielectric barrier located in front of the flat a counter electrode, which takes the role of a collector for the produced fibers;

Fig. 5 presents an embodiment of the electrospinning method is a dielectric barrier and an alternating electric voltage, for the production of polymer fibers by cocurrent single-needle electrospinning is a hollow medical needle and syringe actuated by an infusion pump, and a dielectric barrier in the form of an insulating coating on the ground a rotating metal drum, depositing the manufactured polymer fibers and flat fiber structure on the insulating coating;

Fig. 6 presents one variant, an implementation of the electrospinning method is a dielectric barrier and an alternating electric voltage, for the production of polymer fibers by co-current single-needle electrospinning, a medical hollow needle and syringe actuated by an infusion pump, and a dielectric barrier on which a dense or a porous tape of insulating material which carries the produced non-woven fibrous structure;

Fig. 7 presents a schematic version of the implementation of the electrical supply of a device for electrofibration with a dielectric barrier and a high alternating sinusoidal voltage with an industrial frequency (50 IIz).

Fig. 8 represents the external static voltammetric characteristic of the electrospinning process is a dielectric barrier and an alternating sinusoidal electric voltage is an industrial frequency, which expresses the dependence of the average value of the electric current on the effective value of the voltage'' ¹ . lav- (p(Vrms), in air, at normal atmospheric pressure and ambient temperature. Three possible electrospinning modes are presented: normal or non-plasma (plasmaless) mode; plasma mode in oxygen- and ozone-containing plasma and dielectric barrier discharge; plasma mode a dielectric barrier discharge, in an environment of nitrogen oxides (NOx);

Fig. 9 presents another variant where the electrical supply of the electrospinning device is a dielectric barrier and a high DC voltage is an industrial frequency of 50 Hz.

Fig. 10 presents an embodiment where the electrical supply of the electrofibration device is a dielectric barrier that uses two sources of high voltage - one of high alternating voltage with an industrial frequency and the other, high direct voltage.

Fig. 11 shows the transition of a single-wire single-needle AC electrospinning device into an emergency mode of operation, as a result of the occurrence of a creeping electrical discharge between the grounded housing of the infusion pump and the electrospinning liquid placed at a high electrical potential in the medical syringe.

Fig. 12 presents a technical approach that provides a secure isolation barrier between the high-voltage fluid in the syringe and the grounded housing of the infusion pump, referred to herein as the "syringe-in-syringe" approach. Goy uses a larger syringe into which the small syringe containing the electrospinning solution is placed to provide the necessary level of electrical isolation between the conductive electrospinning fluid and the infusion pump housing;

Fig. 13 presents a high-resolution scanning electron microscope (SEM) image of the electrospun dielectric-barrier, single-half-cycle rectified voltage is an industrial frequency, fibrous structure of 5 wt. % collagen solution (type 1, from bovine skin) in a mixture of two solvents hexafluoroisopropanol (PIR) and tetrafluoroethylene (TFE), in the ratio HFIP:TFE = 4:1, fig. 13a. The cross-linking of the produced fibrous structure is carried out in glutaraldehyde (GTA) vapor, at atmospheric pressure and room temperature for 24 hours. 11defects characteristic of cross-linked collagen fibrous structures observed in practice are shown, fig. 13b: A - string of beads; B - string of spindle-shaped formations; With branches from the fiber; and D - fiber fusions.

Fig. 14 presents high-resolution scanning electron microscope (SEM) images of fiber structures that reveal the morphology of the fabricated, by slsktrofilvance is a dielectric barrier and a semi-semiconductor rectified voltage is an industrial frequency (50 Hz), of 5 wt. % solution of collagen (type 1, bovine skin) in hexafluoroisopropanol (IIFIP): first, collagenous fibrous structure, immediately after sclstrofibrillation. fig. 14a,b; second, collagenous fibrous structure, after cross-linking in glutaric anhydride (GTA) vapor, for 24 hours, at normal atmospheric pressure and room temperature, fig. 14c, d.

Fig. 15 presents images of fibrous structures, is a high resolution, from a scanning electron microscope (SEM), produced by electrospinning is a dielectric barrier and a single half-period rectified voltage is an industrial frequency (50 Hz): first, of 5 wt. % collagen solution (type 1. from bovine skin) in HFIP, is different hollow needle size 19G (II) = 0.686 mm) and 18G (II) 0.838 mm), fig. 15a, b; second, from 10 wt. % collagen solution in IIFIP, is hollow needle size 19G (II) 0.686 mm), Fig. 15s.

Fig. 16 presents images of fibrous structures, is a high resolution, from a scanning electron microscope (SEM), produced by electrospinning is a dielectric barrier and a half-cycle rectified voltage is an industrial frequency (50 Hz), from a collagen solution modified is 0.8 wt. % hyaluronic acid (HAGAG), in HFIP: first, after slsktrofibration. fig. 16p, b and second, after cross-linking the fibrous structures in GTA vapor, at room temperature, for 30 hours. fig. 1 bd, is.

Fig. 17 presents images of fibrous structures, is a high resolution, from a scanning electron microscope (SEM), produced by slsktrofibrovance is a dielectric barrier and a half-cycle rectified voltage is an industrial frequency (50 Hz), from a collagen solution modified is 0.8 wt. % chondroitin sulfate (CSGAG), in HFIP:

first, immediately after electrospinning, fig. 17a, b; secondly, after subsequent immersing the microfiber structure in GTA vapor, at room temperature, for 30 hours. fig. 17c, d.

Fig. 18 presents images of fibrous structures, is a high resolution, from a scanning electron microscope (SFM), produced by electrospinning is a dielectric barrier and a single half-cycle rectified voltage is an industrial frequency (50 Hz), of 6 wt. % solutions of modified collagen in HFIP and subsequent cross-linking of the slsktrofibrous structure in GTA vapor. at room temperature for 30 hours. Collagen modified is hyaluronic acid (IIAGAG) and is chondroitin sulfate (CSGAG) introduced as 0.04 wt. % acetic acid solution: IIAGAG - 0.8 wt. % and CSGAG 0.8 wt. %, fig. 18α b and c; IIAGAG - 0.8 wt. % and CSGAG 1.6 wt. %. fig. 18<7. is.

