Microfluidic-based wet spinning of individual solid polymer fibers

Abstract

The invention relates to a method for preparing a polymer precursor for use in the preparation of a polymer precursor from a precursor liquid (L1) comprising an aggregatable, polymerizable and / or crosslinkable polymer precursor by microfluidically-based wet spinning, in particular a method for producing individual solid polymer fibers from a precursor liquid comprising a polymerizable and / or crosslinkable polymer precursor, comprising the following steps: a) introducing the precursor liquid (L1) into a first capillary (11) protruding coaxially into a second capillary (12); b) producing a liquid fiber having a core-shell structure in a second capillary (12); c) optionally, injecting the liquid fiber having a core-shell structure produced in step b) into a third capillary (13) to produce a fiber having a core-shell-sheath structure; d) guiding the liquid fibers having a core-shell structure, optionally having a sheath, as produced in step b) or in step c) through the stationary liquid phase (SP); e) curing the liquid sheet of fibers having a core-shell structure at least in one of steps c) and d) to provide fibers having a liquid core (22) embedded in the cured shell (21); f) collecting fibers; g) after step f), curing the liquid core (22) of fibres; h) removing the solidified shell (21) from the solid core (22 ') to obtain a solid polymer fiber.

Description

Technical Field

[0001] The present invention relates to a method for producing individual solid polymer fibers from a precursor liquid comprising polymerizable and / or crosslinkable polymer precursors by microfluidic-based wet spinning. Furthermore, the present invention relates to a microfluidic-based wet spinning device for producing individual solid polymer fibers. Background Art

[0002] Synthetic fibers are used for the manufacture of materials in many technical fields (for example, ranging from optics to textiles to mechanical engineering). Usually, synthetic fibers are produced by spinning. Thus, depending on the material of the synthetic fiber, continuous filaments or fiber mats are produced by different spinning techniques. For example, melt spinning allows the production of synthetic fibers from molten thermoplastic materials. Another method called solution spinning uses a spinning solution of a precursor material contained in a solvent, whereby the precursor material of the spinning solution is solidified to form the target fiber. Solution spinning can be performed completely differently. Well-known methods are especially dry spinning, wet spinning, dry-jet wet spinning and electrostatic spinning.

[0003] For example, WO 2014 / 143866 A1 (Arsenal Medical, Inc.) discloses a method for obtaining multicomponent fibers by coaxial electrospinning. Thus, a fiber is provided, which comprises (a) a polymer core comprising a polymer forming a core and (b) a polymer sheath comprising a polymer forming a sheath different from the polymer forming the core. Examples of polymers forming the core include, for example, cross-linked polysiloxanes and thermoplastic polymers, etc. Examples of polymers forming the sheath include, for example, solvent-soluble polymers, degradable polymers, and polymers forming hydrogels, etc. However, the method produces a fiber web formed by a collection of fairly fine fibers interwoven to form a three-dimensional network, but individual fibers cannot be directly produced in a targeted manner.

[0004] KR 10169598 B1 (Dong-A Univ.Res.Found for Industry-Academy Coop.) relates to a method for manufacturing polymer fibers using a microfluidic device, and in particular to a method for manufacturing polymer fibers by injecting a precursor solution and a support cross-linking solution into a microfluidic device. The method comprises the following steps: (1) preparing (i) a precursor solution containing a monomer, a cross-linking agent, an alginate and a photoinitiator and (ii) an alginate cross-linking solution containing a metal cation; (2) injecting the precursor solution and the alginate cross-linking solution into a microfluidic device to manufacture a metal-alginate support structure; (3) photopolymerizing the monomer by irradiating with a light source in the microfluidic device to manufacture a cross-linked polymer / alginate support composite fiber; and (4) reacting the manufactured cross-linked polymer / alginate support composite fiber with a chelating agent to remove the alginate support from the polymer / alginate support composite fiber to obtain an unsupported cross-linked polymer fiber. However, the fibers produced in this manner contain considerable defects, making them unsuitable for optical applications, for example. Furthermore, this method is only practical for producing hydrophilic fibers, the precursors of which are miscible with aqueous alginate solutions. However, it is not possible to produce hydrophobic fibers, such as polydimethylsiloxane (PDMS) fibers, from other precursors that are immiscible with aqueous alginate solutions.

[0005] Therefore, there is a need to develop new and improved processes for producing polymer fibers which at least partially overcome the above-mentioned disadvantages. Summary of the invention

[0006] The object of the present invention is to provide a new and improved solution for producing polymer fibers. In particular, the method should allow the production of individual polymer fibers consisting of different materials and having various thicknesses and lengths in a targeted manner. It is further preferred that the solution should make it possible to produce polymer fibers that are as uniform as possible and, in particular, have a quality suitable for optical applications.

[0007] Surprisingly, it has been found that these objects can be achieved with a method according to claim 1 .

[0008] Thus, according to a first aspect, the present invention relates to a method for producing individual solid polymer fibers by microfluidic-based wet spinning from a precursor liquid comprising agglomerable, polymerizable and / or crosslinkable polymer precursors, in particular from a precursor liquid comprising polymerizable and / or crosslinkable polymer precursors, the method comprising the following steps:

[0009] a) introducing the precursor liquid into the first capillary through the first inlet, whereby at least the downstream end of the first capillary coaxially protrudes into the second capillary, and injecting the precursor liquid into the second capillary to obtain a core flow of the precursor liquid in the second capillary;

[0010] b) producing a liquid fiber having a core-sheath structure in the second capillary by simultaneously introducing a sheath liquid into the second capillary through a second inlet so that the second liquid forms a tubular and coaxial sheath flow around the core flow of the precursor liquid;

[0011] c) optionally, injecting the liquid fiber having a core-sheath structure produced in step b) into a third capillary to obtain a core-sheath flow in the third capillary, whereby at least the downstream end of the second capillary coaxially protrudes into the third capillary, and simultaneously introducing a third liquid into the third capillary through a third inlet, so that in the third capillary the third liquid forms a tubular and concentric sheath flow surrounding the core-sheath flow, thereby producing a liquid fiber having a core-sheath-sheath structure;

[0012] d) guiding the liquid fiber having a core-shell structure (optionally with a sheath) as produced in step b) or in step c) through a stationary liquid phase;

[0013] e) solidifying the sheath liquid of the fiber with core-sheath structure in at least one of steps c) and d), in particular by using a solidifying agent for the sheath liquid as a third liquid in step c) and / or as a fixed liquid phase in step d), to provide a fiber with core-sheath structure having a liquid core embedded in a solidified sheath;

[0014] f) collecting from said stationary liquid phase said fibers in the form of fibers having a liquid core embedded in a solidified shell;

[0015] g) after step f), solidifying the liquid core of the fiber having a liquid core embedded in a solidified shell by aggregation, polymerization and / or crosslinking, in particular by polymerization and / or crosslinking, to obtain a fiber having a solid core within the solidified shell;

[0016] h) removing the solidified shell from the solid core to obtain the solid polymer fiber.

