Patent Publication Number: US-8540504-B2

Title: Equipment for electrospinning

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-In-Part of co-pending application Ser. No. 11/877,123 filed on Oct. 23, 2007, and for which priority is claimed under 35 U.S.C. §120; and this application claims priority of Application No. 096114167 filed in Taiwan on Apr. 20, 2007 under 35 U.S.C. §119; the entire contents of all are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electrospinning technique, and more particularly to an electrospinning equipment and an electrode structure thereof. 
     BACKGROUND OF THE INVENTION 
     The principle of the electrospinning technique is to provide a high-voltage electric field in an area which threads pass through after jetted from a spinning device, and when jetted from a spinneret of the spinning device, the threads are electrically charged by the spinning process; therefore, because of the electric property of the threads, the effect of the electric field on the threads results in finer threads. For the present techniques, the diameter of the threads can be as small as one hundred nanometers. 
     Please refer to  FIG. 1 , which shows a schematic diagram of an electrospinning equipment in the prior art. An electrospinning equipment  1  includes a collector  14  and a power supply PS electrically connected to a material supply  10 , wherein the material supply  10  faces the collector  14 ; namely the normal to the plane of the collector  14  is parallel to the direction in which the material supply  10  supplies a material, and a diffusion electric field ef 1  is generated therebetween. Besides, the material supply  10  usually is a capillary and has a spinneret  12  which a polymer solution FS is jetted from to form a thread F 1 . Ideally the thread F 1  extends straightly toward the collector  14 , but actually the thread F 1  fluctuates transversely resulting from the electric charge repulsion inside the thread F 1 , and hence the thread F 1  is usually deposited on the collector  14  disorderly. Therefore, the electrospinning technique is mostly applied to nonwoven manufacturing for its disordered arranging feature. On the contrary, it is difficult to roll the thread F 1  on a roller used in other techniques, and rearranging the thread F 1  and rolling it on the roller is unrealistic since it is time-consuming. 
     Please refer to  FIG. 2 , which shows a schematic diagram of another electrospinning equipment in the prior art. The electrospinning equipment comprises a first power supply PS 1  electrically connected to a material supply  10  usually being a capillary and having a spinneret  12 , a second power supply PS 2  electrically connected to a circle  2 , and a third power supply PS 3  electrically connected to a collector  14 . Compared with the electrospinning equipment  1  shown in  FIG. 1 , the one shown in  FIG. 2  is to configure the circle  2  between the spinneret  12  and the collector  14  for forming stable threads without transverse fluctuation by providing an electric potential for the circle  2  through the second power supply PS 2 , wherein the electric potential of the circle  2  is higher than that of the collector  14  but lower than that of the material supply  10 . Therefore, an upper electric field ef 2   a  is generated between the circle  2  and the spinneret  12 , and a lower electric field ef 2   b  is generated between the circle  2  and the collector  14 . A former thread F 2   a  jetted from the spinneret  12  and passing through the upper electric field ef 2   a  is in a straight state without transverse fluctuation. However, after passing through the circle  2  and reaching the area between the circle  2  and the collector  14 , the former thread F 2   a  becomes a latter thread F 2   b , and a diffusion is formed again. Nevertheless, the range of the transverse fluctuation of the latter thread F 2   b  is smaller than that of the thread F 1  shown in  FIG. 1 . Nevertheless, the range is not small enough to rearrange the thread F 2   a  as a long straight state in a simple way. 
     Accordingly, in the field of electrospinning technique, a new structure is necessary for the thread to be deposited on the collector stably without transverse fluctuation. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, an electrospinning equipment including a power supply, a collector and a material supply is provided, wherein the material supply facing the collector is electrically connected to the power supply and has a spinneret and a guide unit coupled to the spinneret and bent toward the collector, and the spinneret is configured at a central portion of the guide unit. 
     Preferably, the power supply further includes a first electrode and a second electrode, wherein the first electrode is electrically connected to the guide unit, and the second electrode is mounted under the collector. 