Fig. 19 presents optical-microscopic images - magnification x 40. from an optical microscope Binocular digital microscope, ΟΡΊ'ΙΚΛ (Italy), of a fibrous structure of collagen fibers (type 1, from bovine skin) produced by electrospinning a dielectric barrier and an alternating sinusoidal voltage is industrial frequency. of 5 wt. % collagen solution in IIFIP: first, immediately after electrospinning, fig. 19a; second, after subsequent exposure of the collagen fibers to GTA vapor, at room temperature, for 24 hours. Fig. 19b.

Examples of implementation of the invention

According to the one presented in fig. 1 technological scheme of single-jet or multi-jet single-needle electrospinning is a dielectric barrier and high alternating voltage is an industrial frequency, electrospinning is carried out in three ways, depending on the spatial location of the electric field E relative to the ground acceleration g: (a) horizontal, fig. 1a. in which the action of the weight (P - m.g) is neutralized, since the ground acceleration g is indicated transverse to the electric field £; (b) vertically down, fig. 1b, the ground acceleration g acts in the direction of the electric field E, with the weight P and the electric field strength E acting together against the surface tension forces in the fibering fluid; (f) vertically upwards, fig. 1 f, the ground acceleration g acts in opposition to the electric field E, where the weight P acts together with the surface tension forces against the force of the electric field E. The effect of the weight (the ground acceleration g) on the electrofiber is determined by whether the weight P acts in the direction or in the opposite direction of the electric forces that must overcome the 27 surface tension γ to form one or more Taylor Cones and start the process of stui and ovlakpyavaps formation.

According to fig. 1a, electrospinning takes place in the interelectrode space 1 of the device for the production of polymer fibers, and more precisely in the working air gap 2. located between the tip of the high-voltage electrode 3 and the dielectric barrier 4. which lies directly on the counter electrode 5, electrically connected to ground the gel 6. The electrofibration takes place entirely in the volume of the working air gap 2. The high-voltage electrode 3 belongs to the electrofibration 7, while the dielectric (insulating) barrier 4 and the grounded counter electrode 5 belong to the collector 8, on the surface of which the polymer fibers 9 are deposited and builds the fibrous structure 10. 11 the rotary electrode 5 and the dielectric barrier 4 located directly on it together form the so-called collector 17 of the produced polymer fibers 9.

To the two electrodes, the high-voltage electrode 3. representing a "submerged" hollow medical needle and the grounded counter-electrode 5, ss applies an increasing high alternating voltage, from the source 11, until the process of electrofibration is manifested, as first, ss forms like a (micro) jet 12, from the exhaust pressure 13, which originates from the surface of the Taylor cone 14, occupying the corresponding area (of the Taylor cone) 15, and spreads to the so-called close area 16 of the working air gap 2; secondly, the straight jet 12 lengthens and thins under the action of the electric field, loses its stability, and in the form of an unstable jet 17 begins to move in a spiral with a continuously expanding ss diameter, in the far region 18 of the working air gap 2, after which breaks down into individual fibers 9. which are deposited on the dielectric barrier 4, so that the cc forms a fibrous structure 10, which the cc removes continuously or once. It is possible to additionally place a substrate, not shown in the figure, on the dielectric barrier 4, on which to permanently deposit the produced fibrous structure 10.

The electrospinning fluid 13 is pre-charged into the medical syringe 19 after the plunger 20 cc is pulled back to allow the electrospinning fluid 13 to enter and fill the barrel 21. The "clogged" hollow needle, ie. the high-voltage electrode 3, cc connects to the full syringe 19, then the syringe 19 cc fixes to the working member 22 of the infusion pump 23, so that the piston 20 cc moves linearly forward from the working member 22 of the infusion pump 23. But this way, the liquid for electrospinning 13 is fed continuously at a constant volumetric flow rate, from the syringe 19, through the tip of the hollow needle 3, into the working air gap 2 for electrospinning, under the action of the high alternating electric voltage from the source 11. The "clogged" hollow needle 3 is a medical needle of feathering steel, the end of which is cut at an angle to its axis.

The "clogged" hollow needle 3. together with the syringe 19 and the infusion pump 23, form the so-called electrofilament 7. Usually, the electrofilament 7, together with the formed Ziller cone 14, are considered as a source of a stable stream 12. The electrofilament is carried out completely in the far region 18 of the working air gap 2. The fibrous structure 10, which is produced on the dielectric barrier 4, consists of randomly and unordered polymer fibers 9.

The electrospinning device is composed of three main components (assemblies): (1) Electrospinning unit 7, which forms on the tip of the hollow needle 3 one or more Tsilr cones 14, from which one or more straight steady jets 12 are ejected in the direction of the counter electrode 5, which starts electroplating; (2) Collector 8, composed of the dielectric barrier 4 and the grounded anti-slip electrode 5. which determines the manner and degree of arrangement of the produced polymer fibers 9 in the fibrous structure 10; (3) A source of high alternating voltage 11. which changes periodically in time in magnitude and/or direction, with a certain frequency.

The dielectric barrier 4 pushes the electric field into the working air gap 2 and significantly increases the intensity of the electric field at the end of the hollow needle 3, creating conditions for the manifestation of the electrofibration process at lower values of the applied alternating voltage.

At a high intensity of the electric field, maximally close in value to the electric strength of the air (E _rea k- 3.17 MV/m, at 50 Hz and standard conditions according to IURLS), multiple jets can be produced from the exit hole of the hollow needle 3. 12, which have as their starting point the set of Ziller cones 14 that appeared. An external indicator of this is the appearance of a dielectric barrier discharge at the end of the hollow needle 3, or the appearance of a characteristic glow and smell of ozone. This is now multi-flow single-needle electrospinning, which has increased performance over the single-flow single-needle electrospinning considered.