[0017] The method of the present invention utilizes a removable shell as a tubular mold for shaping and trapping a curable polymer precursor in a core channel. This does not require premixing of the curable polymer precursor and the shell liquid. This allows the production of a wider range of individual polymer fibers, and by adjusting the size of the capillary, polymer fibers with various thicknesses up to several millimeters and lengths exceeding one meter can be produced in a highly targeted manner. In addition, the polymer fibers that can be obtained using the method of the present invention are highly uniform and, depending on the materials used, are even suitable for optical applications.

[0018] Furthermore, during the process of the invention, fibers are produced having a liquid core embedded in a solidified sheath. This allows the solidification of the liquid curable polymer precursor to be separated from the wet spinning process.

[0019] In contrast, in existing microfluidic spinning methods, such as described in KR 10169598 B1, solidification of the polymer fibers must be induced during the spinning process, especially when the flow of the liquid in the wet spinning device is well maintained. In addition, such methods require rapid solidification of the precursor fluid during a relatively short spinning process, thus limiting the materials suitable for fiber production. In addition, because specific polymer materials require different solidification methods, such as photo-induced polymerization, chemical crosslinking and / or solvent exchange, microfluidic wet spinning devices must be designed and manufactured under specific considerations, thus making polymer fiber production quite complicated for the user.

[0020] All these disadvantages can be circumvented with the method of the present invention, whereby the solidification of the liquid curable polymer precursor can be separated in time and place from the wet spinning process and in particular the solidification of the shell. Thus, for example, if desired, the solidification of the liquid curable polymer precursor can be achieved outside the wet spinning apparatus and over any long period of time.

[0021] Therefore, in a preferred embodiment, steps g) and / or h) are performed outside the stationary liquid phase and / or in time after steps a) to e).

[0022] In particular, unlike processes such as common melt spinning or thermal drawing, the method of the present invention allows the production of high-quality continuous polymer optical fibers (POFs) even when using sensitive functional molecules such as perovskite nanocrystals.

[0023] Furthermore, with the method of the invention, polymer optical fibers (POF) with a low elastic modulus of <3 MPa or even <1 MPa can be obtained. Such POFs are characterized by increased sensitivity to small pressures and cannot be produced by ordinary molding techniques because the fibers will break during demolding due to the too low elastic modulus.

[0024] In particular, the polymerizable and / or cross-linkable polymer precursor is selected from polymerizable and / or cross-linkable monomers, oligomers and / or polymers.

[0025] For example, the precursor liquid comprises:

[0026] - polyols capable of forming polyurethane polymers as well as diisocyanates, triisocyanates and / or polyurethane prepolymers

[0027] - Epoxy resin, optionally with a hardener

[0028] - Crosslinkable silicone polymers, especially polydimethylsiloxane polymers

[0029] - ethylenically unsaturated monomers, in particular olefins, vinyl monomers, alkenyl monomers and / or (meth)acrylates,

[0030] - monomers having amine, carboxyl and / or acyl groups capable of forming polyamides, such as amino acids, and / or

[0031] - monomers and / or oligomers containing reactive groups for click chemistry and capable of forming polymers, for example monomers and / or oligomers containing groups that react in azide-alkyne cycloaddition reactions, thiol-ene reactions and / or amino-alkyne reactions,

[0032] - monomers selected from α-hydroxy acids, in particular lactic acid or its cyclic diester lactide, glycolic acid, mandelic acid and / or citric acid;

[0033] - Aggregable polymers, in particular polylactic acid (PLA) and / or polycaprolactone (PCL).

[0034] According to a particularly preferred embodiment, the precursor liquid comprises a (meth)acrylate and / or a crosslinkable polydimethylsiloxane polymer.

[0035] Examples of aggregable polymers are polylactic acid (PLA) and / or polycaprolactone (PCL). Such polymers can be solidified by polymer aggregation via solvent exchange. Thus, in particular, the aggregable polymer is dissolved in one or more solvents as a precursor liquid.

[0036] However, other polymerizable and / or cross-linkable polymer precursors may also be used, depending on the desired solid polymer fibers.

[0037] A further preferred polymerizable precursor is lactic acid or its cyclic diester lactide.

[0038] Other highly preferred polymerizable precursors are polyols capable of forming polyurethane polymers as well as diisocyanates, triisocyanates and / or polyurethane prepolymers.

[0039] Further preferred polymerizable precursors are mixtures of crosslinkable silicone polymers or olefin polymers and / or macromonomers (eg dodecyl dimethacrylate and (meth)acrylate precursors), especially those capable of forming amphiphilic polymer co-networks.

[0040] In particular, the precursor liquid further comprises, for example, a solvent, a crosslinking agent, a thermal polymerization initiator, a photopolymerization initiator, a chain transfer agent, a functional molecule and / or a molecular weight regulator. In particular, these substances are selected depending on the specific polymerizable and / or crosslinkable polymer precursor, and are added in particular to enable the liquid core to be cured and controlled in step g).

[0041] Functional molecules can be selected, for example, from fluorophores, chromophores and / or nanoparticles. For example, such molecules can be incorporated into the fiber to adapt the fiber to a specific application. In particular, the functional molecules can comprise nanocrystals, such as perovskite nanocrystals.

[0042] The shell liquid is in particular a solution of a solvent, especially water, and a solvent-soluble, non-crosslinked polymer.

[0043] In particular, the shell liquid is a solution of water and a homopolymer and / or copolymer formed, for example, from one or more of the following monomers: ethylene oxide, vinyl pyrrolidone, vinyl alcohol, vinyl acetate, vinyl pyridine, methyl vinyl ether, acrylic acid and its salts, methacrylic acid and its salts, hydroxyethyl methacrylate, acrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, alkyloxazolines, sugar monomers, polysaccharides, dextran, alginates, amino acids, hydrophilic polypeptides, proteins and / or gelatin.

[0044] Particularly preferably, the shell liquid is an aqueous hydrogel precursor solution, in particular an aqueous polysaccharide solution. Particularly preferably, the shell liquid is an aqueous alginate solution, in particular an aqueous alkali metal alginate solution, such as a sodium alginate solution. These types of solutions result in the production of highly stable shells and are compatible with a variety of precursor liquids. In addition, these solutions can be easily removed later.

[0045] In particular, the concentration of the homopolymer and / or copolymer, in particular the hydrogel precursor, in particular the alginate, is 0.05-10 wt. %, in particular 0.1-5 wt. %, in particular 1-3 wt. %, relative to the total weight of the shell liquid.

[0046] In particular, the precursor liquid is substantially immiscible with the shell liquid. Thus, in step b), a well-defined phase interface between the core and the shell in the liquid fiber can be obtained. In addition, diffusion of the precursor liquid into the solidified shell is reduced.

[0047] In step d), the liquid fibers having a core-sheath structure (optionally with a sheath) as produced in step b) or in step c) are preferably introduced into the stationary liquid phase below the liquid level of the stationary liquid phase. This reduces turbulence and improves the overall quality of the obtainable fibers.

[0048] Thus, preferably, the second capillary or the third capillary (if the latter is present) is immersed in the stationary liquid phase.

