Abstract:
Device and method for preparing filament yarn of composite nanofibers. The device includes pairs of electrospinning nozzles on a frame and filament guiding roller pair under the frame. The spouts of each pair of nozzles are oppositely facing. The method includes feeding polymer solutions to the pairs of nozzles, applying high DC voltage with opposite polarity respectively to each one of the pairs of nozzles, forming composite nanofibers by attracting nanofibers with opposite charge from each nozzle and striking together of the charged nanofibers, pulling/stretching the composite nanofibers to form filament yarn of composite nanofibers, drawing down the filament yarn of composite nanofibers from the first pair of nozzles and using it as a carrier to receive the nanofibers with opposite charge electrospun from the second pair of nozzles and coated by the same so as to form multi-layer (e.g., two- or more-layer) filament yarn of composite nanofibers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    is application is a National Phase Patent Application and claims the priority of International Application Number PCT/CN2006/003014, filed on Nov. 10, 2006, which claims priority of Chinese Patent Application Number 200610095384.0, filed on Jan. 11, 2006. 
     
    
     FIELD OF THE TECHNOLOGY 
       [0002]    The present invention relates to device and method for preparing filament yarn of composite nanofibers. It belongs to the technical field of manufacturing special fibers. 
       BACKGROUND OF THE INVENTION 
       [0003]    With social development and improvement of people&#39;s lives, fiber industry has faced great challenges in recent years as single components could not meet the requirement of fibers with more functions. Various types of composite fibers have been developed, such as core-sheath, filling, bilateral, sea-island and other types of composite fibers. US Patent (No. 4,717,325) designed a spinneret assembly with composite feed plates. Passages are aligned with the orifices in the first plate and feed core material. Each core material passage is surrounded by several feed passages for sheath material, forming core-sheath type composite fibers. 
         [0004]    Electrospinning, an efficient and versatile method that uses an electric field to manufacture polymer nanofibers, has attracted more and more attention. Electrospun fibers have large porosity and high surface area to volume ratio, making them excellent candidates for a number of applications as high efficient filters, biomedical materials, chemical sensors, protective materials, nano-composite materials, etc. 
         [0005]    However, there exist problems of fiber loss and unstable dispersion due to the nano-/micro-meter size of the electrospun fibers, and repellent force between nanofibers carried charges with same polarity. Electrospun nanofibers are often collected as randomly oriented structures in the form of nonwoven mats. It is difficult to manufacture continuous nanofiber yarns or filaments. 
         [0006]    Although tremendous progress has been made in the fabrication of aligned nanofibers by electrospinning, a major challenge remains in the search for an efficient means to manufacture continuous aligned filament yarns. Electrospun fibers can be aligned more or less parallel to each other when a drum rotating at high speed is used as the collector. Another method is to deposit nanofibers into water to eliminate the charges of nanofibers which are collected together, and yarns are drawn out. Others obtain aligned fiber yarns by linking and twisting the electrospun nanofibers deposited on the steel drum. 
         [0007]    Therefore, it is necessary to invent a more efficient method to prepare filament yarn of composite nanofibers. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is to provide device and method for preparing filament yarn of composite nanofibers which can manufacture filament yarn of composite nanofibers simply and efficiently. 
       Technical Process 
       [0009]    Device for preparing filament yarn of composite nanofibers, comprising: pairs of electrospinning nozzles, filament guiding roller pair, frame, fixed sticks and base. Two columns of oppositely disposed pairs of electrospinning nozzles are fixed on frame. Each pair of electrospinning nozzles is in either same or different planes. The frame is connected to base by vertical fixed sticks. Filament guiding roller pair is located in the plane of frame with same distance away from two spouts of each electrospinning nozzles pair. The frame is set at an adjustable acute angle to the fixed sticks. The roller pair is at the end of pairs of electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 2-50 cm. Distance between two spouts of oppositely disposed pair of electrospinning nozzles is 10-100 cm. Plane of frame is set at angle of 0-90° to fixed sticks. The detailed procedures for preparing filament yarn of composite nanofibers are as follows: 
         [0000]    1) Polymer solutions are fed to pairs of electrospinning nozzles on frame.
 
2) High electrical voltages with opposite polarities are applied to two oppositely disposed pairs of electrospinning nozzles, respectively.
 
