Method and apparatus for manufacturing polymer fiber shells via electrospinning

Abstract

An apparatus for manufacturing a polymer fiber shell from liquefied polymer is provided. The apparatus includes: (a) a precipitation electrode being for generating the polymer fiber shell thereupon; (b) a dispenser, being at a first potential relative to the precipitation electrode so as to generate an electric field between the precipitation electrode and the dispenser, the dispenser being for: (i) charging the liquefied polymer thereby providing a charged liquefied polymer; and (ii) dispensing the charged liquefied polymer in a direction of the precipitation electrode; and (c) a subsidiary electrode being at a second potential relative to the precipitation electrode, the subsidiary electrode being for modifying the electric field between the precipitation electrode and the dispenser.

What is claimed is:  
     
         1 . An apparatus for manufacturing polymer fiber shell from liquefied polymer, the apparatus comprising: 
 (a) a precipitation electrode being for generating the polymer fiber shell thereupon;    (b) a dispenser, being at a first potential relative to said precipitation electrode so as to generate an electric field between said precipitation electrode and said dispenser, said dispenser being for: 
 (i) charging the liquefied polymer thereby providing a charged liquefied polymer; and  
 (ii) dispensing said charged liquefied polymer in a direction of said precipitation electrode; and  
   (c) a subsidiary electrode being at a second potential relative to said precipitation electrode, said subsidiary electrode being for modifying said electric field between said precipitation electrode and said dispenser.    
     
     
         2 . The apparatus of  claim 1 , wherein said subsidiary electrode serves for reducing non-uniformities in said electric field between said precipitation electrode and said dispenser.  
     
     
         3 . The apparatus of  claim 1 , wherein said subsidiary electrode serves for controlling fiber orientation of said polymer fiber shell generated upon said precipitation electrode.  
     
     
         4 . The apparatus according to  claim 1 , wherein said dispenser comprises a mechanism for forming a jet of said charged liquefied polymer.  
     
     
         5 . The apparatus according to  claim 1 , further comprising a bath for holding the liquefied polymer.  
     
     
         6 . The apparatus according to  claim 4 , wherein said mechanism for forming a jet of said charged liquefied polymer includes a dispensing electrode.  
     
     
         7 . The apparatus according to  claim 1 , wherein said dispenser is operative to move along a longitudinal axis of said precipitation electrode.  
     
     
         8 . The apparatus according to  claim 1 , wherein said precipitation electrode includes at least one rotating mandrel.  
     
     
         9 . The apparatus according to  claim 8 , wherein said rotating mandrel is a cylindrical mandrel.  
     
     
         10 . The apparatus according to  claim 9 , wherein said cylindrical mandrel is of a diameter selected from a range of 0.11 to 20 millimeters.  
     
     
         11 . The apparatus according to  claim 8 , wherein said rotating mandrel is an intricate-profile mandrel.  
     
     
         12 . The apparatus according to  claim 11 , wherein said intricate-profile mandrel includes sharp structural elements.  
     
     
         13 . The apparatus according to  claim 1 , wherein said precipitation electrode includes at least one structural element selected from the group consisting of a protrusion, an orifice, a groove, and a grind.  
     
     
         14 . The apparatus according to  claim 1 , wherein said subsidiary electrode is of a shape selected from the group consisting of a plane, a cylinder, a torus and a wire.  
     
     
         15 . The apparatus according to  claim 1 , wherein said subsidiary electrode is operative to move along a longitudinal axis of said precipitation electrode.  
     
     
         16 . The apparatus according to  claim 1 , wherein said subsidiary electrode is tilted at angle with respect to a longitudinal axis of said precipitation electrode, said angle is ranging between 45 and 90 degrees.  
     
     
         17 . The apparatus according to  claim 1 , wherein said subsidiary electrode is positioned at a distance of 5-70 millimeters from said precipitation electrode.  
     
     
         18 . The apparatus according to  claim 1 , wherein said subsidiary electrode is positioned at a distance δ from said precipitation electrode, δ being equal to 12βR(1−V 2 /V 1 ), where β is a constant ranging between about 0.7 and about 0.9, R is a curvature-radius of the polymer fiber shell formed on said precipitation electrode, V 1  is said first potential and V 2  is said second potential.  
     
     
         19 . A method for forming a liquefied polymer into a non-woven polymer fiber shell, the method comprising: 
 (a) charging the liquefied polymer thereby producing a charged liquefied polymer;    (b) subjecting said charged liquefied polymer to a first electric field;    (c) dispensing said charged liquefied polymer within said first electric field in a direction of a precipitation electrode, said precipitation electrode being, designed and configured for generating the polymer fiber shell thereupon;    (d) providing a second electric field being for modifying said first electric field; and    (e) using said precipitation electrode to collect said charged liquefied polymer thereupon, thereby forming the non-woven polymer fiber shells.    
     
     
         20 . The method according to  claim 19 , wherein said first electric field is defined between said precipitation electrode and a dispensing electrode being at a first potential relative to said precipitation electrode.  
     
     
         21 . The method according to  claim 20 , wherein step (c) is effected by dispensing said charged liquefied polymer from said dispensing electrode.  
     
     
         22 . The method according to  claim 19 , further comprising moving said dispensing electrode along a longitudinal axis of said precipitation electrode during step (c).  
     
     
         23 . The method according to  claim 19 , wherein said precipitation electrode includes at least one rotating mandrel.  
     
     
         24 . The method according to  claim 23 , wherein said rotating mandrel is a cylindrical mandrel.  
     