[0049] In particular, the third liquid in step c) and / or the stationary liquid phase in step d) comprises or consists of a polar solvent, in particular methanol, ethanol and / or water, in particular water.

[0050] In particular, the temperature of the stationary liquid phase may be between 0 and 95°C, in particular between 15 and 90°C, and in particular between room temperature and 80°C.

[0051] According to a first preferred embodiment, the temperature of the stationary liquid phase is between 15 and 30° C., in particular room temperature.

[0052] In a second preferred embodiment, the temperature of the stationary liquid phase is an elevated temperature, in particular above room temperature, in particular above 30° C. This allows a pre-curing step and / or a partial curing of the liquid core to be carried out in the stationary liquid phase.

[0053] In particular, the temperature of the stationary liquid phase is between 45-85° C., in particular between 55-75° C., in particular between 60-70° C., for example 65° C. These temperatures are particularly advantageous when using crosslinkable siloxane polymers, in particular polydimethylsiloxane polymers, as precursor liquids and / or when producing PDMS fibers.

[0054] In particular, the third liquid in step c) and / or the stationary liquid phase in step d) is a solidifying agent for the shell liquid and is selected from divalent metal cations, in particular from Ca 2+ Mg 2+ 、Zn 2+ , Fe 2+ , Cu 2+ and / or Ba 2+ Particularly preferred is Ca 2+ Aqueous solution of salt, such as CaCl 2 of aqueous solution.

[0055] In particular, the salt of a divalent metal cation (especially CaCl 2 ) in an aqueous solution in a concentration of 0.05 to 10% by weight, in particular 0.1 to 5% by weight, and especially 0.5 to 2% by weight.

[0056] According to a particularly preferred embodiment, an optional step c) is performed, and in step c), a curing agent for the shell liquid selected from an aqueous solution of a salt of a divalent metal cation is used as the third liquid. In this case, the shell of the liquid fiber with a core-shell structure is directly solidified by the concentric sheath flow of the third liquid in the third capillary. Thus, the third liquid forms another tubular mold to shape and trap the liquid fiber with a core-shell structure. This can further improve the uniformity of the liquid fiber. In this case, the stationary liquid phase in step d) allows the fiber to be spun out from the device in a smooth and stable manner. In particular, the stationary liquid phase in step d) is an aqueous solution, such as water.

[0057] According to another highly preferred embodiment, step c) is not carried out and in step d) a solidifying agent for the shell liquid selected from aqueous solutions of salts of divalent metal cations is used as a stationary liquid phase. In this case, the shell of the liquid fiber with a core-shell structure solidifies within the stationary liquid phase, which additionally allows the fiber to be spun out of the device in a smooth and stable manner.

[0058] According to a preferred embodiment, in the liquid fiber having a core-sheath structure produced in the second capillary, the sheath liquid is in direct contact with the precursor liquid at least in the downstream section of the second capillary.

[0059] Thus, preferably, the downstream end of the first capillary is located in the second capillary, whereby in the flow direction of the liquid fiber, the downstream end of the first capillary is particularly located in the upper half, in particular the upper quarter, of the second capillary. In this case, if a third capillary is present, the downstream end of the second capillary is particularly located in the third capillary.

[0060] In particular, with respect to the upstream end, at least the outer diameter (in particular the inner diameter and the outer diameter) of the first capillary tapers towards the downstream end, in particular in a stepped manner, in particular to form a first capillary nozzle. Likewise, in a preferred embodiment, with respect to the upstream end, at least the outer diameter (in particular the inner diameter and the outer diameter) of the second capillary tapers towards the downstream end, in particular in a stepped manner, in particular to form a second capillary nozzle.

[0061] This allows focusing the flow of the precursor liquid when it is injected into the second capillary and allows focusing the liquid fiber having a core-sheath structure when leaving the second capillary. However, other configurations may also be suitable.

[0062] Particularly, the length of the tapered section of the first capillary is 25-75%, especially 40-60% of the entire length of the first capillary; and, particularly, the length of the tapered section of the second capillary is 25-75%, especially 40-60% of the entire length of the second capillary.

[0063] According to another preferred embodiment, in the liquid fiber having a core-shell structure produced in the second capillary, the shell liquid and the precursor liquid in the liquid fiber having a core-shell structure are separated by the first capillary when flowing through the second capillary. In other words, in this case, the shell liquid and the precursor liquid are not in direct contact in the second capillary.

[0064] Thus, preferably, the first capillary tube extends completely through the second capillary tube, and preferably, in the flow direction of the liquid fiber, the downstream end of the first capillary tube is located further downstream than the downstream end of the second capillary tube. If a third capillary tube is present, the downstream ends of the first capillary tube and the second capillary tube are located in the third capillary tube, in particular in the upper half of the third capillary tube, in particular in the upper quarter.

[0065] Thus, in particular, before the precursor fluid is introduced into the hollow center section of the pre-cured shell fluid through the further downstream first capillary, the sheath fluid first contacts the shell fluid in the third capillary to pre-cured the shell fluid. Thus, the pre-cured shell fluid is still a fluid, but forms a more stable interface with the precursor fluid, which further reduces mixing of the fluids at the interface.

[0066] Therefore, the expression "whereby at least the downstream end of the first capillary protrudes coaxially into the second capillary" is particularly interpreted to include the first capillary extending completely through the second capillary, and, preferably, in the flow direction of the liquid fiber, the downstream end of the first capillary is located further downstream of the downstream end of the second capillary.

[0067] In the embodiment in which the first capillary extends completely through the second capillary, the first capillary and the second capillary and optionally the third capillary in particular each have a constant inner and / or outer diameter.

[0068] Embodiments where the shell liquid and the precursor liquid are not in direct contact in the second capillary and embodiments where the first capillary extends completely through the second capillary allow the shell liquid to be pre-cured before it contacts the precursor liquid. This is due to the extended first capillary or core channel, respectively. This improves the stability of the liquid fiber with a core-shell structure by having an at least partially gelled shell at the beginning of the core-shell interface. Therefore, due to the less fluid or non-liquid nature of the shell liquid (hydrogel flow), the fluctuations of the core-shell interface are reduced.

[0069] Thus: These embodiments provide, inter alia, polymer fibers with better structural consistency and / or allow fibers to be spun at lower spinning rates (thus making post-spinning in-line processing, such as UV irradiation and automated collection, easier).

[0070] Independent of the specific embodiment, in particular, the inner diameter of the first capillary at the downstream end is equal to 40-60%, especially 45-55% of the inner diameter of the second capillary at the upstream end; and, in particular, the inner diameter of the second capillary at the downstream end is equal to 40-60%, especially 45-55% of the inner diameter of the third capillary at the upstream end. This allows the production of liquid fibers with a core-sheath structure at a preferred ratio of core thickness to sheath thickness in the second capillary.

[0071] In particular, the inner diameter of the second capillary at the upstream end is equal to 110-150%, in particular 120-140%, of the outer diameter of the first capillary at the downstream end; and, in particular, the inner diameter of the third capillary at the upstream end is equal to 110-150%, in particular 120-140%, of the outer diameter of the second capillary at the downstream end. These configurations allow the first capillary to be introduced into the second capillary and leave an annular opening at the upstream end of the second capillary for introducing liquid. This is also true for the second capillary and the third capillary.

