Continuous production of thermochromic yarns

Abstract

A method of continuous production of thermochromic nanofiber yarns is described. The method includes applying a first thermochromic material to a nanofiber sheet, and then twisting that nanofiber sheet into a first thermochromic yarn. A second thermochromic material is optionally applied to the first thermochromic yarn to produce a second thermochromic yarn. Alternatively, a homogeneous mixture of the first and the second thermochromic materials is applied to a nanofiber sheet in a single layer to produce a thermochromic nanofiber yarn. The thermochromic yarn can be a single ply yarn or a multi-ply yarn depending on the color to be displayed.

What is claimed is: 
     
         1 . A method comprising:
 drawing a nanofiber sheet from a nanofiber forest;   applying a first thermochromic material to the nanofiber sheet;   twisting the nanofiber sheet with the first thermochromic material into a first thermochromic nanofiber yarn; and   applying a second thermochromic material to the first thermochromic nanofiber yarn to produce a second thermochromic nanofiber yarn.   
     
     
         2 . The method of  claim 1 , further comprising heating the first thermochromic nanofiber yarn before applying the second thermochromic material. 
     
     
         3 . The method of  claim 2 , wherein heating the first thermochromic yarn comprises heating to a first temperature of from 90° C. to 115° C. 
     
     
         4 . The method of  claim 1 , further comprising heating the second thermochromic nanofiber yarn after applying the first thermochromic material and the second thermochromic material. 
     
     
         5 . The method of  claim 4 , wherein heating the second thermochromic yarn comprises heating to a second temperature of from 90° C. to 115° C. 
     
     
         6 . The method of  claim 1 , wherein the first thermochromic material is applied to the nanofiber sheet as a solution of a first solvent and the first thermochromic material. 
     
     
         7 . The method of  claim 1 , wherein the second thermochromic material is applied to the first thermochromic nanofiber yarn as a solution of a second solvent and the second thermochromic material. 
     
     
         8 . The method of  claim 1 , wherein the first thermochromic material has a first transition temperature. 
     
     
         9 . The method of  claim 8 , wherein the second thermochromic material has a second transition temperature different from the first transition temperature. 
     
     
         10 . The method of  claim 9 , wherein the second thermochromic nanofiber yarn displays:
 a first color below the first transition temperature;   a second color different from the first color between the first transition temperature and the second transition temperature; and   a third color different from the first and second colors above the second transition temperature.   
     
     
         11 . The method of  claim 1 , wherein a diameter of the first thermochromic nanofiber yarn and the second thermochromic nanofiber yarn is at least 5 microns. 
     
     
         12 . The method of  claim 1 , further comprising:
 drawing an additional nanofiber sheet from the nanofiber forest;   applying a third thermochromic material to the additional nanofiber sheet;   twisting the additional nanofiber sheet with the third thermochromic material into a third thermochromic nanofiber yarn; and   plying the third thermochromic nanofiber yarn with the second thermochromic nanofiber yarn to produce a multi-ply thermochromic nanofiber yarn.   
     
     
         13 . The method of  claim 12 , wherein the third thermochromic material has a third transition temperature different from a first transition temperature and a second transition temperature. 
     
     
         14 . The method of  claim 1 , further comprising adding a conductive material to the nanofiber sheet. 
     
     
         15 . The method of  claim 1 , further comprising adding a metallic nanoparticle to the nanofiber sheet. 
     
     
         16 . A method comprising:
 drawing a nanofiber sheet from a nanofiber forest;   applying a mixture of a first thermochromic material and a second thermochromic material to the nanofiber sheet; and   twisting the nanofiber sheet with the first and the second thermochromic materials into a thermochromic nanofiber yarn.   
     
     
         17 . The method of  claim 16 , wherein the mixture of the first thermochromic material and the second thermochromic material is homogeneous. 
     
     
         18 . The method of  claim 17 , the mixture comprises equal parts of the first and the second thermochromic materials. 
     
     
         19 . The method of  claim 18 , wherein the mixture of the first thermochromic material and the second thermochromic material is applied to the nanofiber sheet in a single layer.