     Preferably, the second electrode is configured in a distance away from the collector. 
     Preferably, the guide unit further includes an inner surface, and distances between each spot on the inner surface and the second electrode are equal. 
     Preferably, the guide unit is formed by extending outward from the spinneret toward the collector. 
     Preferably, the guide unit further includes an indentation surface facing the collector, and the indentation surface has an opening at a most distant location thereof from the collector, and the spinneret is located at the opening. 
     In accordance with another aspect of the present invention, an extension structure for an electrospinning equipment is provided. The extension structure includes an opening portion, a spinneret receiving portion and a body, wherein a width of the opening portion is larger than that of the spinneret receiving portion. 
     Preferably, the body is in a shape of a body portion of one selected from a group consisting of a bowl, a disc and a dome. 
     Preferably, the opening portion is in a shape of a fringe of the one selected from a group consisting of the bowl, the disc and the dome. 
     Preferably, the spinneret receiving portion is a center of the one selected from a group consisting of the bowl, the disc and the dome. 
     Preferably, the extension structure further includes an inner surface and an outer surface, wherein the inner surface borders the outer surface on the opening portion, and the spinneret receiving portion of the extension structure is positioned at a location most distant from the opening portion. 
     Preferably, the extension structure is a tube, wherein the opening portion and the spinneret receiving portion are openings of the tube, and the tube is diverged from one of the openings to the other one. 
     In accordance with a further aspect of the present invention, an electrospinning method is provided. The electrospinning method includes steps of (1) providing a material supply, (2) providing a collector under the material supply, and (3) generating an electric field between the material supply and the collector, wherein a pattern of the electric field is convergent from the material supply to the collector. 
     Preferably, the electric field is generated by providing an extension structure extending outward from the material supply toward the collector. 
     Preferably, the extension structure has a body, and the body is in a shape of a body portion of one selected from a group consisting of a bowl, a disc and a dome. 
     Preferably, the electric field is generated by a power supply having a first electrode coupled to the material supply and a second electrode, where the collector is located between the second electrode and the material supply. 
     Preferably, the electrospinning method further includes a step of (4) moving the collector to make a thread deposited at different locations of the collector. 
     Additional objects and advantages of the invention will be set forth in the following descriptions with reference to the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an electrospinning equipment in the prior art; 
         FIG. 2  is a schematic diagram showing another electrospinning equipment in the prior art; 
         FIG. 3  shows the electrospinning equipment according to a preferred embodiment of the present invention; 
         FIG. 4  is a 3D schematic view of the extension structure of the electrospinning equipment according to a preferred embodiment of the present invention; 
         FIG. 5  is a 3D schematic view of the extension structure of the electrospinning equipment according to another preferred embodiment of the present invention; 
         FIG. 6  is a cross-sectional view of the extension structure of the electrospinning equipment according to a further preferred embodiment of the present invention; 
         FIG. 7  is a 3D schematic view of the extension structure of the electrospinning equipment according to further another preferred embodiment of the present invention; and 
         FIG. 8  shows the application of the electrospinning equipment in the present invention. 
         FIG. 9  shows the electrospinning equipment according to another preferred embodiment of the present invention. 
         FIG. 10  shows the electrospinning equipment according to the other preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purposes of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
     Please refer to  FIG. 3 , which shows a schematic diagram of the electrospinning equipment according to a preferred embodiment of the present invention. The electrospinning equipment includes a material supply  10  facing a collector  31 , wherein the material supply  10  is usually made as a capillary and has a spinneret  12 , and the collector  31  is used for collecting a thread F formed by a polymer solution FS jetted from the spinneret  12 . Additionally, the material supply  10  is connected to a power supply PS; usually a first electrode  30   a  is connected to the material supply  10 , and a second electrode  30   b  is mounted under the collector  31 . While one of the first electrode  30   a  and the second electrode  30   b  is the anode, the other one is the cathode. 