One embodiment of the electrospinning method and device is a dielectric barrier and alternating voltage shown in FIG. 2, it is characterized by the fact that a composite shape is used in the collector 8 to produce two stable electrospinning jets 12 and a single-spindle hollow needle 3. A process of multi-jet single-needle electrospinning is presented, which is caused by the used shape of the collector.

An embodiment of the electrospinning method and device is a dielectric barrier and alternating voltage shown in FIG. For. it is characterized by the fact that three syringes - 19-1, 19-2 and 193 - which superimpose the polymer fibers 9 produced by the three unstable jets 17, are simultaneously fed from one infusion pump 23, through the movement of the working body 22, with a liquid for electrofibration , forming in a certain way the fibrous structure 10, on the surface of the dielectric barrier 4. The different shapes of the fibrous structure 10 are obtained depending on the distance between the three hollow needles 3, fig. 3: (1) At a sufficiently large "critical" distance between the needles 3, the ss form three separate fibrous structures 10-1, 10-2 and 10-3, fig. 3b, while in smaller rasgoyapia ss produces one common fibrous structure 10. formed by the overlap of the three independent fibrous structures - 10-1, 10-2 and 10-3. The use of many, parallel working hollow needles 3 on one collector 8 allows the production of fibrous structures 10 of different thickness, shape, density and porosity. Not only that, the use of multiple syringes - 19-1, 19-2 and 19-3, filled with polymeric liquids of different nature, allows to produce composite fibrous structures 10.

Another embodiment of the method and device for multi-jet and needleless (or nozzleless) free surface electrospinning is a dielectric barrier and high alternating voltage shown in FIG. 4, is characterized in that the plurality of straight jets 12 cc form from the free surface of the thin layer 24 of the electrospinning liquid 13. which cc entrains onto the surface of a rotating drum 25. The rotating drum 25 is partially immersed in a bath 26 containing the electrospinning liquid 13. so that, during the slow rotation of the drum 25, it can continuously maintain the free surface 24 of the liquid 13. Each of the jets 12 has as its origin a Taylor cone formed under the action of the electric field. not shown in the figure. The body of the tub 27 is insulated from the grounded parts 28 is a solid insulation 29, 30 which provides the required level of electrical insulation. The high electrical potential is transmitted to the electrospinning fluid 13 via the electrode 30 insulated from the tub body 27.

Another embodiment of the method and device for co-jet single-needle or single-nozzle electrospinning, with a dielectric barrier and an alternating electric voltage, shown in FIG. 5, it is characterized by the fact that it uses a grounded rotating drum-collector 31, representing a metal drum 32, fulfilling the official purpose of the counter electrode 5, on which the insulating coating 33, fulfilling the official purpose of the dielectric barrier 4, is applied, to increase the degree of arrangement of the manufactured polymer fibers along the direction of rotation of the drum-collector 31. The arrangement enables the improvement of many physico-chemical properties of the produced fiber structure 10. For this purpose, the drum-collector 31 rotates at an angular speed no greater than a limit value, characteristic of the polymer material, below which the appearance of defects begins, as a result of tearing of the produced polymer fibers 9.

The variant of implementation of the method and device for co-current single-needle electrospinning with a dielectric barrier and alternating electric voltage, shown in fig. 6. is characterized by the fact that the produced polymer fibers 9 are deposited and arranged in the form of a fibrous structure 10 on a continuously moving belt 34, which at a constant linear speed is rewound from the passive roller 35 onto the traction roller < 36.

The embodiment of the electrical supply of the electrospinning device is a dielectric barrier and an alternating sinusoidal voltage is an industrial frequency, shown in fig. 7, is characterized by the fact that the high-voltage supply source 11 consists of the following cascade-connected transformers: (1) The isolation transformer - 230/230 V _rm s, 37, which galvanically separates the circuit of the high-voltage supply source 11 from the 230 V _rm electrical network s. 50 Πζ; (2) Two autotransformers - 220/250 V _rms , 38 and 39, for coarse and fine regulation of the high output voltage; (3) Step-up transformer 0.1/35 kV _rm s, 40, which supplies the high alternating voltage directly to the high-voltage electrode 3 and the collector 8. consisting of the dielectric barrier 4 and the grounded anti-electric barrier 5. The selection of a suitable technological mode is carried out but the readings of the high-voltage voltmeter 41, which shows the selected effective value of the operating voltage Vrms', and the ammeter 42, from the magnetoelectric measuring system, which is included in the diagonal of the bridge circuit (Grc circuit) for rectifying the current 43. formed by the four diodes - D1 , D2, D3 and D4 to show the average value of the current lav.

The external static characteristic of the process taking place in the electrospinning device with a dielectric barrier and an alternating electric voltage, shown in fig. 8, is of the type "average value of the electric current - effective value of the voltage", or lav - φ(ItD. It covers three operating modes of electrofibration: (1) Normal (no discharge) mode of electrofibration 44. which takes place at voltages less than the ignition voltage 45 of the dielectric barrier discharge and currents below the critical ignition current 46 of the dielectric barrier discharge; (2) Plasma (oxygen- and ozone-containing) mode of electrofibration 47 supported by the dielectric barrier discharge, which takes place at voltages greater than the critical ignition voltage 45 and currents above the critical ignition current ₄₆ of the dielectric barrier discharge; greater than the critical ignition voltage 48 and currents below the critical ignition current 49 of the dielectric barrier discharge.

Dielectric barrier discharge electrospinning is characterized by the fact that it takes place at a constant value of the discharge firing voltage for firing mode 47 this is voltage 45. while for firing mode 50 this is voltage 48. The differences between the two voltages 45 and 51. for the burning mode 47, and between the two voltages 48 and 52, for the burning mode 50, determine the voltage drop across the dielectric barrier, upon ignition of the dielectric barrier discharge, in the selected burning mode.