     
         25 . The method according to  claim 24 , wherein said cylindrical mandrel is of a diameter selected from a range of 0.1 to 20 millimeters.  
     
     
         26 . The method according to  claim 23 , wherein said rotating mandrel is an intricate-profile mandrel.  
     
     
         27 . The method according to  claim 26 , wherein said intricate-profile mandrel includes sharp structural elements.  
     
     
         28 . The method according to  claim 25 , wherein said precipitation electrode includes at least one structural element selected from the group consisting of a protrusion, an orifice, a groove, and a grind.  
     
     
         29 . The method according to  claim 20 , wherein said second electric field is defined by a subsidiary electrode being at a second potential relative to said precipitation electrode.  
     
     
         30 . The method according to  claim 29 , wherein said subsidiary electrode serves for reducing non-uniformities in said first electric field.  
     
     
         31 . The method according to  claim 19 , wherein said subsidiary electrode serves for controlling fiber orientation of said polymer fiber shell generated upon said precipitation electrode.  
     
     
         32 . The method according to  claim 29 , wherein said subsidiary electrode is of a shape selected from the group consisting of a plane, a cylinder, a torus and a wire.  
     
     
         33 . The method according to  claim 29 , further comprising moving said subsidiary electrode along said precipitation electrode during step (e).  
     
     
         34 . The method according to  claim 29 , further comprising tilting said subsidiary electrode at angle with respect to a longitudinal axis of said precipitation electrode, said angle ranging between 45 and 90 degrees.  
     
     
         35 . The method according to  claim 29 , wherein said subsidiary electrode is positioned at a distance of 5-50 millimeters from said precipitation electrode.  
     
     
         36 . The method according to  claim 29 , wherein said subsidiary electrode is positioned at a distance δ from said precipitation electrode, δ being equal to 12βR(1−V 2 /V 1 ), where β is a constant ranging between about 0.7 and about 0.9, R is a curvature-radius of the polymer fiber shell formed on said precipitation electrode, V 1  is said first potential and V 2  is said second potential.  
     
     
         37 . An apparatus for manufacturing a polymer fiber shell from liquefied polymer, the apparatus comprising: 
 (a) a dispenser, for: 
 (i) charging the liquefied polymer thereby providing a charged liquefied polymer; and  
 (ii) dispensing said charged liquefied polymer; and  
   (b) a precipitation electrode being at a potential relative to said dispenser thereby generating an electric field between s aid precipitation electrode and said dispenser, said precipitation electrode being for collecting said charged liquefied polymer drawn by said electric field, to thereby form the polymer fiber shell thereupon, wherein said precipitation electrode is designed so as to reduce non-uniformities in said electric field.    
     
     
         38 . The apparatus according to  claim 37 , wherein said dispenser comprises a mechanism for forming a jet of said charged liquefied polymer.  
     
     
         39 . The apparatus according to  claim 37 , further comprising a bath for holding the liquefied polymer.  
     
     
         40 . The apparatus according to  claim 38 , wherein said mechanism for forming a jet of said charged liquefied polymer includes a dispensing electrode.  
     
     
         41 . The apparatus according to  claim 37 , wherein said precipitation electrode is formed from a combination of electroconductive and non-electroconductive materials.  
     
     
         42 . The apparatus according to  claim 41 , wherein a surface of said precipitation electrode is formed from a predetermined pattern of said electroconductive and non-electroconductive materials.  
     
     
         43 . The apparatus according to  claim 37 , wherein said precipitation electrode is formed from at least two layers.  
     
     
         44 . The apparatus according to  claim 43 , wherein said at least two layers include an electroconductive layer and a partial electroconductive layer.  
     
     
         45 . The apparatus according to  claim 44 , wherein said partial electroconductive layer is formed from a combination of an electroconductive material and at least one dielectric material.  
     
     
         46 . The apparatus according to  claim 45 , wherein said dielectric material is selected from a group consisting of polyamide, polytetrafluoroethylene and polyacrylonitrile.  
     
     
         47 . The apparatus according to  claim 45 , wherein said dielectric material is Titanium Nitride.  
     
     
         48 . The apparatus according to  claim 44 , wherein said partially electroconductive layer, is of a thickness selected from a range of 0.1 to 90 microns.  
     
     
         49 . The apparatus according to  claim 37 , wherein said precipitation electrode is of a diameter selected from a range of 0.1 to 20 millimeters.  
     
     
         50 . The apparatus according to  claim 37 , wherein said precipitation electrode includes at least one rotating mandrel.  
     
     
         51 . The apparatus according to  claim 50 , wherein said rotating mandrel is a cylindrical mandrel.  
     
     
         52 . A tubular structure manufactured by the apparatus of  claim 1 .  
     
     
         53 . A tubular structure manufactured by the method of  claim 29 .  
     
     
         54 . A tubular structure manufactured by the apparatus of  claim 37 .  
     
     
         55 . The apparatus of  claim 1 , wherein said subsidiary electrode serves to minimize a volume charge generated between said dispenser and said precipitation electrode.  
     
     
         56 . The method according to  claim 29 , wherein said subsidiary electrode serves to minimize a volume charge generated between said precipitation electrode and said dispensing electrode.  
     
     
         57 . The apparatus according to  claim 1 , wherein said dispenser and said subsidiary electrode are operative to move synchronically along a longitudinal axis of said precipitation electrode.  
     
     
         58 . The method according to  claim 29 , further comprising synchronically moving both said dispensing electrode and said subsidiary electrode along said precipitation electrode.