3) Nanofibers with opposite charges from each pair of electrospinning nozzles attract and strike together during the journey in the air, or the nanofibers attract and deposit on polymer fibrous carrier drawn down, forming composite nanofibers. The composite nanofibers are pulled and/or stretched, resulting in continuous filament yarn of composite nanofibers.
 
4) The filament yarn of composite nanofibers fabricated by the first pair of electrospinning nozzles are drawn down and used as a carrier to receive the nanofibers with opposite charge electrospun out from the second pair of nozzles. The coated filament yarn of composite nanofibers is then drawn down and/or stretched, forming two-layer filament yarn of composite nanofibers.
 
5) In turn, filament yarn of composite nanofibers fabricated by former pair of electrospinning nozzles are drawn down and used as a carrier to receive the nanofibers with opposite charge electrospun out from latter pair of nozzles. The coated filament yarn of composite nanofibers is then drawn down and/or stretched by filament guiding roller pair  2 , forming multi-layer filament yarn of composite nanofibers.
 
         [0010]    High electrical voltages with opposite polarities applied to two oppositely disposed pairs of electrospinning nozzles are fixed at 3-200 kV, respectively. Polymer solutions fed to electrospinning nozzles are polymer solutions, additive-containing polymer solutions, or mixture of inorganic particles and polymer solutions. Polymers are any of polyolefin, halogen-substituted polyolefin, silicone, polyether, polyamide, polyester, polycarbonate, polyurethane, epoxy resin, polyacrylonitrile, polyacrylic acid, polyacrylates, polyphenyl ether, polyanhydride, poly(α-amine acid), polyphenyl sulfide ether, or mixtures of above two or more polymers, or any of cellulose, cellulose derivatives, dextran, silk fibroin, chitosan, chitosan derivatives, hyaluronic acid, hyaluronic acid derivatives, collagen, carrageenan, sodium alginate, calcium alginate, chondroitin sulphate, gelatin, agar, dextran, fibril, fibrinogen, keratin, casein, albumin, elastin, or their derivatives or mixtures of above two or more polymers, or any of bioabsorbable synthetic polymers, such as poly-L-lactic acid, poly-(D,L)-lactic acid, poly glycolic acid, polycaprolactone, polybutyrolactone, polyvalerolactone, poly-p-dioxane, polyanhydride, poly(α-amine acid), or copolymer synthesized from two or more monomers as follows: L-lactic acid, D, L-lactic acid, glycolic acid, 3-hydroxyl butanoic acid, 3-hydroxyl pentanoic acid, caprolactone, butyrolactone, valerolactone, amine acid, or mixtures of above two or more polymers. Inorganic particles are nano-antibacterial agents, catalysts, or carbon nanotubes. 
         [0011]    Additives are any of antibiotics, immunosuppressants, antibacterial agents, hormone, vitamin, amino acids, peptides, proteins, enzymes, growth factor, antibacterial drugs, dope, hemostasis agents, anodyne, anti-hyperpiesia agents and anti-tumour agents, or mixtures of above two or more agents. 
       ADVANTAGES 
       [0012]    The present invention has following advantages: 
         [0000]    (1) The present invention utilizes a method for preparing filament yarn of composite nanofibers, where electrospinning nozzles oppositely disposed are electrically charged by high DC voltages with opposite polarities. Nanofibers electrospun from the two nozzles which carry charges with opposite polarities attract each other, strike together, and neutralize their charges. The present method shows a less dispersion and loss of nanofibers in the air. Furthermore, grounded metal collector used in conventional electrospinning method is unnecessary in the present invention.
 
(2) In the present invention, frame is set at an adjustable acute angle to fixed sticks to avoid any slightly disturbed or unstable spinning jet.
 
(3) The present invention can manufacture filament yarn of composite nanofibers simply and efficiently.
 
(4) In the present invention, different polymer solutions or additive-containing polymer solutions can be fed to two spouts of electrospinning nozzles pair oppositely disposed respectively, resulting in the formation of composite filament yarn of multi-component nanofibers.
 
(5) In the present invention, filament yarn of composite nanofibers with different composition and nano-structure can be produced by the use of multiple pairs of electrospinning nozzles. Thicker multi-layer filament yarn of composite nanofibers may exhibit good mechanical properties.
 