Another option is to implement the electrical supply of the electrospinning device with a dielectric barrier, shown in fig. 9. is characterized by the fact that a high pulsating voltage is applied to the high-voltage electrode 3, obtained after one half-period rectification of the alternating sinusoidal voltage with an industrial frequency (50 I Iz) from the diode 53. connected to the high-voltage output of the booster (0.1/35 KV _rm s) transformer 40, and the rotor electrode 5 is grounded through the ammeter 42.

Oedipus another version of the implementation of the electrical supply to the device for electrofibration with a dielectric barrier, shown in fig. 10, characterized in that the high voltage electrode 3 is placed under a high alternating sinusoidal voltage (ACV) with an industrial frequency (50 Hz) from the power source 54, and the counter electrode 5 is placed under a high direct voltage (DCV) from the source 55. so the ratio of the amplitude value of the alternating voltage (Vpcak). relative to the DC voltage value (Vdc), be less than unity: Vpeak/Voc < 1.

1[remaining pas sdjet single-needle electrospinning device in emergency mode of operation is shown in fig. 11, which is the result of the appearance of a creeping electric discharge 56, on the inner surface of the cylinder 21, which belongs to the syringe 19, - between the piston 20 and the grounded housing 57 of the infusion pump 23. The circuit of the creeping electric discharge ss closes through the boundary gap 58 .determined by the clearance between the piston 20 and the cylinder 21 filled with the conductive liquid for electro-fibration 13 and the liquid-filled hollow metal needle 3. Thus, after the supply of a sufficiently high value, between the metal hollow needle 3 and the housing 57 of the infusion pump 23, the current of the surface electric discharge flows but the inside of the cylinder 21, which shuts the working gap 2, with which the process of electrofibration ss ceases - it goes into an emergency mode of operation, which ss terminates automatically from the power source 11.

The embodiment of the method and device for single-jet single-needle (or single-nozzle) electrofibration with a dielectric barrier and variable electric voltage, shown in fig. 12. is characterized in that the syringe 19 filled with the conductive electrospinning fluid 13. is placed inside a larger syringe 59. so that the hollow needle 3 protrudes through the front of the syringe 59. 11o thus conditions have been created to prevent the occurrence of a creeping electric discharge: first, the creeping path has been extended many times; second, the syringe body 59 is made of polypropylene (PP). which is a good insulator. The electrospinning fluid 13 exits under pressure through the front opening of the hollow needle 3. which is generated by the movement of the working member 22 of the infusion pump 23. The working member 22 acts forcefully on the piston 60 of the large syringe 59 and drives it, which in turn transmits the movement on the piston 20 and the small syringe 19. as a result of which the liquid 13 flows out of the front opening (end) of the hollow needle 3.

A high-resolution scanning electron microscope (SEM) image of the electrospun dielectric barrier and one half-cycle rectified voltage industrial frequency fiber structure of 5 wt. % solution of collagen (type 1. from bovine skin) in a mixture of the two solvents hexafluoroisopropanol (HFIP) and tetrafluoroethylene (TFE), in the ratio IIFIP:TFE= 4:1, is presented in Fig. 13a. The cross-linking of the produced fibrous structure was carried out in glutaraldehyde (GTA) vapor, for 24 hours, at room temperature. Characteristic defects of the produced cross-linked collagen fibers that are observed in practice are presented, fig. 13b: (A) String of spherical formations (beads); (C) String of fusiform formations; (C) Branches emerging from the fiber; (D) Fusion of two fibers. Scratch studies were performed at solvent ratios {IIFIP:TFE)\ 4:1, 1:1 and 1:4, only one image (IIFIP'.TFE 4:1) is presented, as the observed defects of the successfully produced long collagen fibers are characteristic of all three cases.

High resolution images are presented, Fig. 14, from a scanning electron microscope (SEM), which reveal the morphology of the produced by electrospinning is a dielectric barrier and a single half-period rectified voltage is an industrial frequency, fibrous structures, of 5 wt. % collagen solution (type 1, from bovine skin) in IIFIP: first, of a collagen fibrous structure, immediately after its production, at low (a) and high magnification (b); second, of a collagen fibrous structure, after its cross-linking in pari pa GTA. for 24 h, at low (f) and high magnification (d). Electrofibration is carried out successfully - the resulting collagen fibers are long, fine and without defects. At higher magnification, Fig. 13b, it can be seen that these are nanoscale fibers. Collagen fibers are smooth, without rough areas, fig. 13c and d. After cross-linking, the resulting fibrous structures, fig. 13c and d, some fusion and clustering of the collagen fibers is observed - however, the formation of defects along the fibers, such as beading and cracks, is not observed.

Fig. 11 is another high-resolution scanning electron microscope (SEM) image of fibrous structures produced by electrospinning is a dielectric barrier and a half-cycle rectified voltage is an industrial frequency, Fig. 15, of 5 wt. % collagen solution (type 1, from bovine skin), in HFJP, is a different hollow needle size: 19G (inner diameter ID - 0.686 mm), fig. 15a, and 18G (internal diameter ID = 0.838 mm), Figs. 15b; of 10 wt. % collagen solution in HFIP, is hollow needle size 19G (internal diameter II) 0.686 mm), Fig. 15s. The manufactured coatings have a diameter that varies widely from 40 to 320 mm.

The influence of the size of the hollow needle on the morphology of the produced fibrous structures is illustrated, at the same concentration of collagen in the solution - 5 wt. %, fig. 15a and b: it is immediately noticeable that the fibers produced with the smaller needle size 18G, i.e. with the larger II), are visibly finer, but have numerous defects, in the form of a string of beads, fig. 15b.

The influence of collagen concentration in the 5 wt solution is also illustrated. % and 10 wt. %, on the morphology of the produced fibrous structures, at the same internal size of the needle (19G): the greater concentration of the collagen 10 wt. % in the solution leads to the appearance of many branches and fusions of the fibers, as well. although rarely, to the formation of multiple defects on the fibers - in the form of a string of beads, fig. 15s.