     Moreover, in order to overcome the drawback of the unstable electric field in the prior art, a guide unit  3 , which is a 3D sheet-form structure, is coupled to the material supply  10  in the present invention. Please refer to  FIG. 3  which shows a cross-sectional view of the guide unit  3 , wherein the guide unit  3  is formed by extending outward from the material supply  10  and bending toward the collector  31 . As a result, the guide unit  3  is a downcast curve as shown in  FIG. 3  and is an extension structure having an indentation surface facing the collector  31 . In addition, the indentation surface has an opening at a most distant location of the guide unit  3  from the collector, and the spinneret  12  is located at the opening. The second electrode  30   b  is a point-like electrode, and an electric field ef 3  is generated and a pattern of the electric field ef 3  converges from the indentation surface of the guide unit  3  to the second electrode  30   b , so that the electric field ef 3  is controlled in quite a stable state. Thus, when the polymer solution FS in the material supply  10  is jetted from the spinneret  12  and affected by the downward convergent electric field ef 3  pattern, the lower the higher-density the electric field ef 3  becomes, and hence the thread F does not fluctuate transversely. Therefore, the thread F reaches the collector  31  almost in a straight state, and it is much easier to arrange the thread F deposited on the collector  31 . Although the transverse fluctuation of the thread F still occurs slightly, it can be controlled in a range by using the guide unit  3  of the present invention and is unlike the thread that is irregular and substantial swinging in the prior art. 
     Furthermore, unlike the second electrode connected to the collector directly in the prior art, the second electrode  30   b  is configured in a distance g nearby but away from the collector  31 . Thus, the collector  31  can shift above the second electrode  30   b , and the thread F can be deposited on the collector  31  in different layouts through the arrangement of the shifting direction thereof. 
     In addition, the shape of the guide unit  3  can be defined as a partial surface of a sphere, wherein the second electrode  30   b  is the center of the sphere, and the distance between the second electrode  30   b  and the spinneret  12  is the radius of the sphere. That is to say, distances between each spot on the inner surface of the guide unit  3  and the second electrode  30   b  are equal, which achieves a more stable electric field. 
     Please refer to  FIG. 4 , which is a 3D schematic view of the extension structure of the electrospinning equipment according to a preferred embodiment of the present invention, which is also a new invention of an electrode structure of the electrospinning equipment. As shown in  FIG. 4 , the guide unit  3  includes an opening portion  32 , a spinneret receiving portion  34  and a body, wherein the body of the guide unit  3  is in a shape of a body portion of one selected from a group consisting of a bowl, a disc and a dome. If the distance between the opening portion  32  and the spinneret receiving portion  34  is shorter, such as a distance shorter than the radius of the opening portion  32 , the guide unit is like a disc. If the distance therebetween is about equal to the radius of the opening portion  32 , the guide unit is like a bowl. If the distance therebetween is longer than the radius of the opening portion  32  a certain extent, the guide unit is like a cup. The radius of the opening portion  32  is longer than that of the spinneret receiving portion  34 , and the spinneret  12  is configured at the spinneret receiving portion  34  as shown in  FIG. 3 . Besides, the body of the guide unit  3  between the spinneret receiving portion  34  and the opening portion  32  is in a shape of a curve surface and is extending outward. 
     Please refer to  FIG. 4  again, which shows the guide unit  3  of the present invention in another aspect. The guide unit  3  includes an inner surface  33   a  and an outer surface  33   b , wherein the inner surface  33   a  borders the outer surface  33   b  on the opening portion  32 , and the spinneret receiving portion  34  is positioned at a location most distant from the opening portion  32 . Moreover, a space surrounded by the inner surface  33   a  is an electric field space  33 . In a further aspect of the guide unit  3  of the present invention, the guide unit  3  is a tube, wherein the opening portion  32  and the spinneret receiving portion  34  are openings of the tube, and the tube is diverged from the spinneret receiving portion  34  to the opening portion  32 . 