(6) In the present invention, nanofibers from oppositely disposed electrospinning nozzles which carry charges with opposite polarities can deposit on polymer fiber carrier, and then drawn down by filament guiding roller pair set under frame with a less dispersion or loss of nanofibers. And, multi-layer filament yarn of composite nanofibers with polymer fiber carrier as core is produced having excellent mechanical properties.
 
(7) The present invention can produce filament yarns of composite nanofibers including nano-particles as combined with electro-spraying technique.
 
(8) The present invention can manufacture filament yarn of composite nanofibers having potential applications in tissue engineered scaffolds and textiles, etc.
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is structure scheme of the present invention. 
           [0014]      FIG. 2  is principle scheme of the present invention. 
           [0015]    The two figures include pairs of electrospinning nozzles  1 , filament guiding roller pair  2 , frame  3 , fixed sticks  4  and base  5 . 
           [0016]      FIG. 3  is photograph of PLLA filament yarns of composite nanofibers. 
           [0017]      FIG. 4  is photograph of PLLA filament yarns of composite nanofibers. 
           [0018]      FIG. 5  is SEM image of PLLA filament yarns of composite nanofibers. 
           [0019]      FIG. 6  is SEM image of PU/PVDF filament yarn of composite nanofibers. 
           [0020]      FIG. 7  is SEM image of PAN filament yarn of composite nanofibers. 
           [0021]      FIG. 8  is SEM image of PVDF filament yarn of composite nanofibers. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Device for preparing filament yarn of composite nanofibers, comprising: pairs of electrospinning nozzles  1 , filament guiding roller pair  2 , frame  3 , fixed sticks  4  and base  5 . Two columns of oppositely disposed pairs of electrospinning nozzles  1  are fixed on frame  3 . Each pair of electrospinning nozzles is in either same or different planes. The frame  3  is connected to base  5  by vertical fixed sticks  4 . Filament guiding roller pair  2  is located in the plane of frame  3  with same distance away from two spouts of each electrospinning nozzles pair. The roller pair  2  is at the end of pairs of electrospinning nozzles  1 . The frame  3  is set at an adjustable acute angle to the fixed sticks  4 . 
         [0023]    The detailed procedures for preparing filament yarn of composite nanofibers are as follows: 
         [0000]    1) Polymer solutions are fed to pairs of electrospinning nozzles  1  on frame  3 .
 
2) High electrical voltages with opposite polarities are applied to two oppositely disposed pairs of electrospinning nozzles  1 , respectively.
 
3) Nanofibers with opposite charge from each pair of electrospinning nozzles attract and strike together during the journey in the air, forming composite nanofibers. The composite nanofibers are pulled and/or stretched, resulting in continuous filament yarn of composite nanofibers.
 
4) The filament yarn of composite nanofibers fabricated by the first pair of electrospinning nozzles are drawn down and used as a carrier to receive the nanofibers with opposite charge electrospun out from the second pair of nozzles. The coated filament yarn of composite nanofibers is then drawn down and/or stretched, forming two-layer filament yarn of composite nanofibers.
 
5) In turn, filament yarn of composite nanofibers fabricated by former pair of electrospinning nozzles are drawn down and used as a carrier to receive the nanofibers with opposite charge electrospun out from latter pair of nozzles. The coated filament yarn of composite nanofibers is then drawn down and/or stretched by filament guiding roller pair  2 , forming multi-layer filament yarn of composite nanofibers.
 