Also presented are high-resolution scanning electron microscope (SEM) images of fibrous structures fabricated by electrospinning with a dielectric barrier and an industrial-frequency single-half-cycle rectified voltage of 5 wt. % solution of collagen (type 1, from bovine skin) in HF1P, the collagen being modified with an equal amount of hyaluronic acid (IIAGAG) - 0.8 wt. %, fig. 16: after electrospinning, fig. 16a,b; and after cross-linking in GTA vapor, at room temperature, for 30 hours. fig. 16c, d. The good fibrinization of the IIAGAG-modified collagen is illustrated, but also the appearance of numerous defects along the fiber branches, and in places the formation of nodules and balls. At a higher magnification, the branching and merging of the fibers become more visible.

11 are representative high-resolution scanning electron microscope (SEM) images of fibrous structures. fabricated by electrospinning with a dielectric barrier and industrial frequency single half-cycle rectified voltage, from a modified collagen solution in IIFIP. with collagen modified with chondroitin sulfate (CSGAG). in an amount of 0.8 wt. %, introduced as 0.04 wt. % acetic acid solution, fig. 17: first, immediately after electrospinning. fig. 17a,b; second, after subsequent cross-linking of the electrofibrous structure in GIA vapor, at room temperature, for 30 hours. fig. 17c, d. The good electrofibrization of the CSGAG-modified collagen is illustrated, as well as the appearance of multiple defects along the collagen fibers - multiple branches, and in places the formation of knots and balls. At higher magnification, branching and merging of fibers become more visible.

11 are high-resolution scanning electron microscope (SEM) images of fibrous structures produced by electrospinning with a dielectric barrier and an industrial-frequency single-semi-cycle rectified voltage of 6 wt. % solutions of modified collagen in IIFIP and subsequent cross-linking of the slsktrofibrous structure in GIA vapor, at room temperature, for 30 hours; collagen is modified with hyaluronic acid (HAGAG) and is chondroitin sulfate (CSGAG) introduced as 0.04 wt. % acetic acid solution, fig. 18: HAGAG - 0.8 wt. % and CSGAG - 0.8 wt. %, Fig. 18a,b,c; IIAGAG - 0.8 wt. % and CSGAG - 1.6 wt. %. fig. 18d, f. The successful electrospinning of the modified collagen is illustrated, but with the presence of multiple branching defects and multiple beads along the fibers. At higher magnification, characteristic fusions are also noticeable.

11 are optical-microscopic images magnification x 40. from an optical microscope Binocular digital microscope, OPTIKA (Italy), of the produced fibrous structure of collagen fibers (type 1. from bovine skin) produced by electrospinning with a dielectric barrier, at an alternating sinusoidal voltage with industrial frequency. of 5 wt. % collagen solution in IIFIP, fig. 19: first, immediately after electrospinning, fig. 19a; and second, after subsequent cross-linking of the collagen fibers in GTA vapor, at room temperature, for 24 hours. Fig. 19b. Collagen fibers are susceptible to electrofibration in an alternating sinusoidal electric field of industrial frequency, in the presence of a dielectric barrier. Before cross-linking, the collagen fibers are randomly arranged in the fibrous structure. After cross-linking, however, the collagen fibers clustered, with the formation of multiple nodules distributed across the image field.

Implementation examples

The invention is illustrated by the following examples, which do not limit in any way its possible applications and the use of other variants of the method and device for electrofibration with a dielectric barrier at alternating electric voltage.

Example 1. A nonwoven fibrous structure of nanofibers is produced by electrospinning with a dielectric barrier and a single half-cycle rectified voltage is 36 industrial frequency, from a collagen solution and subsequent cross-linking of the produced collagen fibers to acquire their operational properties.

The technology of electrospinning from a polymer solution includes three stages of implementation: (1) Selection of solvent and preparation of the collagen solution; (2) Electrospinning of the collagen solution; (3) Cross-linking of the produced fibrous structure (scaffold, mat, scaffold), in cross-linking agent vapor, at room temperature, for a certain technological time.

The following starting materials were used: (1) Collagen: type 1. from bovine skin: Collapro Bovine Premium of Ilulsh Protein Technologies, The Netherlands; (2) Solvent: (1,1,1,3,3,3hexafluoro-2-propanol or hexafluoroisopropanol (hcxafluoroisopropanol, (CP3)2CHOH, IIFIP), 99 1%, by Alfa Aesar. Germany, CAS RN 920-66- 1, molar mass: 168.038 g/moL density: 1.596 g/mL, boiling point: t- 58.2 °C; (3) Cross-linking agent: 50% aqueous solution of glutaraldehyde (glutaraldehyde. CsIIsO, GTA), at Alfa Aesar, CAS RN 111-30-8, molar mass: 100.117 g/mol, boiling point: 187 °C.

There are four determining factors for solvent selection: relative permittivity, electrical conductivity, viscosity, and surface tension of the solvent. Furthermore, the choice of hexafluoroisopropanol as a collagen solvent was based primarily on existing successful practices [14, 15 and 16].

Additionally, screening experiments were carried out on electrospinning from solutions of the following two known solvents: hexafluoroisopropanol and tetrafluoroethylene (tetrafluoroethylene, C2F4, TFEd), CAS NR 116-14-3, molar mass: 100.02 g/mol, density 1.519 g/cm ³ . boiling point: -76.3 °C), in ratios 1:4; 1:1 and 4:1.1 resulted in much finer fibers than those with hexafluoroisopropanol, comparison in Fig. 13 (at IIE1P-.TFE ratio 4:1) and fig. 14a (ΙΙΕΙΡ), but it is multiple defects in the form of a "string" of beads. Therefore, mixtures of the two solvents, in the three selected ratios, proved to be unsuitable, as fine long fibers were produced but with numerous defects. Thus, based on these studies, hexafluoroisopropanol was chosen as the collagen solvent.

The following electrospinning collagen solutions were prepared, concentration 3, 4, 5. 6, 8. 9. 10, 11 and 12 wt. % collagen in hexafluoroisopropanol. The weighed amount of collagen is poured with the solvent, wait 24 h for the collagen to swell, after which the solution is stirred and homogenized intensively with a laboratory shaking machine.