     Please refer to  FIG. 5 , which shows a 3D schematic view of the extension structure of the electrospinning equipment according to another preferred embodiment of the present invention. The extension structure  4  includes an opening portion  42 , a spinneret receiving portion  44  and a body, wherein the opening portion  42  and the spinneret receiving portion  44  are respectively located at the two ends of the extension structure  4 , and the body therebetween is a wave-shape structure which increases the strength of the extension structure  4  and keeps it away from deformed easily due to crashes and squeezes. The same with the guide unit  3  shown in  FIG. 4 , the extension structure  4  includes an inner surface  43   a  and an outer surface  43   b , wherein the inner surface  43   a  borders the outer surface  43   b  on the opening portion  42 , and a width of the opening portion  42  is larger than that of the spinneret receiving portion  44 . In addition, a space surrounded by the inner surface  43   a  is an electric field space  43 . 
     Please refer to  FIG. 6 , which is a cross-sectional view of the extension structure of the electrospinning equipment according to a further preferred embodiment of the present invention. The cross-sectional view of the extension structure  5  is a square appearance, and the shape of the body thereof is a cylinder or a box. The extension structure  5  also includes an opening portion  52 , a spinneret receiving portion  54  and a body, wherein a width of the opening portion  52  is obviously larger than that of the spinneret receiving portion  54 , and an electric field space  53  is formed inside the extension structure  5 . The extension structure  5  is coupled to the material supply  10 , and the spinneret  12  is configured in the extension structure  5 ; the electric field space  53  is formed between the spinneret  12  and the collector  31 . 
     Please refer to  FIG. 7 , which is a 3D schematic view of the extension structure of the electrospinning equipment according to further another preferred embodiment of the present invention, wherein the extension structure  6  is in a shape of a multilateral pyramid. In this preferred embodiment, the extension structure  6  is in a shape of a quadrilateral pyramid, wherein a spinneret receiving portion  64  is configured on the top of the pyramid, and an opening portion  62  also having a width larger than that of the spinneret receiving portion  64  is located at the base of the pyramid. 
     Therefore, the extension structure of the present invention is generally a structure coupled to the material supply  10 , and is formed by extending outward from the spinneret  12  toward the collector  31 . That is to say, no matter what shape the extension structure is, such as the various ones disclosed in  FIGS. 3-7 , the basic shape of the extension structure is that the width of the end connected to the material supply (which is the spinneret receiving portion) is smaller than that of the end away from the material supply (which is the opening portion), which means the circumference, the diameter, the edge length or the cross-section area measure of the opening portion is larger than that of the spinneret receiving portion. In other words, in the present invention, the spinneret receiving portion is connected to the opening portion by a body structure, and the body structure can be made by shell manufacturing for the convenience of the manufacturing process or for the necessity of light-weight. 
     The aim of the present invention is to let the thread reach the collector stably without transverse fluctuation. The method to achieve the aim is to stabilize the electric field between the material supply and the collector, and further to restrict the thread jetted from the material supply, so that the thread can reach the collector nearly without transverse fluctuation. In accordance with a further aspect of the present invention, an electrospinning method is provided. Referring to  FIG. 3 , the electrospinning method includes steps of (1) providing a material supply  10 , (2) providing a collector  31  under the material supply  10 , and (3) generating an electric field ef 3  between the material supply  10  and the collector  31 , wherein a pattern of the electric field ef 3  is convergent from the material supply  10  to the collector  31 . 
     More briefly, the method of the present invention is to generate an electric field between the material supply and the collector, and the electric field pattern is convergent from the material supply to the collector. As shown in  FIG. 3 , the material supply  10  is located above the collector  31 , wherein the pattern of the electric field ef 3  is like a shape of an inverted cone. 
     As to the method to generate the electric field ef 3 , it is achieved by forming an extension structure  3  by extending outward from the material supply  10  toward the collector  31 . The body of the extension structure  3  is in a shape of a body portion of one selected from a group consisting of a bowl, a disc and a dome. 