         [0024]    The detailed procedures for preparing filament yarn of composite nanofibers can also be: 1) Polymer solutions are fed to pairs of electrospinning nozzles  1  on frame  3 . 2) High electrical voltages with opposite polarities are applied to two oppositely disposed pairs of electrospinning nozzles  1 , respectively. 3) Nanofibers with opposite charge from each pair of electrospinning nozzles  1  attract and deposit on polymer fibrous carrier drawn down, forming composite nanofibers. The composite nanofibers are pulled and/or stretched, resulting in continuous filament yarn of composite nanofibers. 
         [0025]    Distance between two neighbouring electrospinning nozzles  1  on the same column of frame  3  is 2-50 cm. Distance between two spouts of oppositely disposed pair of electrospinning nozzles  1  is 10-100 cm. Plane of frame  3  is set at angle of 0-90° to fixed sticks  4 . High electrical voltages with opposite polarities applied to two oppositely disposed pairs of electrospinning nozzles  1  are fixed at 5-200 kV, respectively. 
         [0026]    Polymer solutions fed to electrospinning nozzles are polymer solutions, additive-containing polymer solutions, or mixture of inorganic particles and polymer solutions. Polymers are any of polyolefin, halogen-substituted polyolefin, silicone, polyether, polyamide, polyester, polycarbonate, polyurethane, epoxy resin, polyacrylonitrile, polyacrylic acid, polyacrylates, polyphenyl ether, polyanhydride, poly(α-amine acid), polyphenyl sulfide ether, or mixtures of above two or more polymers, or any of cellulose, cellulose derivatives, dextran, silk fibroin, chitosan, chitosan derivatives, hyaluronic acid, hyaluronic acid derivatives, collagen, carrageenan, sodium alginate, calcium alginate, chondroitin sulphate, gelatin, agar, dextran, fibril, fibrinogen, keratin, casein, albumin, elastin, or their derivatives or mixtures of above two or more polymers, or any of bioabsorbable synthetic polymers, such as poly-L-lactic acid, poly-(D,L)-lactic acid, poly glycolic acid, polycaprolactone, polybutyrolactone, polyvalerolactone, poly-p-dioxane, polyanhydride, poly(α-amine acid), or copolymer synthesized from two or more monomers as follows: L-lactic acid, D, L-lactic acid, glycolic acid, 3-hydroxyl butanoic acid, 3-hydroxyl pentanoic acid, caprolactone, butyrolactone, valerolactone, amine acid, or mixtures of above two or more polymers. Inorganic particles are nano-antibacterial agents, catalysts, or carbon nanotubes. Additives are any of antibiotics, immunosuppressants, antibacterial agents, hormone, vitamin, amino acids, peptides, proteins, enzymes, growth factor, antibacterial drugs, dope, hemostasis agents, anodyne, anti-hyperpiesia agents and anti-tumour agents, or mixtures of above two or more agents. 
         [0027]    The present invention can manufacture filament yarn of composite nanofibers having potential applications in regeneration medicine and textiles, etc. 
       EXAMPLE 1 
       [0028]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 90° to fixed sticks  4 . 
         [0029]    10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 15 g poly-lactide-co-glycolide (Poly-LA-co-GA, PLGA, weight ratio of LA:GA=50:50, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame  3  is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 90° to fixed sticks  4 . High DC voltages of +20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.5 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair which is set at the end of pairs of electrospinning nozzles on the plane of the frame. The drawing speed of filament guiding roller pair was 8 cm/s. And, three-layer filament yarn of PLLA/PLGA composite nanofibers is obtained. 
       EXAMPLE 2 
       [0030]    A device for electrospinning is used comprising frame  3  having four pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 90° to fixed sticks  4 . 
         [0031]    10 g poly-L-lactic acid (PLLA, Mq=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 4 spinnerets. 10 g polycaprolactone (PCL, Mw=90,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 4 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame  3  is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 90° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.5 mm, respectively. The drawing speed of filament guiding roller pair  2  was 8 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, multi-layer filament yarn of PLLA/PCL composite nanofibers is obtained. 
       EXAMPLE 3 
       [0032]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 90° to fixed sticks  4 . 
         [0033]    10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 3 spinnerets of which inner diameter is 0.8 mm. 35 g zein (Mw=35,000 g/mol) was dissolved in 100 ml aqueous ethanol solution with ethanol/water volume ratio of 80/20, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets of which inner diameter is 1.2 mm. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 90° to fixed sticks  4 . High DC voltages of +25 kV were applied to two columns of oppositely disposed electrospinning nozzles, respectively. The drawing speed of filament guiding roller pair  2  was 8 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, three-layer filament yarn of PLLA/zein composite nanofibers is obtained. 
       EXAMPLE 4 
       [0034]    A device for electrospinning is used comprising frame  3  having four pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 90° to fixed sticks  4 . 
