Electrospinning with reduced current or using fluid of reduced conductivity

Abstract

A method comprises: dissolving an aromatic side chain polymer in a terpene, terpenoid, or aromatic solvent; dissolving an inorganic salt in a polar organic solvent; mixing the salt solution and the polymer solution; and using a predominantly terpene, terpenoid, or aromatic solvent phase of the mixture as electrospinning fluid. The fluid is electrospun from spinning tip(s) onto a target substrate. The inorganic salt and the polar organic solvent are chosen so as not to cause substantial precipitation of the polymer upon mixing with the polymer solution. The terpene, terpenoid, or aromatic solvent can comprises D-limonene, the aromatic side chain polymer can comprise polystyrene, the polar organic solvent can comprise dimethyl formamide, and the inorganic salt can comprise LiCl, AgNO3, CuCl2, or FeCl3. The method can further comprise electrospinning the fluid with the fluid and spinning tips electrically isolated from a voltage source that drives the electrospinning.

1 . A method comprising:
 dissolving an aromatic side chain polymer in a terpene, terpenoid, or aromatic solvent to form a polymer solution;   dissolving an amount of inorganic salt in an amount of polar organic solvent to form a salt solution;   mixing the salt solution and the polymer solution to form a mixture; and   using a resulting predominantly terpene, terpenoid, or aromatic solvent phase of the mixture as an electrospinning fluid by electrospinning the fluid from one or more spinning tips onto a target substrate,   wherein the inorganic salt and the polar organic solvent do not cause substantial precipitation of the polymer upon mixing with the polymer solution.   
     
     
         2 . The method of  claim 1  wherein the polymer solution is between about 20% and about 40% by weight of the polymer, the salt solution is between about 0.02% and about 5% by weight of the salt, and the mixture is between about 10% and about 30% by volume of the salt solution. 
     
     
         3 . The method of  claim 1  wherein the polymer solution is between about 20% and about 40% by weight of the polymer, the amount of salt results in a mole ratio between about 0.5:1 and about 20:1 of the salt to the polymer in the mixture, and the amount of polar organic solvent results in a mole ratio between about 1:1 and about 1:4 of the polar organic solvent to the terpene, terpenoid, or aromatic solvent in the mixture. 
     
     
         4 . The method of  claim 1  wherein the terpene, terpenoid, or aromatic solvent comprises D-limonene, the aromatic side chain polymer comprises polystyrene, the polar organic solvent comprises dimethyl formamide, and the inorganic salt comprises LiCl, AgNO 3 , CuCl 2 , or FeCl 3 . 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1  further comprising allowing the predominantly terpene, terpenoid, or aromatic solvent phase of the mixture to separate and then removing it from the mixture. 
     
     
         8 . The method of  claim 1  wherein the spinning tips and the electrospinning fluid are electrically isolated from a voltage source that drives the electrospinning. 
     
     
         9 . The method of  claim 1  wherein the target substrate is electrically insulating. 
     
     
         10 . The method of  claim 1  wherein the target substrate is electrically isolated. 
     
     
         11 . The method of  claim 1  wherein an average diameter of electrospun fibers produced by the electrospinning of the fluid is substantially independent of a voltage applied to drive the electrospinning or whether the fluid and the spinning tips are electrically isolated. 
     
     
         12 . An apparatus comprising:
 a first substantially planar conductive grid, mesh, or perforated plate;   one or more spinning tips arranged to eject fluid unimpeded through the first grid, mesh, or plate;   a fluid reservoir connected to deliver fluid to be ejected by the spinning tips;   a second substantially planar conductive grid, mesh, or plate arranged substantially parallel to and spaced apart from the first grid, mesh, or plate so that fluid ejected from the spinning tips is directed toward the second grid, mesh, or plate; and   a voltage supply connected to provide an electrical potential difference between the first grid, mesh, or plate and the second grid, mesh, or plate,   wherein the apparatus can be arranged in a first configuration with the fluid reservoir and the spinning tips electrically isolated.   
     
     
         13 . The apparatus of  claim 12  wherein the apparatus can be arranged in a second configuration with a conduction path between (i) the voltage supply and (ii) the fluid reservoir or the spinning tips. 
     
     
         14 . The apparatus of  claim 13  wherein:
 each spinning tip comprises (i) a corresponding metal tube electrically connected to the first grid, mesh, or plate and extending toward the second grid mesh, or plate, and (ii) a corresponding electrically insulating capillary tube positioned within the corresponding metal tube and connected to the fluid reservoir; 
 the capillary tubes are longitudinally moveable within the corresponding metal tubes; 
 in the first configuration the insulating capillary tubes are recessed within the corresponding metal tubes; and 
 in the second configuration the insulating capillary tubes extend from the corresponding metal tubes toward the second grid, mesh, or plate. 
 
     
     
         15 . A composition of matter comprising the electrospinning fluid of  claim 1 . 
     
     
         16 . A composition of matter comprising the electrospinning fluid of  claim 2 . 
     
     
         17 . A composition of matter comprising the electrospinning fluid of  claim 3 . 
     
     
         18 . A composition of matter comprising the electrospinning fluid of  claim 4 . 
     
     
         19 . A composition of matter comprising a plurality nanofibers produced by the process of  claim 1 . 
     
     
         20 . A composition of matter comprising a plurality nanofibers produced by the process of  claim 2 . 
     
     
         21 . A composition of matter comprising a plurality nanofibers produced by the process of  claim 3 . 
     
     
         22 . A composition of matter comprising a plurality nanofibers produced by the process of  claim 4 .