Electrofibrous current is carried out at a high one-half-period rectified voltage, an industrial frequency of 50 Hz, which changes asymmetrically and pulsating in time, i.e. is obtained after one-way rectification of the input sinusoidal voltage is industrial frequency, fig. 9, which has an effective value of V _rms — 230 V.

Measure cc: (a) The effective value of the voltage V _rms , at the output of the step-up transformer 40. is the voltmeter 41, from the capacitive measuring system; (b) The average value of the single half-cycle rectified current I _av , measured by the ammeter 42, of the magnetoslsktric measuring system. In this way, the operating point of electrospinning is selected from the external static characteristic lav (p(V _rm s) and the electrospinning device. It works with voltage values V _rms below the critical voltage 45. characterizing the transition to the dielectric barrier discharge regime, i.e. f. in the first area 44 of electrofibration - without barrier electric discharge, Fig. 8.

Regular experimental studies show that the "syringe-in-syringe" method should be used. fig. 12 to provide a sufficiently good isolation between the electrospinning fluid 13, which is energized with respect to ground, and the grounded infusion pump housing 57. An indication is the appearance of a visible creeping electric discharge 56, which starts from the fluid 13, through the gap 58, located ss between the piston 20 and the cylinder 21 of the syringe 19, along the inner surface of the cylinder 21 to the grounded housing of the infusion pump 57, fig. 11

Electrofibrillation begins after the small medical syringe 19, of 1 mL, made of polypropylene (PP), is filled with the electrofibrillation liquid 13 - a solution of collagen in the solvent IIFIP, by pulling the plunger 20 back, fig. 12. The 3cc hollow needle is then attached to the small syringe 19 and thus loaded into the large 5 mL syringe (PP) 59. with the plunger 60 removed. Then, the plunger 60 closes the syringe 59. so that its movement can now is transmitted directly to the piston 20 of the small syringe 19. In turn, the large syringe 59 cc loads into the infusion pump 23, so that the progressive movement of the working body 22 cc transmits to the piston 20. through the piston 60. Hook. the infusion pump 23 provides a constant flow rate of the electrospinning fluid 13 through the opening at the tip of the metal hollow needle 3. fig. 12. The electrospinning device is ready for operation.

Electrospinning starts immediately, after applying a single half-cycle rectified voltage of frequency 50 Hz, directly between the hollow needle 3 and the grounded electrode 5. and the process ft of electrospinning takes place in the working air space 2, between the hollow needle 3 and the dielectric barrier 4. fig. 12. The thickness of the polystrafluorostyrene (PTFE) dielectric barrier is 2 mm.

Susceptibility of the collagen solution to electrofibration was investigated in the following intervals of variation of the process parameters: (1) Working air gap - <5 is [100; 300] mm; (2) Electrofibration voltage - rms value: V _rms is [10; 30] kVrms; (3) Volumetric flow rate (or flow rate) of the collagen solution - Q is [1; 100] pL/min; (4) Inner diameter (ID) and size of hollow needle - ID is 10.413 b 0.019; 0.838 4- 0.0381 mm, [G22 * G18|.

It found the following, depending on the concentration of collagen in the electrospinning solution: (1) The collagen solution was amenable to electrospinning at collagen concentrations of 5 wt. % to 10 wt. % - obtain ss long flawless collagen fibers 9. which ss deposit on the dielectric barrier 4. (2) At collagen concentration 4 wt. % cc receive short collagen fibers 9. which hardly reach the collector 8 - they just fly through the air. (3) At a concentration of 3 wt. % electro-fibration is no longer observed. (4) At high values of collagen concentration 11 wt. % and 12 wt. %, the needle clogging, which is why it is impossible to carry out electrospinning on the polymer solution.

The best results are achieved with: (1) Working air gap - b * 180 mm; (2) Electrofibration voltage - V _rms = 25 kVrms; (3) Volume flow rate (or flow rate) of the collagen solution - Q - 60 pL/min; (4) Inner diameter (ID) and size of hollow needle — ID = 0.686 mm (G19). The productivity of this single jet single needle electrospinning is Q = 60 pL/min = 3.6 mL/h = 0.0036 I,/h.

The fiber morphology was examined with a scanning electron microscope SEM-FIB Tcscan Lyra I XMU (Czech Republic). SEM-images are presented, is a high resolution, so collagen fibers (structures) produced by electrospinning is a dielectric barrier, at a monopolar rectified voltage is an industrial frequency, and a collagen concentration of 5 wt. %, - immediately after electrospinning and after cross-linking in glutaric anhydride, at room temperature for 24 hours. 11roizvsdepits collagen fibers are long, smooth and without defects, fig. 14a, b. The diameter of the produced fibers is in the nanoscale region, Fig. 14b. Only after crushing of the fibrous structures is observed fusion and grouping of the fibers, but no defects are observed fig. 14c, d. After omrszhvansto. the fusion and grouping of the fibers increases the size of the resulting neoplasms, fig. 14d.

Fiberglass. obtained by electrospinning, are usually monolithic with a cylindrical shape, even when superimposed already "dry". Often, however, fiber defects are observed: "ball" (A), "spindle" (B), "branch" (C) or "fusion" (D) type. Branches starting from the fiber are formed when many electrical charges accumulate on it. It is assumed that when the polymer fiber reaches the collector wet, flaxlike fibers are formed, as well as fusion between the fibers at the points of contact, Fig. 14b.

The effect of collagen concentration 5 wt is illustrated. % and 10 wt. %, in IIFIP solution, at the same needle size (19G): at a collagen concentration of 10 wt. % the appearance of defects on individual fibers is observed - in the form of "stringed" balls (f), fig. 15s. The most effective collagen electrospinning concentration range remains 5 to 6 wt. % in IIFIP solution.

At the same collagen concentration - 5 wt. %. fibers produced with a smaller needle size (18G), or larger ID = 0.838 mm, are visibly finer, but individual defective fibers with multiple beads appear, Fig. 15s.