         [0035]    10 g polyacrylonitrile (PAN, Mw=130,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 4 spinnerets. 10 g polyphenyl ether sulphone (PES, melt flow rate 3.9 g/10 min, 320° C.) was dissolved in 100 ml dimethyl sulphone, and the prepared solution was fed to the other column of electrospinning nozzles containing 4 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 90° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.5 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 8 cm/s. And, multi-layer filament yarn of PAN/PPES composite nanofibers is obtained. 
       EXAMPLE 5 
       [0036]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0037]    10 g poly-L-lactic acid (PLLA, M11=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 15 g poly-lactide-co-glycolide (Poly-LA-co-GA, PLGA, weight ratio of LA:GA=50:50, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 15 g polyurethane (PU) was dissolved in 100 ml N, N-dimethyl formamide. 10 g polycaprolactone (PCL, Mw=90,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide. After complete dissolution, solutions were fed to two columns of oppositely disposed 4 electrospinning nozzles, respectively. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of PLLA/PLGA/PU/PCL composite nanofibers is obtained. 
       EXAMPLE 6 
       [0038]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0039]    1 g hyaluronic acid (HA, Mw=100,000 g/mol) was dissolved in 100 ml distilled water. 0.5 g chitosan was dissolved in 100 ml 0.1 mol/L acetic acid solution. 10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 15 g poly-lactide-co-glycolide (Poly-LA-co-GA, PLGA, weight ratio of LA:GA=50:50, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 15 g polyurethane (PU) was dissolved in 100 ml N, N-dimethyl formamide. 10 g polycaprolactone (PCL, Mw=90,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide. After complete dissolution, solutions were fed to two columns of oppositely disposed 6 electrospinning nozzles, respectively. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of HA/chitosan/PLLA/PLGA/PU/PCL composite nanofibers is obtained. 
       EXAMPLE 7 
       [0040]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0041]    1 g hyaluronic acid (HA, Mw=100,000 g/mol) was dissolved in 100 ml distilled water, and the prepared solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of HA/PLLA composite nanofibers is obtained. 
       EXAMPLE 8 
       [0042]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0043]    1 g hyaluronic acid (HA, Mw=100,000 g/mol) was dissolved in 100 ml distilled water, and 0.2 g brophenol was added into the solution. After complete dissolution of brophenol, the solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent consisting of 50 ml acetone and 50 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of HA/brophenol/PLLA composite nanofibers is obtained. 
       EXAMPLE 9 
       [0044]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0045]    10 g polyacrylonitrile (PAN) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 15 g polyurethane (PU) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Drawing speed of filament guiding roller pair is 5 cm/s. Nanofibers from the oppositely disposed electrospinning nozzles which carry charges with opposite polarities deposited on polyester fibers and then drawn out by filament guiding roller pair  2  set under frame. Multi-layer filament yarns of composite nanofibers whose core is polyester fibers with shell of composite PAN/PU nanofibers were drawn out and collected by the filament guiding roller pair. 
       EXAMPLE 10 
       [0046]    A device for electrospinning is used comprising frame  3  having four pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 45° to fixed sticks  4 . 
         [0047]    10 g polyurethane (PU) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 4 spinnerets. 10 g polycaprolactone was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 4 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 45° to fixed sticks  4 . High DC voltages of +15 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. Drawing speed of filament guiding roller pair  2  is 5 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by the filament guiding roller pair, collecting as continuous multi-layer filament yarn of PU/PCL composite nanofibers. 
       EXAMPLE 11 
       [0048]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0049]    10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 100 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to the two columns of oppositely disposed 4 electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. The drawing speed of filament guiding roller pair  2  was 5 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, filament yarn of PLLA composite nanofibers is obtained. 
       EXAMPLE 12 
       [0050]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0051]    10 g polycaprolactone (PCL) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the first pair of electrospinning nozzles. 15 g poly-lactide-co-glycolide (Poly-LA-co-GA, PLGA, weight ratio of LA:GA=50:50, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, 0.3 g brophenol was then added into the solution. After complete dissolution of brophenol, the solution was fed to the second pair of electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of +10 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, two-layer filament yarn of PCL/PLGA composite nanofibers is obtained. 
       EXAMPLE 13 
       [0052]    A device for electrospinning is used comprising frame  3  having ten pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 30° to fixed sticks  4 . 