[0072] For example, the inner diameter of the first capillary at the downstream end is 0.3-5.0 mm, and / or the inner diameter of the second capillary at the upstream end is 0.7-6.0 mm; and, in particular, the inner diameter of the second capillary at the downstream end is 0.3-5.0 mm, and / or the inner diameter of the third capillary at the upstream end is 0.7-6.0 mm. However, the inner diameter and the outer diameter are preferably selected depending on the desired thickness of the fiber to be produced.

[0073] In particular, the shell liquid is introduced into the second capillary at its upstream end face, in particular through an annular opening formed by the first capillary and / or the downstream end of the first capillary coaxially protruding into or extending through the second capillary; and, in particular, the third liquid is introduced into the third capillary at its upstream end face, in particular through an annular opening formed by the downstream end of the second capillary coaxially protruding into the third capillary.

[0074] In particular, before the shell liquid is introduced into the second capillary or the third capillary, the shell liquid is guided along the outer surface of the first capillary (especially the tapered section); and, in particular, before the third liquid is introduced into the third capillary, the third liquid is guided along the outer surface of the second capillary (especially along the tapered section).

[0075] This allows the production of a highly laminar flow of the corresponding liquid in the capillary.

[0076] Preferably, the flow rate ratio of core flow: sheath flow is 1:0.1-10, particularly 1:0.5-1.5, particularly 1:0.8-1.2; and, in particular, the flow rate ratio of core flow: sheath flow: sheath flow is 1:(0.1-10):(1-50), particularly 1:0.5-1.5:2-15, particularly 1:0.5-0.9:5-12. With such a ratio, a highly laminar flow can be achieved and high-quality fibers can be produced.

[0077] Flow rate refers to volumetric flow rate, or the volume of liquid passing through per unit time.

[0078] In particular, the flow of the precursor liquid in the second capillary, the flow of the liquid fiber with a core-shell structure in the second capillary, the core-shell flow in the third capillary and / or the flow of the liquid fiber with a core-shell-sheath structure are controlled to flow in layers. This can be achieved by appropriate sizes of the capillaries and the flow rate of the liquid.

[0079] In particular, the diameters of the first, second and optionally third capillaries and / or the flow rates of the core, shell and optionally sheath flows are chosen such that the solid polymer fibers obtainable in step h) have a diameter of 1-5'000 μm, in particular 10-2'500 μm, for example 100-1'500 μm.

[0080] Preferably, the capillary is embedded in the solid material, in particular, the capillary is passed through the solid material along a straight line. Thus, preferably, around each tapered section of the capillary and / or around the first capillary and the second capillary section, an annular cavity is formed for guiding liquid between the outer surface and / or outer surface of the tapered section of the corresponding capillary and the solid material, and thus each cavity can be entered from the outside by a free passage in the solid material forming the second inlet and optionally the third inlet. The solid material is, for example, an inorganic material and / or a plastic material. The inorganic material is, for example, glass. The plastic material is, for example, a photopolymerized resin, polydimethylsiloxane and / or poly(methyl methacrylate) (PMMA).

[0081] In particular, the capillary is made of glass. Since glass is highly inert to various chemicals, the method of the present invention can be implemented with essentially any type of substance. However, capillaries made of plastic and / or metal materials may also be suitable.

[0082] In particular, curing the core of the core-sheath fiber in step g) is achieved by irradiation with electromagnetic radiation and / or heating. This allows the precursor liquid to be cured and / or polymerized in the core of the fiber. Suitable radiation sources and / or heat sources are known to those skilled in the art.

[0083] Typically, for photopolymerization, a UV radiation source is used.Thus, preferably, curing of the core of the core-sheath fiber in step g) is achieved by electromagnetic radiation having a wavelength of 280-380 nm.

[0084] Heating may be achieved at a temperature in the range of, for example, 40-200° C., such as 60-100° C., in particular for a period of 10 minutes to 10 hours, especially 0.5-5 hours.

[0085] Aggregation in step g) can be achieved, for example, by polymer aggregation via solvent exchange. In this case, the fiber with a solid core comprises aggregated polymers. This means non-covalently bonded polymers. For example, the bonding between polymers in the fiber is achieved, for example, by weak intermolecular forces, such as van der Waals forces.

[0086] However, depending on the specific composition of the precursor liquid, other measures may also be suitable for solidification.

[0087] The removal of the solidified shell from the solid core is achieved in particular by dissolving the solidified shell in a solvent, such as an aqueous solution. In particular, the solvent is an aqueous alkali metal salt solution (e.g. NaCl solution) and / or a solvent containing a cation capable of binding divalent metal cations, in particular Ca 2+ Mg 2+ 、Zn 2+ , Fe 2+ , Cu 2+ and / or Ba 2+ The present invention relates to the presence of an aqueous solution of a chelating agent (e.g. ethylenediaminetetraacetic acid). This results in an efficient and reliable method for removing the shell. However, other techniques can also be used to remove the solidified shell.

[0088] In particular, during or after step f), the fiber with a core embedded in a solidified shell is taken up on a storage unit, in particular a winder and / or a reel. Thus, in particular, the fiber with a core embedded in a solidified shell is guided by one or more godet units.

[0089] In particular, individual solid polymer fibres are produced without applying an electric field and / or the method of the invention does not comprise the step of applying an electric field to produce the fibres.

[0090] Another aspect of the invention relates to liquid fibers having a liquid core embedded in a liquid shell, whereby the liquid core is made from a precursor liquid comprising polymerizable and / or cross-linkable polymer precursors and the liquid shell is an aqueous hydrogel precursor solution.

[0091] Another aspect of the invention relates to a fiber having a liquid core embedded in a solidified shell, whereby the liquid core is made from a precursor liquid comprising a polymerizable and / or cross-linkable polymer precursor and the solidified shell is a hydrogel.

[0092] Furthermore, the present invention relates to solid fibers having a cured core embedded in a cured shell, whereby the core is made from a cured precursor liquid comprising a polymerizable and / or cross-linkable polymer precursor and the cured shell is a hydrogel.

[0093] Furthermore, the present invention relates to solid fibers obtained or obtainable by the above-described process.

[0094] With the above-mentioned fiber, liquid core, solidified core, shell liquid and solidified shell are constituted, constructed and / or obtainable as described above in combination with the method of the present invention. Preferably, the diameter of the liquid core or solidified core is 1-5'000 μm, in particular 10-2'500 μm, for example 100-1'500 μm. The length of the fiber is preferably at least 10 cm, in particular at least 25 cm, in particular at least 50 cm or at least 100 cm. According to another advantageous embodiment, the length of the fiber is at least 10 m, in particular at least 100 m, in particular at least 1,000 m.