Example 2. Collagen fibers and fibrous structures can be modified by adding various polymers to collagen, such as hydroxyapatite, hyaluronic acid, chondroitin sulfate, etc., [14, 15 and 16].

Experimental studies were undertaken on the electrospinning of collagen (type 1, bovine skin) solutions at IIFIP, under the conditions of Example 1, attempting to modify the collagen with two glycosaminoglycans (GAGs): chondroitin sulfate (CSGAG) and hyaluronic acid ( IIAGAG). Collagen, along with selected GAGs, was dissolved in IIFIP for 24 h, then stirred and homogenized to undergo electrospinning as 6 wt. % solution, according to the method described in example 1.

Screening studies were performed using selected GAGs alone: IIAGAG - at 0.8 wt. %; CSGAG in 0.8 and 1.6 wt. %; and co: IIAGAG at 0.8 wt. % and CSGAG - 0.8 wt. %; and IIAGAG at 0.8 wt. % and CSGAG - 1.6 wt. %. The fiberglass structure was crosslinked in glutaric anhydride (GTA) vapor at room temperature for 30 hours

Electrospinning is carried out under the best conditions of example 1.

11rsdstavspi are images of fibrous structures, with high resolution from a scanning electron microscope - SEM-FIB Tcscan Eyra I XMU, Czech Republic, revealing the morphology of fibers produced by electrospinning is a dielectric barrier, at a single half-cycle rectified voltage is an industrial frequency (50 Hz):

In the high-resolution scanning electron microscope (SEM) images, the morphology of the modified 0.8 wt. % IIAGAG collagen fibers, at different magnification, immediately after electrospinning, Fig. 16a and b, and after aging for 30 hours in GTA, FIG. 1 was, d. The electrospinning is successful, the fibers are prone to branching, fusion and spillage, fig. 16b and d. Collagen fibers with a significant difference in diameter are obtained, fig. 1 was and d. Increasing the concentration of IIAGAG to 1.6 wt. % makes electrofibrization of the solution impossible.

Through high-resolution images from a scanning electron microscope (SEM). presented the morphology of chondroitin sulfate (CSGAG) modified collagen fibers after exposure for 30 hours in GTA vapor as follows: CSGAG 0.8 wt. %, fig. 17a, b; CSGAG - 1.6 wt. %, fig. 17d, f. Electrospinning is successful, too many flat fibers, branches and fusions are observed, fig. 17b. It is apparent that the CSGAG imported into the l.6wt. %, is characterized by fewer mergers and branches, fig. 17d. Increasing the CSGAG concentration above 1.6 wt. % makes it impossible to electrofibrate the solution.

These experimental studies are complemented by the simultaneous modification of collagen by IIAGAG and CSGAG. High-resolution scanning electron microscope (SEM) images of fibrous structures are presented. produced by electrospinning is a dielectric barrier, at single half-cycle rectified voltage is an industrial frequency, of 6 wt. % solution of modified collagen (type 1, from bovine skin) in Π1ΊΡ and subsequent cross-linking of the electrofibrous structure, in GTA vapor, at room temperature for 30 hours: IIAGAG - 0.8 wt. % and CSGAG - 0.8 wt. %, fig. 18a, b, f; IIAGAG 0.8 wt. % and CSGAG -- 1.6 wt. %. fig. 18d, f. It can be seen that the higher concentration of CSGAG — 1.6 wt. %, gives significantly worse results in terms of the observed fusion of the modified collagen fibers, fig. 18d. Moreover, long fibers without defects are observed, is much smaller in diameter - it can be assumed that these are fibers of pure collagen, Fig. 18. The simultaneously modified IIAGAG (0.8 wt. %) and CSGAG (0.8 wt. %) collagen not only lends itself much better to electrospinning. but regardless of fusions it shows small fiber sizes, fig. 18.

In conclusion, it should be pointed out that electrospinning susceptibility of the modified collagen - simultaneously with HAGAG and CSGAG is facilitated, but the good quality of the fiber structure should be leading in this approach. A follow-up response should be sought promptly. to minimize fiber fusion. Unmodified collagen not only lends itself well to electrofibration, but also provides good quality in the fiber structure.

11rimsr 3.

A fibrous structure (non-woven fabric, mat) is produced from nanocoating. by electrospinning a dielectric barrier, at industrial frequency AC voltage (50 Hz), from a collagen solution (type 1, from bovine skin) in HFIP and subsequent omrszvance of the produced collagen fibers in GTA vapor, at room temperature for 24 hours.

Electrofibrating is carried out under the following technological parameters: (1) Working air gap <5 = 180 mm; (2) Electrofibration voltage rms value 23 kVrms; (3) Volumetric flow rate (or consumption) of the collagen solution - Q = 130pL/min; (4) Inner diameter (ID) and hollow needle size ID 0.686 mm (G19). Under these conditions, the productivity of this AC single-needle electrospinning is Q 130 pL/min = 7.8 mL/h 0.0078 L/h.

Optical-microscopic images (x 40) from an optical microscope Binocular digital microscope, 2М camera DM15, ΟΡΤΙΚΛ (Italy) are presented in fig. 19: immediately after electrospinning, fig. 19a, and after immersion in GTA vapor, at room temperature h .

for 24 hours, fig. 19b.

It can be noted that: (1) Collagen fibers lend themselves well to electrofibration in an alternating electric field; (2) Before omrszvance, the collagen fibers are randomly arranged in the fibrous structure; (3) After cross-linking, the collagen fibers are clustered, and the formation of multiple nodules is observed.