         [0053]    50 g poly-L-lactic acid (PLLA, Mq=150,000 g/mol) was dissolved in a mixed solvent of 250 ml acetone and 250 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 10 spinnerets. 5 g hyaluronic acid (HA, Mw=1,000,000 g/mol) was dissolved in 500 ml distilled water, and the prepared solution was fed to the other column of electrospinning nozzles containing 10 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Planes of frame and fixed sticks were set at an angle of 30°. High DC voltages of ±50 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Drawing speed of filament guiding roller pair  2  is 5 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by the filament guiding roller pair, collecting as continuous filament yarn of PLLA/HA composite nanofibers with diameter of ca. 150 micros. 
       EXAMPLE 14 
       [0054]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 30° to fixed sticks  4 . 
         [0055]    0.5 g chitosan was dissolved in 100 ml 0.1 mol/L acetic acid solution, and the prepared solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 10 g polycaprolactone (PCL) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 20 cm. Planes of frame and fixed sticks were set at an angle of 30°. High DC voltages of +20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.6 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of chitosan/PCL composite nanofibers is obtained. 
       EXAMPLE 15 
       [0056]    A device for electrospinning is used comprising frame  3  having four pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 90° to fixed sticks  4 . 
         [0057]    10 g polycarbonate (PC, Mw=100,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 4 spinnerets. 10 g polyphenyl ether sulphone (PES, melt flow rate 3.9 g/10 min, 320° C.) was dissolved in 100 ml dimethyl sulphone, and the prepared solution was fed to the other column of electrospinning nozzles containing 4 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 90° to fixed sticks  4 . High DC voltages of +20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.5 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 8 cm/s. And, multi-layer filament yarn of PC/PPES composite nanofibers is obtained. 
       EXAMPLE 16 
       [0058]    A device for electrospinning is used comprising frame  3  having four pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 30° to fixed sticks  4 . 
         [0059]    10 g polyacrylonitrile (PAN, Mw=130,000 g/mol) was dissolved in 100 ml N, N-dimethyl fommamide, and 0.1 g single wall carbon nanotubes were added into the solution. After completely homogeneous dispersion of the nanotubes by ultrasonic vibration, the solution was fed to one column of electrospinning nozzles containing 4 spinnerets. 10 g polyphenyl ether sulphone (PES, melt flow rate 3.9 g/10 min, 320° C.) was dissolved in 100 ml dimethyl sulphone, and the prepared solution was fed to the other column of electrospinning nozzles containing 4 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Planes of frame and fixed sticks were set at an angle of 30°. High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.5 mm, respectively. Drawing speed of the filament guiding roller pair is 8 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by the filament guiding roller pair, collecting as continuous filament yarn of single wall carbon nanotubes and PC/PPES composite nanofibers. 
       EXAMPLE 17 
       [0060]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0061]    1 g hyaluronic acid (HA, Mw=100,000 gμmol) was dissolved in 100 ml distilled water, and 10 mg bone morphogenetic protein were added into the solution. After completely dissolution of the bone morphogenetic protein, the solution was fed to one column of electrospinning nozzles containing 3 spinnerets. 10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 3 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of HA/PLLA composite nanofibers is obtained. 
       EXAMPLE 18 
       [0062]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0063]    20 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 100 ml acetone and 50 ml N,N-dimethyl formamide, and 1 g β-tricalcium phosphate (β-TCP) nano-particles with diameters of ca. 300 nm were added into the solution. After completely homogeneous dispersion of the nano-particles by ultrasonic vibration, the solution was fed to two columns of oppositely disposed 4 electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 0° to fixed sticks  4 . High DC voltages of ±50 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . The drawing speed of filament guiding roller pair  2  was 5 cm/s. And, filament yarn of PLLA/β-TCP composite nanofibers is obtained. 
       EXAMPLE 19 
       [0064]    A device for electrospinning is used comprising frame  3  having twenty-five pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0065]    100 g poly-L-lactic acid (PLLA, Mη=150,000 g/mol) was dissolved in a mixed solvent of 500 ml acetone and 500 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 25 spinnerets. 10 g hyaluronic acid (HA, Mw—1,000,000 g/mol) was dissolved in 1000 ml distilled water, and the prepared solution was fed to the other column of electrospinning nozzles containing 25 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 2 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of ±120 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. Drawing speed of the filament guiding roller pair  2  is 10 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by the filament guiding roller pair, collecting as continuous filament yarn of PLLA/HA composite nanofibers with diameter of ca. 200 micros. 