[0095] Another aspect relates to a microfluidic-based wet spinning apparatus for producing individual solid polymer fibers from a precursor liquid comprising polymerizable and / or cross-linkable polymer precursors, whereby the apparatus comprises:

[0096] a) a first inlet for introducing the precursor liquid into the first capillary, whereby at least the downstream end of the first capillary coaxially protrudes into the second capillary for injecting the precursor liquid into the second capillary to obtain a core flow of the precursor liquid in the second capillary;

[0097] b) a second inlet configured to introduce a sheath liquid into the second capillary, so that the second liquid forms a tubular and coaxial sheath flow around the core flow of the precursor liquid, thereby producing a liquid fiber having a core-sheath structure in the second capillary;

[0098] c) optionally, a third capillary, whereby at least the downstream end of the second capillary coaxially protrudes into the third capillary so that the liquid fiber with a core-sheath structure that can be produced in the second capillary can be injected into the third capillary to obtain a core-sheath flow in the third capillary, whereby the third capillary has a third inlet for introducing a third liquid into the third capillary so that in the third capillary the third liquid forms a tubular and concentric sheath flow around the core-sheath flow, whereby a liquid fiber with a core-sheath-sheath structure can be produced;

[0099] d) a container for providing a stationary liquid phase for guiding through a liquid fiber having a core-shell structure (optionally with a sheath) as may be produced in the second capillary or the third capillary;

[0100] e) a device for collecting the fibers in the form of fibers having a core embedded in a solidified shell from the stationary liquid phase, in particular a storage unit, in particular a winder and / or a reel;

[0101] f) means for solidifying the core of the core-sheath fiber by polymerization and / or crosslinking to obtain a fiber having a solid core within a solidified sheath, in particular means for emitting electromagnetic radiation and / or heating means;

[0102] g) means for removing the solidified shell from the solid core to obtain solid polymer fibers; in particular a further container for immersing and / or guiding through the fibers having the solid core embedded in the solidified shell.

[0103] Thus, preferably, the capillary and the inlet are configured and arranged as described above in connection with the method of the present invention.

[0104] Furthermore, the device preferably comprises at least two, in particular at least three independently controllable pump devices for introducing the precursor liquid into the first capillary, the shell liquid into the second capillary and optionally the third liquid into the third capillary.

[0105] In yet another aspect, the present invention relates to the use of an apparatus as described above for producing individual solid polymer fibers from a precursor liquid comprising polymerizable and / or cross-linkable polymer precursors.

[0106] Further advantageous embodiments and combinations of features emerge from the following detailed description and from the entirety of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] The accompanying drawings used to explain the embodiments show:

[0108] Figure 1 Schematic cross section of a first microfluidic wet spinning apparatus for producing individual solid polymer fibers from a precursor liquid comprising a polymerizable and / or cross-linkable polymer precursor;

[0109] Figure 2 exist Figure 1 Cross-section of a liquid fiber with a core-sheath-sheath structure flowing through the final capillary at section S.

[0110] Figure 3 Schematic illustration of the transformation from a fiber having a liquid core embedded in a solidified shell (A) to a fiber having a solidified core embedded in a solidified shell (B) to a solid target fiber after removal of the shell (C);

[0111] Figure 4 Thin polydimethylsiloxane (PDMS) fiber (A) produced by the method of the present invention

[0112] and thick PDMS fibers (B); digital micrograph (C) showing the light-guiding behavior of thick PDMS fibers;

[0113] Figure 5 Polyacrylate fibers produced by the method of the present invention: (A) thick polyacrylate fibers; (B) thin polyacrylate fibers and (C) digital micrographs showing the light guiding behavior of polyacrylate fibers;

[0114] Figure 6 a schematic cross-section of a second microfluidic wet spinning apparatus for producing individual solid polymer fibers from a precursor liquid comprising a polymerizable and / or cross-linkable polymer precursor;

[0115] Figure 7 Polylactic acid (PLA) fibers produced by the method of the present invention;

[0116] Figure 8 Amphiphilic polymer optical fiber (polysiloxane / polyacrylate amphiphilic polymer co-network) produced by the method of the present invention;

[0117] Fig. 9 Polyurethane fibers produced by the method of the present invention;

[0118] Fig.10 Graph showing the mechanical behavior of a soft POF produced by the method of the present invention under tensile loading;

[0119] Fig.11 Graph showing the reduction in light intensity in a polymer optical fiber (POF) as a function of applied pressure.

[0120] In the figures, the same components are given the same reference numerals. Example

[0121] The first wet spinning device and operation method

[0122] Figure 1A schematic cross section of a first microfluidic wet spinning device 10 of the present invention for producing a single solid polymer fiber with the method of the present invention is shown. At the upper end, the device 10 includes a first capillary 11 coaxially protruding into the upper end 12a of the second capillary 12. The lower ends 11b, 12b of both the first capillary 11 and the second capillary 12 are tapered so as to form a glass nozzle. The tapered lower end 12b of the second capillary 12 coaxially protrudes into the third capillary 13 in the form of a straight glass capillary. The three capillaries 11, 12, 13 are embedded in a solid block 14 of a synthetic material (i.e., a PDMS elastomer), and each has a length of, for example, 40 mm. The two upper capillaries 11, 12 have an outer diameter of, for example, 1 mm and an inner diameter of 0.772 mm at their upper ends 11a, 12a. At their lower ends 11b, 12b, the two upper capillaries 11, 12 have, for example, an outer diameter of 0.6 mm and an inner diameter of 0.4 mm. The lowermost capillary 13 has, for example, an outer diameter of 1 mm and an inner diameter of 0.772 mm over its entire length.

[0123] The upper end 11 a (ie, the upstream end) of the topmost capillary 11 is open and forms a first inlet I1 for introducing the first liquid L1 (eg, precursor liquid).

[0124] An annular opening is formed at the upper or upstream end faces of the two lower capillaries 12, 13, which allows the second liquid L2 (e.g., shell liquid) and the third liquid L3 (e.g., sheath liquid) to be introduced into the respective capillaries 12, 13. The annular opening is communicated with an annular cavity 14a, 14b formed around each tapered section of the two upper capillaries 11, 12. The annular cavity 14a, 14b is configured to guide the liquids L2, L3 between the outer surface of the tapered section of the respective capillaries 11, 12 and the solid material 14. Each annular cavity 14a, 14b can be entered from the outside through a free passage in the solid material, forming a second inlet 12 for the second liquid L2 and a third inlet 13 for the third liquid L3.

[0125] The lower end 13b of the third capillary 13 protrudes into a container 15 containing a stationary liquid phase SP. In addition, there are three godet rollers 16 arranged to direct the fibers produced from the container 15 to a storage unit 17 in the form of a winder for taking up the fibers.

[0126] The device can be operated, for example, as follows: a first liquid L1 (e.g., a precursor liquid containing a polymerizable and / or cross-linkable polymer precursor) is introduced into the topmost capillary 11 at the first inlet I1. Then, the first liquid L1 is injected into the second capillary 12 to obtain a core flow of the first liquid in the second capillary 12.

[0127] In the second capillary 12, a second liquid L2 (e.g., a hydrogel precursor) is simultaneously introduced into the second capillary 12 through the second inlet 12 and the annular cavity 14a, so that the second liquid L2 forms a tubular and coaxial shell flow surrounding the core flow of the first liquid L1, thereby producing a liquid fiber with a core-shell structure.