Literature

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Claims (14)

1. Method for the production of polymer fibers by fiberization in an electric field, or electrospinning, of an electrically conductive polymer-containing liquid - solution, emulsion or melt, in which electrically charged microjets emanate from a limited or unlimited (free) surface of the electrospinning liquid placed under high electric potential from the electrode of the (electro)fiber, and under the action of the electric field are directed through the near and far region of the working air space to the counter electrode, grounded or placed under a high electric potential of the opposite sign, to effect elongation, thinning and disintegration of the jets of multiple polymer fibers and their deposition in the form of a flat non-woven fibrous structure on the counter electrode, which plays the role of a stationary or moving collector, characterized in that between the high-voltage electrode (3) of the electrofiber (7) and the counter electrode ( 5) a high alternating electric voltage is applied, changing periodically in magnitude and/or direction in time, and across the path of the microjets for fiberization (17), immediately next to the counter electrode (5), a solid dielectric barrier (4) is placed, with thickness from 1 to 20 mm, relative dielectric permittivity from 2 to 10, specific electrical conductivity - over 1 pS/m, and (di)electric strength - over 9 MV/m, which in turn assumes the role of a stationary or moving collector (8) for the manufactured polymer fibers (9) and the nonwoven fiber structure (10). 2. A method for the production of polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that the counter electrode (5) has a shape and dimensions that concentrate the electric field, i.e. increase and distribute its intensity on the surface of the dielectric barrier (4). 3. A method for the production of polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 2, characterized in that the counter electrode (5) has the form of a rotating metal drum (25), the axis of which is located transversely to the movement of the unstable microjets (17) in the working air gap (2), and its linear speed of rotation does not exceed the critical speed of deposition of the fibers 9 on the surface of the drum (25). 4. A method for the production of polymer nano- and microfibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that the dielectric barrier (4) is an insulating coating (33) on the electrically active surface of the counter electrode ( 5) - on the side of the high-voltage electrode (3), or on the surface of the metal drum (32). 5. A method for the production of polymer fibers by electrospinning with a dielectric barrier and an alternating electric voltage, according to claim 1, characterized in that the counter electrode (5) is an electrically conductive coating on the dielectric barrier (4) and together with it forms an electrically isolated metal collector (8), on the dielectric surface of which the manufactured polymer fibers (9) are deposited and the fiber structure (Y) is built. 6. A method for the production of polymer fibers by electrospinning with a dielectric barrier and high alternating electric voltage, according to claim 1, characterized in that the produced polymer fibers (9) are deposited on a stationary or moving support (tape) 34 located on the dielectric barrier (4), which takes the role of the collector (8) for the produced polymer fibers (9) and the constructed fibrous structure (10). 7. A method for producing polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that the high alternating electric voltage is a sinusoidal electric voltage with an industrial frequency. 8. A method for producing polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that the high alternating electric voltage is a pulsating electric voltage that changes in time in the form of periodically repeating unipolar pulses, with a repetition rate of 10 to 1000 Hz and a duty cycle of 10 % to 90 %. 9. Method for the production of polymer fibers by electrospinning with a dielectric barrier and pulsating electric voltage, according to claim 8, characterized in that the pulsating electric voltage is a single half-period rectified voltage with an industrial frequency. 10. A method for the production of polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that the high-voltage electrode (3) of the electrospinning machine (7) is placed under a high alternating sinusoidal voltage with an industrial frequency to earth (6), and the counter electrode (5) is placed under a high constant voltage, also relative to earth (6), and the ratio of the amplitudes of the alternating (Preak) and constant (Kps) voltage is: VpeaklVDC < 1. 11. A method for producing polymer fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that a high alternating sinusoidal is applied between the high voltage electrode (3) of the electrospinning machine (7) and the counter electrode (5) industrial frequency voltage, the value of which exceeds the first critical ignition voltage (45) of a dielectric barrier discharge that burns in air, at atmospheric pressure and room temperature, so that the electrospinning takes place in the oxygen- and ozone-containing nerve-weighted cold plasma of the dielectric barrier discharge. 12. A method for producing fibers by electrospinning with a dielectric barrier and a high alternating electric voltage, according to claim 1, characterized in that a high alternating sinusoidal voltage is applied between the high voltage electrode (3) of the electrospinning machine (7) and the counter electrode (5) with an industrial frequency, the value of which exceeds the second critical ignition voltage (48) of a dielectric barrier discharge, in air at atmospheric pressure and room temperature, so that electrospinning takes place in the non-equilibrium cold plasma of a dielectric barrier discharge containing nitrogen oxides (NO _X ) . 13. Device for the production of polymer fibers by electrospinning with a dielectric barrier and high alternating electric voltage, which consists of a source of high alternating electric voltage and two electrodes, the first is a high-voltage electrode (3), which is the main component of the electrospinning machine (7 ) and is a capillary metal tube - a hollow needle made of stainless steel, through which the liquid for electrospinning (13) in the form of a straight microjet (12) enters the working air gap (2), and the electrospinning machine (7) also includes a medical syringe (19) , representing a glass or plastic cylinder (21) with a piston (20) moving tightly inside it, filled with the liquid for electrospinning (13), to which the hollow needle (3) is connected, and the electrospinner (7) also includes an infusion pump (23) ), driving the piston (20) of the syringe (19) at a constant linear speed, which determines a constant flow rate of the electrospinning liquid (13) through the cylindrical hole at the end of the hollow needle (3), and the second, is a counter electrode (5) , which is located opposite the hollow needle (3), at the end of the working air gap (2), transverse to the axis of the hollow needle (3), characterized by the fact that in the interelectrode space (1), transverse to the axis of the hollow needle (3), directly on the active surface of the counter electrode (5) a solid dielectric barrier (4) is located, which follows the profile of the electrically active surface of the counter electrode (5) and plays the role of a stationary or moving collector (8) for the produced polymer fibers (9) and the built-up fibrous structure (10). 14. Device for the production of fibers by electrospinning with a dielectric barrier and high alternating electric voltage, according to claim 13, characterized in that the electrospinning liquid (13) located in the cylinder (21) of the medical syringe (19) is electrically isolated from the grounded housing (57) of the infusion pump (23) by being placed inside a larger medical syringe (59) so that the hollow needle (3) of the small syringe (19) protrudes through the front opening of the large syringe (59), and the plunger (60) of the large syringe (59) to directly drive the plunger (20) of the small syringe (19).