       EXAMPLE 20 
       [0066]    A device for electrospinning is used comprising frame  3  having ten pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0067]    50 g poly-L-lactic acid (PLLA, M=150,000 g/mol) was dissolved in a mixed solvent of 250 ml acetone and 250 ml N,N-dimethyl formamide, and the prepared solution was fed to two columns of oppositely disposed 20 electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 8 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of +80 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. Drawing speed of filament guiding roller pair  2  is 5 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by the filament guiding roller pair, collecting as continuous PLLA composite nanofiber yarns with diameter of ca. 100 micros. 
       EXAMPLE 21 
       [0068]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0069]    10 g poly-L-lactic acid (PLLA, M11=150,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 2 spinnerets. 1.5 g collagen was dissolved in 30 ml hexafluoro-2-propanol (HFIP), and the prepared solution was fed to the other column of electrospinning nozzles containing 2 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of ±30 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. The drawing speed of filament guiding roller pair  2  was 3 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, filament yarn of PLLA/collagen composite nanofibers is obtained. 
       EXAMPLE 22 
       [0070]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 30° to fixed sticks  4 . 
         [0071]    10 g poly (vinylidenefluoride) (PVDF) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide, and the prepared solution was fed to two columns of oppositely disposed 4 electrospinning nozzles. Distance between two neighbouring electrospinning nozzles on the same column of frame is 15 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 40 cm. Plane of frame  3  is set at angle of 30° to fixed sticks  4 . High DC voltages of ±30 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. The drawing speed of filament guiding roller pair  2  was 3 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, filament yarn of PVDF composite nanofibers is obtained. 
       EXAMPLE 23 
       [0072]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0073]    10 g poly (vinylidenefluoride) (PVDF) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 2 spinnerets. 15 g polyurethane (PU) was dissolved in 100 ml N, N-dimethyl formamide, and the prepared solution was fed to the other column of electrospinning nozzles containing 2 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. The drawing speed of filament guiding roller pair  2  was 3 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, filament yarn of PVDF/PU composite nanofibers is obtained. 
       EXAMPLE 24 
       [0074]    A device for electrospinning is used comprising frame  3  having two pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0075]    10 g poly-L-lactic acid (PLLA, M11=150,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N,N-dimethyl formamide, and the prepared solution was fed to one column of electrospinning nozzles containing 2 spinnerets. 10 g poly (vinyl pyrrolidone) (PVP K30, BASF) was dissolved in 50 ml acetone, and the prepared solution was fed to the other column of electrospinning nozzles containing 2 spinnerets. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of ±20 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 1.2 mm, respectively. The drawing speed of filament guiding roller pair  2  was 3 cm/s. Nanofibers exiting from the electrospinning nozzles were induced and drawn out by filament guiding roller pair  2  which is set at the end of pairs of electrospinning nozzles on the plane of the frame  3 . And, filament yarn of PLLA/PVP composite nanofibers is obtained. 
       EXAMPLE 25 
       [0076]    A device for electrospinning is used comprising frame  3  having three pairs of electrospinning nozzles  1  in two columns, filament guiding roller pair  2  set at the end of pairs of electrospinning nozzles. The frame  3  was set at angle of 0° to fixed sticks  4 . 
         [0077]    10 g poly-L-lactic acid (PLLA, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 15 g poly-lactide-co-glycolide (Poly-LA-co-GA, PLGA, weight ratio of LA:GA=50:50, Mη=100,000 g/mol) was dissolved in a mixed solvent of 50 ml acetone and 50 ml N, N-dimethyl formamide. 1 g hyaluronic acid (HA, Mw=100,000 g/mol) was dissolved in 100 ml distilled water. 0.3 g chitosan was dissolved in 100 ml 0.1 mol/L acetic acid solution. 1.5 g collagen was dissolved in hexafluoro-2-propanol (HFIP). 10 g polycaprolactone (PCL, Mw=90,000 g/mol) was dissolved in 100 ml N, N-dimethyl formamide. After complete dissolution, solutions were fed to two columns of oppositely disposed 6 electrospinning nozzles, respectively. Distance between two neighbouring electrospinning nozzles on the same column of frame is 10 cm, and distance between two tips of oppositely disposed pair of electrospinning nozzles is 30 cm. Plane of frame  3  is set parallel to fixed sticks  4 . High DC voltages of +15 kV were applied to two columns of oppositely disposed electrospinning nozzles with inner diameter of 0.8 mm, respectively. Filament yarn of composite nanofibers fabricated by former pair of electrospinning nozzles are drawn out and subsequently wrapped around composite nanofibers from latter pair of two oppositely charged electrospinning nozzles. The nanofibers are then drawn out and/or stretched by filament guiding roller pair, forming filament yarn of composite nanofibers.