[0128] Then, the liquid fiber with a core-shell structure produced in the second capillary 12 is injected into the third capillary 13 to obtain a core-shell flow in the third capillary 13. Thus, the third liquid L3 or sheath liquid (e.g., a curing agent for the second liquid) is introduced into the third capillary 13 through the third inlet 13 and the annular cavity 14b, so that the third liquid L3 forms a tubular and concentric sheath flow around the core-shell flow in the third capillary 13, thereby producing a liquid fiber with a core-shell-sheath structure.

[0129] The liquid fiber having a core-sheath-sheath structure thus produced is then guided through a stationary liquid phase SP and taken up on a storage unit 17 (ie, a winder).

[0130] Figure 2 Show in Figure 1 sectional view of a liquid fiber having a core-shell-sheath structure at the S section of FIG. Specifically, the liquid precursor liquid L1 forms the core of the liquid fiber, whereby the core is encapsulated in the sheet liquid L2. Therefore, the sheet liquid L2 forms a tubular coaxial shell flow around the core flow of the precursor liquid L1. Similarly, the sheath liquid L3 forms a tubular coaxial shell flow around the shell flow L2. Thus, due to contact with the sheath liquid L3, the shell liquid L2 (e.g., a hydrogel precursor) solidifies, thereby producing a fiber such as Figure 3 - A shows a fiber with a liquid core 22 of precursor liquid L1 embedded in a solidified shell 21 .

[0131] However, in an alternative embodiment, instead of introducing a liquid into the first inlet, a first liquid (i.e., a precursor liquid containing a polymerizable and / or cross-linkable polymer precursor) is introduced into the second inlet 12. Then, a second liquid (e.g., a hydrogel precursor) is introduced into the third inlet 13. In this case, the third liquid is not used. Instead, the stationary liquid phase SP contains a curing agent for the second liquid. It can be said that in this alternative, the second inlet 12 serves as the first inlet and the third inlet 13 serves as the second inlet.

[0132] Independently of the above procedure, after removing the fiber from the stationary phase SP, as Figure 3 Specifically, the fiber having the liquid core 22 in the solidified shell 21 is subjected to a solidification treatment ST. For example, by irradiating the fiber with UV light and / or by providing thermal energy to solidify the precursor liquid in the liquid fiber core 22. This produces Figure 3- A fiber shown as B, which has a solid core 22 ′ within a solidified sheath 21 .

[0133] Subsequently, in a removal step RS, the solidified sheath 21 is removed from the fiber, for example by immersing the fiber in a solvent, to obtain a Figure 3 -C shows a solid target fiber without a shell.

[0134] Production of PDMS optical fibers

[0135] As an example, a PDMS optical fiber is manufactured using the above-described apparatus 10 according to the above-described alternative embodiment without using the inlet I1. TM A liquid polymer precursor in the form of 184 (base:crosslinker ratio = 1; available from Dow) was introduced into inlet I2 (flow rate: 50 μL / min), and an aqueous alginate solution (at H 2 O 2 wt %) CaCl 2 Aqueous solution (in H 2 O) is used as the stationary liquid phase SP in the container 15.

[0136] PDMS fibers with different diameters were produced as follows: To produce thin fibers, a glass capillary (tip dimensions: OD = 0.6 mm, ID = 0.4 mm) with an OD of 1 mm and an ID of 0.722 mm was used as the second capillary 12, and a capillary with an OD of 1 mm and an ID of 0.722 mm was used as the third capillary. For thick fibers, capillaries with larger diameters (OD of 1.5 mm and ID of 1 mm) have been used.

[0137] In these examples, the liquid core of Sylgard 184 polymer precursor was cured by heating (80° C., 2 hours) and the shell was removed in a sodium chloride solution.

[0138] Figure 4 Photographs showing two types of fibers obtained in this way: the left side (A) shows a fiber with a diameter of 700 μm, while the right side (B) shows a fiber with a diameter of 1'304 μm. As is evident from the digital micrograph (C), the fibers are suitable for guiding visible light.

[0139] Production of Polyacrylate Optical Fiber

[0140] As another example, a polyacrylate polymer optical fiber was produced using the above-described apparatus 10. Thus, an acrylate monomer precursor (Norland Optical Adhesive 83H, i.e., NOA83H) was used as a precursor liquid and introduced into the inlet I1. An aqueous alginate solution (in H 2O) was used as the shell liquid and introduced into inlet I2, while CaCl 2 Aqueous solution (in H 2 O 0.7 wt %) are used as the third liquid or sheath flow respectively and introduced into the inlet I3. Polyacrylate fibers with different diameters are achieved by controlling the flow rates of the core and the shell. Coarse fibers are produced with the following flow rates: 500 μL / min for the precursor liquid, 300 μL / min for the sheet liquid, and 5000 μL / min for the sheath liquid. Fine fibers are produced with the following flow rates: 50 μL / min for the precursor liquid, 40 μL / min for the sheet liquid, and 300 μL / min for the sheath liquid.

[0141] In this example, the UV irradiation (at 10 mW / cm 2 , 365 nm wavelength for 20 minutes) to cure the liquid core of the NOA83H monomer precursor.

[0142] Figure 5 Photographs showing thicker fibers (A) and thinner fibers (B) having a diameter of 372 μm or 325 μm, respectively. As is evident from the digital micrograph (C), the fibers are suitable for guiding visible light.

[0143] Second wet spinning device and operation method

[0144] Figure 6 A schematic cross section of a second inventive microfluidic wet spinning device 10' for producing individual solid polymer fibers with the method of the present invention is shown. The second device 10' comprises a first capillary 11' at the upper end, which coaxially extends through a second capillary 12' and terminates at an upper end 13a' of a third capillary 13'. The lower end 12b' of the second capillary 13' also coaxially protrudes into the upper end 13a' of the third capillary 13'. Thus, the lower end 11b' of the first capillary 11' protrudes beyond the lower end 12b' of the second capillary 12'.

[0145] In this embodiment, all capillaries 11 ', 12', 13' have constant inner and outer diameters.

[0146] The upper end 11a' (i.e., the upstream end) of the topmost capillary 11' is open and forms a first inlet I1' for introducing the first liquid L1 (e.g., precursor liquid). Annular openings are formed at the upper or upstream end faces of the two lower capillaries 12', 13', which allow the second liquid L2 (e.g., shell liquid) and the third liquid L3 (e.g., sheath liquid) to be introduced into the corresponding capillaries 12', 13' through the inlets I2', I3'.

[0147] The lower end 13b' of the third capillary 13' protrudes into a container 15' containing a stationary liquid phase (e.g., water). Figure 1 Similar godet rollers and storage units as shown (in Figure 6 not shown).

[0148] The device 10' can be operated, for example, as follows: a first liquid L1 (e.g., a precursor liquid containing a polymerizable and / or cross-linkable polymer precursor) is introduced into the topmost capillary 11' at the first inlet I1'. Then, the first liquid L1 is guided into the second capillary 12' to obtain a core flow of the first liquid in the second capillary 12'. Thus, the core flow is confined within the first capillary 11' extending through the second capillary 12'.