     Please refer to  FIG. 3  again. The electric field ef 3  is generated by a power supply PS having a first electrode  30   a  coupled to the material supply  10  and a second electrode  30   b , where the collector  31  is located between the second electrode  30   b  and the material supply  10 . In other words, as shown in  FIG. 3 , the second electrode  30   b  is mounted under the collector  31 . In addition, the second electrode  30   b  is configured in a distance g away from the collector  31 , so that the collector  31  is movable for changing the location which the thread F is deposited at after jetted from the material supply  10 . 
     Please refer to  FIG. 8 , which shows the application of the electrospinning equipment in the present invention. The material supply  10  is located above the collector  31 , and the thread F is jetted from the spinneret  12  toward the collector  31  and deposited on the collector  31  through a stable and straight route using the extension structure  3  of the present invention. As shown in  FIG. 8 , due to the movable collector  31 , a flex diagram of the thread F can be weaved thereon. At the moment shown in  FIG. 8 , the collector  31  is moving toward a direction D to deposit the thread F toward the opposite direction of the direction D. 
     Alternatively, the present invention could be demonstrated in other embodiments as illustrated in  FIGS. 9 and 10 . Please refer to  FIG. 9 . Firstly, the extension structure  7  (or the guide unit  7 ) forms a spherical or oval enclosed structure  7  covering the material supply  70 , the spinneret  72  and the collector  731 , so as to form an enclosed space  71  between the enclosed structure  7  and the collector  731 . The material supply  70  is connected with a first power supply PS 1 , wherein the first electrode  730   a  and the second electrode  730   b  are connected with the material supply  70  and the collector  731 , respectively. The enclosed structure  7  is connected with a second power supply PS 2 , wherein the third electrode  730   c  and the fourth electrode  730   d  are connected with the upper section of the enclosed structure  7  and the collector  731 , respectively. The enclosed structure  7  further comprises an insulating structure  74 , which is located on both end of the enclosed structure  7  and is connected to the collector  731 . As a result, the inner space of the enclosed structure  7 , or the enclosed space  71 , can generate an electric field ef 3 . It is to be noticed that the center  710  of the spherical enclosed structure  7  or the focal point  710  of the oval enclosed structure  7  needs to be located on the collector  731  so that the electric field ef 3  can converge toward the collector  731  to allow the thread F firmly spray thereon. Moreover, the power supplies PS 1  and PS 2  in this embodiment are not limited, they can be replaced with one power supply connected to the enclosed structure  7 , the material supply  70  and the collector  731  at the same time. 
     In  FIG. 9 , the material supply  70  is coupled but separated from the enclosed structure  7 ; while it is also possible to allow them to be connected with each other as shown in  FIG. 10 , which demonstrates that the enclosed structure  8  covering the spinneret  82  and the collector  831  so as to form an enclosed space  81  between the enclosed structure  8  and the collector  831 , wherein the material supply  80  is partially enclosed by the enclosed structure  8 , and the enclosed structure  8  further includes a spinneret receiving portion  834  for connecting with the spinneret  82 , and an insulating structure  84  located on both end of the enclosed structure  8  and is connected to the collector  831 . Still, the center  810  of the spherical enclosed structure  8  or the focal point  810  of the oval enclosed structure  8  needs to be located on the collector  831 , to make the electric field ef 3  converge toward the collector  831  therefore. Basically, the enclosed structure  7 ,  8  as demonstrated in  FIGS. 9-10  would make the thread collection become much more firm and stable than the traditional structure, since the thread F in the enclosed space  71 ,  81  will not be affected by the factors or interferences outside of the enclosed structure  7 ,  8 , and therefore exclude all the negative effect, so that the objective of the present invention can be well and efficiently achieved. 
     In conclusion, in order to prevent the fluctuation of the thread during the electrospinning process, the present invention provides a special electric field between the material supply and the collector, wherein the electric field pattern is convergent from the material supply to the collector, so that the thread reaches the collector stably without fluctuation after jetted from the material supply. The convergent electric field pattern is generated by providing the extension structure of the present invention extending outward from the material supply toward the collector, wherein one of the extension structure is like an inverted bowl. Therefore, the equipment and method disclosed herein provide more possibility for electrospinning technique. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.