[0149] In the second capillary 12', a liquid fiber having a core-shell structure is produced by simultaneously introducing a second liquid L2 (e.g., a hydrogel precursor) into the second capillary 12' through the second inlet 12' so that the second liquid L2 forms a tubular and coaxial shell flow around the first capillary 11' and a core flow of the first liquid L1 flowing therein. Thus, in the second capillary 12', the liquids L1 and L2 are separated by the first capillary 11'. However, they form a liquid fiber having a core-shell structure.

[0150] Then, the liquid fiber with a core-shell structure produced in the second capillary 12' is injected into the third capillary 13', whereby the third liquid L3 or sheath liquid (e.g., a curing agent for the second liquid) is introduced into the third capillary 13' through the third inlet 13', so that the third liquid L3 forms a tubular and concentric sheath flow around the core-shell flow in the third capillary 13'. Thus, the third liquid L3 first contacts the second liquid L2 in the precuring zone PZ, whereby the sheet liquid L2 is precured by the sheath liquid L3. Subsequently, the precursor fluid L1 is introduced into the hollow central section in the precured shell fluid L2 through the first capillary 11' further downstream, thereby producing a liquid fiber with a core-shell-sheath structure.

[0151] and Figure 1 Compared with the embodiment shown in Figure 6 In the embodiment of the present invention, the pre-cured shell fluid L2 forms a more stable interface with the precursor fluid L1, which further reduces mixing of the fluids.

[0152] Then, if Figure 1 As explained, the liquid fiber produced in this way with a core-sheath-sheath structure is guided through a stationary liquid phase and wound up on a reservoir.

[0153] Those skilled in the art will appreciate that, without departing from the spirit or essential characteristics of the present invention, the present invention can be embodied in other specific forms. Therefore, the examples disclosed at present are considered in all aspects to be illustrative and not restrictive.

[0154] In particular, if, for example, the production of fibers is always carried out in accordance with an alternative embodiment, the device 10 can be configured with only two capillaries.

[0155] In order to produce fibers with different diameters, capillaries 11 , 12 , 13 with other dimensions are foreseen.

[0156] Figure 7 A photograph showing polylactic acid (PLA) fibers produced using the method of the present invention. Thus, using a non-toxic solvent (i.e., (dihydroglucosone; polar solvent)) instead of the toxic solvent (eg dichloromethane) usually used in the known production process.

[0157] Figure 8 A photograph showing an amphiphilic polymer optical fiber consisting of a polysiloxane / polyacrylate amphiphilic polymer co-network produced by the process of the present invention. The fiber has a low elastic modulus E of ∼2 MPa. Such fibers can be produced from precursors with very low viscosities, which has not been possible to date with any other method.

[0158] Fig. 9 Polyurethane fibers produced from polyol and isocyanate precursors using the process of the present invention are shown.

[0159] Fig.10 A plot of strain (ε) versus stress (σ) obtained by tensile testing of a soft polymer optical fiber (POF) produced according to the method of the present invention is shown. The data show that the elastic modulus (E) is only about 0.35 MPa.

[0160] Fig.11 It is shown that the light intensity of polymer optical fibers (POFs) with low elastic modulus (E ~ 0.35 MPa and 1 MPa) produced according to the method of the present invention decreases as a function of applied pressure compared to conventional fibers (E ~ 5 MPa).

Claims

1. A method for producing individual solid polymer fibers from a precursor liquid comprising agglomerable, polymerizable and / or cross-linkable polymer precursors, in particular from a precursor liquid comprising a polymerizable and / or cross-linkable polymer precursor, by microfluidics-based wet spinning, the method comprising the following steps: a) introducing the precursor liquid (L1) into a first capillary (11) through a first inlet (I1), whereby at least a downstream end (11b) of the first capillary (11) coaxially protrudes into a second capillary (12), and injecting the precursor liquid (L1) into the second capillary (12) to obtain a core flow of the precursor liquid in the second capillary (12); b) producing a liquid fiber having a core-sheath structure in the second capillary (12) by simultaneously introducing a sheath liquid (L2) into the second capillary (12) through a second inlet (I2) so that the sheath liquid (L2) forms a tubular and coaxial sheath flow around the core flow of the precursor liquid; c) optionally, injecting the liquid fiber with a core-sheath structure produced in step b) into a third capillary (13) to obtain a core-sheath flow in the third capillary (13), whereby at least the downstream end (12b) of the second capillary (12) coaxially protrudes into the third capillary (13), and simultaneously introducing a third liquid (L3) into the third capillary (13) through a third inlet (I3), so that the third liquid forms a tubular and concentric sheath flow around the core-sheath flow in the third capillary (13), thereby producing a liquid fiber with a core-sheath-sheath structure; d) guiding the liquid fiber having a core-shell structure, optionally with a sheath, as produced in step b) or in step c) through a stationary liquid phase (SP); e) solidifying the liquid sheath of the fiber with a core-sheath structure or with a core-sheath-sheath structure in at least one of steps c) and d), in particular by using a solidifying agent for the sheath liquid as the third liquid (L3) in step c) and / or as the stationary liquid phase (SP) in step d), to provide a fiber having a liquid core (22) embedded in a solidified sheath (21); f) collecting said fibers from said stationary liquid phase (SP) in the form of fibers having a liquid core (22) embedded in said solidified shell (21); g) after step f), solidifying the liquid core (22) of the fiber having a liquid core embedded in a solidified shell by aggregation, polymerization and / or crosslinking, in particular by polymerization and / or crosslinking, to obtain a fiber having a solid core (22') in the solidified shell (21); h) removing said solidified shell (21) from said solid core (22') to obtain said solid polymer fiber.

2. The method according to claim 1, wherein the precursor liquid (L1) comprises one or more of the following substances: - polyols capable of forming polyurethane polymers as well as diisocyanates, triisocyanates and / or polyurethane prepolymers - Epoxy resin, optionally with a hardener - Crosslinkable silicone polymers, especially polydimethylsiloxane polymers - ethylenically unsaturated monomers, in particular olefins, vinyl monomers, alkenyl monomers and / or (meth)acrylates, - monomers having amine, carboxyl and / or acyl groups capable of forming polyamides, such as amino acids, - monomers and / or oligomers containing reactive groups for click chemistry and capable of forming polymers, for example monomers and / or oligomers containing groups that react in azide-alkyne cycloaddition reactions, thiol-ene reactions and / or amino-alkyne reactions, - monomers selected from α-hydroxy acids, in particular lactic acid or its cyclic diester lactide, glycolic acid, mandelic acid and / or citric acid; - Aggregable polymers, in particular polylactic acid (PLA) and / or polycaprolactone (PCL).

3. The method according to any one of the preceding claims, whereby the precursor liquid (L1) further comprises a solvent, a crosslinking agent, a thermal polymerization initiator, a photopolymerization initiator, a chain transfer agent, a functional molecule and / or a molecular weight regulator.

4. A method according to any one of the preceding claims, wherein the shell liquid (L2) is a solution of a solvent, especially water, and a solvent-soluble non-crosslinked polymer, in particular the shell liquid is a solution of water and a homopolymer and / or copolymer formed from one or more of the following monomers: ethylene oxide, vinyl pyrrolidone, vinyl alcohol, vinyl acetate, vinyl pyridine, methyl vinyl ether, acrylic acid and its salts, methacrylic acid and its salts, hydroxyethyl methacrylate, acrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, alkyloxazolines, sugar monomers, polysaccharides, dextran, alginates, amino acids, hydrophilic polypeptides, proteins and / or gelatin.

5. Method according to any of the preceding claims, whereby the shell liquid (L2) is an aqueous hydrogel precursor solution, in particular an aqueous polysaccharide solution, especially an aqueous alginate solution, in particular an aqueous alkali metal alginate solution.

6. The method according to any one of the preceding claims, whereby the third liquid (L3) in step c) and / or the stationary liquid phase (SP) in step d) is a solidifying agent for the shell liquid (L2) selected from divalent metal cations, in particular selected from Ca 2+ Mg 2+ 、Zn 2+ , Fe 2+ , Cu 2+ and / or Ba 2+ An aqueous solution of a salt.

7. The method according to any one of the preceding claims, wherein step c) is carried out and in step c) a curing agent for the shell liquid is used which is selected from divalent metal cations, in particular from Ca 2+ Mg 2+ 、Zn 2+ , Fe 2+ , Cu 2+ and / or Ba 2+ wherein the stationary liquid phase in step d) is an aqueous solution, such as water.

8. A method according to any one of the preceding claims, whereby, with respect to the upstream end (11a), at least the outer diameter, in particular the inner diameter and the outer diameter of the first capillary (11) tapers, in particular in a step-like manner, at the downstream end (11b), in particular to form a first capillary nozzle; and, in particular, with respect to the upstream end (12a), at least the outer diameter, in particular the inner diameter and the outer diameter of the second capillary (12) tapers, in particular in a step-like manner, at the downstream end (12b), in particular to form a second capillary nozzle.

9. A method according to any one of the preceding claims, whereby the sheet liquid (L2) is introduced into the second capillary (12) at the upstream end face (12a) of the second capillary, in particular through an annular opening formed by the downstream end (11b) of the first capillary (11) protruding coaxially into the second capillary (12); and, in particular, the third liquid (L3) is introduced into the third capillary (13) at the upstream end face (13a) of the third capillary, in particular through an annular opening formed by the downstream end (12b) of the second capillary (12) protruding coaxially into the third capillary (13).

10. A method according to any one of the preceding claims, whereby the flow rate ratio of core flow:shell flow is 1:0.1-10, in particular 1:(0.5-1.5), in particular 1:(0.8-1.2); and, in particular, the flow rate ratio (volume per time) of core flow:shell flow:sheath flow is 1:(0.1-10):(1-50), in particular 1:(0.5-1.5):(2-15), in particular 1:(0.5-0.9):(5-12).

11. The method according to any of the preceding claims, whereby the diameters of the first, second and optionally third capillaries and / or the flow rates of the core flow, the shell flow and optionally the sheath flow are selected such that the diameter of the solid polymer fiber obtained in step h) is 1-5'000 μm, in particular 10-2'500 μm, for example 100-1'500 μm.

12. Method according to any one of the preceding claims, whereby the solidification of the liquid core (22) of the core-sheath fibres in step g) is achieved by irradiation with electromagnetic radiation and / or heating.

13. The method according to any of the preceding claims, whereby the removal of the solidified shell (21) from the solid core (22') is achieved by dissolving the solidified shell (21) in a solvent, such as an aqueous solution, in particular in an aqueous alkali metal salt solution, such as a NaCl solution.

14. The method according to any one of the preceding claims, whereby steps g) and / or h) are performed outside the stationary liquid phase (SP) and / or in time after steps a) to e).

15. The method according to any one of the preceding claims, wherein in the liquid fiber with a core-shell structure produced in the second capillary (12'), the shell liquid (L2) and the precursor liquid (L1) in the liquid fiber with a core-shell structure are separated by the first capillary (11') when flowing through the second capillary (12').

16. A method according to claim 15, whereby the first capillary (11') extends completely through the second capillary (12') and, in the flow direction of the liquid fiber, the downstream end (11b') of the first capillary (11') is located further downstream than the downstream end (12b') of the second capillary (12b').

17. A microfluidic-based wet spinning device (10) for producing individual solid polymer fibers from a precursor liquid (L1) comprising agglomerable, polymerizable and / or crosslinkable polymer precursors, in particular from a precursor liquid comprising polymerizable and / or crosslinkable polymer precursors, in particular using a method according to any one of claims 1 to 16, whereby the device comprises: a) a first inlet (i1) for introducing the precursor liquid (L1) into the first capillary (11), whereby at least the downstream end (11b) of the first capillary (11) coaxially protrudes into the second capillary (12), for injecting the precursor liquid (L1) into the second capillary (12) to obtain a core flow of the precursor liquid in the second capillary (12); b) a second inlet (I2) configured to introduce a sheet liquid (L2) into the second capillary (12) so that the sheet liquid forms a tubular and coaxial shell flow around the core flow of the precursor liquid, thereby producing a liquid fiber having a core-shell structure in the second capillary (12); c) optionally, a third capillary (13), whereby at least the downstream end (12b) of the second capillary (12) coaxially protrudes into the third capillary (13), so that the liquid fiber with a core-shell structure that can be produced in the second capillary (12) can be injected into the third capillary (13) to obtain a core-shell flow in the third capillary (13), whereby the third capillary (13) has a third inlet (I3) for introducing a third liquid (L3) into the third capillary (13), so that in the third capillary (13) the third liquid forms a tubular and concentric sheath flow surrounding the core-shell flow, thereby producing a liquid fiber with a core-shell-sheath structure; d) a container (15) for providing a stationary liquid phase (SP) for guiding through a liquid fiber having a core-shell structure, optionally with a sheath, as may be produced in said second capillary (12) or said third capillary (13); e) means for collecting said fibers from said stationary liquid phase (SP) in the form of fibers having a liquid core (22) embedded in a solidified shell (21), in particular a storage unit (17), in particular a winder and / or a reel; f) means for solidifying the liquid core (22) of the core-sheath fiber by aggregation, polymerization and / or crosslinking, in particular by polymerization and / or crosslinking, to obtain a fiber having a solid core (22') inside the solidified sheath (21), in particular means for emitting electromagnetic radiation and / or heating means; g) means for removing said solidified shell from said solid core (22') to obtain said solid polymer fibers, in particular for immersing and / or guiding through a further container said fibers having a solid core embedded in said solidified shell.

18. A microfluidic-based wet spinning device (10') according to claim 17, wherein the first capillary (11') extends completely through the second capillary (12'), and, preferably, in the flow direction of the liquid fiber, the downstream end (11b') of the first capillary (11') is located further downstream of the downstream end (12b') of the second capillary (12b'); and, if a third capillary is present, the downstream ends of the first capillary and the second capillary (11', 12') are located within the third capillary (13'), in particular within the upper half of the third capillary (13'), in particular within the upper quarter.

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